From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rob Herring Subject: Re: Reg: Adding a gpio initialization sequence in dts is valid or not Date: Wed, 08 Aug 2012 08:30:20 -0500 Message-ID: <502269EC.2070008@gmail.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Sender: "devicetree-discuss" To: Leela Krishna Amudala Cc: devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, thomas.ab-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org List-Id: devicetree@vger.kernel.org On 08/08/2012 04:52 AM, Leela Krishna Amudala wrote: > Hello All, > > I came across that to set power to an LCD, few panels require a pull > up/pull down operation on single GPIO line > and few panels need some gpio line setting sequence with some delay in between. > > For my development board, user manual says that I have to do a > sequence of gpio line settings with some delay in between > to set power to LCD and currently I'm doing it as > > pull_up(gpio_line_5) > some_delay(x) > pull_down(gpio_line_5) > some_delay(x) > pull_up(gpio_line_5) > > I want to read this GPIO line from device tree and parse it and do the > above sequence in the driver. > I'm thinking to follow the below approach to get this done. > See the thread "runtime interpreted power sequences" > Putting the sequence in dts file like below for an LCD which requires > gpio sequence > lcd-reset-gpio = <&gpx1 5 1 3 0>, (3 - for pull up) > <&gpx1 5 1 1 0>, (1 - for pull down) > <&gpx1 5 1 3 0>; (3 - for pull up) > delay = x; > > and only one gpio entry in the case of LCD which doesn't require gpio > sequence setting > lcd-reset-gpio = <&gpx1 5 1 3 0>, (3 - pull up) > > The 4 arguments in the above handle denotes > > <[phandle of the gpio controller node] > [pin number within the gpio controller] > [mux function] > [pull up/down] > [drive strength]> > The gpio controller defines the number of gpio cells. So technically you could do that if you're defining the gpio controller's binding, but I don't think thats a good idea. If the binding is already defined, then you can't really change it anyway. Rob > My board requires one gpio line to pull up->pull down->pull up to set > power and similarly > other boards may require two gpio lines to follow the sequence in that > case number of entries > in dts file will increase. > > I want to know whether the above approach is acceptable in device-tree or not. > > Best Wishes, > Leela Krishna Amudala. > _______________________________________________ > devicetree-discuss mailing list > devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org > https://lists.ozlabs.org/listinfo/devicetree-discuss >