Re: [PATCH 06/19] drm/amd/display/dc/calcs/dce_calcs: Move some large variables from the stack to the heap

[Alex Deucher]

+ Harry, Nick

On Fri, Mar 19, 2021 at 4:24 AM Lee Jones <lee.jones@xxxxxxxxxx> wrote:
>
> Fixes the following W=1 kernel build warning(s):
>
>  drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dce_calcs.c: In function ‘calculate_bandwidth’:
>  drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dce_calcs.c:2016:1: warning: the frame size of 1216 bytes is larger than 1024 bytes [-Wframe-larger-than=]
>
> Cc: Harry Wentland <harry.wentland@xxxxxxx>
> Cc: Leo Li <sunpeng.li@xxxxxxx>
> Cc: Alex Deucher <alexander.deucher@xxxxxxx>
> Cc: "Christian König" <christian.koenig@xxxxxxx>
> Cc: David Airlie <airlied@xxxxxxxx>
> Cc: Daniel Vetter <daniel@xxxxxxxx>
> Cc: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> Cc: amd-gfx@xxxxxxxxxxxxxxxxxxxxx
> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
> ---
>  .../gpu/drm/amd/display/dc/calcs/dce_calcs.c  | 32 ++++++++++++++++---
>  1 file changed, 28 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c b/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c
> index e633f8a51edb6..9d8f2505a61c2 100644
> --- a/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c
> +++ b/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c
> @@ -98,16 +98,16 @@ static void calculate_bandwidth(
>         int32_t num_cursor_lines;
>
>         int32_t i, j, k;
> -       struct bw_fixed yclk[3];
> -       struct bw_fixed sclk[8];
> +       struct bw_fixed *yclk;
> +       struct bw_fixed *sclk;
>         bool d0_underlay_enable;
>         bool d1_underlay_enable;
>         bool fbc_enabled;
>         bool lpt_enabled;
>         enum bw_defines sclk_message;
>         enum bw_defines yclk_message;
> -       enum bw_defines tiling_mode[maximum_number_of_surfaces];
> -       enum bw_defines surface_type[maximum_number_of_surfaces];
> +       enum bw_defines *tiling_mode;
> +       enum bw_defines *surface_type;
>         enum bw_defines voltage;
>         enum bw_defines pipe_check;
>         enum bw_defines hsr_check;
> @@ -122,6 +122,22 @@ static void calculate_bandwidth(
>         int32_t number_of_displays_enabled_with_margin = 0;
>         int32_t number_of_aligned_displays_with_no_margin = 0;
>
> +       yclk = kcalloc(3, sizeof(*yclk), GFP_KERNEL);
> +       if (!yclk)
> +               return;
> +
> +       sclk = kcalloc(8, sizeof(*sclk), GFP_KERNEL);
> +       if (!sclk)
> +               goto free_yclk;
> +
> +       tiling_mode = kcalloc(maximum_number_of_surfaces, sizeof(*tiling_mode), GFP_KERNEL);
> +       if (!tiling_mode)
> +               goto free_sclk;
> +
> +       surface_type = kcalloc(maximum_number_of_surfaces, sizeof(*surface_type), GFP_KERNEL);
> +       if (!surface_type)
> +               goto free_tiling_mode;
> +


Harry or Nick can correct me if I'm wrong, but for this patch and the
next one, I think this can be called from an atomic context.

Alex

>         yclk[low] = vbios->low_yclk;
>         yclk[mid] = vbios->mid_yclk;
>         yclk[high] = vbios->high_yclk;
> @@ -2013,6 +2029,14 @@ static void calculate_bandwidth(
>                         }
>                 }
>         }
> +
> +       kfree(surface_type);
> +free_tiling_mode:
> +       kfree(tiling_mode);
> +free_yclk:
> +       kfree(yclk);
> +free_sclk:
> +       kfree(sclk);
>  }
>
>  /*******************************************************************************
> --
> 2.27.0
>
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