| Message ID | 20240726092829.2042624-1-chenhuacai@loongson.cn (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | PCI: Prevent LS7A Bus Master clearing on kexec | expand |
On Fri, Jul 26, 2024 at 05:28:29PM +0800, Huacai Chen wrote: > This is similar to commit 62b6dee1b44aa23b39355 ("PCI/portdrv: Prevent > LS7A Bus Master clearing on shutdown"), which prevents LS7A Bus Master > clearing on kexec. > > Only skip Bus Master clearing on bridges because endpoint devices still > need it. I think we need some explanation here and a hint in the comment below about why this is needed. I guess the point is to work around the LS7A defect that clearing PCI_COMMAND_MASTER prevents MMIO requests from going downstream, and we may need to do that even after .shutdown(), e.g., to print console messages? And in this case we rely on .shutdown() for the downstream devices to disable interrupts and DMA? s/62b6dee1b44aa23b39355/62b6dee1b44a/ > Signed-off-by: Ming Wang <wangming01@loongson.cn> > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn> > --- > drivers/pci/pci-driver.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c > index f412ef73a6e4..b7d3a4d8532f 100644 > --- a/drivers/pci/pci-driver.c > +++ b/drivers/pci/pci-driver.c > @@ -517,7 +517,7 @@ static void pci_device_shutdown(struct device *dev) > * If it is not a kexec reboot, firmware will hit the PCI > * devices with big hammer and stop their DMA any way. > */ > - if (kexec_in_progress && (pci_dev->current_state <= PCI_D3hot)) > + if (kexec_in_progress && !pci_is_bridge(pci_dev) && (pci_dev->current_state <= PCI_D3hot)) > pci_clear_master(pci_dev); > } > > -- > 2.43.5 >
On Fri, Aug 2, 2024 at 7:12 AM Bjorn Helgaas <helgaas@kernel.org> wrote: > > On Fri, Jul 26, 2024 at 05:28:29PM +0800, Huacai Chen wrote: > > This is similar to commit 62b6dee1b44aa23b39355 ("PCI/portdrv: Prevent > > LS7A Bus Master clearing on shutdown"), which prevents LS7A Bus Master > > clearing on kexec. > > > > Only skip Bus Master clearing on bridges because endpoint devices still > > need it. > > I think we need some explanation here and a hint in the comment below > about why this is needed. > > I guess the point is to work around the LS7A defect that clearing > PCI_COMMAND_MASTER prevents MMIO requests from going downstream, and > we may need to do that even after .shutdown(), e.g., to print console > messages? > > And in this case we rely on .shutdown() for the downstream devices to > disable interrupts and DMA? Yes, this is the key point, I will add the above information to the commit message. > > s/62b6dee1b44aa23b39355/62b6dee1b44a/ OK, thanks. Huacai > > > Signed-off-by: Ming Wang <wangming01@loongson.cn> > > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn> > > --- > > drivers/pci/pci-driver.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c > > index f412ef73a6e4..b7d3a4d8532f 100644 > > --- a/drivers/pci/pci-driver.c > > +++ b/drivers/pci/pci-driver.c > > @@ -517,7 +517,7 @@ static void pci_device_shutdown(struct device *dev) > > * If it is not a kexec reboot, firmware will hit the PCI > > * devices with big hammer and stop their DMA any way. > > */ > > - if (kexec_in_progress && (pci_dev->current_state <= PCI_D3hot)) > > + if (kexec_in_progress && !pci_is_bridge(pci_dev) && (pci_dev->current_state <= PCI_D3hot)) > > pci_clear_master(pci_dev); > > } > > > > -- > > 2.43.5 > >
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c index f412ef73a6e4..b7d3a4d8532f 100644 --- a/drivers/pci/pci-driver.c +++ b/drivers/pci/pci-driver.c @@ -517,7 +517,7 @@ static void pci_device_shutdown(struct device *dev) * If it is not a kexec reboot, firmware will hit the PCI * devices with big hammer and stop their DMA any way. */ - if (kexec_in_progress && (pci_dev->current_state <= PCI_D3hot)) + if (kexec_in_progress && !pci_is_bridge(pci_dev) && (pci_dev->current_state <= PCI_D3hot)) pci_clear_master(pci_dev); }
This is similar to commit 62b6dee1b44aa23b39355 ("PCI/portdrv: Prevent LS7A Bus Master clearing on shutdown"), which prevents LS7A Bus Master clearing on kexec. Only skip Bus Master clearing on bridges because endpoint devices still need it. Signed-off-by: Ming Wang <wangming01@loongson.cn> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn> --- drivers/pci/pci-driver.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)