Re: [PATCH] PCI: Add Max Payload Size quirk for ASMedia ASM1062 SATA controller

[Bjorn Helgaas <helgaas@kernel.org>]

[+cc Zachary, author of 8a3ebd8de328]

Thanks for the report and the patch, Marek!

On Wed, Mar 17, 2021 at 12:59:24PM +0100, Marek Behún wrote:
> The ASMedia ASM1062 SATA controller causes an External Abort on
> controllers which support Max Payload Size >= 512. It happens with
> Aardvark PCIe controller (tested on Turris MOX) and also with DesignWare
> controller (armada8k, tested on CN9130-CRB):
> 
>   ata1: SATA link up 6.0 Gbps (SStatus 133 SControl 300)
>   ata1.00: ATA-9: WDC WD40EFRX-68WT0N0, 80.00A80, max UDMA/133
>   ata1.00: 7814037168 sectors, multi 0: LBA48 NCQ (depth 32), AA
>   ERROR:   Unhandled External Abort received on 0x80000000 at EL3!
>   ERROR:    exception reason=1 syndrome=0x92000210
>   PANIC at PC : 0x00000000040273bc
> 
> Limiting Max Payload Size to 256 bytes solves this problem.
> 
> On Turris MOX this problem first appeared when the pci-aardvark
> controller started using the pci-emul-bridge API, in commit 8a3ebd8de328
> ("PCI: aardvark: Implement emulated root PCI bridge config space").

Any ideas about why 8a3ebd8de328 made a difference?  Could there be a
defect in 8a3ebd8de328?  Or maybe before 8a3ebd8de328 we didn't
actually read or update MPS settings in the hardware?

> On armada8k this was always a problem because it has HW root bridge.

Can you please open a report at bugzilla.kernel.org and attach the
complete "sudo lspci -vv" output for both systems?  I think it's OK to
collect these with the patch applied; we should still be able to see
the information we use to compute the MPS values.  But please include
the CONFIG_PCIE_BUS_* settings and any "pcie_bus_*" kernel command
line arguments.

This quirk suggests that there's a hardware defect in the ASMedia
ASM1062.  But if that's really the case, we should see reports on lots
of platforms, and I'm only aware of these two.  You do mention that it
was always a problem on armada8k; if you know of other reports of
that, please include URLs in the bugzilla.

If the problem only occurs on these platforms, my first guess would be
a hardware defect in these platforms or a software defect in the PCIe
controller driver.  It wouldn't surprise me if we have a generic PCI
core defect in how we set MPS, either.

> Signed-off-by: Marek Behún <kabel@kernel.org>
> Reported-by: Rötti <espressobinboardarmbiantempmailaddress@posteo.de>
> Cc: Pali Rohár <pali@kernel.org>
> Cc: stable@vger.kernel.org
> ---
>  drivers/pci/quirks.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 653660e3ba9e..a561136efb08 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -3251,6 +3251,11 @@ DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_SOLARFLARE,
>  			 PCI_DEVICE_ID_SOLARFLARE_SFC4000A_1, fixup_mpss_256);
>  DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_SOLARFLARE,
>  			 PCI_DEVICE_ID_SOLARFLARE_SFC4000B, fixup_mpss_256);
> +/*
> + * For some reason DECLARE_PCI_FIXUP_HEADER does not work with pci-aardvark
> + * controller. We have to use DECLARE_PCI_FIXUP_EARLY.
> + */

This is curious, too.  If we need the quirk, I'd like to run this down
to figure out why we need an EARLY instead of HEADER quirk.
Differences like that suggest a bug elsewhere, or at least an
unnecessary difference between PCIe controller drivers.

> +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_ASMEDIA, 0x0612, fixup_mpss_256);
>  
>  /*
>   * Intel 5000 and 5100 Memory controllers have an erratum with read completion
> -- 
> 2.26.2
>