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

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Date:   Fri, 19 Mar 2021 14:26:31 -0400
From:   Harry Wentland <harry.wentland@....com>
To:     Alex Deucher <alexdeucher@...il.com>,
        Lee Jones <lee.jones@...aro.org>
Cc:     Leo Li <sunpeng.li@....com>, LKML <linux-kernel@...r.kernel.org>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        David Airlie <airlied@...ux.ie>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        Alex Deucher <alexander.deucher@....com>,
        Colin Ian King <colin.king@...onical.com>,
        Christian König <christian.koenig@....com>,
        Harry Wentland <hwentlan@....com>,
        "Kazlauskas, Nicholas" <nicholas.kazlauskas@....com>
Subject: Re: [PATCH 06/19] drm/amd/display/dc/calcs/dce_calcs: Move some large
 variables from the stack to the heap

On 2021-03-19 2:13 p.m., Alex Deucher wrote:
> + Harry, Nick
> 
> On Fri, Mar 19, 2021 at 4:24 AM Lee Jones <lee.jones@...aro.org> 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@....com>
>> Cc: Leo Li <sunpeng.li@....com>
>> Cc: Alex Deucher <alexander.deucher@....com>
>> Cc: "Christian König" <christian.koenig@....com>
>> Cc: David Airlie <airlied@...ux.ie>
>> Cc: Daniel Vetter <daniel@...ll.ch>
>> Cc: Colin Ian King <colin.king@...onical.com>
>> Cc: amd-gfx@...ts.freedesktop.org
>> Cc: dri-devel@...ts.freedesktop.org
>> Signed-off-by: Lee Jones <lee.jones@...aro.org>
>> ---
>>   .../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.
> 

 From what I can see this doesn't seem the case. If I'm missing 
something someone please correct me.

This and the next (06/19) patch are both
Reviewed-by: Harry Wentland <harry.wentland@....com>

Harry

> 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
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@...ts.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel>

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