From mboxrd@z Thu Jan 1 00:00:00 1970 From: Krzysztof Kozlowski Subject: Re: [PATCH v2] pwm: samsung: fix to use lowest div for large enough modulation bits Date: Tue, 16 Aug 2016 18:25:25 +0200 Message-ID: <20160816162525.GA9249@kozik-lap> References: <1470133006-4272-1-git-send-email-sw0312.kim@samsung.com> <20160816142201.12672-1-sw0312.kim@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Return-path: Content-Disposition: inline In-Reply-To: <20160816142201.12672-1-sw0312.kim@samsung.com> Sender: linux-kernel-owner@vger.kernel.org To: Seung-Woo Kim Cc: linux-samsung-soc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, k.kozlowski@samsung.com, thierry.reding@gmail.com, linux-pwm@vger.kernel.org, tomasz.figa@gmail.com, jy0922.shim@samsung.com, krzk@kernel.org List-Id: linux-pwm@vger.kernel.org On Tue, Aug 16, 2016 at 11:22:01PM +0900, 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 except s3c24xx, 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' > [...] > [] (ubsan_epilogue) from [] (__ubsan_handle_shift_out_of_bounds+0xd8/0x120) > [] (__ubsan_handle_shift_out_of_bounds) from [] (pwm_samsung_config+0x508/0x6a4) > [] (pwm_samsung_config) from [] (pwm_apply_state+0x174/0x40c) > [] (pwm_apply_state) from [] (pwm_fan_probe+0xc8/0x488) > [] (pwm_fan_probe) from [] (platform_drv_probe+0x70/0x150) > [...] > > Cc: Tomasz Figa > Signed-off-by: Seung-Woo Kim > --- > Changes from v1 > * Remove too complex condition, instead, just checking simple variant->bits as Krzysztof's suggestion > * Add comment from Tomasz > > The UBSAN warning from ARM is reported with the patch in following link: > https://patchwork.kernel.org/patch/9189575/ > --- > drivers/pwm/pwm-samsung.c | 15 ++++++++++++--- > 1 file changed, 12 insertions(+), 3 deletions(-) Reviewed-by: Krzysztof Kozlowski Best regards, Krzysztof