[PATCH] drm/amdgpu: modify system reference clock source for navi+

[Alex Deucher]

WIth Kevin's comments addressed, the patch is:
Reviewed-by: Alex Deucher <alexander.deucher at amd.com>

On Tue, May 18, 2021 at 5:36 AM Wang, Kevin(Yang) <Kevin1.Wang at amd.com> wrote:
>
> [AMD Official Use Only]
>
>
>
>
> ________________________________
> From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> on behalf of Aaron Liu <aaron.liu at amd.com>
> Sent: Tuesday, May 18, 2021 2:26 PM
> To: amd-gfx at lists.freedesktop.org <amd-gfx at lists.freedesktop.org>
> Cc: Deucher, Alexander <Alexander.Deucher at amd.com>; Huang, Ray <Ray.Huang at amd.com>; Liu, Aaron <Aaron.Liu at amd.com>
> Subject: [PATCH] drm/amdgpu: modify system reference clock source for navi+
>
> Starting from Navi+, the rlc reference clock is used for system clock
> from vbios gfx_info table. It is incorrect to use core_refclk_10khz of
> vbios smu_info table as system clock.
>
> Signed-off-by: Aaron Liu <aaron.liu at amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_atomfirmware.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_atomfirmware.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_atomfirmware.c
> index 8c417014ca89..83ca58426139 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_atomfirmware.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_atomfirmware.c
> @@ -546,6 +546,21 @@ int amdgpu_atomfirmware_get_clock_info(struct amdgpu_device *adev)
>                  ret = 0;
>          }
>
> +       /* if asic is Navi+, the rlc reference clock is used for system clock
> +        * from vbios gfx_info table */
> +       if (adev->asic_type >= CHIP_NAVI10) {
> +               index = get_index_into_master_table(atom_master_list_of_data_tables_v2_1,
> +                                                  gfx_info);
> +               if (amdgpu_atom_parse_data_header(mode_info->atom_context, index, NULL,
> +                                         &frev, &crev, &data_offset)) {
> +                       struct atom_gfx_info_v2_2 *gfx_info = (struct atom_gfx_info_v2_2*)
> +                               (mode_info->atom_context->bios + data_offset);
> +                       if ((frev >= 2) && (crev >= 2))
> [kevin]:
> There is a hidden danger here. We can't assume that the higher version (frev) is compatible with old one.
> the code should change to if (frev == 2) && (crev >= 2)) {} ...
>
> +                               spll->reference_freq = le32_to_cpu(gfx_info->rlc_gpu_timer_refclk);
> +                       ret = 0;
> +               }
> +       }
> +
>          return ret;
>  }
>
> --
> 2.25.1
>
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