From: Maxime Ripard <maxime@cerno.tech>
To: Stephen Boyd <sboyd@kernel.org>
Cc: Daniel Vetter <daniel.vetter@intel.com>,
David Airlie <airlied@linux.ie>,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Mike Turquette <mturquette@baylibre.com>,
Thomas Zimmermann <tzimmermann@suse.de>,
dri-devel@lists.freedesktop.org, Eric Anholt <eric@anholt.net>,
Daniel Vetter <daniel@ffwll.ch>,
linux-kernel@vger.kernel.org,
Russell King <linux@armlinux.org.uk>,
Dave Stevenson <dave.stevenson@raspberrypi.com>,
Phil Elwell <phil@raspberrypi.com>,
Tim Gover <tim.gover@raspberrypi.com>,
Dom Cobley <dom@raspberrypi.com>,
linux-clk@vger.kernel.org
Subject: Re: [PATCH 0/2] clk: Implement a clock request API
Date: Mon, 24 May 2021 14:48:11 +0200 [thread overview]
Message-ID: <20210524124811.74g75n672wrpzqqi@gilmour> (raw)
In-Reply-To: <20210503083221.qsdurp2f3bkwfa6d@gilmour>
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Hi Stephen, Mike,
On Mon, May 03, 2021 at 10:32:21AM +0200, Maxime Ripard wrote:
> Hi Stephen,
>
> On Fri, Apr 30, 2021 at 01:59:39PM -0700, Stephen Boyd wrote:
> > Quoting Maxime Ripard (2021-04-13 03:13:18)
> > > Hi,
> > >
> > > This is a follow-up of the discussion here:
> > > https://lore.kernel.org/linux-clk/20210319150355.xzw7ikwdaga2dwhv@gilmour/
> > >
> > > This implements a mechanism to raise and lower clock rates based on consumer
> > > workloads, with an example of such an implementation for the RaspberryPi4 HDMI
> > > controller.
> > >
> > > There's a couple of things worth discussing:
> > >
> > > - The name is in conflict with clk_request_rate, and even though it feels
> > > like the right name to me, we should probably avoid any confusion
> > >
> > > - The code so far implements a policy of always going for the lowest rate
> > > possible. While we don't have an use-case for something else, this should
> > > maybe be made more flexible?
> >
> > I'm definitely confused how it is different from the
> > clk_set_rate_exclusive() API and associated
> > clk_rate_exclusive_get()/clk_rate_exclusive_put(). Can you explain
> > further the differences in the cover letter here?
>
> The exclusive API is meant to prevent the clock rate from changing,
> allowing a single user to make sure that no other user will be able to
> change it.
>
> What we want here is instead to allow multiple users to be able to
> express a set of minimum rates and then let the CCF figure out a rate
> for that clock that matches those constraints (so basically what
> clk_set_min_rate does), but then does allow for the clock to go back to
> its initial rate once that constraint is not needed anymore.
>
> So I guess it's more akin to clk_set_min_rate with rollback than the
> exclusive API?
Is that rationale good enough, or did you expect something else?
Maxime
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next prev parent reply other threads:[~2021-05-24 12:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-13 10:13 [PATCH 0/2] clk: Implement a clock request API Maxime Ripard
2021-04-13 10:13 ` [PATCH 1/2] clk: Introduce " Maxime Ripard
2021-04-13 10:13 ` [PATCH 2/2] drm/vc4: hdmi: Convert to the new " Maxime Ripard
2021-04-30 8:48 ` [PATCH 0/2] clk: Implement a " Maxime Ripard
2021-04-30 20:59 ` Stephen Boyd
2021-05-03 8:32 ` Maxime Ripard
2021-05-24 12:48 ` Maxime Ripard [this message]
2021-06-16 10:05 ` Maxime Ripard
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