Multi Function Devices (MFDs) have multiple sub module whose driver is
developed in different sub-system like GPIO, regulators, RTC, clock etc.
The device tree of such device contains multiple sub-node which contains
the properties of these sub-modules.
The sub module gets of_node handle either by the dev->of_node or by getting
the child node handle from parent DT handle by finding child name on parent's
of_node.
To provide the of_node of sub-module directly, currently there is only one
approach:
- Add compatible value when defining the sub-module in mfd core and
add this properties when adding DT.
Introduce the of_node_name of each sub devices which is set when defining
the mfd_cells of the sub devices and get the handle of these child node
when adding the mfd_devices by getting the sub-node handle with matching
the node name getting the sub-node handle with matching the node name.
Signed-off-by: Laxman Dewangan <ldewangan@xxxxxxxxxx>
---
Creating this patch based on the discussion on patch
[PATCH 1/4] mfd: add support for AMS AS3722 PMIC
The discussion on above patch is not concluded and want to have
further discussion on this patch.
Documentation/devicetree/bindings/mfd/mfd-core.txt | 57 ++++++++++++++++++++
drivers/mfd/mfd-core.c | 10 +++-
include/linux/mfd/core.h | 6 ++
3 files changed, 71 insertions(+), 2 deletions(-)
create mode 100644 Documentation/devicetree/bindings/mfd/mfd-core.txt
diff --git a/Documentation/devicetree/bindings/mfd/mfd-core.txt b/Documentation/devicetree/bindings/mfd/mfd-core.txt
new file mode 100644
index 0000000..d68c893
--- /dev/null
+++ b/Documentation/devicetree/bindings/mfd/mfd-core.txt
@@ -0,0 +1,57 @@
+MFD DT binding document
+-----------------------
+
+Multi Function Devices (MFDs) have multiple sub module whose driver is developed
+in different sub-system like GPIO, regulators, RTC, clock etc. The device
+tree of such device contains multiple sub-node which contains the properties
+of these sub-modules.
+The sub modules get of_node handle either by the dev->of_node or by getting
+the child node handle from parent DT handle by finding child name on parent's
+of_node.
+To provide the of_node of sub-module directly, there is two approach:
+- Add compatible value when defining the sub-module in mfd core and
+ add this properties when adding DT.
+- Add the of_node_name when defining the sub-module in mfd core and
+ add keep same name of child node when adding DT.
+
+If none of above matches then sub-module driver will not get their of_node
+and they need to derive the method to get their node from parent node.
+
+Examples:
+DT file:
+--------
+ mfd_device_dt {
+ ....
+ gpio_child {
+ /* Properties which need by gpio sub module */
+ };
+
+ rtc_child {
+ /* Properties which need by rtc sub module */
+ };
+
+ regulator_child {
+ /* Properties which need by regulator sub module */
+ };
+ };
+
+
+Driver code:
+-----------
+static struct mfd_cell mfd_abc_devs[] = {
+ {
+ .name = "mfd-abc-gpio",
+ .of_node_name = "gpio_child";
+ },
+ {
+ .name = "mfd-abc-regulator",
+ .of_node_name = "regulator_child";
+ },
+ {
+ .name = "mfd-abc-rtc",
+ .of_node_name = "rtc_child";
+ },
+};
+
+Here sub-node names are gpio_child, rtc_child, regulator_child and it is same
+as of_node_name defined in the driver.
diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c
index f421586..88836c2 100644
--- a/drivers/mfd/mfd-core.c
+++ b/drivers/mfd/mfd-core.c
@@ -99,9 +99,15 @@ static int mfd_add_device(struct device *parent, int id,
pdev->dev.dma_mask = parent->dma_mask;
pdev->dev.dma_parms = parent->dma_parms;
- if (parent->of_node && cell->of_compatible) {
+ if (parent->of_node && (cell->of_compatible || cell->of_node_name)) {
for_each_child_of_node(parent->of_node, np) {
- if (of_device_is_compatible(np, cell->of_compatible)) {
+ if (cell->of_compatible &&
+ of_device_is_compatible(np, cell->of_compatible)) {
+ pdev->dev.of_node = np;
+ break;
+ }
+ if (cell->of_node_name && np->name &&
+ !strcmp(cell->of_node_name, np->name)) {
pdev->dev.of_node = np;
break;
}
diff --git a/include/linux/mfd/core.h b/include/linux/mfd/core.h
index cebe97e..4cf891f 100644
--- a/include/linux/mfd/core.h
+++ b/include/linux/mfd/core.h
@@ -45,6 +45,12 @@ struct mfd_cell {
const char *of_compatible;
/*
+ * Device tree sub-node name.
+ * See: Documentation/devicetree/bindings/mfd/mfd-core.txt
+ */
+ const char *of_node_name;
+
+ /*
* These resources can be specified relative to the parent device.
* For accessing hardware you should use resources from the platform dev
*/
--
1.7.1.1
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