From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759801AbcILPDl (ORCPT ); Mon, 12 Sep 2016 11:03:41 -0400 Received: from mail-wm0-f53.google.com ([74.125.82.53]:36748 "EHLO mail-wm0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759050AbcILPDi (ORCPT ); Mon, 12 Sep 2016 11:03:38 -0400 Subject: Re: [PATCH] ARM: dts: omap3-gta04: reduce panel backlight PWM frequency to 83Hz To: David Rivshin References: <954d43b570092fe92b8b49cf8f475c027d3d8342.1473066997.git.hns@goldelico.com> <20160910031736.xwnepaoifpedqfbr@squirrel.local> <57D40F2C.7000805@baylibre.com> <20160912104155.267876a2.drivshin@awxrd.com> Cc: Matthijs van Duin , "H. Nikolaus Schaller" , =?UTF-8?Q?Beno=c3=aet_Cousson?= , Tony Lindgren , Rob Herring , Mark Rutland , Russell King , marek@goldelico.com, linux-omap@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, letux-kernel@openphoenux.org From: Neil Armstrong Organization: Baylibre Message-ID: Date: Mon, 12 Sep 2016 17:03:32 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <20160912104155.267876a2.drivshin@awxrd.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/12/2016 04:41 PM, David Rivshin wrote: > On Sat, 10 Sep 2016 15:48:28 +0200 > Neil Armstrong wrote: > >> Le 10/09/2016 05:17, Matthijs van Duin a écrit : >>> On Mon, Sep 05, 2016 at 11:16:38AM +0200, H. Nikolaus Schaller wrote: >>>> This helps to get 100% intensity closer to "always on". [...] >>> } >>> >>> At the time I used a scope to check the exact behaviour of dmtimer pwm >>> on a dm814x. My notes mention (when pwm enabled): >>> match < reload output on continuous >>> match == reload output on 1 cycle, off period-1 cycles >>> match == -2 output on period-1 cycles, off 1 cycle >>> match == -1 output freezes >>> >>> Hope this helps >> >> Hi, >> >> I think these corner cases should definitely be handled in the dmtimer driver. > > Do you mean to modify the dmtimer driver itself, or the pwm-omap-dmtimer > driver? > > IIRC from the last time I was in the pwm-omap-dmtimer driver, it seemed to > me that the 0% and 100% cases could/should be handled as simple special > cases there. I think the dmtimer driver itself has the necessary API to the > HW, but I'd need to re-familiarize myself with it to remember the details > of what I was thinking. > > Actually, I did mention some thoughts on this a previous thread where > Adam Ford was using pwm-omap-dmtimer for a backlight: > http://www.spinics.net/lists/linux-omap/msg126006.html > So it may be as simple as using PWM_OMAP_DMTIMER_TRIGGER_NONE and passing > def_on according to whether 0 or 100% duty were requested (and polarity). Yes it's exactly what I was talking about. > > >> >> I'll try to post a fix to handle these, thanks for the original code dump. >> >>> >>> Matthijs >>> >> >> Neil Thanks, Neil From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Armstrong Subject: Re: [PATCH] ARM: dts: omap3-gta04: reduce panel backlight PWM frequency to 83Hz Date: Mon, 12 Sep 2016 17:03:32 +0200 Message-ID: References: <954d43b570092fe92b8b49cf8f475c027d3d8342.1473066997.git.hns@goldelico.com> <20160910031736.xwnepaoifpedqfbr@squirrel.local> <57D40F2C.7000805@baylibre.com> <20160912104155.267876a2.drivshin@awxrd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20160912104155.267876a2.drivshin-WHIoityCHfoAvxtiuMwx3w@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: David Rivshin Cc: Matthijs van Duin , "H. Nikolaus Schaller" , =?UTF-8?Q?Beno=c3=aet_Cousson?= , Tony Lindgren , Rob Herring , Mark Rutland , Russell King , marek-xXXSsgcRVICgSpxsJD1C4w@public.gmane.org, linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, letux-kernel-S0jZdbWzriLCfDggNXIi3w@public.gmane.org List-Id: devicetree@vger.kernel.org On 09/12/2016 04:41 PM, David Rivshin wrote: > On Sat, 10 Sep 2016 15:48:28 +0200 > Neil Armstrong wrote: > >> Le 10/09/2016 05:17, Matthijs van Duin a écrit : >>> On Mon, Sep 05, 2016 at 11:16:38AM +0200, H. Nikolaus Schaller wrote: >>>> This helps to get 100% intensity closer to "always on". [...] >>> } >>> >>> At the time I used a scope to check the exact behaviour of dmtimer pwm >>> on a dm814x. My notes mention (when pwm enabled): >>> match < reload output on continuous >>> match == reload output on 1 cycle, off period-1 cycles >>> match == -2 output on period-1 cycles, off 1 cycle >>> match == -1 output freezes >>> >>> Hope this helps >> >> Hi, >> >> I think these corner cases should definitely be handled in the dmtimer driver. > > Do you mean to modify the dmtimer driver itself, or the pwm-omap-dmtimer > driver? > > IIRC from the last time I was in the pwm-omap-dmtimer driver, it seemed to > me that the 0% and 100% cases could/should be handled as simple special > cases there. I think the dmtimer driver itself has the necessary API to the > HW, but I'd need to re-familiarize myself with it to remember the details > of what I was thinking. > > Actually, I did mention some thoughts on this a previous thread where > Adam Ford was using pwm-omap-dmtimer for a backlight: > http://www.spinics.net/lists/linux-omap/msg126006.html > So it may be as simple as using PWM_OMAP_DMTIMER_TRIGGER_NONE and passing > def_on according to whether 0 or 100% duty were requested (and polarity). Yes it's exactly what I was talking about. > > >> >> I'll try to post a fix to handle these, thanks for the original code dump. >> >>> >>> Matthijs >>> >> >> Neil Thanks, Neil -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html