On Wed, Mar 20, 2019 at 4:33 AM Nathan Chancellor
<natechancellor@xxxxxxxxx> wrote:
>
> 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.
>
> Fixes: 870b996f955f ("drm/amd/powerplay: set defalut dpm table for smu")
> Link: https://github.com/ClangBuiltLinux/linux/issues/425
> Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Applied. thanks!
Alex
> ---
> drivers/gpu/drm/amd/powerplay/vega20_ppt.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/powerplay/vega20_ppt.c b/drivers/gpu/drm/amd/powerplay/vega20_ppt.c
> index 7e9e8ad9a300..41e6f49c9cb6 100644
> --- 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,
> --
> 2.21.0
>
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