drm/amd/powerplay: Zero initialize num_of_levels in vega20_set_single_dpm_table

When building with -Wsometimes-uninitialized, Clang warns:

drivers/gpu/drm/amd/amdgpu/../powerplay/vega20_ppt.c:456:2: warning:
variable 'num_of_levels' is used uninitialized whenever '?:' condition
is false [-Wsometimes-uninitialized]
        smu_read_smc_arg(smu, &num_of_levels);
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/../powerplay/inc/amdgpu_smu.h:608:3: note:
expanded from macro 'smu_read_smc_arg'
        ((smu)->funcs->read_smc_arg? (smu)->funcs->read_smc_arg((smu), (arg)) : 0)
         ^~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/../powerplay/vega20_ppt.c:457:7: note:
uninitialized use occurs here
        if (!num_of_levels) {
             ^~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/../powerplay/vega20_ppt.c:456:2: note: remove
the '?:' if its condition is always true
        smu_read_smc_arg(smu, &num_of_levels);
        ^
drivers/gpu/drm/amd/amdgpu/../powerplay/inc/amdgpu_smu.h:608:3: note:
expanded from macro 'smu_read_smc_arg'
        ((smu)->funcs->read_smc_arg? (smu)->funcs->read_smc_arg((smu), (arg)) : 0)
         ^
drivers/gpu/drm/amd/amdgpu/../powerplay/vega20_ppt.c:446:27: note:
initialize the variable 'num_of_levels' to silence this warning
        uint32_t i, num_of_levels, clk;
                                 ^
                                  = 0
1 warning generated.

The if statement it mentions as potentially problematic is currently
always true because the read_smc_arg callback is assigned at the
bottom of this file but Clang can't tell that. If the callback were
ever to disappear, num_of_levels would never be initialized. Just
zero initialize it to ensure that the intent behind this code
remains the same.

Link: https://github.com/ClangBuiltLinux/linux/issues/425
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/powerplay/vega20_ppt.c b/drivers/gpu/drm/amd/powerplay/vega20_ppt.c
index 7e9e8ad9a3000110a2aaeda889feafef56b7cee1..41e6f49c9cb6e8127ff4fb73f32ffe233dff8f64 100644 (file)
--- a/drivers/gpu/drm/amd/powerplay/vega20_ppt.c
+++ b/drivers/gpu/drm/amd/powerplay/vega20_ppt.c
@@ -443,7 +443,7 @@ vega20_set_single_dpm_table(struct smu_context *smu,
                            PPCLK_e clk_id)
 {
        int ret = 0;
-       uint32_t i, num_of_levels, clk;
+       uint32_t i, num_of_levels = 0, clk;
 
        ret = smu_send_smc_msg_with_param(smu,
                        SMU_MSG_GetDpmFreqByIndex,