From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Subject: Re: [PATCH v1 1/3] gpio: defer probe if pinctrl cannot be found Date: Fri, 10 Jul 2015 11:07:27 -0600 Message-ID: <559FFBCF.4020906@wwwdotorg.org> References: <1435754753-31307-1-git-send-email-tomeu.vizoso@collabora.com> <1435754753-31307-2-git-send-email-tomeu.vizoso@collabora.com> <559FE471.1030408@wwwdotorg.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Tomeu Vizoso Cc: Rob Herring , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-gpio-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Linus Walleij , Grant Likely , Rob Herring , Alexandre Courbot List-Id: devicetree@vger.kernel.org On 07/10/2015 10:21 AM, Tomeu Vizoso wrote: > On 10 July 2015 at 17:27, Stephen Warren wrote: >> On 07/10/2015 03:29 AM, Tomeu Vizoso wrote: >>> >>> On 1 July 2015 at 19:36, Rob Herring wrote: >>>> >>>> On Wed, Jul 1, 2015 at 7:45 AM, Tomeu Vizoso >>>> wrote: >>>>> >>>>> When an OF node has a pin range for its GPIOs, return -EPROBE_DEFER if >>>>> the pin controller isn't available. >>>>> >>>>> Otherwise, the GPIO range wouldn't be set at all unless the pin >>>>> controller probed always before the GPIO chip. >>>>> >>>>> With this change, the probe of the GPIO chip will be deferred and will >>>>> be retried at a later point, hopefully once the pin controller has been >>>>> registered and probed already. >>>> >>>> >>>> This will break cases where the pinctrl driver does not exist, but the >>>> DT contains pinctrl bindings. We can have similar problems already >>>> with clocks though. However, IMO this problem is a bit different in >>>> that pinctrl is more likely entirely optional while clocks are often >>>> required. You may do all pin setup in bootloader/firmware on some >>>> boards and not others. Of course then why put pinctrl in the DT in >>>> that case? They could be present just due to how chip vs. board dts >>>> files are structured. >>> >>> >>> I see. My instinct tells me that it would be better if the gpio-ranges >>> property was set in the board dts, but I don't really know what each >>> mach does with its DTSs. >> >> >> That doesn't make sense; the mapping between GPIO controller pins and pin >> controller pins is a property of the SoC not the board. > > From what Rob said above, apparently some boards will rely on the pin > setup done by the bootloader, and some other boards with the same soc > will want to do it in the kernel. So it's not really a difference in > the hw itself, but what expectations exist about the firmware on a > specific board. Sure, but none of that changes the mapping between the GPIO and pin controller pins.