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Wed, 29 Jul 2020 16:34:41 -0700 Received: by xsjhyunkubuntu (Postfix, from userid 13638) id F00F62C1BFF; Wed, 29 Jul 2020 16:30:48 -0700 (PDT) From: Hyun Kwon To: Laurent Pinchart , Daniel Vetter , dri-devel@lists.freedesktop.org Subject: [PATCH v2 1/1] drm: xlnx: zynqmp: Use switch - case for link rate downshift Date: Wed, 29 Jul 2020 16:30:45 -0700 Message-Id: <1596065445-4630-1-git-send-email-hyun.kwon@xilinx.com> X-Mailer: git-send-email 2.7.4 X-RCIS-Action: ALLOW X-TM-AS-Product-Ver: IMSS-7.1.0.1224-8.2.0.1013-23620.005 X-TM-AS-User-Approved-Sender: Yes;Yes X-EOPAttributedMessage: 0 X-MS-Office365-Filtering-HT: Tenant X-MS-PublicTrafficType: Email MIME-Version: 1.0 X-MS-Office365-Filtering-Correlation-Id: cee61fdc-930a-4317-5976-08d83417f825 X-MS-TrafficTypeDiagnostic: DM6PR02MB4188: X-Microsoft-Antispam-PRVS: X-Auto-Response-Suppress: DR, RN, NRN, OOF, AutoReply X-MS-Oob-TLC-OOBClassifiers: OLM:6790; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: GLsXeuRuKU8AJqN8TfTtIsDafV9lZ6KFbjH3CWIxKeFVbxXYqiJdC92OXubMfQBFgDhGHvffhnnFrIxpYaOcDFuLq7cTPZGo4uebDwLr8O9XKlUXRp6Xaey4emy/GJyQp4kEG+4OFaKxN1TBn+oR/n3+eZfRH1baKv7ozccHtno8IKH1WBBH9lMq7yuo0v2uYML1W/VTrY/2QarmxsHUMKqZYKU2/JHI9GUfBQP3Cp40vDCIoRVvN49Ael5VMPt9X7CqyhJsPZQvDBf/+RBxS4IEtE7i0wku7Mdtd27djPFEt/9N7Z8tiRO1vE+Qjin2nId4G5QILo8JR4/akiyCGeZMgZmM9nR1gPc3aIOdR4o46CdAB8I5J4022vd3S47lbEXUgLQ/0i9HMdVU2SiIGA== X-Forefront-Antispam-Report: CIP:149.199.60.83; CTRY:US; LANG:en; SCL:1; SRV:; IPV:NLI; SFV:NSPM; H:xsj-pvapsmtpgw01; PTR:unknown-60-83.xilinx.com; CAT:NONE; SFTY:; SFS:(396003)(39860400002)(136003)(376002)(346002)(46966005)(70206006)(70586007)(82740400003)(336012)(426003)(81166007)(107886003)(2616005)(82310400002)(356005)(6266002)(54906003)(8936002)(316002)(110136005)(36756003)(47076004)(26005)(42186006)(5660300002)(186003)(8676002)(44832011)(2906002)(478600001)(6666004)(83380400001)(4326008); DIR:OUT; SFP:1101; X-OriginatorOrg: xilinx.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 29 Jul 2020 23:34:42.4954 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: cee61fdc-930a-4317-5976-08d83417f825 X-MS-Exchange-CrossTenant-Id: 657af505-d5df-48d0-8300-c31994686c5c X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=657af505-d5df-48d0-8300-c31994686c5c; Ip=[149.199.60.83]; Helo=[xsj-pvapsmtpgw01] X-MS-Exchange-CrossTenant-AuthSource: SN1NAM02FT031.eop-nam02.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR02MB4188 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: Hyun Kwon , Dan Carpenter Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Use switch - case to downshift from the current link rate. It's a small loop now, so fine to be replaced with switch - case. With a loop, it is confusing and hard to follow as reported below. The patch d76271d22694: "drm: xlnx: DRM/KMS driver for Xilinx ZynqMP DisplayPort Subsystem" from Jul 7, 2018, leads to the following static checker warning: drivers/gpu/drm/xlnx/zynqmp_dp.c:594 zynqmp_dp_mode_configure() error: iterator underflow 'bws' (-1)-2 Reported-by: Dan Carpenter Signed-off-by: Hyun Kwon Reviewed-by: Laurent Pinchart --- v2 - Convert the for loop into switch - case --- --- drivers/gpu/drm/xlnx/zynqmp_dp.c | 29 ++++++++++++++++------------- 1 file changed, 16 insertions(+), 13 deletions(-) diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c index b735072..5d6adeaa 100644 --- a/drivers/gpu/drm/xlnx/zynqmp_dp.c +++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c @@ -567,34 +567,37 @@ static int zynqmp_dp_mode_configure(struct zynqmp_dp *dp, int pclock, u8 current_bw) { int max_rate = dp->link_config.max_rate; - u8 bws[3] = { DP_LINK_BW_1_62, DP_LINK_BW_2_7, DP_LINK_BW_5_4 }; + u8 bw_code; u8 max_lanes = dp->link_config.max_lanes; u8 max_link_rate_code = drm_dp_link_rate_to_bw_code(max_rate); u8 bpp = dp->config.bpp; u8 lane_cnt; - s8 i; - if (current_bw == DP_LINK_BW_1_62) { + /* Downshift from current one */ + switch (current_bw) { + case DP_LINK_BW_5_4: + bw_code = DP_LINK_BW_2_7; + break; + case DP_LINK_BW_2_7: + bw_code = DP_LINK_BW_1_62; + break; + case DP_LINK_BW_1_62: dev_err(dp->dev, "can't downshift. already lowest link rate\n"); return -EINVAL; - } - - for (i = ARRAY_SIZE(bws) - 1; i >= 0; i--) { - if (current_bw && bws[i] >= current_bw) - continue; - - if (bws[i] <= max_link_rate_code) - break; + default: + /* If not given, start with max supported */ + bw_code = max_link_rate_code; + break; } for (lane_cnt = 1; lane_cnt <= max_lanes; lane_cnt <<= 1) { int bw; u32 rate; - bw = drm_dp_bw_code_to_link_rate(bws[i]); + bw = drm_dp_bw_code_to_link_rate(bw_code); rate = zynqmp_dp_max_rate(bw, lane_cnt, bpp); if (pclock <= rate) { - dp->mode.bw_code = bws[i]; + dp->mode.bw_code = bw_code; dp->mode.lane_cnt = lane_cnt; dp->mode.pclock = pclock; return dp->mode.bw_code;