i2c: imx: fix missing stop condition in single-master mode

JIRA: https://issues.redhat.com/browse/RHEL-116101

commit 768776d
Author: Stefan Eichenberger <stefan.eichenberger@toradex.com>
Date:   Mon Dec 16 16:16:40 2024 +0100

    i2c: imx: fix missing stop condition in single-master mode

    A regression was introduced with the implementation of single-master
    mode, preventing proper stop conditions from being generated. Devices
    that require a valid stop condition, such as EEPROMs, fail to function
    correctly as a result.

    The issue only affects devices with the single-master property enabled.

    This commit resolves the issue by re-enabling I2C bus busy bit (IBB)
    polling for single-master mode when generating a stop condition. The fix
    further ensures that the i2c_imx->stopped flag is cleared at the start
    of each transfer, allowing the stop condition to be correctly generated
    in i2c_imx_stop().

    According to the reference manual (IMX8MMRM, Rev. 2, 09/2019, page
    5270), polling the IBB bit to determine if the bus is free is only
    necessary in multi-master mode. Consequently, the IBB bit is not polled
    for the start condition in single-master mode.

    Fixes: 6692694 ("i2c: imx: do not poll for bus busy in single master mode")
    Signed-off-by: Stefan Eichenberger <stefan.eichenberger@toradex.com>
    Reviewed-by: Frank Li <Frank.Li@nxp.com>
    Reviewed-by: Francesco Dolcini <francesco.dolcini@toradex.com>
    Link: https://lore.kernel.org/r/20241216151829.74056-1-eichest@gmail.com
    Signed-off-by: Andi Shyti <andi.shyti@kernel.org>

Signed-off-by: Jared Kangas <jkangas@redhat.com>

Author: rh-jkangas

drivers/i2c/busses/i2c-imx.c

@@ -532,22 +532,20 @@ static void i2c_imx_dma_free(struct imx_i2c_struct *i2c_imx)
 
 static int i2c_imx_bus_busy(struct imx_i2c_struct *i2c_imx, int for_busy, bool atomic)
 {
+	bool multi_master = i2c_imx->multi_master;
 	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);
 
 		/* check for arbitration lost */
-		if (temp & I2SR_IAL) {
+		if (multi_master && (temp & I2SR_IAL)) {
 			i2c_imx_clear_irq(i2c_imx, I2SR_IAL);
 			return -EAGAIN;
 		}
 
-		if (for_busy && (temp & I2SR_IBB)) {
+		if (for_busy && (!multi_master || (temp & I2SR_IBB))) {
 			i2c_imx->stopped = 0;
 			break;
 		}