linux-kernel - [PATCH v5] i2c: npcm: Add clock toggle recovery

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Message-Id: <20250527030506.79191-1-mohammed.0.elbadry@gmail.com>
Date: Mon, 26 May 2025 20:05:06 -0700
From: Mohammed Elbadry <mohammed.0.elbadry@...il.com>
To: andi.shyti@...nel.org
Cc: avifishman70@...il.com,
	tmaimon77@...il.com,
	tali.perry1@...il.com,
	venture@...gle.com,
	yuenn@...gle.com,
	benjaminfair@...gle.com,
	openbmc@...ts.ozlabs.org,
	linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
Subject: [PATCH v5] 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>
Reviewed-by: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
---
 drivers/i2c/busses/i2c-npcm7xx.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
index de713b5747fe..4738fc450a6b 100644
--- a/drivers/i2c/busses/i2c-npcm7xx.c
+++ b/drivers/i2c/busses/i2c-npcm7xx.c
@@ -2178,10 +2178,15 @@ 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));
+		ret = npcm_i2c_recovery_tgclk(&bus->adap);
+		if (ret) {
+			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 ret;
+		}
 	}
 
 	npcm_i2c_int_enable(bus, true);
-- 
2.39.5 (Apple Git-154)