linux-kernel - Re: [PATCH v4 5/6] pwm: meson: don't carry internal clock elements around

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Date: Wed, 24 Jan 2024 10:59:43 +0100
From: Jerome Brunet <jbrunet@...libre.com>
To: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc: Jerome Brunet <jbrunet@...libre.com>, Thierry Reding
 <thierry.reding@...il.com>, Neil Armstrong <neil.armstrong@...aro.org>,
 Rob Herring <robh+dt@...nel.org>, Krzysztof Kozlowski
 <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>,
 Kevin Hilman <khilman@...libre.com>, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-amlogic@...ts.infradead.org,
 linux-pwm@...r.kernel.org, JunYi Zhao <junyi.zhao@...ogic.com>
Subject: Re: [PATCH v4 5/6] pwm: meson: don't carry internal clock elements
 around


On Wed 24 Jan 2024 at 10:48, Uwe Kleine-König <u.kleine-koenig@...gutronix.de> wrote:

> [[PGP Signed Part:Undecided]]
> Hello Jerome,
>
> On Wed, Jan 24, 2024 at 10:16:17AM +0100, Jerome Brunet wrote:
>> On Wed 24 Jan 2024 at 10:02, Uwe Kleine-König <u.kleine-koenig@...gutronix.de> wrote:
>> > On Fri, Dec 22, 2023 at 12:16:53PM +0100, Jerome Brunet wrote:
>> >> @@ -442,6 +439,13 @@ static int meson_pwm_init_channels(struct device *dev)
>> >>  		struct meson_pwm_channel *channel = &meson->channels[i];
>> >>  		struct clk_parent_data div_parent = {}, gate_parent = {};
>> >>  		struct clk_init_data init = {};
>> >> +		struct clk_divider *div;
>> >> +		struct clk_gate *gate;
>> >> +		struct clk_mux *mux;
>> >> +
>> >> +		mux = devm_kzalloc(dev, sizeof(*mux), GFP_KERNEL);
>> >> +		if (!mux)
>> >> +			return -ENOMEM;
>> >
>> > I don't like this change. While it doesn't increase the memory used, it
>> > fragments the used memory and increases the overhead of memory
>> > management and the number of devm allocations.
>> >
>> > Are these members of meson_pwm_channel in the way for anything later?
>> 
>> Not really. It is just not useful on the SoCs which do use it and not
>> used at all starting from s4/a1.
>
> This remembers me about the old pwm-imx driver. This was essentially a
> single file containing two drivers just because both types appeared on
> imx machines. Later it was split into imx1 and imx27.
>
> I didn't look at the relevant differences between the existing driver
> and the changes needed for s4, but please don't repeat this issue for
> meson. Not sure this fear is justified, just saying ...

Noted. Don't worry. s4 is indeed the same PWM block as before, just
mux/div/gate migrated from the pwm IP to the main clk controller.
That's all ... I know ;)

Only the clock registration should change and simplify.

>
> Best regards
> Uwe


-- 
Jerome