Re: [PATCH] PCI: quirks: Quirk PCI d3hot delay for AMD xhci

["Limonciello, Mario" <mario.limonciello@amd.com>]

On 7/29/2021 16:06, Bjorn Helgaas wrote:
> On Thu, Jul 29, 2021 at 03:42:58PM -0500, Limonciello, Mario wrote:
>> On 7/29/2021 15:39, Bjorn Helgaas wrote:
>>> On Wed, Jul 21, 2021 at 10:58:58PM -0400, Alex Deucher wrote:
>>>> From: Marcin Bachry <hegel666@gmail.com>
>>>>
>>>> Renoir needs a similar delay.
>>>>
>>>> [Alex: I talked to the AMD USB hardware team and the
>>>>    AMD windows team and they are not aware of any HW
>>>>    errata or specific issues.  The HW works fine in
>>>>    windows.  I was told windows uses a rather generous
>>>>    default delay of 100ms for PCI state transitions.]
>>>>
>>>> Signed-off-by: Marcin Bachry <hegel666@gmail.com>
>>>> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
>>>
>>> Added stable tag and applied to pci/pm for v5.15, thanks!
>>
>> Thanks Bjorn!
>>
>> Given how small/harmless this is and 5.14 isn't cut yet, any chance this
>> could still make one of the -rcX rather than wait for 5.14.1 instead?
> 
> Done.

Thanks!

> 
> What's the rest of the story here?  Aare we working around a defect in
> these XHCI controllers?  A defect in Linux?  Obviously nobody wants to
> have to add a quirk for every new Device ID.  It's not like this
> should be hard to figure out for your hardware guys in the lab, and if
> it turns out to be a Linux problem, we should fix it so everybody
> benefits.
> 

Maybe you missed the embedded message from Alex above.  We had a 
discussion with our internal team that works with Windows on this, and 
they told us the default delay is significantly more generous on Windows.

>>>> Cc: mario.limonciello@amd.com
>>>> Cc: prike.liang@amd.com
>>>> Cc: shyam-sundar.s-k@amd.com
>>>> ---
>>>>
>>>> Bjorn,
>>>>
>>>> With the above comment in mind, would you consider this patch
>>>> or would you prefer to increase the default timeout on Linux?
>>>> 100ms seems a bit long and most devices seems to work within
>>>> that limit.  Additionally, this patch doesn't seem to be
>>>> required on all AMD platforms with the affected USB controller,
>>>> so I suspect the current timeout on Linux is probably about
>>>> right.  Increasing it seems to fix some of the marginal cases.
>>>>
>>>> Alex
>>>>
>>>>    drivers/pci/quirks.c | 1 +
>>>>    1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
>>>> index 22b2bb1109c9..dea10d62d5b9 100644
>>>> --- a/drivers/pci/quirks.c
>>>> +++ b/drivers/pci/quirks.c
>>>> @@ -1899,6 +1899,7 @@ static void quirk_ryzen_xhci_d3hot(struct pci_dev *dev)
>>>>    }
>>>>    DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_AMD, 0x15e0, quirk_ryzen_xhci_d3hot);
>>>>    DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_AMD, 0x15e1, quirk_ryzen_xhci_d3hot);
>>>> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_AMD, 0x1639, quirk_ryzen_xhci_d3hot);
>>>>    #ifdef CONFIG_X86_IO_APIC
>>>>    static int dmi_disable_ioapicreroute(const struct dmi_system_id *d)
>>>> -- 
>>>> 2.31.1
>>>>
>>