linux-kernel - [PATCH v4] i2c: npcm: Add clock toggle recovery

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Message-ID: <20250328193252.1570811-1-mohammed.0.elbadry@gmail.com>
Date: Fri, 28 Mar 2025 19:32:50 +0000
From: mohammed.0.elbadry@...il.com
To: 
Cc: Tali Perry <tali.perry1@...il.com>,
	Mohammed Elbadry <mohammed.0.elbadry@...il.com>,
	Avi Fishman <avifishman70@...il.com>,
	Tomer Maimon <tmaimon77@...il.com>,
	Patrick Venture <venture@...gle.com>,
	Nancy Yuen <yuenn@...gle.com>,
	Benjamin Fair <benjaminfair@...gle.com>,
	Andi Shyti <andi.shyti@...nel.org>,
	openbmc@...ts.ozlabs.org,
	linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v4] i2c: npcm: Add clock toggle recovery

From: Tali Perry <tali.perry1@...il.com>

During init of the bus, the module checks that the bus is idle.
If one of the lines are stuck try to recover them first before failing.
Sometimes SDA and SCL are low if improper reset occurs (e.g., reboot).

Signed-off-by: Tali Perry <tali.perry1@...il.com>
Signed-off-by: Mohammed Elbadry <mohammed.0.elbadry@...il.com>
---
 drivers/i2c/busses/i2c-npcm7xx.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
index 2fe68615942e..caf9aa1e6319 100644
--- a/drivers/i2c/busses/i2c-npcm7xx.c
+++ b/drivers/i2c/busses/i2c-npcm7xx.c
@@ -1967,10 +1967,14 @@ static int npcm_i2c_init_module(struct npcm_i2c *bus, enum i2c_mode mode,
 
 	/* Check HW is OK: SDA and SCL should be high at this point. */
 	if ((npcm_i2c_get_SDA(&bus->adap) == 0) || (npcm_i2c_get_SCL(&bus->adap) == 0)) {
-		dev_err(bus->dev, "I2C%d init fail: lines are low\n", bus->num);
-		dev_err(bus->dev, "SDA=%d SCL=%d\n", npcm_i2c_get_SDA(&bus->adap),
-			npcm_i2c_get_SCL(&bus->adap));
-		return -ENXIO;
+		dev_warn(bus->dev, " I2C%d SDA=%d SCL=%d, attempting to recover\n", bus->num,
+				 npcm_i2c_get_SDA(&bus->adap), npcm_i2c_get_SCL(&bus->adap));
+		if (npcm_i2c_recovery_tgclk(&bus->adap)) {
+			dev_err(bus->dev, "I2C%d init fail: SDA=%d SCL=%d\n",
+				bus->num, npcm_i2c_get_SDA(&bus->adap),
+				npcm_i2c_get_SCL(&bus->adap));
+			return -ENXIO;
+		}
 	}
 
 	npcm_i2c_int_enable(bus, true);
-- 
2.49.0.472.ge94155a9ec-goog