From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Turquette Subject: Re: [PATCH v4 1/2] ARM: keystone: pm: switch to use generic pm domains Date: Mon, 24 Nov 2014 22:44:06 -0800 Message-ID: <20141125064406.12298.57929@quantum> References: <1415631557-22897-1-git-send-email-grygorii.strashko@ti.com> <546F8B39.1080106@ti.com> <2997659.fTX2lvxXfH@wuerfel> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8BIT Return-path: In-Reply-To: <2997659.fTX2lvxXfH@wuerfel> Sender: linux-pm-owner@vger.kernel.org To: Arnd Bergmann , linux-arm-kernel@lists.infradead.org Cc: Grygorii Strashko , Geert Uytterhoeven , Kevin Hilman , "devicetree@vger.kernel.org" , Ulf Hansson , "linux-pm@vger.kernel.org" , Dmitry Torokhov , "Rafael J. Wysocki" , "linux-kernel@vger.kernel.org" , Grant Likely , Rob Herring , ssantosh@kernel.org List-Id: devicetree@vger.kernel.org Quoting Arnd Bergmann (2014-11-24 02:50:28) > On Friday 21 November 2014 20:58:01 Grygorii Strashko wrote: > > Hi Kevin, > > On 11/21/2014 10:06 AM, Geert Uytterhoeven wrote: > > > On Fri, Nov 21, 2014 at 2:30 AM, Kevin Hilman wrote: > > >> Geert Uytterhoeven writes: > > >> > > >> So now I'm confused about why the PM domain has to do anything special > > >> if the presence/absence of the clocks is already handled by the DT. > > > > > > Just adding a clock property to a device node in DT doesn't enable the clock > > > automatically, nor make it runtime-managed automatically. > > > Compare this to e.g. pinctrl, where adding pinctrl properties to DT does enable > > > them automatically, without the driver for the device having to care about it. > > > > > > Drivers interfacing external hardware typically do care about clocks, as they > > > have to program clock generators for the external hardware interface (e.g. > > > driving spi or i2c buses at specific frequencies). > > But is this a property of the driver or of the device? If this is true > independent of the driver implementation, I don't see a problem with > the approach of linking to a power-domain that automatically manages > all clocks for the devices that need this, and requires the driver to > manage them itself when there are any clocks that can't be handled > with the generic clk-power-domain implementation. > > > > > In non-DT case, we have possibility to divide clocks on "fck" and "opt" > > (The way it can be done is not convenient, but it is - .con_id). > > > > For DT-case - no way now. Also, PM domains are not physically present on > > Keystone 2 and GPD was selected as glue layer to integrate DT, pm_clk and > > PM runtime all together (one big-fat-global PM domain :). > > > > So, I was able to find only following way to define "fck" clocks in DT: > > clocks = <&papllclk>, <&clkcpgmac>, <&chipclk12>; > > clock-names = "clk_pa", "clk_cpgmac", "cpsw_cpts_rft_clk"; > > fck-clocks = <&papllclk>, <&clkcpgmac>; > > As you can see - this will lead to data duplication in DT ( > > > > Any propositions are welcome? > > > > Unfortunately, It seems that if we would not able to find DT solution > > then there will be following ways to move forward: > > - "remove the power domain proxy from your drivers and use the clocks directly" > > ((c) Arnd Bergmann). > > [As possibility - It can be allowed to use clk_pm APIs by drivers] > > - continue using platform specific implementations. > > Could the driver maybe identify the clocks that it wants to manage itself > to the pm-domain code? If it's safe for a device to have the clock turned > on at the default rate before loading the driver, any device that is connected > to the simple clk-pm-domain code could have all its clocks start out as > owned by the pm-domain, but then claim the clocks it needs to reprogram for > itself and take them out of the pmdomain. I was thinking along similar lines. The functional versus optional stuff is really a property of the consuming device, not the clock signal itself. Instead of adding a new property to the clock binding (e.g. fck-clocks or optional-clocks), could we simply wrap those lists of clocks in another node? E.g: mandatory-clocks { clocks = <&papllclk>, <&clkcpgmac>; clock-names = "clk_pa", "clk_cpgmac"; } clocks = <&papllclk>, <&clkcpgmac>, <&chipclk12>; clocks = <&clkcpgmac>; clock-names = "cpsw_cpts_rft_clk"; } I'm showing my DT ignorance on this one. I haven't really thought through how these sub-nodes would work with of_clk_* handlers in drivers/clk/clkdev.c. Regards, Mike > > Arnd > -- > To unsubscribe from this list: send the line "unsubscribe linux-pm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html