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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4BF92C433EF for ; Fri, 15 Jul 2022 08:53:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234156AbiGOIw6 (ORCPT ); Fri, 15 Jul 2022 04:52:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45128 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233906AbiGOIwn (ORCPT ); Fri, 15 Jul 2022 04:52:43 -0400 Received: from mailgw02.mediatek.com (unknown [210.61.82.184]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 52A7E84EE3; Fri, 15 Jul 2022 01:51:35 -0700 (PDT) X-UUID: d721200affec4765846b864848f39bc9-20220715 X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.1.8,REQID:34ea4b4a-b427-491f-97f1-0940e2b80b57,OB:0,LO B:0,IP:0,URL:0,TC:0,Content:0,EDM:0,RT:0,SF:51,FILE:0,RULE:Release_Ham,ACT ION:release,TS:51 X-CID-INFO: VERSION:1.1.8,REQID:34ea4b4a-b427-491f-97f1-0940e2b80b57,OB:0,LOB: 0,IP:0,URL:0,TC:0,Content:0,EDM:0,RT:0,SF:51,FILE:0,RULE:Release_Ham,ACTIO N:release,TS:51 X-CID-META: VersionHash:0f94e32,CLOUDID:b1b695d7-5d6d-4eaf-a635-828a3ee48b7c,C OID:9a8e9ef91b98,Recheck:0,SF:28|17|19|48,TC:nil,Content:0,EDM:-3,IP:nil,U RL:0,File:nil,QS:nil,BEC:nil,COL:0 X-UUID: d721200affec4765846b864848f39bc9-20220715 Received: from mtkmbs10n1.mediatek.inc [(172.21.101.34)] by mailgw02.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-GCM-SHA384 256/256) with ESMTP id 1312067785; Fri, 15 Jul 2022 16:51:29 +0800 Received: from mtkcas11.mediatek.inc (172.21.101.40) by mtkmbs10n1.mediatek.inc (172.21.101.34) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.2.792.15; Fri, 15 Jul 2022 16:51:27 +0800 Received: from mtksdccf07 (172.21.84.99) by mtkcas11.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Fri, 15 Jul 2022 16:51:27 +0800 Message-ID: <05e7ace27af21d141c1ecd79fb45f6e5e9d32582.camel@mediatek.com> Subject: Re: [PATCH v14 05/10] drm/mediatek: Add MT8195 Embedded DisplayPort driver From: CK Hu To: Bo-Chen Chen , , , , , , , , , , CC: , , , , , , , , , , , , Date: Fri, 15 Jul 2022 16:51:27 +0800 In-Reply-To: <20220712111223.13080-6-rex-bc.chen@mediatek.com> References: <20220712111223.13080-1-rex-bc.chen@mediatek.com> <20220712111223.13080-6-rex-bc.chen@mediatek.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.2 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-MTK: N Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Bo-Chen: On Tue, 2022-07-12 at 19:12 +0800, Bo-Chen Chen wrote: > From: Markus Schneider-Pargmann > > This patch adds a embedded displayport driver for the MediaTek mt8195 > SoC. > > It supports the MT8195, the embedded DisplayPort units. It offers > DisplayPort 1.4 with up to 4 lanes. > > The driver creates a child device for the phy. The child device will > never exist without the parent being active. As they are sharing a > register range, the parent passes a regmap pointer to the child so > that > both can work with the same register range. The phy driver sets > device > data that is read by the parent to get the phy device that can be > used > to control the phy properties. > > This driver is based on an initial version by > Jitao shi > > Signed-off-by: Markus Schneider-Pargmann > Signed-off-by: Guillaume Ranquet > Signed-off-by: Bo-Chen Chen > --- [snip] > +static void mtk_dp_hpd_sink_event(struct mtk_dp *mtk_dp) > +{ > + ssize_t ret; > + u8 sink_count; > + u8 link_status[DP_LINK_STATUS_SIZE] = {}; > + u32 sink_count_reg = DP_SINK_COUNT_ESI; > + u32 link_status_reg = DP_LANE0_1_STATUS; > + > + ret = drm_dp_dpcd_readb(&mtk_dp->aux, sink_count_reg, > &sink_count); According to your last reply, if drm_dp_dpcd_readb() fail, we could skip below statement. So this just for error checking? If so, the next drm_dp_dpcd_read() would also do the error checking, so the checking here is redundant. Regards, CK > + if (ret < 1) { > + drm_err(mtk_dp->drm_dev, "Read sink count failed\n"); > + return; > + } > + > + drm_dbg(mtk_dp->drm_dev, > + "read sink count from dpcd: %d\n", sink_count); > + > + ret = drm_dp_dpcd_read(&mtk_dp->aux, link_status_reg, > link_status, > + sizeof(link_status)); > + if (!ret) { > + drm_err(mtk_dp->drm_dev, "Read link status failed\n"); > + return; > + } > + > + if (!drm_dp_channel_eq_ok(link_status, mtk_dp- > >train_info.lane_count)) { > + drm_err(mtk_dp->drm_dev, "Channel EQ failed\n"); > + return; > + } > + > + if (link_status[1] & DP_REMOTE_CONTROL_COMMAND_PENDING) > + drm_dp_dpcd_writeb(&mtk_dp->aux, > DP_DEVICE_SERVICE_IRQ_VECTOR, > + DP_REMOTE_CONTROL_COMMAND_PENDING); > +} > +