[PATCH 3/3] i2c: qcom-cci: Fix CCI clock rate enforcement

[Loic Poulain]

The hw_params timing values (thigh, tlow, etc.) are in CCI clock ticks
and were calibrated for a specific clock rate per hardware variant. If
the clock is running at a different rate the I2C timings will be wrong,
potentially violating the I2C specification.

Rather than just warning about a mismatch, actively set the clock to the
expected rate at probe time. Warn if the rate could not be applied so the
user is informed that timings may be incorrect.

Signed-off-by: Loic Poulain <loic.poulain@xxxxxxxxxxxxxxxx>
---
 drivers/i2c/busses/i2c-qcom-cci.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/i2c/busses/i2c-qcom-cci.c b/drivers/i2c/busses/i2c-qcom-cci.c
index 5f74edde8558382e63e2c3d0fbe19489f325e8ce..e001c0d565cebd386fd67b1d9d532360b29c67d0 100644
--- a/drivers/i2c/busses/i2c-qcom-cci.c
+++ b/drivers/i2c/busses/i2c-qcom-cci.c
@@ -519,6 +519,7 @@ static int cci_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct device_node *child;
 	struct resource *r;
+	struct clk *cci_clk;
 	struct cci *cci;
 	int ret, i;
 	u32 val;
@@ -587,6 +588,15 @@ static int cci_probe(struct platform_device *pdev)
 		return dev_err_probe(dev, -EINVAL, "not enough clocks in DT\n");
 	cci->nclocks = ret;
 
+	cci_clk = devm_clk_get(dev, "cci");
+	if (IS_ERR(cci_clk))
+		return dev_err_probe(dev, PTR_ERR(cci_clk), "failed to get CCI clock\n");
+
+	clk_set_rate(cci_clk, cci->data->cci_clk_rate);
+	if (clk_get_rate(cci_clk) != cci->data->cci_clk_rate)
+		dev_warn(dev, "CCI clock is not at expected %lu Hz\n",
+			 cci->data->cci_clk_rate);
+
 	ret = cci_enable_clocks(cci);
 	if (ret < 0)
 		return ret;

-- 
2.34.1