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Tue, 15 Sep 2026 23:19:00 -0700 From: Wayne Chang To: Heikki Krogerus , Greg Kroah-Hartman , Jon Hunter , "Thierry Reding" CC: , , , Wayne Chang , Subject: [PATCH v2] usb: typec: ucsi_ccg: Add retry mechanism in ccg_read Date: Wed, 16 Sep 2026 14:18:58 +0800 Message-ID: <20260916061858.1471606-1-waynec@nvidia.com> X-Mailer: git-send-email 2.25.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-NVConfidentiality: public Content-Transfer-Encoding: 8bit Content-Type: text/plain X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN3PEPF00022BC6:EE_|CH1PPFE5ACC0FD2:EE_ X-MS-Office365-Filtering-Correlation-Id: 5d6fbe48-c47c-4d24-b775-08df13ba7450 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700016|1800799024|82310400026|376014|23010399003|18002099003|10067099003|56012099006|11063799006; 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In these cases, i2c_transfer() returns -EREMOTEIO. The CCG4 is EOL, and Infineon no longer supports firmware updates, so a software workaround is necessary. Attempt the read up to CCG_READ_MAX_RETRIES (4) times in total when -EREMOTEIO is returned, sleeping ~1 ms via fsleep() between attempts. This allows recovery from transient I2C failures without affecting other error paths. The sleep is safe because ccg_read() is called both from process context and from ccg_irq_handler(), which runs in threaded IRQ context (registered via request_threaded_irq() with a NULL hard-IRQ handler), so sleeping is allowed in both cases. Fixes: 247c554a14aa ("usb: typec: ucsi: add support for Cypress CCGx") Cc: stable@vger.kernel.org Signed-off-by: Wayne Chang --- v1 -> v2: Per Heikki's review: - Fix off-by-one: CCG_READ_MAX_RETRIES was 3 but the loop ran 4 times (retry_count <= CCG_READ_MAX_RETRIES). Changed the macro to 4 (the actual total attempt count) and the loop condition to retry_count < CCG_READ_MAX_RETRIES, so the name and the loop bound now agree. Adjusted the "skip the sleep on the last attempt" check to retry_count == CCG_READ_MAX_RETRIES - 1 to match. - Use fsleep(1000) instead of usleep_range(1000, 2000). - Reworded the commit message to say "up to CCG_READ_MAX_RETRIES (4) times in total" instead of the ambiguous "up to three times (four attempts total)" that prompted the off-by-one question. drivers/usb/typec/ucsi/ucsi_ccg.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/drivers/usb/typec/ucsi/ucsi_ccg.c b/drivers/usb/typec/ucsi/ucsi_ccg.c index 91c2958a708c..4b6c53d2a998 100644 --- a/drivers/usb/typec/ucsi/ucsi_ccg.c +++ b/drivers/usb/typec/ucsi/ucsi_ccg.c @@ -135,6 +135,8 @@ struct version_format { #define NVIDIA_FTB_DP_OFFSET (2) #define NVIDIA_FTB_DBG_OFFSET (3) +#define CCG_READ_MAX_RETRIES 4 + struct version_info { struct version_format base; struct version_format app; @@ -255,6 +257,7 @@ static int ccg_read(struct ucsi_ccg *uc, u16 rab, u8 *data, u32 len) }; u32 rlen, rem_len = len, max_read_len = len; int status; + int retry_count; /* check any max_read_len limitation on i2c adapter */ if (quirks && quirks->max_read_len) @@ -266,7 +269,17 @@ static int ccg_read(struct ucsi_ccg *uc, u16 rab, u8 *data, u32 len) rlen = min_t(u16, rem_len, max_read_len); msgs[1].len = rlen; put_unaligned_le16(rab, buf); - status = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs)); + + for (retry_count = 0; retry_count < CCG_READ_MAX_RETRIES; retry_count++) { + status = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs)); + + /* Only retry on -EREMOTEIO, and not after the last attempt */ + if (status != -EREMOTEIO || retry_count == CCG_READ_MAX_RETRIES - 1) + break; + + fsleep(1000); + } + if (status < 0) { dev_err(uc->dev, "i2c_transfer failed %d\n", status); pm_runtime_put_sync(uc->dev); base-commit: 940de590b839f71d6dc846160534bf202401b8b7 -- 2.25.1