From 61e6fe59ede155881a622f5901551b1cc8748f6a Mon Sep 17 00:00:00 2001
From: Christian Eggers <ceggers@arri.de>
Date: Fri, 9 Oct 2020 13:03:20 +0200
Subject: [PATCH] i2c: imx: Don't generate STOP condition if arbitration has been lost
Git-commit: 61e6fe59ede155881a622f5901551b1cc8748f6a
Patch-mainline: v5.10-rc7
References: git-fixes

If arbitration is lost, the master automatically changes to slave mode.
I2SR_IBB may or may not be reset by hardware. Raising a STOP condition
by resetting I2CR_MSTA has no effect and will not clear I2SR_IBB.

So calling i2c_imx_bus_busy() is not required and would busy-wait until
timeout.

Signed-off-by: Christian Eggers <ceggers@arri.de>
Tested (not extensively) on Vybrid VF500 (Toradex VF50):

Tested-by: Krzysztof Kozlowski <krzk@kernel.org>
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Cc: stable@vger.kernel.org # Requires trivial backporting, simple remove                           # the 3rd argument from the calls to                           # i2c_imx_bus_busy().
Signed-off-by: Wolfram Sang <wsa@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/i2c/busses/i2c-imx.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index a2abae124342..e6f8d6e45a15 100644
--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -615,6 +615,8 @@ static void i2c_imx_stop(struct imx_i2c_struct *i2c_imx, bool atomic)
 		/* Stop I2C transaction */
 		dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);
 		temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+		if (!(temp & I2CR_MSTA))
+			i2c_imx->stopped = 1;
 		temp &= ~(I2CR_MSTA | I2CR_MTX);
 		if (i2c_imx->dma)
 			temp &= ~I2CR_DMAEN;
@@ -778,9 +780,12 @@ static int i2c_imx_dma_read(struct imx_i2c_struct *i2c_imx,
 		 */
 		dev_dbg(dev, "<%s> clear MSTA\n", __func__);
 		temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+		if (!(temp & I2CR_MSTA))
+			i2c_imx->stopped = 1;
 		temp &= ~(I2CR_MSTA | I2CR_MTX);
 		imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
-		i2c_imx_bus_busy(i2c_imx, 0, false);
+		if (!i2c_imx->stopped)
+			i2c_imx_bus_busy(i2c_imx, 0, false);
 	} else {
 		/*
 		 * For i2c master receiver repeat restart operation like:
@@ -905,9 +910,12 @@ static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs,
 				dev_dbg(&i2c_imx->adapter.dev,
 					"<%s> clear MSTA\n", __func__);
 				temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+				if (!(temp & I2CR_MSTA))
+					i2c_imx->stopped =  1;
 				temp &= ~(I2CR_MSTA | I2CR_MTX);
 				imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
-				i2c_imx_bus_busy(i2c_imx, 0, atomic);
+				if (!i2c_imx->stopped)
+					i2c_imx_bus_busy(i2c_imx, 0, atomic);
 			} else {
 				/*
 				 * For i2c master receiver repeat restart operation like:
-- 
2.26.2