| Message ID | 20230227201340.2087605-1-sdalvi@google.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2] PCI: dwc: Wait for link up only if link is started | expand |
On Mon, Feb 27, 2023, Sajid Dalvi <sdalvi@google.com> wrote: > > In dw_pcie_host_init() regardless of whether the link has been started > or not, the code waits for the link to come up. Even in cases where > start_link() is not defined the code ends up spinning in a loop for 1 > second. Since in some systems dw_pcie_host_init() gets called during > probe, this one second loop for each pcie interface instance ends up > extending the boot time. > > Call trace when start_link() is not defined: > dw_pcie_wait_for_link << spins in a loop for 1 second > dw_pcie_host_init > > Signed-off-by: Sajid Dalvi <sdalvi@google.com> (CC'ed Krzysztof Kozlowski) Acked-by: Jingoo Han <jingoohan1@gmail.com> It looks good to me. I also checked the previous thread. I agree with Krzysztof's opinion that we should include only hardware-related features into DT. Thank you. Best regards, Jingoo Han > --- > drivers/pci/controller/dwc/pcie-designware-host.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c > index 9952057c8819..9709f69f173e 100644 > --- a/drivers/pci/controller/dwc/pcie-designware-host.c > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c > @@ -489,10 +489,10 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp) > ret = dw_pcie_start_link(pci); > if (ret) > goto err_remove_edma; > - } > > - /* Ignore errors, the link may come up later */ > - dw_pcie_wait_for_link(pci); > + /* Ignore errors, the link may come up later */ > + dw_pcie_wait_for_link(pci); > + } > > bridge->sysdata = pp; > > -- > 2.39.2.722.g9855ee24e9-goog >
Thanks for your review Jingoo. Sajid On Tue, Feb 28, 2023 at 4:04 PM Han Jingoo <jingoohan1@gmail.com> wrote: > > On Mon, Feb 27, 2023, Sajid Dalvi <sdalvi@google.com> wrote: > > > > In dw_pcie_host_init() regardless of whether the link has been started > > or not, the code waits for the link to come up. Even in cases where > > start_link() is not defined the code ends up spinning in a loop for 1 > > second. Since in some systems dw_pcie_host_init() gets called during > > probe, this one second loop for each pcie interface instance ends up > > extending the boot time. > > > > Call trace when start_link() is not defined: > > dw_pcie_wait_for_link << spins in a loop for 1 second > > dw_pcie_host_init > > > > Signed-off-by: Sajid Dalvi <sdalvi@google.com> > > (CC'ed Krzysztof Kozlowski) > > Acked-by: Jingoo Han <jingoohan1@gmail.com> > > It looks good to me. I also checked the previous thread. > I agree with Krzysztof's opinion that we should include > only hardware-related features into DT. > Thank you. > > Best regards, > Jingoo Han > > > --- > > drivers/pci/controller/dwc/pcie-designware-host.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c > > index 9952057c8819..9709f69f173e 100644 > > --- a/drivers/pci/controller/dwc/pcie-designware-host.c > > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c > > @@ -489,10 +489,10 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp) > > ret = dw_pcie_start_link(pci); > > if (ret) > > goto err_remove_edma; > > - } > > > > - /* Ignore errors, the link may come up later */ > > - dw_pcie_wait_for_link(pci); > > + /* Ignore errors, the link may come up later */ > > + dw_pcie_wait_for_link(pci); > > + } > > > > bridge->sysdata = pp; > > > > -- > > 2.39.2.722.g9855ee24e9-goog > >
On Tue, Feb 28, 2023 at 10:36 PM Sajid Dalvi <sdalvi@google.com> wrote: > > Thanks for your review Jingoo. > Sajid > > On Tue, Feb 28, 2023 at 4:04 PM Han Jingoo <jingoohan1@gmail.com> wrote: > > > > On Mon, Feb 27, 2023, Sajid Dalvi <sdalvi@google.com> wrote: > > > > > > In dw_pcie_host_init() regardless of whether the link has been started > > > or not, the code waits for the link to come up. Even in cases where > > > start_link() is not defined the code ends up spinning in a loop for 1 > > > second. Since in some systems dw_pcie_host_init() gets called during > > > probe, this one second loop for each pcie interface instance ends up > > > extending the boot time. > > > > > > Call trace when start_link() is not defined: > > > dw_pcie_wait_for_link << spins in a loop for 1 second > > > dw_pcie_host_init > > > > > > Signed-off-by: Sajid Dalvi <sdalvi@google.com> > > > > (CC'ed Krzysztof Kozlowski) > > > > Acked-by: Jingoo Han <jingoohan1@gmail.com> > > > > It looks good to me. I also checked the previous thread. > > I agree with Krzysztof's opinion that we should include > > only hardware-related features into DT. > > Thank you. > > > > Best regards, > > Jingoo Han > > > > > --- > > > drivers/pci/controller/dwc/pcie-designware-host.c | 6 +++--- > > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c > > > index 9952057c8819..9709f69f173e 100644 > > > --- a/drivers/pci/controller/dwc/pcie-designware-host.c > > > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c > > > @@ -489,10 +489,10 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp) > > > ret = dw_pcie_start_link(pci); > > > if (ret) > > > goto err_remove_edma; > > > - } > > > > > > - /* Ignore errors, the link may come up later */ > > > - dw_pcie_wait_for_link(pci); > > > + /* Ignore errors, the link may come up later */ > > > + dw_pcie_wait_for_link(pci); > > > + } > > > > > > bridge->sysdata = pp; > > > > > > -- > > > 2.39.2.722.g9855ee24e9-goog > > > @bhelgaas Can this be picked up in your tree: https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/ Thanks Sajid
On Thu, Mar 16, 2023 at 06:05:02PM -0500, Sajid Dalvi wrote: > On Tue, Feb 28, 2023 at 10:36 PM Sajid Dalvi <sdalvi@google.com> wrote: > > > > Thanks for your review Jingoo. > > Sajid > > > > On Tue, Feb 28, 2023 at 4:04 PM Han Jingoo <jingoohan1@gmail.com> wrote: > > > > > > On Mon, Feb 27, 2023, Sajid Dalvi <sdalvi@google.com> wrote: > > > > > > > > In dw_pcie_host_init() regardless of whether the link has been started > > > > or not, the code waits for the link to come up. Even in cases where > > > > start_link() is not defined the code ends up spinning in a loop for 1 > > > > second. Since in some systems dw_pcie_host_init() gets called during > > > > probe, this one second loop for each pcie interface instance ends up > > > > extending the boot time. > > > > > > > > Call trace when start_link() is not defined: > > > > dw_pcie_wait_for_link << spins in a loop for 1 second > > > > dw_pcie_host_init > > > > > > > > Signed-off-by: Sajid Dalvi <sdalvi@google.com> > > > > > > (CC'ed Krzysztof Kozlowski) > > > > > > Acked-by: Jingoo Han <jingoohan1@gmail.com> > > > > > > It looks good to me. I also checked the previous thread. > > > I agree with Krzysztof's opinion that we should include > > > only hardware-related features into DT. > > > Thank you. > > > > > > Best regards, > > > Jingoo Han > > > > > > > --- > > > > drivers/pci/controller/dwc/pcie-designware-host.c | 6 +++--- > > > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > > > > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c > > > > index 9952057c8819..9709f69f173e 100644 > > > > --- a/drivers/pci/controller/dwc/pcie-designware-host.c > > > > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c > > > > @@ -489,10 +489,10 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp) > > > > ret = dw_pcie_start_link(pci); > > > > if (ret) > > > > goto err_remove_edma; > > > > - } > > > > > > > > - /* Ignore errors, the link may come up later */ > > > > - dw_pcie_wait_for_link(pci); > > > > + /* Ignore errors, the link may come up later */ > > > > + dw_pcie_wait_for_link(pci); > > > > + } > > > > > > > > bridge->sysdata = pp; > > > > > > > > -- > > > > 2.39.2.722.g9855ee24e9-goog > > > > > > @bhelgaas Can this be picked up in your tree: > https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/ This patch seems fine to me. The question I have though is why the *current* code is written the way it is. Perhaps it is just the way it is, I wonder whether this change can trigger a regression though. I guess the only way to know is merging this path and check the fallout. Lorenzo
On Wed, Apr 05, 2023 at 03:24:36PM +0200, Lorenzo Pieralisi wrote: > On Thu, Mar 16, 2023 at 06:05:02PM -0500, Sajid Dalvi wrote: > > On Tue, Feb 28, 2023 at 10:36 PM Sajid Dalvi <sdalvi@google.com> wrote: > > > > > > Thanks for your review Jingoo. > > > Sajid > > > > > > On Tue, Feb 28, 2023 at 4:04 PM Han Jingoo <jingoohan1@gmail.com> wrote: > > > > > > > > On Mon, Feb 27, 2023, Sajid Dalvi <sdalvi@google.com> wrote: > > > > > > > > > > In dw_pcie_host_init() regardless of whether the link has been started > > > > > or not, the code waits for the link to come up. Even in cases where > > > > > start_link() is not defined the code ends up spinning in a loop for 1 > > > > > second. Since in some systems dw_pcie_host_init() gets called during > > > > > probe, this one second loop for each pcie interface instance ends up > > > > > extending the boot time. > > > > > > > > > > Call trace when start_link() is not defined: > > > > > dw_pcie_wait_for_link << spins in a loop for 1 second > > > > > dw_pcie_host_init > > > > > > > > > > Signed-off-by: Sajid Dalvi <sdalvi@google.com> > > > > > > > > (CC'ed Krzysztof Kozlowski) > > > > > > > > Acked-by: Jingoo Han <jingoohan1@gmail.com> > > > > > > > > It looks good to me. I also checked the previous thread. > > > > I agree with Krzysztof's opinion that we should include > > > > only hardware-related features into DT. > > > > Thank you. > > > > > > > > Best regards, > > > > Jingoo Han > > > > > > > > > --- > > > > > drivers/pci/controller/dwc/pcie-designware-host.c | 6 +++--- > > > > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > > > > > > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c > > > > > index 9952057c8819..9709f69f173e 100644 > > > > > --- a/drivers/pci/controller/dwc/pcie-designware-host.c > > > > > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c > > > > > @@ -489,10 +489,10 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp) > > > > > ret = dw_pcie_start_link(pci); > > > > > if (ret) > > > > > goto err_remove_edma; > > > > > - } > > > > > > > > > > - /* Ignore errors, the link may come up later */ > > > > > - dw_pcie_wait_for_link(pci); > > > > > + /* Ignore errors, the link may come up later */ > > > > > + dw_pcie_wait_for_link(pci); > > > > > + } > > > > > > > > > > bridge->sysdata = pp; > > > > > > > > > > -- > > > > > 2.39.2.722.g9855ee24e9-goog > > > > > > > > > @bhelgaas Can this be picked up in your tree: > > https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/ > > This patch seems fine to me. The question I have though is why the > *current* code is written the way it is. Perhaps it is just the way > it is, I wonder whether this change can trigger a regression though. The new code will look basically like this: if (!dw_pcie_link_up(pci)) { dw_pcie_start_link(pci); dw_pcie_wait_for_link(pci); } If the link is already up by the time we get here, this change means we won't get this message emitted by dw_pcie_wait_for_link(): dev_info(pci->dev, "PCIe Gen.%u x%u link up\n", ...) I don't know how important that is, but I bet somebody cares about it. From the commit log, I expected the patch to do something based on whether ->start_link() was defined, but there really isn't a direct connection, so maybe the log could be refined. Bjorn
On 04/05/2023, Bjorn Helgaas wrote: > On Wed, Apr 05, 2023 at 03:24:36PM +0200, Lorenzo Pieralisi wrote: > > On Thu, Mar 16, 2023 at 06:05:02PM -0500, Sajid Dalvi wrote: > > > On Tue, Feb 28, 2023 at 10:36 PM Sajid Dalvi <sdalvi@google.com> wrote: > > > > > > > > Thanks for your review Jingoo. > > > > Sajid > > > > > > > > On Tue, Feb 28, 2023 at 4:04 PM Han Jingoo <jingoohan1@gmail.com> wrote: > > > > > > > > > > On Mon, Feb 27, 2023, Sajid Dalvi <sdalvi@google.com> wrote: > > > > > > > > > > > > In dw_pcie_host_init() regardless of whether the link has been started > > > > > > or not, the code waits for the link to come up. Even in cases where > > > > > > start_link() is not defined the code ends up spinning in a loop for 1 > > > > > > second. Since in some systems dw_pcie_host_init() gets called during > > > > > > probe, this one second loop for each pcie interface instance ends up > > > > > > extending the boot time. > > > > > > > > > > > > Call trace when start_link() is not defined: > > > > > > dw_pcie_wait_for_link << spins in a loop for 1 second > > > > > > dw_pcie_host_init > > > > > > > > > > > > Signed-off-by: Sajid Dalvi <sdalvi@google.com> > > > > > > > > > > (CC'ed Krzysztof Kozlowski) > > > > > > > > > > Acked-by: Jingoo Han <jingoohan1@gmail.com> > > > > > > > > > > It looks good to me. I also checked the previous thread. > > > > > I agree with Krzysztof's opinion that we should include > > > > > only hardware-related features into DT. > > > > > Thank you. > > > > > > > > > > Best regards, > > > > > Jingoo Han > > > > > > > > > > > --- > > > > > > drivers/pci/controller/dwc/pcie-designware-host.c | 6 +++--- > > > > > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > > > > > > > > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c > > > > > > index 9952057c8819..9709f69f173e 100644 > > > > > > --- a/drivers/pci/controller/dwc/pcie-designware-host.c > > > > > > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c > > > > > > @@ -489,10 +489,10 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp) > > > > > > ret = dw_pcie_start_link(pci); > > > > > > if (ret) > > > > > > goto err_remove_edma; > > > > > > - } > > > > > > > > > > > > - /* Ignore errors, the link may come up later */ > > > > > > - dw_pcie_wait_for_link(pci); > > > > > > + /* Ignore errors, the link may come up later */ > > > > > > + dw_pcie_wait_for_link(pci); > > > > > > + } > > > > > > > > > > > > bridge->sysdata = pp; > > > > > > > > > > > > -- > > > > > > 2.39.2.722.g9855ee24e9-goog > > > > > > > > > > > > @bhelgaas Can this be picked up in your tree: > > > https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/ > > > > This patch seems fine to me. The question I have though is why the > > *current* code is written the way it is. Perhaps it is just the way > > it is, I wonder whether this change can trigger a regression though. > > The new code will look basically like this: > > if (!dw_pcie_link_up(pci)) { > dw_pcie_start_link(pci); > dw_pcie_wait_for_link(pci); > } > > If the link is already up by the time we get here, this change means > we won't get this message emitted by dw_pcie_wait_for_link(): > > dev_info(pci->dev, "PCIe Gen.%u x%u link up\n", ...) > > I don't know how important that is, but I bet somebody cares about it. > > From the commit log, I expected the patch to do something based on > whether ->start_link() was defined, but there really isn't a direct > connection, so maybe the log could be refined. > > Bjorn > > -- > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com. > After taking a deeper dive into this patch, I found that [1] changes the original intent which was to skip the call to dw_pcie_wait_for_link() when pci->ops->start_link is NULL. I talked to Sajid offline and he agreed we should put back the start_link NULL check. The updated patch should look like this: if (!dw_pcie_link_up(pci) && pci->ops && pci->ops->start_link) { ret = dw_pcie_start_link(pci); if (ret) goto err_free_msi; dw_pcie_wait_for_link(pci); } ...which will ensure that we don't call dw_pcie_wait_for_link() when pci->ops->start_link is NULL. With regards to the log, I think there are 2 ways to solve this: 1) We could also call dw_pcie_wait_for_link() in a new else if dw_pcie_link_up() returns 1. 2) We could add this to the top of dw_pcie_wait_for_link() and leave the code as is: if (!pci->ops || !pci->ops->start_link) return 0; I kind of like (2) since that solves both Sajid's original issue and will keep the original log. [1] https://lore.kernel.org/all/20220624143428.8334-14-Sergey.Semin@baikalelectronics.ru/ Regards, Will
On 04/05/2023, William McVicker wrote: > On 04/05/2023, Bjorn Helgaas wrote: > > On Wed, Apr 05, 2023 at 03:24:36PM +0200, Lorenzo Pieralisi wrote: > > > On Thu, Mar 16, 2023 at 06:05:02PM -0500, Sajid Dalvi wrote: > > > > On Tue, Feb 28, 2023 at 10:36 PM Sajid Dalvi <sdalvi@google.com> wrote: > > > > > > > > > > Thanks for your review Jingoo. > > > > > Sajid > > > > > > > > > > On Tue, Feb 28, 2023 at 4:04 PM Han Jingoo <jingoohan1@gmail.com> wrote: > > > > > > > > > > > > On Mon, Feb 27, 2023, Sajid Dalvi <sdalvi@google.com> wrote: > > > > > > > > > > > > > > In dw_pcie_host_init() regardless of whether the link has been started > > > > > > > or not, the code waits for the link to come up. Even in cases where > > > > > > > start_link() is not defined the code ends up spinning in a loop for 1 > > > > > > > second. Since in some systems dw_pcie_host_init() gets called during > > > > > > > probe, this one second loop for each pcie interface instance ends up > > > > > > > extending the boot time. > > > > > > > > > > > > > > Call trace when start_link() is not defined: > > > > > > > dw_pcie_wait_for_link << spins in a loop for 1 second > > > > > > > dw_pcie_host_init > > > > > > > > > > > > > > Signed-off-by: Sajid Dalvi <sdalvi@google.com> > > > > > > > > > > > > (CC'ed Krzysztof Kozlowski) > > > > > > > > > > > > Acked-by: Jingoo Han <jingoohan1@gmail.com> > > > > > > > > > > > > It looks good to me. I also checked the previous thread. > > > > > > I agree with Krzysztof's opinion that we should include > > > > > > only hardware-related features into DT. > > > > > > Thank you. > > > > > > > > > > > > Best regards, > > > > > > Jingoo Han > > > > > > > > > > > > > --- > > > > > > > drivers/pci/controller/dwc/pcie-designware-host.c | 6 +++--- > > > > > > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > > > > > > > > > > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c > > > > > > > index 9952057c8819..9709f69f173e 100644 > > > > > > > --- a/drivers/pci/controller/dwc/pcie-designware-host.c > > > > > > > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c > > > > > > > @@ -489,10 +489,10 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp) > > > > > > > ret = dw_pcie_start_link(pci); > > > > > > > if (ret) > > > > > > > goto err_remove_edma; > > > > > > > - } > > > > > > > > > > > > > > - /* Ignore errors, the link may come up later */ > > > > > > > - dw_pcie_wait_for_link(pci); > > > > > > > + /* Ignore errors, the link may come up later */ > > > > > > > + dw_pcie_wait_for_link(pci); > > > > > > > + } > > > > > > > > > > > > > > bridge->sysdata = pp; > > > > > > > > > > > > > > -- > > > > > > > 2.39.2.722.g9855ee24e9-goog > > > > > > > > > > > > > > > @bhelgaas Can this be picked up in your tree: > > > > https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/ > > > > > > This patch seems fine to me. The question I have though is why the > > > *current* code is written the way it is. Perhaps it is just the way > > > it is, I wonder whether this change can trigger a regression though. > > > > The new code will look basically like this: > > > > if (!dw_pcie_link_up(pci)) { > > dw_pcie_start_link(pci); > > dw_pcie_wait_for_link(pci); > > } > > > > If the link is already up by the time we get here, this change means > > we won't get this message emitted by dw_pcie_wait_for_link(): > > > > dev_info(pci->dev, "PCIe Gen.%u x%u link up\n", ...) > > > > I don't know how important that is, but I bet somebody cares about it. > > > > From the commit log, I expected the patch to do something based on > > whether ->start_link() was defined, but there really isn't a direct > > connection, so maybe the log could be refined. > > > > Bjorn > > > > -- > > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com. > > > > After taking a deeper dive into this patch, I found that [1] changes the > original intent which was to skip the call to dw_pcie_wait_for_link() > when pci->ops->start_link is NULL. I talked to Sajid offline and he > agreed we should put back the start_link NULL check. The updated patch > should look like this: > > if (!dw_pcie_link_up(pci) && pci->ops && pci->ops->start_link) { > ret = dw_pcie_start_link(pci); > if (ret) > goto err_free_msi; > dw_pcie_wait_for_link(pci); > } > > > ...which will ensure that we don't call dw_pcie_wait_for_link() when > pci->ops->start_link is NULL. > > With regards to the log, I think there are 2 ways to solve this: > > 1) We could also call dw_pcie_wait_for_link() in a new else if > dw_pcie_link_up() returns 1. > 2) We could add this to the top of dw_pcie_wait_for_link() and leave the > code as is: > > if (!pci->ops || !pci->ops->start_link) > return 0; > > I kind of like (2) since that solves both Sajid's original issue and > will keep the original log. > > [1] https://lore.kernel.org/all/20220624143428.8334-14-Sergey.Semin@baikalelectronics.ru/ > > Regards, > Will Below is what I'm thinking will do the job. I verified on a Pixel 6 (which doesn't have start_link() defined) that we don't have the 1 second wait from dw_pcie_wait_for_link() during probe. diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c index 8e33e6e59e68..1bf04324ad2d 100644 --- a/drivers/pci/controller/dwc/pcie-designware.c +++ b/drivers/pci/controller/dwc/pcie-designware.c @@ -648,13 +648,16 @@ int dw_pcie_wait_for_link(struct dw_pcie *pci) { u32 offset, val; int retries; + int link_up = dw_pcie_link_up(pci); - /* Check if the link is up or not */ - for (retries = 0; retries < LINK_WAIT_MAX_RETRIES; retries++) { - if (dw_pcie_link_up(pci)) - break; + if (!link_up && !(pci->ops && pci->ops->start_link)) + return 0; + /* Check if the link is up or not */ + for (retries = 0; !link_up && retries < LINK_WAIT_MAX_RETRIES; retries++) { usleep_range(LINK_WAIT_USLEEP_MIN, LINK_WAIT_USLEEP_MAX); + + link_up = dw_pcie_link_up(pci); } if (retries >= LINK_WAIT_MAX_RETRIES) {
On Wed, Apr 05, 2023 at 12:23:47PM -0700, William McVicker wrote: > On 04/05/2023, William McVicker wrote: > > On 04/05/2023, Bjorn Helgaas wrote: > > > On Wed, Apr 05, 2023 at 03:24:36PM +0200, Lorenzo Pieralisi wrote: > > > > On Thu, Mar 16, 2023 at 06:05:02PM -0500, Sajid Dalvi wrote: > > > > > On Tue, Feb 28, 2023 at 10:36 PM Sajid Dalvi <sdalvi@google.com> wrote: > > > > > > > > > > > > Thanks for your review Jingoo. > > > > > > Sajid > > > > > > > > > > > > On Tue, Feb 28, 2023 at 4:04 PM Han Jingoo <jingoohan1@gmail.com> wrote: > > > > > > > > > > > > > > On Mon, Feb 27, 2023, Sajid Dalvi <sdalvi@google.com> wrote: > > > > > > > > > > > > > > > > In dw_pcie_host_init() regardless of whether the link has been started > > > > > > > > or not, the code waits for the link to come up. Even in cases where > > > > > > > > start_link() is not defined the code ends up spinning in a loop for 1 > > > > > > > > second. Since in some systems dw_pcie_host_init() gets called during > > > > > > > > probe, this one second loop for each pcie interface instance ends up > > > > > > > > extending the boot time. > > > > > > > > > > > > > > > > Call trace when start_link() is not defined: > > > > > > > > dw_pcie_wait_for_link << spins in a loop for 1 second > > > > > > > > dw_pcie_host_init > > > > > > > > > > > > > > > > Signed-off-by: Sajid Dalvi <sdalvi@google.com> > > > > > > > > > > > > > > (CC'ed Krzysztof Kozlowski) > > > > > > > > > > > > > > Acked-by: Jingoo Han <jingoohan1@gmail.com> > > > > > > > > > > > > > > It looks good to me. I also checked the previous thread. > > > > > > > I agree with Krzysztof's opinion that we should include > > > > > > > only hardware-related features into DT. > > > > > > > Thank you. > > > > > > > > > > > > > > Best regards, > > > > > > > Jingoo Han > > > > > > > > > > > > > > > --- > > > > > > > > drivers/pci/controller/dwc/pcie-designware-host.c | 6 +++--- > > > > > > > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > > > > > > > > > > > > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c > > > > > > > > index 9952057c8819..9709f69f173e 100644 > > > > > > > > --- a/drivers/pci/controller/dwc/pcie-designware-host.c > > > > > > > > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c > > > > > > > > @@ -489,10 +489,10 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp) > > > > > > > > ret = dw_pcie_start_link(pci); > > > > > > > > if (ret) > > > > > > > > goto err_remove_edma; > > > > > > > > - } > > > > > > > > > > > > > > > > - /* Ignore errors, the link may come up later */ > > > > > > > > - dw_pcie_wait_for_link(pci); > > > > > > > > + /* Ignore errors, the link may come up later */ > > > > > > > > + dw_pcie_wait_for_link(pci); > > > > > > > > + } > > > > > > > > > > > > > > > > bridge->sysdata = pp; > > > > > > > > > > > > > > > > -- > > > > > > > > 2.39.2.722.g9855ee24e9-goog > > > > > > > > > > > > > > > > > > @bhelgaas Can this be picked up in your tree: > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/ > > > > > > > > This patch seems fine to me. The question I have though is why the > > > > *current* code is written the way it is. Perhaps it is just the way > > > > it is, I wonder whether this change can trigger a regression though. > > > > > > The new code will look basically like this: > > > > > > if (!dw_pcie_link_up(pci)) { > > > dw_pcie_start_link(pci); > > > dw_pcie_wait_for_link(pci); > > > } > > > > > > If the link is already up by the time we get here, this change means > > > we won't get this message emitted by dw_pcie_wait_for_link(): > > > > > > dev_info(pci->dev, "PCIe Gen.%u x%u link up\n", ...) > > > > > > I don't know how important that is, but I bet somebody cares about it. > > > > > > From the commit log, I expected the patch to do something based on > > > whether ->start_link() was defined, but there really isn't a direct > > > connection, so maybe the log could be refined. > > > > > > Bjorn > > > > > > -- > > > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com. > > > > > > > After taking a deeper dive into this patch, I found that [1] changes the > > original intent which was to skip the call to dw_pcie_wait_for_link() > > when pci->ops->start_link is NULL. I talked to Sajid offline and he > > agreed we should put back the start_link NULL check. The updated patch > > should look like this: > > > > if (!dw_pcie_link_up(pci) && pci->ops && pci->ops->start_link) { > > ret = dw_pcie_start_link(pci); > > if (ret) > > goto err_free_msi; > > dw_pcie_wait_for_link(pci); > > } > > > > > > ...which will ensure that we don't call dw_pcie_wait_for_link() when > > pci->ops->start_link is NULL. > > > > With regards to the log, I think there are 2 ways to solve this: > > > > 1) We could also call dw_pcie_wait_for_link() in a new else if > > dw_pcie_link_up() returns 1. > > 2) We could add this to the top of dw_pcie_wait_for_link() and leave the > > code as is: > > > > if (!pci->ops || !pci->ops->start_link) > > return 0; > > > > I kind of like (2) since that solves both Sajid's original issue and > > will keep the original log. > > > > [1] https://lore.kernel.org/all/20220624143428.8334-14-Sergey.Semin@baikalelectronics.ru/ > > > > Regards, > > Will > > Below is what I'm thinking will do the job. I verified on a Pixel 6 > (which doesn't have start_link() defined) that we don't have the 1 > second wait from dw_pcie_wait_for_link() during probe. > > diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c > index 8e33e6e59e68..1bf04324ad2d 100644 > --- a/drivers/pci/controller/dwc/pcie-designware.c > +++ b/drivers/pci/controller/dwc/pcie-designware.c > @@ -648,13 +648,16 @@ int dw_pcie_wait_for_link(struct dw_pcie *pci) > { > u32 offset, val; > int retries; > + int link_up = dw_pcie_link_up(pci); > > - /* Check if the link is up or not */ > - for (retries = 0; retries < LINK_WAIT_MAX_RETRIES; retries++) { > - if (dw_pcie_link_up(pci)) > - break; > + if (!link_up && !(pci->ops && pci->ops->start_link)) > + return 0; There is a problem with this approach. A platform driver could enable link training internally, i.e., it does not have the start_link() pointer defined. Then it could call `dw_pcie_wait_for_link` to wait for the link to come up. (See pcie-intel-gw.c for an example of such a platform). Your logic will end up regressing this driver by exiting early. > > + /* Check if the link is up or not */ > + for (retries = 0; !link_up && retries < LINK_WAIT_MAX_RETRIES; retries++) { > usleep_range(LINK_WAIT_USLEEP_MIN, LINK_WAIT_USLEEP_MAX); > + > + link_up = dw_pcie_link_up(pci); > } > > if (retries >= LINK_WAIT_MAX_RETRIES) { > The problem of the log is still not solved for a platform which could have the link up by default, i.e., it does not need to explicitly enable link training.
Here is my attempt at a patch which can satisfy all the requirements
(Ideally, I did not want to use `pci->ops` in the host driver but I
could not figure out any other way):
diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c
b/drivers/pci/controller/dwc/pcie-designware-host.c
index 9952057c8819..39c7219ec7c9 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -485,15 +485,18 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
if (ret)
goto err_remove_edma;
- if (!dw_pcie_link_up(pci)) {
- ret = dw_pcie_start_link(pci);
+ ret = dw_pcie_start_link(pci);
+ if (ret)
+ goto err_remove_edma;
+
+ if (dw_pcie_link_up(pci)) {
+ dw_pcie_print_link_status(pci);
+ } else if (pci->ops && pci->ops->start_link) {
+ ret = dw_pcie_wait_for_link(pci);
if (ret)
- goto err_remove_edma;
+ goto err_stop_link;
}
- /* Ignore errors, the link may come up later */
- dw_pcie_wait_for_link(pci);
-
bridge->sysdata = pp;
ret = pci_host_probe(bridge);
diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 53a16b8b6ac2..03748a8dffd3 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -644,9 +644,20 @@ void dw_pcie_disable_atu(struct dw_pcie *pci, u32 dir, int index)
dw_pcie_writel_atu(pci, dir, index, PCIE_ATU_REGION_CTRL2, 0);
}
-int dw_pcie_wait_for_link(struct dw_pcie *pci)
+void dw_pcie_print_link_status(struct dw_pcie *pci)
{
u32 offset, val;
+
+ offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
+ val = dw_pcie_readw_dbi(pci, offset + PCI_EXP_LNKSTA);
+
+ dev_info(pci->dev, "PCIe Gen.%u x%u link up\n",
+ FIELD_GET(PCI_EXP_LNKSTA_CLS, val),
+ FIELD_GET(PCI_EXP_LNKSTA_NLW, val));
+}
+
+int dw_pcie_wait_for_link(struct dw_pcie *pci)
+{
int retries;
/* Check if the link is up or not */
@@ -662,12 +673,7 @@ int dw_pcie_wait_for_link(struct dw_pcie *pci)
return -ETIMEDOUT;
}
- offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
- val = dw_pcie_readw_dbi(pci, offset + PCI_EXP_LNKSTA);
-
- dev_info(pci->dev, "PCIe Gen.%u x%u link up\n",
- FIELD_GET(PCI_EXP_LNKSTA_CLS, val),
- FIELD_GET(PCI_EXP_LNKSTA_NLW, val));
+ dw_pcie_print_link_status(pci);
return 0;
}
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 79713ce075cc..615660640801 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -429,6 +429,7 @@ void dw_pcie_setup(struct dw_pcie *pci);
void dw_pcie_iatu_detect(struct dw_pcie *pci);
int dw_pcie_edma_detect(struct dw_pcie *pci);
void dw_pcie_edma_remove(struct dw_pcie *pci);
+void dw_pcie_print_link_status(struct dw_pcie *pci);
static inline void dw_pcie_writel_dbi(struct dw_pcie *pci, u32 reg, u32 val)
{
On 04/06/2023, 'Ajay Agarwal' via kernel-team wrote: > Here is my attempt at a patch which can satisfy all the requirements > (Ideally, I did not want to use `pci->ops` in the host driver but I > could not figure out any other way): > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c > b/drivers/pci/controller/dwc/pcie-designware-host.c > index 9952057c8819..39c7219ec7c9 100644 > --- a/drivers/pci/controller/dwc/pcie-designware-host.c > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c > @@ -485,15 +485,18 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp) > if (ret) > goto err_remove_edma; > > - if (!dw_pcie_link_up(pci)) { > - ret = dw_pcie_start_link(pci); > + ret = dw_pcie_start_link(pci); > + if (ret) > + goto err_remove_edma; > + > + if (dw_pcie_link_up(pci)) { > + dw_pcie_print_link_status(pci); > + } else if (pci->ops && pci->ops->start_link) { > + ret = dw_pcie_wait_for_link(pci); > if (ret) > - goto err_remove_edma; > + goto err_stop_link; > } > > - /* Ignore errors, the link may come up later */ > - dw_pcie_wait_for_link(pci); > - > bridge->sysdata = pp; > > ret = pci_host_probe(bridge); > diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c > index 53a16b8b6ac2..03748a8dffd3 100644 > --- a/drivers/pci/controller/dwc/pcie-designware.c > +++ b/drivers/pci/controller/dwc/pcie-designware.c > @@ -644,9 +644,20 @@ void dw_pcie_disable_atu(struct dw_pcie *pci, u32 dir, int index) > dw_pcie_writel_atu(pci, dir, index, PCIE_ATU_REGION_CTRL2, 0); > } > > -int dw_pcie_wait_for_link(struct dw_pcie *pci) > +void dw_pcie_print_link_status(struct dw_pcie *pci) > { > u32 offset, val; > + > + offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP); > + val = dw_pcie_readw_dbi(pci, offset + PCI_EXP_LNKSTA); > + > + dev_info(pci->dev, "PCIe Gen.%u x%u link up\n", > + FIELD_GET(PCI_EXP_LNKSTA_CLS, val), > + FIELD_GET(PCI_EXP_LNKSTA_NLW, val)); > +} > + > +int dw_pcie_wait_for_link(struct dw_pcie *pci) > +{ > int retries; > > /* Check if the link is up or not */ > @@ -662,12 +673,7 @@ int dw_pcie_wait_for_link(struct dw_pcie *pci) > return -ETIMEDOUT; > } > > - offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP); > - val = dw_pcie_readw_dbi(pci, offset + PCI_EXP_LNKSTA); > - > - dev_info(pci->dev, "PCIe Gen.%u x%u link up\n", > - FIELD_GET(PCI_EXP_LNKSTA_CLS, val), > - FIELD_GET(PCI_EXP_LNKSTA_NLW, val)); > + dw_pcie_print_link_status(pci); > > return 0; > } > diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h > index 79713ce075cc..615660640801 100644 > --- a/drivers/pci/controller/dwc/pcie-designware.h > +++ b/drivers/pci/controller/dwc/pcie-designware.h > @@ -429,6 +429,7 @@ void dw_pcie_setup(struct dw_pcie *pci); > void dw_pcie_iatu_detect(struct dw_pcie *pci); > int dw_pcie_edma_detect(struct dw_pcie *pci); > void dw_pcie_edma_remove(struct dw_pcie *pci); > +void dw_pcie_print_link_status(struct dw_pcie *pci); > > static inline void dw_pcie_writel_dbi(struct dw_pcie *pci, u32 reg, u32 val) > { > > -- > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com. > Thanks Ajay for the follow-up patch! I've tested it out on a Pixel 6 and it's working as intended for me. Probing the PCIe RC device now only take 0.02s vs ~1.02s. If others don't object, please send it as a v3 patch. Thanks, Will
diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c index 9952057c8819..9709f69f173e 100644 --- a/drivers/pci/controller/dwc/pcie-designware-host.c +++ b/drivers/pci/controller/dwc/pcie-designware-host.c @@ -489,10 +489,10 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp) ret = dw_pcie_start_link(pci); if (ret) goto err_remove_edma; - } - /* Ignore errors, the link may come up later */ - dw_pcie_wait_for_link(pci); + /* Ignore errors, the link may come up later */ + dw_pcie_wait_for_link(pci); + } bridge->sysdata = pp;
In dw_pcie_host_init() regardless of whether the link has been started or not, the code waits for the link to come up. Even in cases where start_link() is not defined the code ends up spinning in a loop for 1 second. Since in some systems dw_pcie_host_init() gets called during probe, this one second loop for each pcie interface instance ends up extending the boot time. Call trace when start_link() is not defined: dw_pcie_wait_for_link << spins in a loop for 1 second dw_pcie_host_init Signed-off-by: Sajid Dalvi <sdalvi@google.com> --- drivers/pci/controller/dwc/pcie-designware-host.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)