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b=UwHc0Xap3IpcE094oz0WCJgf3L1yZOLS648xCIUrQrGeYvLJIJ0hqS80r8aIqmahr hS1U4Dim52wR8jqV42VmF3GUiArIaZCS/M0spfB+zeOS7NyafFCltURLaawlpDSMoY Fwb9kz4lIMsooliYL07055+YbF8CWCWb9A5BsXLG6pdAtLLtmT373F6Pejja8QMh5u +JzbtupSmVsIWa7Yw0WDC4ifVRHGVmIXC2nEatX4RVFDI9VIQUG2zSt9xse28+ti0i +EJVvZNbAmE1RNxfiScf4vg9Px17c8DUNzs9Jkw/Cn685tFCB2l3UShkgtT3t5tQWS JQJllBRIk73Uw== Message-ID: <4bbee009-3985-4679-a85e-76f4259ff8d6@denx.de> Date: Sun, 22 Sep 2024 22:28:02 +0200 Precedence: bulk X-Mailing-List: imx@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 1/1] pwm: imx27: workaround of the pwm output bug when decrease the duty cycle To: Frank Li Cc: conor+dt@kernel.org, devicetree@vger.kernel.org, festevam@gmail.com, francesco@dolcini.it, imx@lists.linux.dev, jun.li@nxp.com, kernel@pengutronix.de, krzk+dt@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-pwm@vger.kernel.org, p.zabel@pengutronix.de, pratikmanvar09@gmail.com, robh@kernel.org, s.hauer@pengutronix.de, shawnguo@kernel.org, ukleinek@kernel.org, xiaoning.wang@nxp.com References: <20240917192510.3031493-1-Frank.Li@nxp.com> Content-Language: en-US From: Marek Vasut In-Reply-To: <20240917192510.3031493-1-Frank.Li@nxp.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: clamav-milter 0.103.8 at phobos.denx.de X-Virus-Status: Clean Hi, On 9/17/24 9:25 PM, Frank Li wrote: [...] > @@ -223,6 +224,8 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm, > struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip); > unsigned long long c; > unsigned long long clkrate; > + unsigned long flags; > + int val; > int ret; > u32 cr; > > @@ -263,7 +266,69 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm, [...] > + c = clkrate * 1500; > + do_div(c, NSEC_PER_SEC); > + > + local_irq_save(flags); > + val = FIELD_GET(MX3_PWMSR_FIFOAV, readl_relaxed(imx->mmio_base + MX3_PWMSR)); I think the multi-write I mentioned in v5 for > 500 kHz case could further improve the patch, let's see what others think: if (state->period < 2000) { /* 2000ns = 500 kHz */ /* Best effort attempt to fix up >500 kHz case */ udelay(6); /* 2us per FIFO entry, 3 FIFO entries written => 6 us */ writel_relaxed(duty_cycles, imx->mmio_base + MX3_PWMSAR); writel_relaxed(duty_cycles, imx->mmio_base + MX3_PWMSAR); /* Last write is outside, after this conditional */ } else if (duty_cycles ... > + if (duty_cycles < imx->duty_cycle && val < MX3_PWMSR_FIFOAV_2WORDS) { > + val = readl_relaxed(imx->mmio_base + MX3_PWMCNR); > + /* > + * If counter is close to period, controller may roll over when > + * next IO write. > + */ c is only used in this if (duty_cycles ...) { } conditional, the do_div() above can be moved here: c = clkrate * 1500; do_div(c, NSEC_PER_SEC); > + if ((val + c >= duty_cycles && val < imx->duty_cycle) || > + val + c >= period_cycles) > + writel_relaxed(imx->duty_cycle, imx->mmio_base + MX3_PWMSAR); > + } > + writel_relaxed(duty_cycles, imx->mmio_base + MX3_PWMSAR); > + local_irq_restore(flags);