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Wed, 16 Jun 2021 06:05:57 -0400 (EDT) Date: Wed, 16 Jun 2021 12:05:56 +0200 From: Maxime Ripard To: Stephen Boyd Cc: Daniel Vetter , David Airlie , Maarten Lankhorst , Mike Turquette , Thomas Zimmermann , dri-devel@lists.freedesktop.org, Eric Anholt , Daniel Vetter , linux-kernel@vger.kernel.org, Russell King , Dave Stevenson , Phil Elwell , Tim Gover , Dom Cobley , linux-clk@vger.kernel.org Subject: Re: [PATCH 0/2] clk: Implement a clock request API Message-ID: <20210616100556.marhidqeljaxswyf@gilmour> References: <20210413101320.321584-1-maxime@cerno.tech> <161981637939.1363782.4943687720432536625@swboyd.mtv.corp.google.com> <20210503083221.qsdurp2f3bkwfa6d@gilmour> <20210524124811.74g75n672wrpzqqi@gilmour> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <20210524124811.74g75n672wrpzqqi@gilmour> Precedence: bulk List-ID: X-Mailing-List: linux-clk@vger.kernel.org Hi Stephen, Mike, On Mon, May 24, 2021 at 02:48:11PM +0200, Maxime Ripard wrote: > Hi Stephen, Mike, >=20 > On Mon, May 03, 2021 at 10:32:21AM +0200, Maxime Ripard wrote: > > Hi Stephen, > >=20 > > On Fri, Apr 30, 2021 at 01:59:39PM -0700, Stephen Boyd wrote: > > > Quoting Maxime Ripard (2021-04-13 03:13:18) > > > > Hi, > > > >=20 > > > > This is a follow-up of the discussion here: > > > > https://lore.kernel.org/linux-clk/20210319150355.xzw7ikwdaga2dwhv@g= ilmour/ > > > >=20 > > > > This implements a mechanism to raise and lower clock rates based on= consumer > > > > workloads, with an example of such an implementation for the Raspbe= rryPi4 HDMI > > > > controller. > > > >=20 > > > > There's a couple of things worth discussing: > > > >=20 > > > > - 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 confusi= on > > > >=20 > > > > - The code so far implements a policy of always going for the low= est rate > > > > possible. While we don't have an use-case for something else, t= his should > > > > maybe be made more flexible? > > >=20 > > > 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? > >=20 > > 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. > >=20 > > 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. > >=20 > > So I guess it's more akin to clk_set_min_rate with rollback than the > > exclusive API? >=20 > Is that rationale good enough, or did you expect something else? I'm not really sure what to do at this point. It's been over 2 months since I sent this series, and we really need that mechanism in some form or another. I'm really fine with changing that series in any way, but I got no comment that I could address to turn this into something that would be acceptable to you. How can we move this forward? Maxime