linux-kernel - Re: [PATCH v2 0/7] drm/vc4: Fix the core clock behaviour

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Message-ID: <20221013085947.jux4tfbh64ldluin@houat>
Date:   Thu, 13 Oct 2022 10:59:47 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Daniel Vetter <daniel@...ll.ch>, David Airlie <airlied@...ux.ie>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Michael Turquette <mturquette@...libre.com>,
        Scott Branden <sbranden@...adcom.com>,
        Stephen Boyd <sboyd@...nel.org>, Emma Anholt <emma@...olt.net>,
        Ray Jui <rjui@...adcom.com>,
        linux-rpi-kernel@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, Dom Cobley <popcornmix@...il.com>,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 0/7] drm/vc4: Fix the core clock behaviour

Hi Florian,

On Mon, Oct 10, 2022 at 12:07:22PM -0700, Florian Fainelli wrote:
> On 10/10/22 04:44, Maxime Ripard wrote:
> > Hi Florian,
> > 
> > On Tue, Sep 20, 2022 at 02:50:19PM +0200, Maxime Ripard wrote:
> > > Those patches used to be part of a larger clock fixes series:
> > > https://lore.kernel.org/linux-clk/20220715160014.2623107-1-maxime@cerno.tech/
> > > 
> > > However, that series doesn't seem to be getting anywhere, so I've split out
> > > these patches that fix a regression that has been there since 5.18 and that
> > > prevents the 4k output from working on the RaspberryPi4.
> > > 
> > > Hopefully, we will be able to merge those patches through the DRM tree to avoid
> > > any further disruption.
> > 
> > Could you review this? Ideally this would be merged through drm-misc due
> > to the dependencies between the new firmware functions and the DRM
> > patches.
> 
> I suppose I can review the firmware parts if you would like me to

I was of course asking for the firmware parts :)

> for vc4 I am pretty much clueless, and despite efforts from Emma to
> get the vc4 driver to be usable on platforms other than Pi, that never
> happened unfortunately.

Stefan had the same concerns, but I don't think that's a big one. If
needs be, we can move the call to the firware into an if statement or
whatever and support a firmware-less device.

> It would be better to keep the firmware and vc4 drivers decoupled,
> just so "wrong" assumptions are not made, but for all practical
> purposes this is the only combination that exists.

I know, and my initial proposal was relying on a generic CCF function to
implement this. Stephen didn't feel like a single user for it was
enough, and there were some technical drawbacks too that might not have
made this solution robust enough. Hence the firmware solution.

Maxime

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