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

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Date: Tue, 18 Jun 2024 21:11:58 +0200
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...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 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)

Konrad