linux-kernel - [PATCH v1 1/3] i2c: imx: only poll for bus busy in multi master mode

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Message-ID: <20240715151824.90033-2-eichest@gmail.com>
Date: Mon, 15 Jul 2024 17:17:51 +0200
From: Stefan Eichenberger <eichest@...il.com>
To: o.rempel@...gutronix.de,
	kernel@...gutronix.de,
	andi.shyti@...nel.org,
	shawnguo@...nel.org,
	s.hauer@...gutronix.de,
	festevam@...il.com,
	wsa+renesas@...g-engineering.com,
	francesco.dolcini@...adex.com,
	joao.goncalves@...adex.com
Cc: linux-i2c@...r.kernel.org,
	imx@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Stefan Eichenberger <stefan.eichenberger@...adex.com>
Subject: [PATCH v1 1/3] i2c: imx: only poll for bus busy in multi master mode

From: Stefan Eichenberger <stefan.eichenberger@...adex.com>

According to the reference manual it is only necessary to poll for bus
busy and arbitration lost in multi master mode. This helps to avoid
rescheduling while the i2c bus is busy and avoids SMBus devices to
timeout.

Signed-off-by: Stefan Eichenberger <stefan.eichenberger@...adex.com>
---
 drivers/i2c/busses/i2c-imx.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index 3842e527116b7..1add946e3bc20 100644
--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -216,6 +216,8 @@ struct imx_i2c_struct {
 	struct i2c_client	*slave;
 	enum i2c_slave_event last_slave_event;
 
+	bool			multi_master;
+
 	/* For checking slave events. */
 	spinlock_t     slave_lock;
 	struct hrtimer slave_timer;
@@ -481,6 +483,9 @@ static int i2c_imx_bus_busy(struct imx_i2c_struct *i2c_imx, int for_busy, bool a
 	unsigned long orig_jiffies = jiffies;
 	unsigned int temp;
 
+	if (!i2c_imx->multi_master)
+		return 0;
+
 	while (1) {
 		temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR);
 
@@ -540,8 +545,8 @@ static int i2c_imx_trx_complete(struct imx_i2c_struct *i2c_imx, bool atomic)
 		return -ETIMEDOUT;
 	}
 
-	/* check for arbitration lost */
-	if (i2c_imx->i2csr & I2SR_IAL) {
+	/* In multi-master mode check for arbitration lost */
+	if (i2c_imx->multi_master && (i2c_imx->i2csr & I2SR_IAL)) {
 		dev_dbg(&i2c_imx->adapter.dev, "<%s> Arbitration lost\n", __func__);
 		i2c_imx_clear_irq(i2c_imx, I2SR_IAL);
 
@@ -1468,6 +1473,8 @@ static int i2c_imx_probe(struct platform_device *pdev)
 		goto rpm_disable;
 	}
 
+	i2c_imx->multi_master = of_property_read_bool(pdev->dev.of_node, "multi-master");
+
 	/* Set up clock divider */
 	i2c_imx->bitrate = I2C_MAX_STANDARD_MODE_FREQ;
 	ret = of_property_read_u32(pdev->dev.of_node,
-- 
2.43.0