Re: pci_bus warnings about adjacent RW1C bits w/ iproc-pci

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hi, we get about 9 of those messages on the Broadcom Settop box boot.
I think there's more but it is rate limited.  We could do individual
8-bit/16-bit/32-bit writes for the RC itself (we don't currently) but
not for the downstream devices without changes to the HW.  --Jim

On Tue, Oct 10, 2017 at 7:10 AM, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
> On Mon, Oct 09, 2017 at 10:33:01PM -0700, Ray Jui wrote:
>> 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.
>
> This warning is ratelimited, but maybe even that is overkill.  It
> looks like we currently warn on every config write of less than 32
> bits.  How many of those do you see?  Once per boot might be enough,
> or maybe once per device (so we get a hint when loading a new driver).
>
>> 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



[Index of Archives]     [DMA Engine]     [Linux Coverity]     [Linux USB]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [Greybus]

  Powered by Linux