linux-kernel - [PATCH V2] PCA9541: Use I2C adapter timeout value for arbitration timeout

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Message-ID: <20250731125535.22598-1-manikanta.guntupalli@amd.com>
Date: Thu, 31 Jul 2025 18:25:35 +0530
From: Manikanta Guntupalli <manikanta.guntupalli@....com>
To: <git@....com>, <michal.simek@....com>, <peda@...ntia.se>,
	<linux-i2c@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<wsa+renesas@...g-engineering.com>
CC: <radhey.shyam.pandey@....com>, <srinivas.goud@....com>,
	<shubhrajyoti.datta@....com>, <manion05gk@...il.com>, Manikanta Guntupalli
	<manikanta.guntupalli@....com>
Subject: [PATCH V2] PCA9541: Use I2C adapter timeout value for arbitration timeout

Remove existing arbitration timeout macros and use I2C adapter timeout
value for arbitration timeout and forceful bus ownership.

I2C adapter timeout can be configurable from user space, so using it
for arbitration timeout helps in configuring the arbitration timeout
from user space depending on the use case.

Signed-off-by: Manikanta Guntupalli <manikanta.guntupalli@....com>
---
Changes for V2:
Remove existing arbitration timeout macros and use i2c adapter timeout
value.
Change logging and commit details.
Link for V1: https://lore.kernel.org/all/20250711124503.3390451-1-manikanta.guntupalli@amd.com/
---
 drivers/i2c/muxes/i2c-mux-pca9541.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/muxes/i2c-mux-pca9541.c b/drivers/i2c/muxes/i2c-mux-pca9541.c
index 8663c8a7c269..3d8002caf703 100644
--- a/drivers/i2c/muxes/i2c-mux-pca9541.c
+++ b/drivers/i2c/muxes/i2c-mux-pca9541.c
@@ -63,10 +63,6 @@
 #define mybus(x)	(!((x) & MYBUS) || ((x) & MYBUS) == MYBUS)
 #define busoff(x)	(!((x) & BUSON) || ((x) & BUSON) == BUSON)
 
-/* arbitration timeouts, in jiffies */
-#define ARB_TIMEOUT	(HZ / 8)	/* 125 ms until forcing bus ownership */
-#define ARB2_TIMEOUT	(HZ / 4)	/* 250 ms until acquisition failure */
-
 /* arbitration retry delays, in us */
 #define SELECT_DELAY_SHORT	50
 #define SELECT_DELAY_LONG	1000
@@ -229,6 +225,9 @@ static int pca9541_arbitrate(struct i2c_client *client)
 		 */
 		data->select_timeout = SELECT_DELAY_LONG;
 		if (time_is_before_eq_jiffies(data->arb_timeout)) {
+			dev_warn(&client->dev,
+				 "Arbitration timeout on I2C bus, forcing bus ownership\n");
+
 			/* Time is up, take the bus and reset it. */
 			pca9541_reg_write(client,
 					  PCA9541_CONTROL,
@@ -251,10 +250,10 @@ static int pca9541_select_chan(struct i2c_mux_core *muxc, u32 chan)
 	struct pca9541 *data = i2c_mux_priv(muxc);
 	struct i2c_client *client = data->client;
 	int ret;
-	unsigned long timeout = jiffies + ARB2_TIMEOUT;
+	unsigned long timeout = jiffies + (2 * client->adapter->timeout);
 		/* give up after this time */
 
-	data->arb_timeout = jiffies + ARB_TIMEOUT;
+	data->arb_timeout = jiffies + client->adapter->timeout;
 		/* force bus ownership after this time */
 
 	do {
@@ -267,6 +266,7 @@ static int pca9541_select_chan(struct i2c_mux_core *muxc, u32 chan)
 		else
 			msleep(data->select_timeout / 1000);
 	} while (time_is_after_eq_jiffies(timeout));
+	dev_warn(&client->dev, "Failed to acquire I2C bus, timed out\n");
 
 	return -ETIMEDOUT;
 }
-- 
2.34.1