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Fri, 12 Jul 2024 08:26:19 +0200 Message-ID: <78119193-98b7-446f-82d6-37884a5b03ad@gmx.net> Date: Fri, 12 Jul 2024 08:26:17 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/3] pwm: imx27: workaround of the pwm output bug when decrease the duty cycle To: Frank Li , =?UTF-8?Q?Uwe_Kleine-K=C3=B6nig?= , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Philipp Zabel Cc: linux-pwm@vger.kernel.org, devicetree@vger.kernel.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Clark Wang , Jun Li , pratikmanvar09@gmail.com References: <20240711-pwm-v1-0-4d5766f99b8b@nxp.com> <20240711-pwm-v1-3-4d5766f99b8b@nxp.com> Content-Language: en-US From: Stefan Wahren In-Reply-To: <20240711-pwm-v1-3-4d5766f99b8b@nxp.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:lAnRdLo/NzQOq22G2oDt0rwsAIoHHWZflscox3YXMhJtJ1InvcD 2xDGz3CIruiicfCSBF1XCZ7t7tKw5mVL6BFN1FY8rVtg1/t2fBYsX3ipl9XjbPs+RLAqaUo xwao/7pFGcQHOzxxfZQM0gQ4qFidpJ3BGeeqLJSVq5PFR2XQoUPq3B3L/lkFPTzqy5ENLhd 59jjDy6JPhjZOQm5XYEJw== UI-OutboundReport: notjunk:1;M01:P0:4qvoVPpZ5vg=;CqThS0ovliZ34aePm5IljqA3g7M eFJUg+mi1DiRQMo6XQK4zS7G/mDOrh90AxqTHrW5jLGHbk5BUD4SyE64N9qn4ySVW/5kR+YuM LMl8jBNel7WhwBkgHJS33MuDGCzgjet8wSjd8fPJMBIAoIQtOTEPytvRqJm17P5Bt4EwRtSo3 KRH79Id68PWGjYp72gLNmTClEGy57q0dMF5rG3Z76ILcsri6Z/mKLS8H+cRfKm9ZEGdfuRXcF Gj/u40Ed4Z5BN/QS6W350veFGHWjYhOYZVrnhd1q47JoS3uC7xMxhtbkSSGBz8o1uksvq/zes MmRVfFn2TKoaPcFgdspdykWezoIGDhohm33bxM1pi8ROMfTyQVcDP4fSFvxyTopByos1aVsMO jtDnjW9QZc7wIGE80lStJ3FHU2tL3atstd6KxWTy9lcp7dnwo5E8HILBGBFWoJXfuAX9/xcAN 93UboUEl6F8IE+Su9HPYxdzmJvLawaOZF78y2UHMkCdykbamD0CzJ29x6WH863NI6AsVzfjhi /J6XsOG81wTosh3dCvHTd34ym7tOCWb9zUEvdkznYsphzKqMzLPlkSf/U9YhjfrIlL4RCaWuf OkI87OTpTM0oyLxP7zh4bipuqhuqNyncOr27ESNuuiU72xCGWL9wcVE0+Z2PlmlYnpGKnNnH9 tIMSvbcNQZTJ5bdfFoqkepmhQkzEvD07xxM5f9T9TpVaLJwpTLo8CZbpcQDYPIqxxJBhS1z1w oR0z5L4Z2pAPdW0FG3i/tTlKgrTMm7Wiu80qxo24pdQrubmPisvw9XSNVmKWPOBJ7xl1gKqtR rL1TARzAGofrI7h85VaAte7Q== X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240711_232625_034543_CFB4A80B X-CRM114-Status: GOOD ( 15.10 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Frank, Am 11.07.24 um 23:08 schrieb Frank Li: > From: Clark Wang > > When the SAR FIFO is empty, the write value is directly applied to SAR e= ven > though the current period is not over. If the new SAR value is less than > the old one and the counter is greater than the new SAR value, the curre= nt > period will not flip the level. This result in a pulse with a 100% duty > cycle. > > Write the old SAR value before updating the new duty cycle to SAR. This > avoids writing the new value into an empty FIFO. > > This only resolves the issue when the PWM period is longer than 2us > (or <500KHz) because write register is not quick enough when PWM period = is > very short. > > Reviewed-by: Jun Li > Signed-off-by: Clark Wang > Signed-off-by: Frank Li the same patch has been submitted from other people in the past and they received many review comments [1], [2]. Can you please explain which version of the patch this is and does it address any review comments? Best regards [1] - https://lore.kernel.org/linux-pwm/20211220073130.1429723-1-xiaoning.wang@n= xp.com/ [2] - https://lore.kernel.org/linux-pwm/20231229063013.1786-1-pratikmanvar09@gma= il.com/