From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933037AbcI3JmY (ORCPT ); Fri, 30 Sep 2016 05:42:24 -0400 Received: from mail-it0-f54.google.com ([209.85.214.54]:36700 "EHLO mail-it0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932413AbcI3JmQ (ORCPT ); Fri, 30 Sep 2016 05:42:16 -0400 MIME-Version: 1.0 In-Reply-To: <20160929184001.yooxkwulqgioak6a@gobelin> References: <1475166715-7857-1-git-send-email-bgolaszewski@baylibre.com> <1475166715-7857-4-git-send-email-bgolaszewski@baylibre.com> <20160929184001.yooxkwulqgioak6a@gobelin> From: Bartosz Golaszewski Date: Fri, 30 Sep 2016 11:42:14 +0200 Message-ID: Subject: Re: [PATCH 3/6] ARM: dts: da850-lcdk: enable the LCD controller To: Karl Beldan Cc: Kevin Hilman , Michael Turquette , Sekhar Nori , Rob Herring , Mark Rutland , Russell King , Karl Beldan , LKML , arm-soc Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2016-09-29 20:40 GMT+02:00 Karl Beldan : > Hi, > > On Thu, Sep 29, 2016 at 06:31:52PM +0200, Bartosz Golaszewski wrote: >> From: Karl Beldan >> >> This adds the pins used by the LCD controller, and uses 'tilcdc,panel' >> with some default timings for 800x600. >> >> Tested on an LCDK connected on the VGA port (the LCDC is connected to >> this port via a THS8135). >> >> Signed-off-by: Karl Beldan >> [Bartosz: >> - fixed whitespace errors >> - tweaked the description > > The description tweak you mention is the removal of an erratum which is > in the mentioned commit I put on github @ > (https://github.com/kbeldan/linux/commit/b7720bc983c00a083dece119f68ea9d2f522c6c4) > it included an erratum wrt FIFO threshold I think is worth keeping: > { > There is an erratum (fifo-th) "LCDC: Underflow During Initialization": > [...] > "This problem may occur if the LCDC FIFO threshold size ( > LCDDMA_CTRL[TH_FIFO_READY]) is left at its default value after reset. > Increasing the FIFO threshold size will reduce or eliminate underflows. > Setting the threshold size to 256 double words or larger is > recommended." > } Isn't this the issue that is fixed by changing the memory priority for lcdc? > >> - fixed the incorrect hback-porch value > > It can't be a fix, this value depends on the monitor connected. > Thanks, I'm new to drm. From reading the datasheet it seemed to me that this depends on the resolution. FWIW it seems that most LCDs are able to adjust to this themselves - I tested with two different displays and the value I introduced worked on both while the previous one shifted the image to the right. I'll look into that. >> - other minor tweaks] > > I didn't see any other change while diffing. > Dropped the refresh rate from the timings node name. Thanks, Bartosz From mboxrd@z Thu Jan 1 00:00:00 1970 From: bgolaszewski@baylibre.com (Bartosz Golaszewski) Date: Fri, 30 Sep 2016 11:42:14 +0200 Subject: [PATCH 3/6] ARM: dts: da850-lcdk: enable the LCD controller In-Reply-To: <20160929184001.yooxkwulqgioak6a@gobelin> References: <1475166715-7857-1-git-send-email-bgolaszewski@baylibre.com> <1475166715-7857-4-git-send-email-bgolaszewski@baylibre.com> <20160929184001.yooxkwulqgioak6a@gobelin> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 2016-09-29 20:40 GMT+02:00 Karl Beldan : > Hi, > > On Thu, Sep 29, 2016 at 06:31:52PM +0200, Bartosz Golaszewski wrote: >> From: Karl Beldan >> >> This adds the pins used by the LCD controller, and uses 'tilcdc,panel' >> with some default timings for 800x600. >> >> Tested on an LCDK connected on the VGA port (the LCDC is connected to >> this port via a THS8135). >> >> Signed-off-by: Karl Beldan >> [Bartosz: >> - fixed whitespace errors >> - tweaked the description > > The description tweak you mention is the removal of an erratum which is > in the mentioned commit I put on github @ > (https://github.com/kbeldan/linux/commit/b7720bc983c00a083dece119f68ea9d2f522c6c4) > it included an erratum wrt FIFO threshold I think is worth keeping: > { > There is an erratum (fifo-th) "LCDC: Underflow During Initialization": > [...] > "This problem may occur if the LCDC FIFO threshold size ( > LCDDMA_CTRL[TH_FIFO_READY]) is left at its default value after reset. > Increasing the FIFO threshold size will reduce or eliminate underflows. > Setting the threshold size to 256 double words or larger is > recommended." > } Isn't this the issue that is fixed by changing the memory priority for lcdc? > >> - fixed the incorrect hback-porch value > > It can't be a fix, this value depends on the monitor connected. > Thanks, I'm new to drm. From reading the datasheet it seemed to me that this depends on the resolution. FWIW it seems that most LCDs are able to adjust to this themselves - I tested with two different displays and the value I introduced worked on both while the previous one shifted the image to the right. I'll look into that. >> - other minor tweaks] > > I didn't see any other change while diffing. > Dropped the refresh rate from the timings node name. Thanks, Bartosz