On Mon, 25 Jan 2016, Arnd Bergmann wrote:
> The prcmu_config_clkout() function ensures that the 'clkout' argument
> can only be '0' or '1' using an appropriate BUG_ON(), so the compiler
> should know that the div_mask, mask, and bits variables are always
> initialized later on. However, it doesn't understand this in gcc-5.2
> and produces a false positive warning instead:
>
> drivers/mfd/db8500-prcmu.c: In function 'prcmu_config_clkout':
> drivers/mfd/db8500-prcmu.c:762:10: error: 'div_mask' may be used
> uninitialized in this function [-Werror=maybe-uninitialized]
> if (val & div_mask) {
> ^
> drivers/mfd/db8500-prcmu.c:769:13: error: 'mask' may be used uninitialized in
> this function [-Werror=maybe-uninitialized]
> if ((val & mask & ~div_mask) != bits) {
> ^
> drivers/mfd/db8500-prcmu.c:757:7: error: 'bits' may be used uninitialized in
> this function [-Werror=maybe-uninitialized]
>
> Replacing the switch() statement with an equivalent if() lets
> gcc figure this out reliably and avoids the warnings.
>
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> drivers/mfd/db8500-prcmu.c | 7 ++-----
> 1 file changed, 2 insertions(+), 5 deletions(-)
Applied, thanks.
> diff --git a/drivers/mfd/db8500-prcmu.c b/drivers/mfd/db8500-prcmu.c
> index 12099b09a9a7..c0a86aeb1733 100644
> --- a/drivers/mfd/db8500-prcmu.c
> +++ b/drivers/mfd/db8500-prcmu.c
> @@ -739,20 +739,17 @@ int prcmu_config_clkout(u8 clkout, u8 source, u8 div)
> if (!div && !requests[clkout])
> return -EINVAL;
>
> - switch (clkout) {
> - case 0:
> + if (clkout == 0) {
> div_mask = PRCM_CLKOCR_CLKODIV0_MASK;
> mask = (PRCM_CLKOCR_CLKODIV0_MASK | PRCM_CLKOCR_CLKOSEL0_MASK);
> bits = ((source << PRCM_CLKOCR_CLKOSEL0_SHIFT) |
> (div << PRCM_CLKOCR_CLKODIV0_SHIFT));
> - break;
> - case 1:
> + } else {
> div_mask = PRCM_CLKOCR_CLKODIV1_MASK;
> mask = (PRCM_CLKOCR_CLKODIV1_MASK | PRCM_CLKOCR_CLKOSEL1_MASK |
> PRCM_CLKOCR_CLK1TYPE);
> bits = ((source << PRCM_CLKOCR_CLKOSEL1_SHIFT) |
> (div << PRCM_CLKOCR_CLKODIV1_SHIFT));
> - break;
> }
> bits &= mask;
>
--
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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