drm/amd/display: Fix possible use of uninitialized 'max_chunks_fbc_mode' in 'calculat...

'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@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Roman Li <roman.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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 f2dfa96f9ef5d9e4805fdbf592cac078efa391a5..39530b2ea4957cc0a6718f322158e101f15431d0 100644 (file)
--- 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;