Re: [PATCH] PCI: Avoid broken MSI on SB600 USB devices

[Bjorn Helgaas <helgaas@kernel.org>]

On Mon, Mar 21, 2022 at 01:34:46PM -0500, Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelgaas@google.com>
> 
> Some ATI SB600 USB adapters advertise MSI, but if INTx is disabled by
> setting PCI_COMMAND_INTX_DISABLE, MSI doesn't work either.  The PCI/PCIe
> specs do not require software to set PCI_COMMAND_INTX_DISABLE when enabling
> MSI, but Linux has done that for many years.
> 
> Mick reported that 306c54d0edb6 ("usb: hcd: Try MSI interrupts on PCI
> devices") broke these devices.  Prior to 306c54d0edb6, they used INTx.
> Starting with 306c54d0edb6, they use MSI, and and the fact that Linux sets
> PCI_COMMAND_INTX_DISABLE means both INTx and MSI are disabled on these
> devices.
> 
> Avoid this SB600 defect by disabling MSI so we use INTx as before.
> 
> Fixes: 306c54d0edb6 ("usb: hcd: Try MSI interrupts on PCI devices")
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=215690
> Link: https://lore.kernel.org/all/PxIByDyBRcsbpcmVhGSNDFAoUcMmb78ctXCkw6fbpx25TGlCHvA6SJjjFkNr1FfQZMntYPTNyvEnblxzAZ8a6jP9ddLpKeCN6Chi_2FuexU=@protonmail.com/
> BugLink: https://lore.kernel.org/all/20200702143045.23429-1-andriy.shevchenko@linux.intel.com/
> Link: https://lore.kernel.org/r/20220314101448.90074-1-andriy.shevchenko@linux.intel.com
> Reported-by: Mick Lorain <micklorain@protonmail.com>
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

Unless there's objection, I plan to include this in the v5.18 pull
request in the next few days.

It was in the 20220322 linux-next tree:
https://lore.kernel.org/linux-next/20220322203829.2bb0166c@canb.auug.org.au/

> ---
>  drivers/pci/quirks.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index d2dd6a6cda60..5f46fed01e6c 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -1811,6 +1811,18 @@ static void quirk_alder_ioapic(struct pci_dev *pdev)
>  DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL,	PCI_DEVICE_ID_INTEL_EESSC,	quirk_alder_ioapic);
>  #endif
>  
> +static void quirk_no_msi(struct pci_dev *dev)
> +{
> +	pci_info(dev, "avoiding MSI to work around a hardware defect\n");
> +	dev->no_msi = 1;
> +}
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATI, 0x4386, quirk_no_msi);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATI, 0x4387, quirk_no_msi);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATI, 0x4388, quirk_no_msi);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATI, 0x4389, quirk_no_msi);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATI, 0x438a, quirk_no_msi);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATI, 0x438b, quirk_no_msi);
> +
>  static void quirk_pcie_mch(struct pci_dev *pdev)
>  {
>  	pdev->no_msi = 1;
> -- 
> 2.25.1
>