linux-kernel - Re: [PATCH] powerpc/fsl-pci: Fix Class Code of PCIe Root Port

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Message-ID: <87r129bcs8.fsf@mpe.ellerman.id.au>
Date:   Mon, 25 Jul 2022 22:24:39 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Bjorn Helgaas <helgaas@...nel.org>,
        Pali Rohár <pali@...nel.org>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/fsl-pci: Fix Class Code of PCIe Root Port

Bjorn Helgaas <helgaas@...nel.org> writes:
> On Wed, Jul 06, 2022 at 12:10:43PM +0200, Pali Rohár wrote:
>> By default old pre-3.0 Freescale PCIe controllers reports invalid PCI Class
>> Code 0x0b20 for PCIe Root Port. It can be seen by lspci -b output on P2020
>> board which has this pre-3.0 controller:
>> 
>>   $ lspci -bvnn
>>   00:00.0 Power PC [0b20]: Freescale Semiconductor Inc P2020E [1957:0070] (rev 21)
>>           !!! Invalid class 0b20 for header type 01
>>           Capabilities: [4c] Express Root Port (Slot-), MSI 00
>> 
>> Fix this issue by programming correct PCI Class Code 0x0604 for PCIe Root
>> Port to the Freescale specific PCIe register 0x474.
>> 
>> With this change lspci -b output is:
>> 
>>   $ lspci -bvnn
>>   00:00.0 PCI bridge [0604]: Freescale Semiconductor Inc P2020E [1957:0070] (rev 21) (prog-if 00 [Normal decode])
>>           Capabilities: [4c] Express Root Port (Slot-), MSI 00
>> 
>> Without any "Invalid class" error. So class code was properly reflected
>> into standard (read-only) PCI register 0x08.
>> 
>> Same fix is already implemented in U-Boot pcie_fsl.c driver in commit:
>> http://source.denx.de/u-boot/u-boot/-/commit/d18d06ac35229345a0af80977a408cfbe1d1015b
>> 
>> Fix activated by U-Boot stay active also after booting Linux kernel.
>> But boards which use older U-Boot version without that fix are affected and
>> still require this fix.
>> 
>> So implement this class code fix also in kernel fsl_pci.c driver.
>> 
>> Cc: stable@...r.kernel.org
>> Signed-off-by: Pali Rohár <pali@...nel.org>
>
> I assume the powerpc folks will take care of this.

Will do.

cheers