From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id CB213C47088 for ; Sat, 3 Dec 2022 10:19:00 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id AB1A210E1D5; Sat, 3 Dec 2022 10:18:59 +0000 (UTC) Received: from gloria.sntech.de (gloria.sntech.de [185.11.138.130]) by gabe.freedesktop.org (Postfix) with ESMTPS id E815810E1D5 for ; Sat, 3 Dec 2022 10:18:57 +0000 (UTC) Received: from ip5b412258.dynamic.kabel-deutschland.de ([91.65.34.88] helo=diego.localnet) by gloria.sntech.de with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1p1PbV-00075A-UP; Sat, 03 Dec 2022 11:18:41 +0100 From: Heiko =?ISO-8859-1?Q?St=FCbner?= To: Chris Morgan , Linus Walleij Subject: Re: [PATCH V4 2/3] drm/panel: Add Samsung AMS495QA01 MIPI-DSI LCD panel Date: Sat, 03 Dec 2022 11:18:41 +0100 Message-ID: <7746700.MhkbZ0Pkbq@diego> In-Reply-To: References: <20221129172912.9576-1-macroalpha82@gmail.com> <20221129172912.9576-3-macroalpha82@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: devicetree@vger.kernel.org, sam@ravnborg.org, Chris Morgan , dri-devel@lists.freedesktop.org, linux-rockchip@lists.infradead.org, robh+dt@kernel.org, thierry.reding@gmail.com, krzysztof.kozlowski+dt@linaro.org, maccraft123mc@gmail.com Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hi Linus, Am Samstag, 3. Dezember 2022, 10:03:42 CET schrieb Linus Walleij: > On Tue, Nov 29, 2022 at 6:29 PM Chris Morgan wrote: > > > From: Chris Morgan > > > > Support Samsung AMS495QA01 panel as found on the Anbernic RG503. Note > > This panel receives video signals via DSI, however it receives > > commands via 3-wire SPI. > > > > Signed-off-by: Chris Morgan > > Signed-off-by: Maya Matuszczyk > > > +config DRM_PANEL_SAMSUNG_AMS495QA01 > > + tristate "Samsung AMS495QA01 DSI panel" > > I am always a bit careful with these "Samsung" panels. Well the > panel is surely Samsungs and usually it has that name, but very often > it is mainly a display controller, made by someone else, then a physical > panel slapped on and then the actual display controller is obscured. > > Typical example: > panel-novatek-nt35560.c handing Samsung ACX424AKP. > > If you know the actual display controller, then the driver should be > renamed after that, but keeping the compatible and DT bindings > as is. The reason being that tomorrow there is an LG panel > using the same display controller and then we don't get duplicate > code. > > It feels like this is a Novatek controller. Just a feeling I have. > Mostly from the way it does brightness using ELVSS and > gamma. But who knows. Though in past projects I've seen the same display-controller used with different panels (and different dsi-init-sequences). In one project the display manufacturer even EOL'ed the first panel and provided a replacement with said same display controller (and a different init) - but the datasheets for the display-controller were for the same chip still. So while in my experience the actual display name from the manufacturer identifies the display + controller combo, I don't really think you can go the other way with the controller name identifying the display+controller combination. But that whole display business is arcane anyway, so this also only stems from past projects and not factual knowledge ;-) . Heiko