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> --- This is an alternative, lightweight approach replacing the patch [1] and depends on [2]. The issue to address is still removing the call to clk_get_rate() during each transfer, which might reuslt in a deadlock. lockdep also complains about this call chain. Instead of adding a clock notifier, lock the peripheral clock rate and cache the peripheral clock rate. Currently LPI2C is available in the following SoC: * i.MX7ULP * i.MX8ULP * i.MX8DXL * i.MX8X * i.MX8 * i.MX93 Additionally I expect both i.MX91 and i.MX95 to also use this driver. This patch assumes the parent clock rate never changes. This is apparently true for i.MX93 as each I2C has it's own lpi2c*_root clock. On i.MX8 and i.MX8X clocks are managed by SCU with it's own dedicated firmware. I can't say if the clock never changes though. I have no idea about the other SoC. Best regards, Alexander [1] https://lore.kernel.org/all/20240110120556.519800-1-alexander.stein@xxxxxxxxxxxxxxx/ [2] https://lore.kernel.org/all/20240104225512.1124519-2-u.kleine-koenig@xxxxxxxxxxxxxx/ drivers/i2c/busses/i2c-imx-lpi2c.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c index 678b30e90492a..6cbcb27a3b280 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; @@ -207,7 +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); + clk_rate = lpi2c_imx->rate_per; if (!clk_rate) return -EINVAL; @@ -590,6 +591,20 @@ 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); -- 2.34.1
