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 10:48:15 +0100
From: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To: Jerome Brunet <jbrunet@...libre.com>
Cc: 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

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 ...

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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