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Fri, 17 Jul 2020 10:22:18 -0700 (PDT) Subject: Re: [PATCH] pwm: bcm-iproc: handle clk_get_rate() return To: Scott Branden , Thierry Reding , Lee Jones Cc: =?UTF-8?Q?Uwe_Kleine-K=c3=b6nig?= , BCM Kernel Feedback , linux-pwm@vger.kernel.org, linux-kernel@vger.kernel.org, Rayagonda Kokatanur References: <20200717170743.25466-1-scott.branden@broadcom.com> From: Ray Jui Message-ID: <94f2aed1-d88d-3ee0-6e57-917f665951f2@broadcom.com> Date: Fri, 17 Jul 2020 10:22:13 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200717170743.25466-1-scott.branden@broadcom.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/17/2020 10:07 AM, Scott Branden wrote: > From: Rayagonda Kokatanur > > Handle clk_get_rate() returning <= 0 condition to avoid > possible division by zero. > > Fixes: daa5abc41c80 ("pwm: Add support for Broadcom iProc PWM controller") > Signed-off-by: Rayagonda Kokatanur > Signed-off-by: Scott Branden > --- > drivers/pwm/pwm-bcm-iproc.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/pwm/pwm-bcm-iproc.c b/drivers/pwm/pwm-bcm-iproc.c > index 1f829edd8ee7..72a8607b6c8d 100644 > --- a/drivers/pwm/pwm-bcm-iproc.c > +++ b/drivers/pwm/pwm-bcm-iproc.c > @@ -86,6 +86,11 @@ static void iproc_pwmc_get_state(struct pwm_chip *chip, struct pwm_device *pwm, > u32 value, prescale; > > rate = clk_get_rate(ip->clk); > + if (rate == 0) { > + state->period = 0; > + state->duty_cycle = 0; > + return; > + } Based on the pwm core code, 'get_state' expects the following fields to be populated: 'polarity', 'enabled', 'period', and 'duty cycle'. The above logic will leave 'polarity' and 'enabled' completely unpopulated when clock rate is zero. > > value = readl(ip->base + IPROC_PWM_CTRL_OFFSET); > >