i2c: lpi2c: Avoid calling clk_get_rate during transfer

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>

diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
index 6d72e4e126dde6ba07770b20b358ba74dbda78b8..36e8f6196a87b1b960eddbe4f37686cb93335e94 100644 (file)
--- 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);