[PATCH] pci: fix incorrect value returned from pcie_get_speed_cap

[Alex Deucher]

On Tue, Oct 30, 2018 at 12:36 PM Mikulas Patocka <mpatocka at redhat.com> wrote:
>
> The macros PCI_EXP_LNKCAP_SLS_*GB are values, not bit masks. We must mask
> the register and compare it against them.
>
> This patch fixes errors "amdgpu: [powerplay] failed to send message 261
> ret is 0" errors when PCIe-v3 card is plugged into PCIe-v1 slot, because
> the slot is being incorrectly reported as PCIe-v3 capable.
>
> Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
> Fixes: 6cf57be0f78e ("PCI: Add pcie_get_speed_cap() to find max supported link speed")
> Cc: stable at vger.kernel.org      # v4.17+

Acked-by: Alex Deucher <alexander.deucher at amd.com>

>
> ---
>  drivers/pci/pci.c |    8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> Index: linux-4.19/drivers/pci/pci.c
> ===================================================================
> --- linux-4.19.orig/drivers/pci/pci.c   2018-10-30 16:58:58.000000000 +0100
> +++ linux-4.19/drivers/pci/pci.c        2018-10-30 16:58:58.000000000 +0100
> @@ -5492,13 +5492,13 @@ enum pci_bus_speed pcie_get_speed_cap(st
>
>         pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &lnkcap);
>         if (lnkcap) {
> -               if (lnkcap & PCI_EXP_LNKCAP_SLS_16_0GB)
> +               if ((lnkcap & PCI_EXP_LNKCAP_SLS) == PCI_EXP_LNKCAP_SLS_16_0GB)
>                         return PCIE_SPEED_16_0GT;
> -               else if (lnkcap & PCI_EXP_LNKCAP_SLS_8_0GB)
> +               else if ((lnkcap & PCI_EXP_LNKCAP_SLS) == PCI_EXP_LNKCAP_SLS_8_0GB)
>                         return PCIE_SPEED_8_0GT;
> -               else if (lnkcap & PCI_EXP_LNKCAP_SLS_5_0GB)
> +               else if ((lnkcap & PCI_EXP_LNKCAP_SLS) ==PCI_EXP_LNKCAP_SLS_5_0GB)
>                         return PCIE_SPEED_5_0GT;
> -               else if (lnkcap & PCI_EXP_LNKCAP_SLS_2_5GB)
> +               else if ((lnkcap & PCI_EXP_LNKCAP_SLS) == PCI_EXP_LNKCAP_SLS_2_5GB)
>                         return PCIE_SPEED_2_5GT;
>         }
>