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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE81BC43603 for ; Sun, 15 Dec 2019 09:13:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7AFDE206DA for ; Sun, 15 Dec 2019 09:13:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726061AbfLOJNg (ORCPT ); Sun, 15 Dec 2019 04:13:36 -0500 Received: from gloria.sntech.de ([185.11.138.130]:46496 "EHLO gloria.sntech.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726049AbfLOJNf (ORCPT ); Sun, 15 Dec 2019 04:13:35 -0500 Received: from ip5f5a5f74.dynamic.kabel-deutschland.de ([95.90.95.116] helo=phil.localnet) by gloria.sntech.de with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1igPxy-0001xP-1M; Sun, 15 Dec 2019 10:13:30 +0100 From: Heiko Stuebner To: Sam Ravnborg Cc: thierry.reding@gmail.com, mark.rutland@arm.com, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, robh+dt@kernel.org, christoph.muellner@theobroma-systems.com Subject: Re: [PATCH 3/3] drm/panel: add panel driver for Xinpeng XPP055C272 panels Date: Sun, 15 Dec 2019 10:13:29 +0100 Message-ID: <1744285.zQlJhejOUX@phil> In-Reply-To: <20191215082916.GA25772@ravnborg.org> References: <20191209144208.4863-1-heiko@sntech.de> <2272108.TFxdGdtKl4@diego> <20191215082916.GA25772@ravnborg.org> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Hi Sam, Am Sonntag, 15. Dezember 2019, 09:29:16 CET schrieb Sam Ravnborg: > Hi Heiko. > > > Am Samstag, 14. Dezember 2019, 09:17:30 CET schrieb Sam Ravnborg: > > > > +#define dsi_generic_write_seq(dsi, cmd, seq...) do { \ > > > > + static const u8 d[] = { seq }; \ > > > > + int ret; \ > > > > + ret = mipi_dsi_dcs_write(dsi, cmd, d, ARRAY_SIZE(d)); \ > > > > + if (ret < 0) \ > > > > + return ret; \ > > > > + } while (0) > > > This macro return an error code if a write fails. > > > > > > > + > > > > +static int xpp055c272_init_sequence(struct xpp055c272 *ctx) > > > > +{ > > > > + struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev); > > > > + struct device *dev = ctx->dev; > > > > + int ret; > > > > + > > > > + /* > > > > + * Init sequence was supplied by the panel vendor without much > > > > + * documentation. > > > > + */ > > > > + dsi_generic_write_seq(dsi, XPP055C272_CMD_SETEXTC, 0xf1, 0x12, 0x83); > > > But all uses of the macro here ignore the error. > > > > hmm, am I way off track here? > > > > dsi_generic_write_seq(dsi, XPP055C272_CMD_SETEXTC, 0xf1, 0x12, 0x83); > > dsi_generic_write_seq(dsi, XPP055C272_CMD_SETMIPI, > > 0x33, 0x81, 0x05, 0xf9, 0x0e, 0x0e, 0x00, 0x00, > > 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x44, 0x25, > > 0x00, 0x91, 0x0a, 0x00, 0x00, 0x02, 0x4f, 0x01, > > 0x00, 0x00, 0x37); > > ... > > > > should just expand to > > > > do { > > static const u8 d[] = { 0xf1, 0x12, 0x83 }; > > int ret; > > ret = mipi_dsi_dcs_write(dsi, XPP055C272_CMD_SETEXTC, d, ARRAY_SIZE(d)); > > if (ret < 0) > > return ret; > > } while (0) > > do { > > static const u8 d[] = { 0x33, 0x81, 0x05, 0xf9, 0x0e, 0x0e, 0x00, 0x00, > > 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x44, 0x25, > > 0x00, 0x91, 0x0a, 0x00, 0x00, 0x02, 0x4f, 0x01, > > 0x00, 0x00, 0x37 }; > > int ret; > > ret = mipi_dsi_dcs_write(dsi, XPP055C272_CMD_SETMIPI, d, ARRAY_SIZE(d)); > > if (ret < 0) > > return ret; > > } while (0) > > ... > > > > so every write instance will actually return an error if it happens and not > > continue on with the next init item. > The idea was that if a write returned an error then do not even attempt > more writes. So if a write fails we do not loose the original error > code, assuming subsequent write would also fail. Shouldn't the code above do exactly that? ... Because it's like ret = dcs_write(...) if (ret <0) return ret; So if any of the dcs_writes goes wrong it should just return the error code from that write from the function and not try any more writes. (or I'm blind and do not see something ;-) ) Heiko > I have looked through all the panel drivers now, and the majority does > not check if the write goes wrong. > So following the pattern on the other panels you can also decide to just > ignore the return value of mipi_dsi_dcs_write() rahter than trying to > invent the check I tried to explain. > > Sam >