Re: [PATCH] PCI: brcmstb: Assign pcie->gen from pcie_get_link_speed()

[Florian Fainelli <florian.fainelli@broadcom.com>]

On 5/4/26 10:26, Hans Zhang wrote:
> 
> 
> On 5/5/26 00:58, Florian Fainelli wrote:
>> On 5/2/26 04:40, Bjorn Helgaas wrote:
>>> On Fri, May 01, 2026 at 01:24:38PM -0700, Florian Fainelli wrote:
>>>> After commit 03f920936977 ("PCI: controller: Validate max-link-speed"),
>>>> pcie->gen stopped being assigned and as a result the established PCIe
>>>> link would stop supporting Gen3 speeds on 2712 since pcie->gen is used
>>>> to populate LnkCntl2 and LnkCap in brcm_pcie_set_gen().
>>>>
>>>> Link: https://github.com/raspberrypi/linux/issues/7343
>>>> Reported-by: Dom Cobley <popcornmix@gmail.com>
>>>> Reported-by: Phil Elwell <phil@raspberrypi.com>
>>>> Fixes: 03f920936977 ("PCI: controller: Validate max-link-speed")
>>>> Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
>>>> ---
>>>>   drivers/pci/controller/pcie-brcmstb.c | 3 +--
>>>>   1 file changed, 1 insertion(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/ 
>>>> controller/pcie-brcmstb.c
>>>> index 714bcab97b60..6138fc4bc064 100644
>>>> --- a/drivers/pci/controller/pcie-brcmstb.c
>>>> +++ b/drivers/pci/controller/pcie-brcmstb.c
>>>> @@ -2072,8 +2072,7 @@ static int brcm_pcie_probe(struct 
>>>> platform_device *pdev)
>>>>           return PTR_ERR(pcie->clk);
>>>>       ret = of_pci_get_max_link_speed(np);
>>>> -    if (pcie_get_link_speed(ret) == PCI_SPEED_UNKNOWN)
>>>> -        pcie->gen = 0;
>>>> +    pcie->gen = pcie_get_link_speed(ret);
>>>
>>> Take a look at https://sashiko.dev/#/ 
>>> patchset/20260501202438.376033-1- florian.fainelli%40broadcom.com
>>>
>>> The notes at https://github.com/raspberrypi/linux/issues/7343 assumed
>>> PCI_SPEED_UNKNOWN was 0, but in fact it is 0xff, which means you might
>>> want the more defensive patch instead.
>>>
>>> I'll be happy to replace what's on pci/for-linus if so.
>>
>> I am starting to think a revert is the simplest path forward, it's not 
>> clear what pcie_get_link_speed() brings to the table honestly.
> 
> Hi Florian,
> 
> The pcie_get_link_speed function is designed to prevent other Root Port 
> drivers from accessing the array pcie_link_speed out of bounds.

Yes, so that's useful in the first hunk of your commit where we were 
printing the link speed without checking that the 'max-link-speed' would 
be bounds check, however it is not really useful for assigning to 
pcie->gen in our case, so I would prefer the second option:


           ret = of_pci_get_max_link_speed(np);
  -       if (pcie_get_link_speed(ret) == PCI_SPEED_UNKNOWN)
  -               pcie->gen = 0;
  +       pcie->gen = (ret < 0) ? 0 : ret;

Thank you for stepping in!
-- 
Florian