[PATCH v4 15/20] fdt: Add function to return peripheral/clock ID

[Simon Glass]

A common requirement is to find the clock ID for a peripheral. This is the
second cell of the 'clocks' property (the first being the phandle itself).

Signed-off-by: Simon Glass <sjg at chromium.org>
---
Changes in v4:
- Add fdtdec function to return peripheral ID

 include/fdtdec.h |   13 +++++++++++++
 lib/fdtdec.c     |   13 +++++++++++++
 2 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/include/fdtdec.h b/include/fdtdec.h
index 6c0a2d1..f3115a6 100644
--- a/include/fdtdec.h
+++ b/include/fdtdec.h
@@ -272,3 +272,16 @@ int fdtdec_decode_gpio(const void *blob, int node, const char *prop_name,
  * @return 0 if all ok or gpio was FDT_GPIO_NONE; -1 on error
  */
 int fdtdec_setup_gpio(struct fdt_gpio_state *gpio);
+
+/**
+ * Decode a peripheral ID from a device tree node. This may be a temporary
+ * function depending on what happens with clocks in the Linux fdt.
+ *
+ * This works by looking up the peripheral's 'clocks' node and reading out
+ * the second cell, which is the clock number / peripheral ID.
+ *
+ * @param blob		FDT blob to use
+ * @param node		Node to look at
+ * @return
+ */
+int fdtdec_decode_periph_id(const void *blob, int node);
diff --git a/lib/fdtdec.c b/lib/fdtdec.c
index f0b2196..780948c 100644
--- a/lib/fdtdec.c
+++ b/lib/fdtdec.c
@@ -414,3 +414,16 @@ int fdtdec_setup_gpio(struct fdt_gpio_state *gpio)
 		return -1;
 	return 0;
 }
+
+int fdtdec_decode_periph_id(const void *blob, int node)
+{
+	u32 cell[2];
+	int err;
+
+	err = fdtdec_get_int_array(blob, node, "clocks", cell,
+				   ARRAY_SIZE(cell));
+	if (err)
+		return -1;
+
+	return cell[1];
+}
-- 
1.7.7.3