Hi Florian,
This is from the following commit:
commit fb26592301200dbbe4a9943fe188b57a46716900
Author: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Date: Mon Oct 31 16:00:01 2016 -0500
PCI: Warn on possible RW1C corruption for sub-32 bit config writes
Hardware that supports only 32-bit config writes is not spec-compliant.
For example, if software performs a 16-bit write, we must do a 32-bit read,
merge in the 16 bits we intend to write, followed by a 32-bit write. If
the 16 bits we *don't* intend to write happen to have any RW1C (write-one-
to-clear) bits set, we just inadvertently cleared something we shouldn't
have.
Add a rate-limited warning when we do sub-32 bit config writes. Remove
similar probe-time warnings from some of the affected host bridge drivers.
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Enthusiastically-Acked-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
Acked-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx> # rockchip
Acked-by: Thierry Reding <treding@xxxxxxxxxx>
This warning message will show up on every root complex that can only
support 32-bit config register write (instead of 8-bit, 16-bit writes)
and iProc based host controller happens to be one of them.
This limitation violates the PCIe spec as the 32-bit write may clear
RW1C bits of a config register. But I believe those registers are
usually used in AER which we do not currently support in the iProc
based hos controllers.
Regards,
Ray
On Mon, Oct 9, 2017 at 8:58 PM, Florian Fainelli <f.fainelli@xxxxxxxxx> wrote:
> Hi,
>
> With 4.14-rc3 on a BCM5301x device I am seeing the following PCI core
> warnings using pcie_iproc; is this something to be worried about?
>
> [ 2.626059] pcie_iproc_bcma bcma0:7: PCI host bridge to bus 0000:00
>
>
>
> [ 2.632358] pci_bus 0000:00: root bus resource [mem
> 0x08000000-0x0fffffff]
>
>
> [ 2.639207] pci_bus 0000:00: No busn resource found for root bus,
> will use [bus 00-ff]
>
>
> [ 2.647188] pci_bus 0000:00: 2-byte config write to 0000:00:00.0
> offset 0x4 may corrupt adjacent RW1C bits
>
>
> [ 2.656838] pci_bus 0000:00: 2-byte config write to 0000:00:00.0
> offset 0x4 may corrupt adjacent RW1C bits
>
>
> [ 2.666565] pci_bus 0000:00: 2-byte config write to 0000:00:00.0
> offset 0x4c may corrupt adjacent RW1C bits
>
>
> [ 2.676524] pci_bus 0000:00: 2-byte config write to 0000:00:00.0
> offset 0x3e may corrupt adjacent RW1C bits
>
>
> [ 2.686270] pci_bus 0000:00: 2-byte config write to 0000:00:00.0
> offset 0x4 may corrupt adjacent RW1C bits
>
>
> [ 2.695903] pci_bus 0000:00: 1-byte config write to 0000:00:00.0
> offset 0xc may corrupt adjacent RW1C bits
>
>
> [ 2.705531] PCI: bus0: Fast back to back transfers disabled
>
>
>
> [ 2.711086] pci 0000:00:00.0: bridge configuration invalid ([bus
> 00-00]), reconfiguring
>
>
> [ 2.719076] pci_bus 0000:00: 2-byte config write to 0000:00:00.0
> offset 0x3e may corrupt adjacent RW1C bits
>
>
> [ 2.728796] pci_bus 0000:00: 2-byte config write to 0000:00:00.0
> offset 0xc8 may corrupt adjacent RW1C bits
>
>
> [ 2.738513] pci_bus 0000:00: 2-byte config write to 0000:00:00.0
> offset 0x3e may corrupt adjacent RW1C bits
>
>
> [ 2.748225] pci_bus 0000:00: 2-byte config write to 0000:00:00.0
> offset 0x3e may corrupt adjacent RW1C bits
>
>
> [ 2.758262] pci 0000:01:00.0: enabling Extended Tags
>
>
>
> [ 2.763577] PCI: bus1: Fast back to back transfers disabled
>
>
>
> [ 2.769205] pci 0000:00:00.0: BAR 8: assigned [mem
> 0x08000000-0x080fffff]
>
>
> [ 2.776017] pci 0000:01:00.0: BAR 0: assigned [mem
> 0x08000000-0x08003fff 64bit]
>
>
> [ 2.783338] pci 0000:00:00.0: PCI bridge to [bus 01]
>
>
>
> [ 2.788293] pci 0000:00:00.0: bridge window [mem
> 0x08000000-0x080fffff]
>
>
> [ 2.911536] pcie_iproc_bcma bcma0:8: link: UP
>
>
>
> [ 2.916052] pcie_iproc_bcma bcma0:8: PCI host bridge to bus 0001:00
>
>
>
> [ 2.922349] pci_bus 0001:00: root bus resource [mem
> 0x40000000-0x47ffffff]
>
>
> [ 2.929200] pci_bus 0001:00: No busn resource found for root bus,
> will use [bus 00-ff]
>
>
> [ 2.937482] PCI: bus0: Fast back to back transfers disabled
>
>
>
> [ 2.943075] pci 0001:00:00.0: bridge configuration invalid ([bus
> 00-00]), reconfiguring
>
>
> [ 2.951713] PCI: bus1: Fast back to back transfers disabled
>
>
>
> [ 2.957354] pci 0001:00:00.0: BAR 8: assigned [mem
> 0x40000000-0x400fffff]
>
>
> [ 2.964166] pci 0001:01:00.0: BAR 0: assigned [mem
> 0x40000000-0x40007fff 64bit]
>
>
> [ 2.971461] pci 0001:00:00.0: PCI bridge to [bus 01]
>
>
>
> [ 2.976434] pci 0001:00:00.0: bridge window [mem
> 0x40000000-0x400fffff]
> --
> Florian
