From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lothar =?UTF-8?B?V2HDn21hbm4=?= Subject: Re: [PATCH 3/9] drm/panel: simple: make it possible to override LCD bus format Date: Tue, 17 Oct 2017 14:44:23 +0200 Message-ID: <20171017144423.4ddd6047@karo-electronics.de> References: <1507721021-28174-1-git-send-email-LW@KARO-electronics.de> <1507721021-28174-4-git-send-email-LW@KARO-electronics.de> <20171017121240.GD684@ulmo> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Return-path: In-Reply-To: <20171017121240.GD684@ulmo> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Thierry Reding Cc: David Airlie , Mark Rutland , Rob Herring , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: devicetree@vger.kernel.org Hi, On Tue, 17 Oct 2017 14:12:40 +0200 Thierry Reding wrote: > On Wed, Oct 11, 2017 at 01:23:35PM +0200, Lothar Waßmann wrote: > > The baseboards for the Ka-Ro electronics series of i.MX modules > > use a 24bit LCD interface, no matter what LCD bus width the SoC on the > > module provides and what the LCD panel expects. LCDs with 6bit per color > > will ignore the 2 LSBs of each color lane, and modules using a SoC > > that provides only 6bit per color, drive the display information on the > > 6 MSBs of each color lane and tie the 2 LSBs of each color lane to GND. > > > > Thus, no matter what combination of LCD and SoC is used, the LCD port > > can be used without shuffling bit lanes by always configuring the LCD > > output to 24bit mode. > > > > Add a function to handle certain quirks of the LCD interface to the > > panel driver to be able to override the bus format specified in a > > panel's display_mode. > > I think the above paragraph clearly indicates that this is the wrong > place to workaround this. You say yourself that the LCD interface has > quirks that need to be handled, so why do you want to force this > handling into the panel driver? > The quirk is in the interfacing of the SoM's LCD output to the LCD panel. Thus it can be handled in either place. > The panel remains the same, no matter what interface you connect it to. > Because that's just ONE place to change, no matter what LCD driver is being used. Lothar Waßmann -- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758085AbdJQMo1 convert rfc822-to-8bit (ORCPT ); Tue, 17 Oct 2017 08:44:27 -0400 Received: from smtprelay06.ispgateway.de ([80.67.31.101]:38136 "EHLO smtprelay06.ispgateway.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754229AbdJQMo0 (ORCPT ); Tue, 17 Oct 2017 08:44:26 -0400 Date: Tue, 17 Oct 2017 14:44:23 +0200 From: Lothar =?UTF-8?B?V2HDn21hbm4=?= To: Thierry Reding Cc: David Airlie , Mark Rutland , Rob Herring , devicetree@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/9] drm/panel: simple: make it possible to override LCD bus format Message-ID: <20171017144423.4ddd6047@karo-electronics.de> In-Reply-To: <20171017121240.GD684@ulmo> References: <1507721021-28174-1-git-send-email-LW@KARO-electronics.de> <1507721021-28174-4-git-send-email-LW@KARO-electronics.de> <20171017121240.GD684@ulmo> Organization: Ka-Ro electronics GmbH MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT X-Df-Sender: bHdAa2Fyby1lbGVjdHJvbmljcy5kZQ== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Tue, 17 Oct 2017 14:12:40 +0200 Thierry Reding wrote: > On Wed, Oct 11, 2017 at 01:23:35PM +0200, Lothar Waßmann wrote: > > The baseboards for the Ka-Ro electronics series of i.MX modules > > use a 24bit LCD interface, no matter what LCD bus width the SoC on the > > module provides and what the LCD panel expects. LCDs with 6bit per color > > will ignore the 2 LSBs of each color lane, and modules using a SoC > > that provides only 6bit per color, drive the display information on the > > 6 MSBs of each color lane and tie the 2 LSBs of each color lane to GND. > > > > Thus, no matter what combination of LCD and SoC is used, the LCD port > > can be used without shuffling bit lanes by always configuring the LCD > > output to 24bit mode. > > > > Add a function to handle certain quirks of the LCD interface to the > > panel driver to be able to override the bus format specified in a > > panel's display_mode. > > I think the above paragraph clearly indicates that this is the wrong > place to workaround this. You say yourself that the LCD interface has > quirks that need to be handled, so why do you want to force this > handling into the panel driver? > The quirk is in the interfacing of the SoM's LCD output to the LCD panel. Thus it can be handled in either place. > The panel remains the same, no matter what interface you connect it to. > Because that's just ONE place to change, no matter what LCD driver is being used. Lothar Waßmann