linux-kernel - Re: [PATCH V3 RESEND] pwm: meson: add pwm support for S4

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Date:   Mon, 23 Oct 2023 22:40:15 +0300
From:   George Stark <gnstark@...utedevices.com>
To:     Yixun Lan <dlan@...too.org>, JunYi Zhao <junyi.zhao@...ogic.com>
CC:     <thierry.reding@...il.com>, <u.kleine-koenig@...gutronix.de>,
        <neil.armstrong@...aro.org>, <khilman@...libre.com>,
        <jbrunet@...libre.com>, <martin.blumenstingl@...glemail.com>,
        <linux-pwm@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-amlogic@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3 RESEND] pwm: meson: add pwm support for S4

Hello Yixun Lan

On 10/17/23 01:37, Yixun Lan wrote:
> Hi JunYi
> 
> On 13:24 Mon 16 Oct     , JunYi Zhao wrote:
>> From: "junyi.zhao" <junyi.zhao@...ogic.com>
>>
>> Support PWM for S4 soc.
>> Now the PWM clock input is done in independent CLKCTRL registers.
>> And no more in the PWM registers.
>> PWM needs to obtain an external clock source.
>>
>> Signed-off-by: junyi.zhao <junyi.zhao@...ogic.com>
>> ---
>> V2 -> V3:
>> Rebase and Review the latest upstream code again.
>> After reconstruction, stick to the previous code as much as possible.
>>   drivers/pwm/pwm-meson.c | 19 +++++++++++++++++++
>>   1 file changed, 19 insertions(+)
>>
>> diff --git a/drivers/pwm/pwm-meson.c b/drivers/pwm/pwm-meson.c
>> index 25519cddc2a9..fe9fd75747c4 100644
>> --- a/drivers/pwm/pwm-meson.c
>> +++ b/drivers/pwm/pwm-meson.c
>> @@ -99,6 +99,7 @@ struct meson_pwm_channel {
>>   struct meson_pwm_data {
>>   	const char * const *parent_names;
>>   	unsigned int num_parents;
>> +	unsigned int extern_clk;
>>   };
>>   
>>   struct meson_pwm {
>> @@ -396,6 +397,10 @@ static const struct meson_pwm_data pwm_g12a_ao_cd_data = {
>>   	.num_parents = ARRAY_SIZE(pwm_g12a_ao_cd_parent_names),
>>   };
>>   
>> +static const struct meson_pwm_data pwm_s4_data = {
>> +	.extern_clk = true,
>> +};
>> +
>>   static const struct of_device_id meson_pwm_matches[] = {
>>   	{
>>   		.compatible = "amlogic,meson8b-pwm",
>> @@ -429,6 +434,10 @@ static const struct of_device_id meson_pwm_matches[] = {
>>   		.compatible = "amlogic,meson-g12a-ao-pwm-cd",
>>   		.data = &pwm_g12a_ao_cd_data
>>   	},
>> +	{
>> +		.compatible = "amlogic,s4-pwm",
>> +		.data = &pwm_s4_data,
>> +	},
>>   	{},
>>   };
>>   MODULE_DEVICE_TABLE(of, meson_pwm_matches);
>> @@ -451,6 +460,16 @@ static int meson_pwm_init_channels(struct meson_pwm *meson)
>>   		struct clk_parent_data div_parent = {}, gate_parent = {};
>>   		struct clk_init_data init = {};
>>   
>> +		if (meson->data->extern_clk) {
>> +			snprintf(name, sizeof(name), "clkin%u", i);
>> +			channel->clk = devm_clk_get(dev, name);
> use devm_clk_get_optional() which would save you from introducing
> the 'extern_clk' variable

On S4 and other recent chips PWM clock resides in separate IP and it 
must be provided to driver in order to control PWM frequency. So this 
clock is not optional.

> 
>> +			if (IS_ERR(channel->clk)) {
>> +				dev_err(meson->chip.dev, "can't get device clock\n");
>> +				return PTR_ERR(channel->clk);
>> +			}
>> +			continue;
>> +		}
>> +
>>   		snprintf(name, sizeof(name), "%s#mux%u", dev_name(dev), i);
>>   
>>   		init.name = name;
>>
>> base-commit: 4d2c646ac07cf4a35ef1c4a935a1a4fd6c6b1a36
>> -- 
>> 2.41.0
>>
>>
>> _______________________________________________
>> linux-amlogic mailing list
>> linux-amlogic@...ts.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-amlogic
> 

-- 
Best regards
George

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