From mboxrd@z Thu Jan 1 00:00:00 1970 From: Geert Uytterhoeven Date: Thu, 01 May 2014 13:41:11 +0000 Subject: Re: [PATCH/RFC 3/4] of/clk: Register clocks suitable for Runtime PM with the PM core Message-Id: List-Id: References: <1398334403-26181-1-git-send-email-geert+renesas@glider.be> <1398334403-26181-4-git-send-email-geert+renesas@glider.be> <7hoazpdldx.fsf@paris.lan> <20140429131610.29859C4094A@trevor.secretlab.ca> <20140501080331.D3CFAC409DA@trevor.secretlab.ca> In-Reply-To: <20140501080331.D3CFAC409DA@trevor.secretlab.ca> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-arm-kernel@lists.infradead.org Hi Grant, On Thu, May 1, 2014 at 10:03 AM, Grant Likely wrote: > On Wed, 30 Apr 2014 23:54:37 +0200, Geert Uytterhoeven wrote: >> On Tue, Apr 29, 2014 at 3:16 PM, Grant Likely wrote: >> > I also don't like that it tries to set up every clock, but there is no >> > guarantee that the driver will even use it. I would rather see this >> > behaviour linked into the function that obtains the clock at driver >> > .probe() time. That way it can handle deferred probe correctly and it >> > only sets up clocks that are actually used by the driver. >> >> Not every clock. Only the clocks that are advertised by the clock driver as >> being suitable for runtime_pm management. These are typically module >> clocks, that must be enabled for the module to work. The driver doesn't >> always want to handle these explicitly. > > Help me out here becasue I don't understand how that works with this > patch set. From my, admittedly naive, reading it looks like the setup is > being done at device creation time, but if the driver (or module) gets > to declare which clocks need to be enabled in order to work, then that > information is not available at device creation time. Setup is indeed done at registration time. Note the check calling clk_may_runtime_pm(), which is introduced in "[PATCH/RFC 1/4] clk: Add CLK_RUNTIME_PM and clk_may_runtime_pm()". Clock drivers are initialized much earlier, so they can set the CLK_RUNTIME_PM flag for suitable clocks before platform devices are created from DT, cfr. the example for shmobile MSTP clocks in "[PATCH/RFC 4/4] clk: shmobile: mstp: Set CLK_RUNTIME_PM flag". I hope this makes it clear. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds