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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH v4] pwm: atmel: Enable clk when pwm already enabled in bootloader Content-Language: en-US To: =?UTF-8?Q?Uwe_Kleine-K=c3=b6nig?= Cc: thierry.reding@gmail.com, claudiu.beznea@microchip.com, nicolas.ferre@microchip.com, alexandre.belloni@bootlin.com, linux-arm-kernel@lists.infradead.org, linux-pwm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20230712134347.14897-1-aarongt.shen@gmail.com> <20230712135553.trqkxtcuiemwzgwe@pengutronix.de> From: Guiting Shen In-Reply-To: <20230712135553.trqkxtcuiemwzgwe@pengutronix.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed,Jul 12,2023 at 21:55:53PM GMT+8, Uwe Kleine-König wrote: > On Wed, Jul 12, 2023 at 09:43:47PM +0800, Guiting Shen wrote: >> The driver would never call clk_enable() if the PWM channel was already >> enabled in bootloader which lead to dump the warning message "the PWM >> clock already disabled" when turning off the PWM channel. >> >> Add atmel_pwm_enable_clk_if_on() in probe function to enable clock if >> the PWM channel was already enabled in bootloader. >> >> Signed-off-by: Guiting Shen >> --- >> drivers/pwm/pwm-atmel.c | 40 +++++++++++++++++++++++++++++++++++++++- >> 1 file changed, 39 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c >> index cdbc23649032..28ea0f7267ca 100644 >> --- a/drivers/pwm/pwm-atmel.c >> +++ b/drivers/pwm/pwm-atmel.c >> @@ -36,7 +36,7 @@ >> #define PWM_SR 0x0C >> #define PWM_ISR 0x1C >> /* Bit field in SR */ >> -#define PWM_SR_ALL_CH_ON 0x0F >> +#define PWM_SR_ALL_CH_MASK 0x0F >> >> /* The following register is PWM channel related registers */ >> #define PWM_CH_REG_OFFSET 0x200 >> @@ -464,6 +464,37 @@ static const struct of_device_id atmel_pwm_dt_ids[] = { >> }; >> MODULE_DEVICE_TABLE(of, atmel_pwm_dt_ids); >> >> +static int atmel_pwm_enable_clk_if_on(struct atmel_pwm_chip *atmel_pwm) >> +{ >> + unsigned int i; >> + int err; >> + u32 sr; >> + >> + sr = atmel_pwm_readl(atmel_pwm, PWM_SR); >> + if (!(sr & PWM_SR_ALL_CH_MASK)) >> + return 0; >> + >> + for (i = 0; i < atmel_pwm->chip.npwm; i++) { >> + if (!(sr & (1 << i))) >> + continue; >> + >> + err = clk_enable(atmel_pwm->clk); >> + if (err) { >> + dev_err(atmel_pwm->chip.dev, >> + "failed to enable clock for pwm #%d: %pe\n", >> + i, ERR_PTR(err)); >> + >> + while (i--) { >> + if (sr & (1 << i)) >> + clk_disable(atmel_pwm->clk); >> + } >> + return err; >> + } >> + } >> + >> + return 0; >> +} >> + >> static int atmel_pwm_probe(struct platform_device *pdev) >> { >> struct atmel_pwm_chip *atmel_pwm; >> @@ -504,8 +535,15 @@ static int atmel_pwm_probe(struct platform_device *pdev) >> >> platform_set_drvdata(pdev, atmel_pwm); >> >> + ret = atmel_pwm_enable_clk_if_on(atmel_pwm); >> + if (ret < 0) >> + goto remove_pwmchip; >> + >> return ret; >> >> +remove_pwmchip: >> + pwmchip_remove(&atmel_pwm->chip); >> + > > I'd consider it more natural to do the atmel_pwm_enable_clk_if_on() call > before registering the pwmchip. But I guess it works like this, too. > (Well unless it's possible that there are set bits in PWM_SR and the > clock is off.) It need to invoke something like atmel_pwm_disable_clk_if_on() after failing to register the pwmchip when call the atmel_pwm_enable_clk_if_on() first which I feel inconvenient. And it's impossible to enable PWM channels before enabling the clock. The bits set in PWM_SR means that the PWM channel and the clock turn on. -- Best regards, Guiting Shen