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

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, Mar 16, 2021 at 03:28:51PM -0400, Alex Deucher wrote:
> From: Marcin Bachry <hegel666@gmail.com>
> 
> Renoir needs a similar delay.

See https://lore.kernel.org/linux-pci/20210311125322.GA2122226@bjorn-Precision-5520/

This is becoming a problem.  We shouldn't have to merge a quirk for
every new device.  Either the devices are defective, and AMD should
publish errata and have a plan for fixing them, or Linux is broken and
we should fix that.

There are quite a few mechanisms for controlling delays like this
(Config Request Retry Status (PCIe r5.0, sec 2.3.1), Readiness
Notifications (sec 6.23), ACPI _DSM for power-on delays (PCI Firmware
Spec r3.3)), but most are for *reducing* delay, not for extending it.

Linux supports CRS, but not all the others.  Maybe we're missing
something we should support?

How do you deal with these issues for Windows?  If it works on Windows
without quirks, we should be able to make it work on Linux as well.

> Signed-off-by: Marcin Bachry <hegel666@gmail.com>
> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
> ---
>  drivers/pci/quirks.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 653660e3ba9e..36e5ec670fae 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -1904,6 +1904,9 @@ 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);
> +/* Renoir XHCI requires longer delay when transitioning from D0 to
> + * D3hot */

No need for "me too" comments that add no additional information.

> +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)
> -- 
> 2.30.2
>