Re: [Nouveau] [PATCH] drm/nouveau: don't touch has_pr3 for likely-non-NVIDIA device

[Karol Herbst <kherbst@redhat.com>]

hey, thanks for the patch. But I am a bit confused on why that patch
actually helps. It should only be called for nvidia GPUs, but are we
ending up checking it for AMD GPUs as well?

Mind posting the output of lspci -tvnn?

On Thu, Jul 22, 2021 at 5:10 AM Ratchanan Srirattanamet
<peathot@hotmail.com> wrote:
>
> The call site of nouveau_dsm_pci_probe() uses single set of output
> variables for all invocations. So, we must not write anything to them
> until we think this is an NVIDIA device of interest. Otherwise, if we
> are called with another device after the NVIDIA device, we'll clober the
> result of the NVIDIA device.
>
> In this case, if the other device doesn't have _PR3 resources, the
> detection later would miss the presence of power resource support, and
> the rest of the code will keep using Optimus DSM, breaking power
> management for that machine. In particular, this fixes power management
> of the NVIDIA card in Lenovo Legion 5-15ARH05... well, at least
> partially. New error shows up, but this patch is correct in itself
> anyway.
>
> As a bonus, we'll also stop preventing _PR3 usage from the bridge for
> unrelated devices, which is always nice, I guess.
>
> As noted in commit ccfc2d5cdb024 ("drm/nouveau: Use generic helper to
> check _PR3 presence"), care is taken to leave the _PR3 detection outside
> of the optimus_func condition.
>
> https://gitlab.freedesktop.org/drm/nouveau/-/issues/79
>
> Fixes: ccfc2d5cdb024 ("drm/nouveau: Use generic helper to check _PR3
> presence")
> Signed-off-by: Ratchanan Srirattanamet <peathot@hotmail.com>
> ---
>
> Hello,
>
> This is my first time submitting a Linux patch. I've done a
> number of PR/MR workflows on GitHub or GitLab, but never done any
> email-oriented development. So, please excuse me if I'm doing something
> incorrectly.
>
>  drivers/gpu/drm/nouveau/nouveau_acpi.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_acpi.c b/drivers/gpu/drm/nouveau/nouveau_acpi.c
> index 7c15f6448428..c88bda3ac820 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_acpi.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_acpi.c
> @@ -220,15 +220,6 @@ static void nouveau_dsm_pci_probe(struct pci_dev *pdev, acpi_handle *dhandle_out
>         int optimus_funcs;
>         struct pci_dev *parent_pdev;
>
> -       *has_pr3 = false;
> -       parent_pdev = pci_upstream_bridge(pdev);
> -       if (parent_pdev) {
> -               if (parent_pdev->bridge_d3)
> -                       *has_pr3 = pci_pr3_present(parent_pdev);
> -               else
> -                       pci_d3cold_disable(pdev);
> -       }
> -
>         dhandle = ACPI_HANDLE(&pdev->dev);
>         if (!dhandle)
>                 return;
> @@ -249,6 +240,15 @@ static void nouveau_dsm_pci_probe(struct pci_dev *pdev, acpi_handle *dhandle_out
>         *has_opt = !!optimus_funcs;
>         *has_opt_flags = optimus_funcs & (1 << NOUVEAU_DSM_OPTIMUS_FLAGS);
>
> +       *has_pr3 = false;
> +       parent_pdev = pci_upstream_bridge(pdev);
> +       if (parent_pdev) {
> +               if (parent_pdev->bridge_d3)
> +                       *has_pr3 = pci_pr3_present(parent_pdev);
> +               else
> +                       pci_d3cold_disable(pdev);
> +       }
> +
>         if (optimus_funcs) {
>                 uint32_t result;
>                 nouveau_optimus_dsm(dhandle, NOUVEAU_DSM_OPTIMUS_CAPS, 0,
> --
> 2.25.1
>
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