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Fri, 3 May 2024 04:42:18 -0500 From: Sai Pavan Boddu To: , , CC: Michal Simek , Andi Shyti , Lars-Peter Clausen , Wolfram Sang Subject: [PATCH v2] i2c: cadence: Avoid fifo clear after start Date: Fri, 3 May 2024 15:12:08 +0530 Message-ID: <20240503094208.296834-1-sai.pavan.boddu@amd.com> X-Mailer: git-send-email 2.37.6 Precedence: bulk X-Mailing-List: linux-i2c@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SN1PEPF0002636C:EE_|PH7PR12MB6539:EE_ X-MS-Office365-Filtering-Correlation-Id: d01d14eb-40dd-4a44-baf5-08dc6b5554aa X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230031|36860700004|376005|1800799015; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17; CTRY:US; LANG:en; SCL:1; SRV:; IPV:CAL; SFV:NSPM; H:SATLEXMB03.amd.com; PTR:InfoDomainNonexistent; CAT:NONE; SFS:(13230031)(36860700004)(376005)(1800799015); DIR:OUT; SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 May 2024 09:42:21.6010 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: d01d14eb-40dd-4a44-baf5-08dc6b5554aa X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d; Ip=[165.204.84.17]; Helo=[SATLEXMB03.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SN1PEPF0002636C.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB6539 The Driver unintentionally programs ctrl reg to clear the fifo, which happens after the start of transaction. Previously, this was not an issue as it involved read-modified-write. However, this issue breaks i2c reads on QEMU, as i2c-read is executed before guest starts programming control register. Fixes: ff0cf7bca630 ("i2c: cadence: Remove unnecessary register reads") Signed-off-by: Sai Pavan Boddu Acked-by: Michal Simek --- Changes for V2: Fix commit message. drivers/i2c/busses/i2c-cadence.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c index 4bb7d6756947..2fce3e84ba64 100644 --- a/drivers/i2c/busses/i2c-cadence.c +++ b/drivers/i2c/busses/i2c-cadence.c @@ -633,6 +633,7 @@ static void cdns_i2c_mrecv(struct cdns_i2c *id) if (hold_clear) { ctrl_reg &= ~CDNS_I2C_CR_HOLD; + ctrl_reg &= ~CDNS_I2C_CR_CLR_FIFO; /* * In case of Xilinx Zynq SOC, clear the HOLD bit before transfer size * register reaches '0'. This is an IP bug which causes transfer size