linux-kernel - Re: [PATCH v3 02/23] gcc-sdm845: Add rates to the GP clocks

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Date: Wed, 19 Jun 2024 09:31:57 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Konrad Dybcio <konrad.dybcio@...aro.org>
Cc: Dzmitry Sankouski <dsankouski@...il.com>, 
	Sebastian Reichel <sre@...nel.org>, Bjorn Andersson <andersson@...nel.org>, 
	Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Jessica Zhang <quic_jesszhan@...cinc.com>, 
	Sam Ravnborg <sam@...nborg.org>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Lee Jones <lee@...nel.org>, 
	Dmitry Torokhov <dmitry.torokhov@...il.com>, Pavel Machek <pavel@....cz>, Liam Girdwood <lgirdwood@...il.com>, 
	Mark Brown <broonie@...nel.org>, Uwe Kleine-König <ukleinek@...nel.org>, 
	Krzysztof Kozlowski <krzk@...nel.org>, Chanwoo Choi <cw00.choi@...sung.com>, 
	phone-devel@...r.kernel.org, linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	devicetree@...r.kernel.org, linux-input@...r.kernel.org, linux-leds@...r.kernel.org, 
	linux-pwm@...r.kernel.org, linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH v3 02/23] gcc-sdm845: Add rates to the GP clocks

On Tue, Jun 18, 2024 at 09:11:58PM GMT, Konrad Dybcio wrote:
> 
> 
> On 6/18/24 20:55, Dmitry Baryshkov wrote:
> > On Tue, Jun 18, 2024 at 08:50:52PM GMT, Konrad Dybcio wrote:
> > > 
> > > 
> > > On 6/18/24 19:50, Dmitry Baryshkov wrote:
> > > > On Tue, Jun 18, 2024 at 04:59:36PM GMT, Dzmitry Sankouski wrote:
> > > > > sdm845 has "General Purpose" clocks that can be muxed to
> > > > > SoC pins.
> > > > > 
> > > > > Those clocks may be used as e.g. PWM sources for external peripherals.
> > > > > Add more frequencies to the table for those clocks so it's possible
> > > > > for arbitrary peripherals to make use of them.
> > > > > 
> > > > > See also: bf8bb8eaccf(clk: qcom: gcc-msm8916: Add rates to the GP clocks)
> > > > 
> > > > Each time I look at the table attached to the GP CLK, I feel that it's
> > > > plain wrong. In the end the GPCLK can in theory have arbitrary value
> > > > depending on the usecase.
> > > > 
> > > > Bjorn, Konrad, maybe we should add special clk_ops for GP CLK which
> > > > allow more flexibility than a default clk_rcg2_ops?
> > > 
> > > If we can somehow get max m/n/d values for all possible parents, sure
> > 
> > Calculate them at runtime?
> 
> We'd be calculating the mnd values for a frequency that's either equal or
> reasonably close to the one requested. My worry is that we somehow need
> to get the maximum values they can take (unless they're well-known)

One of the options might be to force devices to use
assigned-clock-parent to set GP CLK sorource and pwm-clk as an actual
device using the clock.

-- 
With best wishes
Dmitry