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Message-ID: <5b64f4ef-a62e-80df-80a6-3ab52589588b@i2se.com>
Date: Thu, 15 Sep 2022 08:15:48 +0200
From: Stefan Wahren <stefan.wahren@...e.com>
To: Stephen Boyd <sboyd@...nel.org>,
Broadcom internal kernel review list
<bcm-kernel-feedback-list@...adcom.com>,
Daniel Vetter <daniel@...ll.ch>,
David Airlie <airlied@...ux.ie>, Emma Anholt <emma@...olt.net>,
Florian Fainelli <f.fainelli@...il.com>,
Maxime Ripard <maxime@...no.tech>,
Maxime Ripard <mripard@...nel.org>,
Michael Turquette <mturquette@...libre.com>,
Ray Jui <rjui@...adcom.com>,
Scott Branden <sbranden@...adcom.com>
Cc: linux-arm-kernel@...ts.infradead.org,
linux-rpi-kernel@...ts.infradead.org,
dri-devel@...ts.freedesktop.org, Dom Cobley <popcornmix@...il.com>,
linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/7] clk: bcm: rpi: Add a function to retrieve the
maximum
Hi Stephen,
Am 14.09.22 um 20:20 schrieb Stephen Boyd:
> Quoting Stefan Wahren (2022-09-14 11:09:04)
>> Am 14.09.22 um 20:05 schrieb Stephen Boyd:
>>> Quoting Stefan Wahren (2022-09-14 10:45:48)
>>>> Am 14.09.22 um 17:50 schrieb Stephen Boyd:
>>>>> Furthermore, I wonder if even that part needs to be implemented. Why
>>>>> not make a direct call to rpi_firmware_property() and get the max rate?
>>>>> All of that can live in the drm driver. Making it a generic API that
>>>>> takes a 'struct clk' means that it looks like any clk can be passed,
>>>>> when that isn't true. It would be better to restrict it to the one use
>>>>> case so that the scope of the problem doesn't grow. I understand that it
>>>>> duplicates a few lines of code, but that looks like a fair tradeoff vs.
>>>>> exposing an API that can be used for other clks in the future.
>>>> it would be nice to keep all the Rpi specific stuff out of the DRM
>>>> driver, since there more users of it.
>>> Instead of 'all' did you mean 'any'?
>> yes
> Another idea is to populate an OPP table in the rpi firmware driver for
> this platform device with the adjusted max frequency. That would be an
> SoC/firmware agnostic interface that expresses the constraints.
Do you mean in the source code of this driver or in the DT?
> I'm
> almost certain we talked about this before.
I'm not sure about the context. Do you mean the CPU frequency handling?
I remember it was a hard decision. In the end it was little benefit but
a lot of disadvantages (hard to maintain all theses OPP tables for all
Raspberry Pi boards, doesn't work with already deployed DT). So yes, i'm
part of the problem i mentioned before ;-)
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