Patch "i2c: lpi2c: Avoid calling clk_get_rate during transfer" has been added to the 6.9-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    i2c: lpi2c: Avoid calling clk_get_rate during transfer

to the 6.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     i2c-lpi2c-avoid-calling-clk_get_rate-during-transfer.patch
and it can be found in the queue-6.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 865235dcddaa1b2049681a69a8015e5a9629b46b
Author: Alexander Stein <alexander.stein@xxxxxxxxxxxxxxx>
Date:   Mon Apr 22 13:36:29 2024 +0200

    i2c: lpi2c: Avoid calling clk_get_rate during transfer
    
    [ Upstream commit 4268254a39484fc11ba991ae148bacbe75d9cc0a ]
    
    Instead of repeatedly calling clk_get_rate for each transfer, lock
    the clock rate and cache the value.
    A deadlock has been observed while adding tlv320aic32x4 audio codec to
    the system. When this clock provider adds its clock, the clk mutex is
    locked already, it needs to access i2c, which in return needs the mutex
    for clk_get_rate as well.
    
    Signed-off-by: Alexander Stein <alexander.stein@xxxxxxxxxxxxxxx>
    Reviewed-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
    Reviewed-by: Andi Shyti <andi.shyti@xxxxxxxxxx>
    Signed-off-by: Andi Shyti <andi.shyti@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
index 6d72e4e126dde..36e8f6196a87b 100644
--- a/drivers/i2c/busses/i2c-imx-lpi2c.c
+++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
@@ -99,6 +99,7 @@ struct lpi2c_imx_struct {
 	__u8			*rx_buf;
 	__u8			*tx_buf;
 	struct completion	complete;
+	unsigned long		rate_per;
 	unsigned int		msglen;
 	unsigned int		delivered;
 	unsigned int		block_data;
@@ -212,9 +213,7 @@ static int lpi2c_imx_config(struct lpi2c_imx_struct *lpi2c_imx)
 
 	lpi2c_imx_set_mode(lpi2c_imx);
 
-	clk_rate = clk_get_rate(lpi2c_imx->clks[0].clk);
-	if (!clk_rate)
-		return -EINVAL;
+	clk_rate = lpi2c_imx->rate_per;
 
 	if (lpi2c_imx->mode == HS || lpi2c_imx->mode == ULTRA_FAST)
 		filt = 0;
@@ -611,6 +610,20 @@ static int lpi2c_imx_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	/*
+	 * Lock the parent clock rate to avoid getting parent clock upon
+	 * each transfer
+	 */
+	ret = devm_clk_rate_exclusive_get(&pdev->dev, lpi2c_imx->clks[0].clk);
+	if (ret)
+		return dev_err_probe(&pdev->dev, ret,
+				     "can't lock I2C peripheral clock rate\n");
+
+	lpi2c_imx->rate_per = clk_get_rate(lpi2c_imx->clks[0].clk);
+	if (!lpi2c_imx->rate_per)
+		return dev_err_probe(&pdev->dev, -EINVAL,
+				     "can't get I2C peripheral clock rate\n");
+
 	pm_runtime_set_autosuspend_delay(&pdev->dev, I2C_PM_TIMEOUT);
 	pm_runtime_use_autosuspend(&pdev->dev);
 	pm_runtime_get_noresume(&pdev->dev);