From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752806Ab2A3BoI (ORCPT ); Sun, 29 Jan 2012 20:44:08 -0500 Received: from mail-pz0-f46.google.com ([209.85.210.46]:47509 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752247Ab2A3BoG (ORCPT ); Sun, 29 Jan 2012 20:44:06 -0500 Date: Mon, 30 Jan 2012 09:56:10 +0800 From: Shawn Guo To: Tony Lindgren Cc: Stephen Warren , Dong Aisheng , "devicetree-discuss@lists.ozlabs.org" , "Linus Walleij (linus.walleij@linaro.org)" , "linux-kernel@vger.kernel.org" , "rob.herring@calxeda.com" , "Grant Likely (grant.likely@secretlab.ca)" , Thomas Abraham , "kernel@pengutronix.de" , "Simon Glass (sjg@chromium.org)" , "cjb@laptop.org" , Dong Aisheng-B29396 , "Sascha Hauer (s.hauer@pengutronix.de)" , "linux-arm-kernel@lists.infradead.org" Subject: Re: Pinmux bindings proposal V2 Message-ID: <20120130015607.GA10470@S2101-09.ap.freescale.net> References: <74CDBE0F657A3D45AFBB94109FB122FF1780DAB4CE@HQMAIL01.nvidia.com> <20120123210052.GS22818@atomide.com> <74CDBE0F657A3D45AFBB94109FB122FF178CB81C0D@HQMAIL01.nvidia.com> <20120124012038.GT22818@atomide.com> <74CDBE0F657A3D45AFBB94109FB122FF178CB81EDB@HQMAIL01.nvidia.com> <20120125000407.GU22818@atomide.com> <74CDBE0F657A3D45AFBB94109FB122FF178CB82433@HQMAIL01.nvidia.com> <20120127020832.GJ29812@atomide.com> <20120127065752.GB32740@S2101-09.ap.freescale.net> <20120127170545.GH13504@atomide.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120127170545.GH13504@atomide.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 27, 2012 at 09:05:45AM -0800, Tony Lindgren wrote: > Hi, > > * Shawn Guo [120126 22:15]: > > On Thu, Jan 26, 2012 at 06:08:33PM -0800, Tony Lindgren wrote: > > > * Stephen Warren [120126 11:03]: > > ... > > > > Second, as I mentioned before, while some of the states are certainly > > > > PM-related, I don't think all will be, e.g. the case of running an SD > > > > controller at different clock rates to the SD card, and needing to > > > > set different pin parameters based on the clock rate. Is runtime PM > > > > intended cover that kind of thing? The idea here is that the common > > > > pinctrl binding can allow the driver to require different named states > > > > for those different clock rate cases. > > > > > > For the PM related states, those should be Linux generic. For rate > > > setting sounds like that's really something you should set up as clocks > > > in the Tegra wrapper driver for SDHCI? > > > > > That's right. > > > > > Ideally the SDHCI driver would be completely arch independent, and > > > then the SoC specific wrapper driver would know how to communicate to > > > the pinmux/pinconf framwork or clock framework what it needs using > > > Linux generic APIs. > > > > But that wrapper driver should not be bothered to call pinmux/pinconf > > APIs on pin basis to change the pinctrl configuration. The elegant > > way would be something like the following in case that it switches > > the bus frequency from 50 MHz to 100 MHz. > > > > pmx = pinmux_get(dev, "esdhc_50mhz"); > > ... > > pinmux_put(pmx); > > pmx = pinmux_get(dev, "esdhc_100mhz"); > > ... > > > > The specific mux and config settings of states esdhc_50mhz and > > esdhc_100mhz would be retrieved from device tree. > > Yes whatever mux names can be used, same as with clock framework > for clock names. But that means you'll have to constantly get/put > the mux which is not efficient. > The most important reason that we want to move to pinctrl subsystem is we need its run-time configuration feature for cases like esdhc here. I do not think the switch here is so constant to be inefficient. > Wouldn't it be cleaner to just clk_get esdhc_clk during init, then > do clk_set_rate on it to toggle the rates? > It's not an init-time switch but run-time one. That said, sdhci_ops.set_clock will be called during run-time. > > > So I'd rather stay out of random named states for > > > the pins coming from device tree; If we still need them, they should > > > be common bindings rather than things like "xyz_clock_hack". > > > > > The binding defines the syntax, and I do not see the necessity to > > force the particular state name, which is really pinctrl client > > device specific. > > Do you have some other custom pin state example other than the > clock rate change example above? > I have another case PM related. To aggressively save power, the pins configured for particular function during active mode need to be muxed on gpio mode and output 0 in low-power mode. -- Regards, Shawn