Re: [PATCH] PCI/DPC: Quirk PIO log size for certain Intel PCIe root ports

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, Aug 16, 2022 at 01:20:42PM +0300, Mika Westerberg wrote:
> There is a BIOS bug on Intel Tiger Lake and Alder Lake systems that
> accidentally clears the root port PIO log size even though it should be 4.
> Fix the affected root ports by forcing the log size to be 4 if it is set
> to 0. The BIOS for the next generation CPUs should have this fixed.
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=209943
> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Applied to pci/dpc for v6.1, thanks, Mika!

I updated the commit log to include the fact that the bug also
prevents dumping the RP PIO Log registers, so let me know if that's
not accurate:

    PCI/DPC: Quirk PIO log size for certain Intel Root Ports

    Some Root Ports on Intel Tiger Lake and Alder Lake systems support the RP
    Extensions for DPC and the RP PIO Log registers but incorrectly advertise
    an RP PIO Log Size of zero.  This means the kernel complains that:

      DPC: RP PIO log size 0 is invalid

    and if DPC is triggered, the DPC driver will not dump the RP PIO Log
    registers when it should.

    This is caused by a BIOS bug and should be fixed the BIOS for future CPUs.

    Add a quirk to set the correct RP PIO Log size for the affected Root Ports.

> ---
>  drivers/pci/pcie/dpc.c | 13 ++++++++-----
>  drivers/pci/quirks.c   | 37 +++++++++++++++++++++++++++++++++++++
>  2 files changed, 45 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
> index 3e9afee02e8d..ab06c801a2c1 100644
> --- a/drivers/pci/pcie/dpc.c
> +++ b/drivers/pci/pcie/dpc.c
> @@ -335,11 +335,14 @@ void pci_dpc_init(struct pci_dev *pdev)
>  		return;
>  
>  	pdev->dpc_rp_extensions = true;
> -	pdev->dpc_rp_log_size = (cap & PCI_EXP_DPC_RP_PIO_LOG_SIZE) >> 8;
> -	if (pdev->dpc_rp_log_size < 4 || pdev->dpc_rp_log_size > 9) {
> -		pci_err(pdev, "RP PIO log size %u is invalid\n",
> -			pdev->dpc_rp_log_size);
> -		pdev->dpc_rp_log_size = 0;
> +	/* If not already set by the quirk in quirks.c */
> +	if (!pdev->dpc_rp_log_size) {
> +		pdev->dpc_rp_log_size = (cap & PCI_EXP_DPC_RP_PIO_LOG_SIZE) >> 8;
> +		if (pdev->dpc_rp_log_size < 4 || pdev->dpc_rp_log_size > 9) {
> +			pci_err(pdev, "RP PIO log size %u is invalid\n",
> +				pdev->dpc_rp_log_size);
> +			pdev->dpc_rp_log_size = 0;
> +		}
>  	}
>  }
>  
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 4944798e75b5..260d8b50f68d 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -5956,3 +5956,40 @@ DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x56b1, aspm_l1_acceptable_latency
>  DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x56c0, aspm_l1_acceptable_latency);
>  DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x56c1, aspm_l1_acceptable_latency);
>  #endif
> +
> +#ifdef CONFIG_PCIE_DPC
> +/*
> + * Intel Tiger Lake and Alder Lake BIOS has a bug that clears the DPC
> + * log size of the integrated Thunderbolt PCIe root ports so we quirk
> + * them here.
> + */
> +static void dpc_log_size(struct pci_dev *dev)
> +{
> +	u16 dpc_cap, val;
> +
> +	dpc_cap = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DPC);
> +	if (!dpc_cap)
> +		return;
> +
> +	pci_read_config_word(dev, dpc_cap + PCI_EXP_DPC_CAP, &val);
> +	if (!(val & PCI_EXP_DPC_CAP_RP_EXT))
> +		return;
> +
> +	if (!((val & PCI_EXP_DPC_RP_PIO_LOG_SIZE) >> 8)) {
> +		pci_info(dev, "quirking RP PIO log size\n");
> +		dev->dpc_rp_log_size = 4;
> +	}
> +}
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x461f, dpc_log_size);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x462f, dpc_log_size);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x463f, dpc_log_size);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x466e, dpc_log_size);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a23, dpc_log_size);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a25, dpc_log_size);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a27, dpc_log_size);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a29, dpc_log_size);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a2b, dpc_log_size);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a2d, dpc_log_size);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a2f, dpc_log_size);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a31, dpc_log_size);
> +#endif
> -- 
> 2.35.1
>