linux-kernel - [PATCH v2] i2c: algo-pca: Add 0x78 as SCL stuck low status

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Message-Id: <20200701223912.30864-1-chris.packham@alliedtelesis.co.nz>
Date:   Thu,  2 Jul 2020 10:39:11 +1200
From:   Chris Packham <chris.packham@...iedtelesis.co.nz>
To:     wsa@...nel.org, andriy.shevchenko@...ux.intel.com
Cc:     Mark Tomlinson <mark.tomlinson@...iedtelesis.co.nz>,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chris Packham <chris.packham@...iedtelesis.co.nz>
Subject: [PATCH v2] i2c: algo-pca: Add 0x78 as SCL stuck low status

The PCA9665 datasheet says that I2CSTA = 78h indicates that SCL is stuck
low, this differs to the PCA9564 which uses 90h for this indication.
Treat either 0x78 or 0x90 as an indication that the SCL line is stuck.

Based on looking through the PCA9564 and PCA9665 datasheets this should
be safe for both chips. The PCA9564 should not return 0x78 for any valid
state and the PCA9665 should not return 0x90.

Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
---
Changes in v2:
- Note which status corresponds to which chip
- Move patch commentary to commit message

 drivers/i2c/algos/i2c-algo-pca.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/algos/i2c-algo-pca.c b/drivers/i2c/algos/i2c-algo-pca.c
index 7f10312d1b88..388978775be0 100644
--- a/drivers/i2c/algos/i2c-algo-pca.c
+++ b/drivers/i2c/algos/i2c-algo-pca.c
@@ -314,7 +314,8 @@ static int pca_xfer(struct i2c_adapter *i2c_adap,
 			DEB2("BUS ERROR - SDA Stuck low\n");
 			pca_reset(adap);
 			goto out;
-		case 0x90: /* Bus error - SCL stuck low */
+		case 0x78: /* Bus error - SCL stuck low (PCA9665) */
+		case 0x90: /* Bus error - SCL stuck low (PCA9564) */
 			DEB2("BUS ERROR - SCL Stuck low\n");
 			pca_reset(adap);
 			goto out;
-- 
2.27.0