[PATCH] i2c: lpi2c: Avoid calling clk_get_rate during transfer

21 Nov 2024

From: Alexander Stein alexander.stein@ew.tq-group.com
[ 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@ew.tq-group.com
Reviewed-by: Uwe Kleine-König u.kleine-koenig@pengutronix.de
Reviewed-by: Andi Shyti andi.shyti@kernel.org
Signed-off-by: Andi Shyti andi.shyti@kernel.org
[ Resolve minor conflicts to fix CVE-2024-40965 ]
Signed-off-by: Bin Lan bin.lan.cn@windriver.com
---
 drivers/i2c/busses/i2c-imx-lpi2c.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
index 678b30e90492..5d4f04a3c6d3 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;
@@ -207,9 +208,7 @@ 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;
@@ -590,6 +589,11 @@ static int lpi2c_imx_probe(struct platform_device *pdev)
    if (ret)
    	return ret;
+	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);
-- 
2.43.0



    

Note: The patch differs from the upstream commit:

+Signed-off-by: Bin Lan bin.lan.cn@windriver.com