On Wed, Jul 15, 2020 at 09:27:42PM -0700, Nathan Chancellor wrote:
> Clang warns:
>
> drivers/gpu/drm/i915/display/intel_combo_phy.c:268:3: warning: variable
> 'ret' is uninitialized when used here [-Wuninitialized]
> ret &= check_phy_reg(dev_priv, phy, ICL_PORT_TX_DW8_LN0(phy),
> ^~~
> drivers/gpu/drm/i915/display/intel_combo_phy.c:261:10: note: initialize
> the variable 'ret' to silence this warning
> bool ret;
> ^
> = 0
> 1 warning generated.
>
> In practice, the bug this warning appears to be concerned with would not
> actually matter because ret gets initialized to the return value of
> cnl_verify_procmon_ref_values. However, that does appear to be a bug
> since it means the first hunk of the patch this fixes won't actually do
> anything (since the values of check_phy_reg won't factor into the final
> ret value). Initialize ret to true then make all of the assignments a
> bitwise AND with itself so that the function always does what it should
> do.
>
> Fixes: 239bef676d8e ("drm/i915/display: Implement new combo phy initialization step")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1094
> Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Reviewed-by: Matt Roper <matthew.d.roper@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/display/intel_combo_phy.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_combo_phy.c b/drivers/gpu/drm/i915/display/intel_combo_phy.c
> index eccaa79cb4a9..a4b8aa6d0a9e 100644
> --- a/drivers/gpu/drm/i915/display/intel_combo_phy.c
> +++ b/drivers/gpu/drm/i915/display/intel_combo_phy.c
> @@ -258,7 +258,7 @@ static bool phy_is_master(struct drm_i915_private *dev_priv, enum phy phy)
> static bool icl_combo_phy_verify_state(struct drm_i915_private *dev_priv,
> enum phy phy)
> {
> - bool ret;
> + bool ret = true;
> u32 expected_val = 0;
>
> if (!icl_combo_phy_enabled(dev_priv, phy))
> @@ -276,7 +276,7 @@ static bool icl_combo_phy_verify_state(struct drm_i915_private *dev_priv,
> DCC_MODE_SELECT_CONTINUOSLY);
> }
>
> - ret = cnl_verify_procmon_ref_values(dev_priv, phy);
> + ret &= cnl_verify_procmon_ref_values(dev_priv, phy);
>
> if (phy_is_master(dev_priv, phy)) {
> ret &= check_phy_reg(dev_priv, phy, ICL_PORT_COMP_DW8(phy),
>
> base-commit: ca0e494af5edb59002665bf12871e94b4163a257
> --
> 2.28.0.rc0
>
--
Matt Roper
Graphics Software Engineer
VTT-OSGC Platform Enablement
Intel Corporation
(916) 356-2795
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