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SubjectRe: [PATCH v5] pwm: atmel: Enable clk when pwm already enabled in bootloader
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On Sat,Jul 15,2023 at 20:12:53PM GMT+8, Uwe Kleine-König wrote:
> On Sat, Jul 15, 2023 at 10:36:53AM +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 <aarongt.shen@gmail.com>
>> ---
>> drivers/pwm/pwm-atmel.c | 50 +++++++++++++++++++++++++++++++++++++++--
>> 1 file changed, 48 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c
>> index cdbc23649032..4dd6e1319343 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 +464,45 @@ 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, bool on)
>> +{
>> + unsigned int i, cnt = 0;
>> + int ret = 0;
>> + u32 sr;
>> +
>> + sr = atmel_pwm_readl(atmel_pwm, PWM_SR) & PWM_SR_ALL_CH_MASK;
>> + if (!sr)
>> + return 0;
>> +
>> + for (i = 0; i < atmel_pwm->chip.npwm; i++) {
>> + if (sr & (1 << i))
>> + cnt++;
>> + }
>
> If it's just about counting the set bits, there is the function
> bitmap_weight().

Got it, Thank you.


>> + if (!on)
>> + goto disable_clk;
>> +
>> + for (i = 0; i < cnt; i++) {
>> + ret = clk_enable(atmel_pwm->clk);
>> + if (ret) {
>> + dev_err(atmel_pwm->chip.dev,
>> + "failed to enable clock for pwm #%d: %pe\n",
>> + i, ERR_PTR(ret));
>
> The output is bogus here. If SR is say 0xc, and the second enable
> fails, it's about pwm #3, but then i is 1.

I would just output the error clock message like this to fix it:
dev_err(atmel_pwm->chip.dev,
"failed to enable clock for pwm %pe\n", ERR_PTR(ret));


>> + cnt = i;
>> + goto disable_clk;
>> + }
>> + }
>> +
>> + return 0;
>> +
>> +disable_clk:
>> + while (cnt--)
>> + clk_disable(atmel_pwm->clk);
>> +
>> + return ret;
>> +}
>> +
>> static int atmel_pwm_probe(struct platform_device *pdev)
>> {
>> struct atmel_pwm_chip *atmel_pwm;
>
> Best regards
> Uwe
>

--
Best regards,
Guiting Shen

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