2020-01-30 01:42:50

by Nathan Chancellor

Subject: [PATCH] power: avs: qcom-cpr: Avoid clang -Wsometimes-uninitialized in cpr_scale

Clang warns (trimmed for brevity):

../drivers/power/avs/qcom-cpr.c:570:13: warning: variable 'reg_mask' is
used uninitialized whenever 'if' condition is false
[-Wsometimes-uninitialized]

../drivers/power/avs/qcom-cpr.c:520:13: warning: variable 'new_uV' is
used uninitialized whenever 'if' condition is false
[-Wsometimes-uninitialized]

Due to the fact that Clang's static analysis happens before any
optimization passes are taken into account, it cannot see that both
branches in the if statement must be taken because dir cannot be
something other than UP or DOWN due to the check at the top of this
function. Change the else if condition to else to fix this false
positive.

Fixes: bf6910abf548 ("power: avs: Add support for CPR (Core Power Reduction)")
Link: https://github.com/ClangBuiltLinux/linux/issues/840
Signed-off-by: Nathan Chancellor <[email protected]>
---
drivers/power/avs/qcom-cpr.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/power/avs/qcom-cpr.c b/drivers/power/avs/qcom-cpr.c
index 9192fb747653..e8831e4aee05 100644
--- a/drivers/power/avs/qcom-cpr.c
+++ b/drivers/power/avs/qcom-cpr.c
@@ -517,7 +517,7 @@ static int cpr_scale(struct cpr_drv *drv, enum voltage_change_dir dir)
dev_dbg(drv->dev,
"UP: -> new_uV: %d last_uV: %d perf state: %u\n",
new_uV, last_uV, cpr_get_cur_perf_state(drv));
- } else if (dir == DOWN) {
+ } else {
if (desc->clamp_timer_interval &&
error_steps < desc->down_threshold) {
/*
@@ -567,7 +567,7 @@ static int cpr_scale(struct cpr_drv *drv, enum voltage_change_dir dir)
/* Disable auto nack down */
reg_mask = RBCPR_CTL_SW_AUTO_CONT_NACK_DN_EN;
val = 0;
- } else if (dir == DOWN) {
+ } else {
/* Restore default threshold for UP */
reg_mask = RBCPR_CTL_UP_THRESHOLD_MASK;
reg_mask <<= RBCPR_CTL_UP_THRESHOLD_SHIFT;
--
2.25.0

2020-01-31 00:05:49

by Kevin Hilman

Subject: Re: [PATCH] power: avs: qcom-cpr: Avoid clang -Wsometimes-uninitialized in cpr_scale

Nathan Chancellor <[email protected]> writes:

> Clang warns (trimmed for brevity):
>
> ../drivers/power/avs/qcom-cpr.c:570:13: warning: variable 'reg_mask' is
> used uninitialized whenever 'if' condition is false
> [-Wsometimes-uninitialized]
>
> ../drivers/power/avs/qcom-cpr.c:520:13: warning: variable 'new_uV' is
> used uninitialized whenever 'if' condition is false
> [-Wsometimes-uninitialized]
>
> Due to the fact that Clang's static analysis happens before any
> optimization passes are taken into account, it cannot see that both
> branches in the if statement must be taken because dir cannot be
> something other than UP or DOWN due to the check at the top of this
> function. Change the else if condition to else to fix this false
> positive.
>
> Fixes: bf6910abf548 ("power: avs: Add support for CPR (Core Power Reduction)")
> Link: https://github.com/ClangBuiltLinux/linux/issues/840
> Signed-off-by: Nathan Chancellor <[email protected]>

Acked-by: Kevin Hilman <[email protected]>

Rafael, feel free to queue directly.

Kevin