[PATCH v1 01/55] media: v4l2-common: Add a helper for obtaining the clock producer

[Mehdi Djait]

Introduce a helper for v4l2 sensor drivers on both DT- and ACPI-based
platforms to retrieve a reference to the clock producer from firmware.

This helper behaves the same as clk_get_optional() except where there is
no clock producer like in ACPI-based platforms.

For ACPI-based platforms the function will read the "clock-frequency"
ACPI _DSD property and register a fixed frequency clock with the frequency
indicated in the property.

This function also handles the special ACPI-based system case where:
The clock-frequency _DSD property is present.
A reference to the clock producer is present, where the clock is provided
by a camera sensor PMIC driver (e.g. int3472/tps68470.c)
In this case try to set the clock-frequency value to the provided clock.

Signed-off-by: Mehdi Djait <mehdi.djait@xxxxxxxxxxxxxxx>

diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c
index bd160a8c9efe..c53221165c5a 100644
--- a/drivers/media/v4l2-core/v4l2-common.c
+++ b/drivers/media/v4l2-core/v4l2-common.c
@@ -34,6 +34,9 @@
  * Added Gerd Knorrs v4l1 enhancements (Justin Schoeman)
  */
 
+#include <linux/clk.h>
+#include <linux/clkdev.h>
+#include <linux/clk-provider.h>
 #include <linux/module.h>
 #include <linux/types.h>
 #include <linux/kernel.h>
@@ -673,3 +676,49 @@ int v4l2_link_freq_to_bitmap(struct device *dev, const u64 *fw_link_freqs,
 	return 0;
 }
 EXPORT_SYMBOL_GPL(v4l2_link_freq_to_bitmap);
+
+struct clk *devm_v4l2_sensor_clk_get(struct device *dev, const char *id)
+{
+	const char *clk_id __free(kfree) = NULL;
+	struct clk_hw *clk_hw;
+	struct clk *clk;
+	bool acpi_node;
+	u32 rate;
+	int ret;
+
+	clk = devm_clk_get_optional(dev, id);
+	ret = device_property_read_u32(dev, "clock-frequency", &rate);
+	acpi_node = is_acpi_node(dev_fwnode(dev));
+
+	if (clk) {
+		if (!ret && acpi_node) {
+			ret = clk_set_rate(clk, rate);
+			if (ret) {
+				dev_err(dev, "Failed to set clock rate: %u\n",
+					rate);
+				return ERR_PTR(ret);
+			}
+		}
+		return clk;
+	}
+
+	if (ret)
+		return ERR_PTR(ret);
+
+	if (!IS_ENABLED(CONFIG_COMMON_CLK) || !acpi_node)
+		return ERR_PTR(-ENOENT);
+
+	if (!id) {
+		clk_id = kasprintf(GFP_KERNEL, "clk-%s", dev_name(dev));
+		if (!clk_id)
+			return ERR_PTR(-ENOMEM);
+		id = clk_id;
+	}
+
+	clk_hw = devm_clk_hw_register_fixed_rate(dev, id, NULL, 0, rate);
+	if (IS_ERR(clk_hw))
+		return ERR_CAST(clk_hw);
+
+	return clk_hw->clk;
+}
+EXPORT_SYMBOL_GPL(devm_v4l2_sensor_clk_get);
diff --git a/include/media/v4l2-common.h b/include/media/v4l2-common.h
index 0a43f56578bc..72d8fcc6057f 100644
--- a/include/media/v4l2-common.h
+++ b/include/media/v4l2-common.h
@@ -620,6 +620,31 @@ int v4l2_link_freq_to_bitmap(struct device *dev, const u64 *fw_link_freqs,
 			     unsigned int num_of_driver_link_freqs,
 			     unsigned long *bitmap);
 
+/**
+ * devm_v4l2_sensor_clk_get - lookup and obtain a reference to an optional clock
+ *			      producer for a camera sensor.
+ *
+ * @dev: device for v4l2 sensor clock "consumer"
+ * @id: clock consumer ID
+ *
+ * This function behaves the same way as clk_get_optional() except where there
+ * is no clock producer like in ACPI-based platforms.
+ *
+ * For ACPI-based platforms, the function will read the "clock-frequency"
+ * ACPI _DSD property and register a fixed-clock with the frequency indicated
+ * in the property.
+ *
+ * This function also handles the special ACPI-based system case where:
+ * The clock-frequency _DSD property is present.
+ * A reference to the clock producer is present, where the clock is provided by
+ * a camera sensor PMIC driver (e.g. int3472/tps68470.c)
+ * In this case try to set the clock-frequency value to the provided clock.
+ *
+ * Return:
+ * * pointer to a struct clk on success or an error code on failure.
+ */
+struct clk *devm_v4l2_sensor_clk_get(struct device *dev, const char *id);
+
 static inline u64 v4l2_buffer_get_timestamp(const struct v4l2_buffer *buf)
 {
 	/*