Hi, On 08/02/2016 07:16 PM, Seung-Woo Kim wrote: >>From pwm_samsung_calc_tin(), there is routine to find the lowest > divider possible to generate lower frequency than requested one. > But it is always possible to generate requested frequency with > large enough modulation bits, so this patch fixes to use lowest > div for the case. This patch removes following UBSAN warning: > > UBSAN: Undefined behaviour in drivers/pwm/pwm-samsung.c:197:13 > shift exponent 32 is too large for 32-bit type 'long unsigned int' > [...] > [<c0670248>] (ubsan_epilogue) from [<c06707b4>] (__ubsan_handle_shift_out_of_bounds+0xd8/0x120) > [<c06707b4>] (__ubsan_handle_shift_out_of_bounds) from [<c0694b28>] (pwm_samsung_config+0x508/0x6a4) > [<c0694b28>] (pwm_samsung_config) from [<c069286c>] (pwm_apply_state+0x174/0x40c) > [<c069286c>] (pwm_apply_state) from [<c0b2e070>] (pwm_fan_probe+0xc8/0x488) > [<c0b2e070>] (pwm_fan_probe) from [<c07ba8b0>] (platform_drv_probe+0x70/0x150) > [...] > > Signed-off-by: Seung-Woo Kim <sw0312.kim@xxxxxxxxxxx> > --- > The UBSAN warning from ARM is reported with the patch in following link: > https://patchwork.kernel.org/patch/9189575/ > --- > drivers/pwm/pwm-samsung.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/drivers/pwm/pwm-samsung.c b/drivers/pwm/pwm-samsung.c > index ada2d32..ff0def6 100644 > --- a/drivers/pwm/pwm-samsung.c > +++ b/drivers/pwm/pwm-samsung.c > @@ -193,9 +193,13 @@ static unsigned long pwm_samsung_calc_tin(struct samsung_pwm_chip *chip, > * divider settings and choose the lowest divisor that can generate > * frequencies lower than requested. > */ > - for (div = variant->div_base; div < 4; ++div) > - if ((rate >> (variant->bits + div)) < freq) > - break; > + if (fls(rate) <= variant->bits) { > + div = variant->div_base; It's reasonable to me not to check to decide div at above case. > + } else { > + for (div = variant->div_base; div < 4; ++div) > + if ((rate >> (variant->bits + div)) < freq) > + break; > + } > Reviewed-by: Joonyoung Shim <jy0922.shim@xxxxxxxxxxx> Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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