From mboxrd@z Thu Jan 1 00:00:00 1970 From: Florian Vaussard Subject: Re: [PATCH 1/2] ARM: dts: omap3-overo: Add support for pwm-leds Date: Thu, 24 Jan 2013 22:14:37 +0100 Message-ID: <5101A43D.7080108@epfl.ch> References: <1358963812-19947-1-git-send-email-florian.vaussard@epfl.ch> <1358963812-19947-2-git-send-email-florian.vaussard@epfl.ch> <5101510C.9050407@ti.com> <51015663.8080109@epfl.ch> <5101570A.1030303@ti.com> <5101663C.7020301@epfl.ch> <51016A84.20703@ti.com> Reply-To: florian.vaussard-p8DiymsW2f8@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <51016A84.20703-l0cyMroinI0@public.gmane.org> 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: Peter Ujfalusi Cc: devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: devicetree@vger.kernel.org Hi >> >>>> I am working on a patch for pwm-twl-led to defer using a workqueue right now. >>> >>> Great! >>> The only thing I worry about is the latency we are going to get with the >>> workqueue. >>> >> >> If the latency becomes critical, we can create our own workqueue. > > Hrm, when we handled the led via gpio-leds it was also going through the same > path at the end, via i2c to twl4030. > I think the fix for this is going to be needed in the pwm core level. Just > need to look at the gpio code to have similar handling of might_sleep interfaces. > You are right. But then the pwm core must provide a way to know if the pwm access function are callable from atomic context or not (the gpio framework provides gpio_cansleep()). This implies a good amount of changes to the pwm framework, and currently we are the only driver using non-atomic access. I will take a closer look to the complexity of this solution tomorrow. Florian