linux-kernel - Re: [PATCH 2/2] pwm: meson: support meson A1 SoC family

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Message-ID: <4feb8fe3-af72-4483-87b2-30503328cfe2@salutedevices.com>
Date: Wed, 24 Apr 2024 02:00:20 +0300
From: George Stark <gnstark@...utedevices.com>
To: Jerome Brunet <jbrunet@...libre.com>
CC: <u.kleine-koenig@...gutronix.de>, <neil.armstrong@...aro.org>,
	<khilman@...libre.com>, <martin.blumenstingl@...glemail.com>,
	<thierry.reding@...il.com>, <hkallweit1@...il.com>, <robh+dt@...nel.org>,
	<krzysztof.kozlowski+dt@...aro.org>, <conor+dt@...nel.org>,
	<linux-pwm@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-amlogic@...ts.infradead.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <kernel@...utedevices.com>, George Stark
	<gnstark@...rdevices.ru>, Dmitry Rokosov <ddrokosov@...utedevices.com>
Subject: Re: [PATCH 2/2] pwm: meson: support meson A1 SoC family

Hello Jerome

Thanks for the review


On 4/23/24 20:35, Jerome Brunet wrote:
> 
> On Tue 23 Apr 2024 at 19:10, George Stark <gnstark@...utedevices.com> wrote:
> 
>> From: George Stark <gnstark@...rdevices.ru>
>>
>> Add a compatible string and configuration for the meson A1 SoC family
>> PWM. Additionally, provide an external clock initialization helper
>> specifically designed for these PWM IPs.
>>
>> Signed-off-by: George Stark <gnstark@...rdevices.ru>
>> Signed-off-by: Dmitry Rokosov <ddrokosov@...utedevices.com>
>> ---
>>   drivers/pwm/pwm-meson.c | 35 +++++++++++++++++++++++++++++++++++
>>   1 file changed, 35 insertions(+)
>>
>> diff --git a/drivers/pwm/pwm-meson.c b/drivers/pwm/pwm-meson.c
>> index ea96c5973488..529a541ba7b6 100644
>> --- a/drivers/pwm/pwm-meson.c
>> +++ b/drivers/pwm/pwm-meson.c
>> @@ -462,6 +462,33 @@ static int meson_pwm_init_channels_meson8b_v2(struct pwm_chip *chip)
>>   	return meson_pwm_init_clocks_meson8b(chip, mux_parent_data);
>>   }
>>   
>> +static int meson_pwm_init_channels_ext_clock(struct pwm_chip *chip)
> 
> That kind on naming (ext) is almost sure to clash with whatever comes next.
> Just use the name of the first SoC using the method, a1 for instance.

It's true that pwm core in a1 s4, t7 etc is the same AFAWK.
I just want to clarify your proposal:
I add a1 compatible to the dt-bindings with s4 as fallback,
t7 compatible will be added later in the same way.

Here in the driver I don't mention a1 at all and use s4-centric naming e.g.:

{
	.compatible = "amlogic,meson-s4-pwm",
	.data = &pwm_meson_s4_data
},
static const struct meson_pwm_data pwm_meson_s4_data = {
	.channels_init = meson_pwm_init_channels_s4,
};

right?

>> +{
>> +	struct device *dev = pwmchip_parent(chip);
>> +	struct meson_pwm *meson = to_meson_pwm(chip);
>> +	struct meson_pwm_channel *channels = meson->channels;
>> +	struct clk_bulk_data *clks = NULL;
>> +	unsigned int i;
>> +	int res;
>> +
>> +	res = devm_clk_bulk_get_all(dev, &clks);
>> +	if (res < 0) {
>> +		dev_err(dev, "can't get device clocks\n");
>> +		return res;
>> +	}
> 
> I don't think allocating the 'clk_bulk_data *clks' is necessary or safe.
> We know exactly how many clocks we expect, there is no need for a get all.
> 
>> +
>> +	if (res != MESON_NUM_PWMS) {
>> +		dev_err(dev, "clock count must be %d, got %d\n",
>> +			MESON_NUM_PWMS, res);
>> +		return -EINVAL;
>> +	}
> 
> ... and this only catches the problem after the fact.
> 
> It is probably convinient but not necessary.
> 
>> +
>> +	for (i = 0; i < MESON_NUM_PWMS; i++)
>> +		channels[i].clk = clks[i].clk;
> 
> channels[i].clk could be assigned directly of_clk_get() using clock
> indexes. No extra allocation needed.

if we use of_clk_get then we'll have to free the clock objects in the
end. Could we use devm_clk_bulk_get instead?

>> +
>> +	return 0;
>> +}
>> +
>>   static const struct meson_pwm_data pwm_meson8b_data = {
>>   	.parent_names = { "xtal", NULL, "fclk_div4", "fclk_div3" },
>>   	.channels_init = meson_pwm_init_channels_meson8b_legacy,
>> @@ -500,11 +527,19 @@ static const struct meson_pwm_data pwm_meson8_v2_data = {
>>   	.channels_init = meson_pwm_init_channels_meson8b_v2,
>>   };
>>   
>> +static const struct meson_pwm_data pwm_meson_ext_clock_data = {
>> +	.channels_init = meson_pwm_init_channels_ext_clock,
>> +};
>> +
>>   static const struct of_device_id meson_pwm_matches[] = {
>>   	{
>>   		.compatible = "amlogic,meson8-pwm-v2",
>>   		.data = &pwm_meson8_v2_data
>>   	},
>> +	{
>> +		.compatible = "amlogic,meson-a1-pwm",
>> +		.data = &pwm_meson_ext_clock_data
>> +	},
>>   	/* The following compatibles are obsolete */
>>   	{
>>   		.compatible = "amlogic,meson8b-pwm",
> 
> 

-- 
Best regards
George