[media] smiapp: Verify clock frequency after setting it, prevent changing it

The external clock frequency was set by the driver but the obtained
frequency was never verified. Do that.

Being able to obtain the exact frequency is important as the value is used
for PLL calculations which may result in frequencies that violate the PLL
tree limits.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/i2c/smiapp/smiapp-core.c

@@ -2870,6 +2870,7 @@ static int smiapp_probe(struct i2c_client *client,
 {
 	struct smiapp_sensor *sensor;
 	struct smiapp_hwconfig *hwcfg = smiapp_get_hwconfig(&client->dev);
+	unsigned long rate;
 	unsigned int i;
 	int rval;
 
@@ -2908,6 +2909,14 @@ static int smiapp_probe(struct i2c_client *client,
 		return rval;
 	}
 
+	rate = clk_get_rate(sensor->ext_clk);
+	if (rate != sensor->hwcfg->ext_clk) {
+		dev_err(&client->dev,
+			"can't set clock freq, asked for %u but got %lu\n",
+			sensor->hwcfg->ext_clk, rate);
+		return rval;
+	}
+
 	sensor->xshutdown = devm_gpiod_get_optional(&client->dev, "xshutdown",
 						    GPIOD_OUT_LOW);
 	if (IS_ERR(sensor->xshutdown))