| Message ID | 55A80262.2010401@ti.com (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
On Thu, Jul 16, 2015 at 2:13 PM, Murali Karicheri <m-karicheri2@ti.com> wrote: > On 05/16/2015 10:02 AM, Bjorn Helgaas wrote: >> >> On Wed, May 28, 2014 at 01:14:53PM -0400, Murali Karicheri wrote: >>> >>> Call pcie_bus_configure_settings on ARM, like for other platforms. >>> pcie_bus_configure_settings makes sure the MPS across the bus is >>> uniform and provides the ability to tune the MRSS and MPS to higher >>> performance values. This is particularly important for embedded where >>> there is no firmware to program these PCI-E settings for the OS. >>> >>> Signed-off-by: Murali Karicheri <m-karicheri2@ti.com> >>> >>> CC: Russell King <linux@arm.linux.org.uk> >>> CC: Bjorn Helgaas <bhelgaas@google.com> >>> CC: Arnd Bergmann <arnd@arndb.de> >>> CC: Jason Gunthorpe <jgunthorpe@obsidianresearch.com> >>> CC: Santosh Shilimkar <santosh.shilimkar@ti.com> >>> >>> --- >>> - Fixed comments against initial version >>> arch/arm/kernel/bios32.c | 12 ++++++++++++ >>> 1 file changed, 12 insertions(+) >>> >>> diff --git a/arch/arm/kernel/bios32.c b/arch/arm/kernel/bios32.c >>> index 16d43cd..17a26c1 100644 >>> --- a/arch/arm/kernel/bios32.c >>> +++ b/arch/arm/kernel/bios32.c >>> @@ -545,6 +545,18 @@ void pci_common_init_dev(struct device *parent, >>> struct hw_pci *hw) >>> */ >>> pci_bus_add_devices(bus); >>> } >>> + >>> + list_for_each_entry(sys, &head, node) { >>> + struct pci_bus *bus = sys->bus; >>> + >>> + /* Configure PCI Express settings */ >>> + if (bus && !pci_has_flag(PCI_PROBE_ONLY)) { >>> + struct pci_bus *child; >>> + >>> + list_for_each_entry(child, &bus->children, node) >>> + pcie_bus_configure_settings(child); >> >> >> This patch (8b5742ad156d ("ARM/PCI: Call pcie_bus_configure_settings() to >> set MPS")) has been upstream since v3.16-rc1, but I think we goofed. >> >> The MPS configuration should be done *before* pci_bus_add_devices(). >> After >> pci_bus_add_devices(), drivers may be bound to devices, and the PCI core >> shouldn't touch device configuration while a driver owns the device. >> >> Looking at the code, it seems like it would have been simpler to do this >> in >> the existing loop: >> >> list_for_each_entry(sys, &head, node) { >> struct pci_bus *bus = sys->bus; >> >> if (bus && !pci_has_flag(PCI_PROBE_ONLY)) { >> pci_bus_size_bridges(bus); >> pci_bus_assign_resources(bus); >> list_for_each_entry(child, &bus->children, node) >> pcie_bus_configure_settings(child); >> } >> >> pci_bus_add_devices(bus); >> } >> >> so maybe there's some reason I'm not aware of for not doing it that way? > > > Bjorn, > > This one has escaped my radar and I found it recently while I was searching > for something else. I can't recall why this was not done this way. However I > have tried the below code on Keystone and it works fine. > > diff --git a/arch/arm/kernel/bios32.c b/arch/arm/kernel/bios32.c > index fcbbbb1..17efde7 100644 > --- a/arch/arm/kernel/bios32.c > +++ b/arch/arm/kernel/bios32.c > @@ -520,7 +520,8 @@ void pci_common_init_dev(struct device *parent, struct > hw_pci *hw) > list_for_each_entry(sys, &head, node) { > struct pci_bus *bus = sys->bus; > > - if (!pci_has_flag(PCI_PROBE_ONLY)) { > + if (bus && !pci_has_flag(PCI_PROBE_ONLY)) { > + struct pci_bus *child; > /* > * Size the bridge windows. > */ > @@ -530,25 +531,15 @@ void pci_common_init_dev(struct device *parent, struct > hw_pci *hw) > * Assign resources. > */ > pci_bus_assign_resources(bus); > - } > > + list_for_each_entry(child, &bus->children, node) > + pcie_bus_configure_settings(child); > + } > /* > * Tell drivers about devices found. > */ > pci_bus_add_devices(bus); > } > - > - list_for_each_entry(sys, &head, node) { > - struct pci_bus *bus = sys->bus; > - > - /* Configure PCI Express settings */ > - if (bus && !pci_has_flag(PCI_PROBE_ONLY)) { > - struct pci_bus *child; > - > - list_for_each_entry(child, &bus->children, node) > - pcie_bus_configure_settings(child); > - } > - } > } > > The SATA comes up fine and ahci is able to override the mrrs value as shown > by the log below. > > [ 1.581526] ahci 0001:01:00.0: limiting MRRS to 256 > [ 1.586521] ahci 0001:01:00.0: AHCI 0001.0000 32 slots 2 ports 6 Gbps 0x3 > impl SATA mode > [ 1.594604] ahci 0001:01:00.0: flags: 64bit ncq sntf led only pmp fbs pio > slum part sxs > [ 1.603772] scsi host0: ahci > [ 1.606976] scsi host1: ahci > [ > > If you are fine, I can send a patch for this. Please confirm. Yes, please! I think the existing code that calls pci_bus_add_devices() before configuring MPS is wrong, because MPS should be configured before drivers can claim the device. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/arm/kernel/bios32.c b/arch/arm/kernel/bios32.c index fcbbbb1..17efde7 100644 --- a/arch/arm/kernel/bios32.c +++ b/arch/arm/kernel/bios32.c @@ -520,7 +520,8 @@ void pci_common_init_dev(struct device *parent, struct hw_pci *hw) list_for_each_entry(sys, &head, node) { struct pci_bus *bus = sys->bus; - if (!pci_has_flag(PCI_PROBE_ONLY)) { + if (bus && !pci_has_flag(PCI_PROBE_ONLY)) { + struct pci_bus *child; /* * Size the bridge windows.