[Public]
Reviewed-by: Roman Li <roman.li@xxxxxxx>
> -----Original Message-----
> From: amd-gfx <amd-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of
> Srinivasan Shanmugam
> Sent: Tuesday, February 6, 2024 11:55 PM
> To: Siqueira, Rodrigo <Rodrigo.Siqueira@xxxxxxx>; Pillai, Aurabindo
> <Aurabindo.Pillai@xxxxxxx>
> Cc: amd-gfx@xxxxxxxxxxxxxxxxxxxxx; SHANMUGAM, SRINIVASAN
> <SRINIVASAN.SHANMUGAM@xxxxxxx>; Wentland, Harry
> <Harry.Wentland@xxxxxxx>; Deucher, Alexander
> <Alexander.Deucher@xxxxxxx>
> Subject: [PATCH] drm/amd/display: Fix possible use of uninitialized
> 'max_chunks_fbc_mode' in 'calculate_bandwidth()'
>
> 'max_chunks_fbc_mode' is only declared and assigned a value under a specific
> condition in the following lines:
>
> if (data->fbc_en[i] == 1) {
> max_chunks_fbc_mode = 128 - dmif_chunk_buff_margin; }
>
> If 'data->fbc_en[i]' is not equal to 1 for any i, max_chunks_fbc_mode will not
> be initialized if it's used outside of this for loop.
>
> Ensure that 'max_chunks_fbc_mode' is properly initialized before it's used.
> Initialize it to a default value right after its declaration to ensure that it gets a
> value assigned under all possible control flow paths.
>
> Thus fixing the below:
> drivers/gpu/drm/amd/amdgpu/../display/dc/basics/dce_calcs.c:914
> calculate_bandwidth() error: uninitialized symbol 'max_chunks_fbc_mode'.
> drivers/gpu/drm/amd/amdgpu/../display/dc/basics/dce_calcs.c:917
> calculate_bandwidth() error: uninitialized symbol 'max_chunks_fbc_mode'.
>
> Fixes: 4562236b3bc0 ("drm/amd/dc: Add dc display driver (v2)")
> Cc: Harry Wentland <harry.wentland@xxxxxxx>
> Cc: Alex Deucher <alexander.deucher@xxxxxxx>
> Cc: Rodrigo Siqueira <Rodrigo.Siqueira@xxxxxxx>
> Cc: Aurabindo Pillai <aurabindo.pillai@xxxxxxx>
> Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@xxxxxxx>
> ---
> drivers/gpu/drm/amd/display/dc/basics/dce_calcs.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/basics/dce_calcs.c
> b/drivers/gpu/drm/amd/display/dc/basics/dce_calcs.c
> index f2dfa96f9ef5..39530b2ea495 100644
> --- a/drivers/gpu/drm/amd/display/dc/basics/dce_calcs.c
> +++ b/drivers/gpu/drm/amd/display/dc/basics/dce_calcs.c
> @@ -94,7 +94,7 @@ static void calculate_bandwidth(
> const uint32_t s_high = 7;
> const uint32_t dmif_chunk_buff_margin = 1;
>
> - uint32_t max_chunks_fbc_mode;
> + uint32_t max_chunks_fbc_mode = 0;
> int32_t num_cursor_lines;
>
> int32_t i, j, k;
> --
> 2.34.1
