bus: fsl-mc: add bus rescan attribute

Introduce the rescan attribute as a bus attribute to
synchronize the fsl-mc bus objects and the MC firmware.

To rescan the fsl-mc bus, e.g.,
echo 1 > /sys/bus/fsl-mc/rescan
Acked-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Link: https://lore.kernel.org/r/20210114170752.2927915-5-ciorneiioana@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/stable/sysfs-bus-fsl-mc

+What:		/sys/bus/fsl-mc/rescan
+Date:		January 2021
+KernelVersion:	5.12
+Contact:	Ioana Ciornei <ioana.ciornei@nxp.com>
+Description:	Writing a non-zero value to this attribute will
+		force a rescan of fsl-mc bus in the system and
+		synchronize the objects under fsl-mc bus and the
+		Management Complex firmware.
+Users:		Userspace drivers and management tools

MAINTAINERS

@@ -14649,6 +14649,7 @@ M:	Stuart Yoder <stuyoder@gmail.com>
 M:	Laurentiu Tudor <laurentiu.tudor@nxp.com>
 L:	linux-kernel@vger.kernel.org
 S:	Maintained
+F:	Documentation/ABI/stable/sysfs-bus-fsl-mc
 F:	Documentation/devicetree/bindings/misc/fsl,qoriq-mc.txt
 F:	Documentation/networking/device_drivers/ethernet/freescale/dpaa2/overview.rst
 F:	drivers/bus/fsl-mc/

drivers/bus/fsl-mc/dprc-driver.c

@@ -237,7 +237,7 @@ static void dprc_add_new_devices(struct fsl_mc_device *mc_bus_dev,
  * populated before they can get allocation requests from probe callbacks
  * of the device drivers for the non-allocatable devices.
  */
-static int dprc_scan_objects(struct fsl_mc_device *mc_bus_dev,
+int dprc_scan_objects(struct fsl_mc_device *mc_bus_dev,
 		      bool alloc_interrupts)
 {
 	int num_child_objects;

drivers/bus/fsl-mc/fsl-mc-bus.c

@@ -208,12 +208,53 @@ static struct attribute *fsl_mc_dev_attrs[] = {
 
 ATTRIBUTE_GROUPS(fsl_mc_dev);
 
+static int scan_fsl_mc_bus(struct device *dev, void *data)
+{
+	struct fsl_mc_device *root_mc_dev;
+	struct fsl_mc_bus *root_mc_bus;
+
+	if (!fsl_mc_is_root_dprc(dev))
+		goto exit;
+
+	root_mc_dev = to_fsl_mc_device(dev);
+	root_mc_bus = to_fsl_mc_bus(root_mc_dev);
+	mutex_lock(&root_mc_bus->scan_mutex);
+	dprc_scan_objects(root_mc_dev, NULL);
+	mutex_unlock(&root_mc_bus->scan_mutex);
+
+exit:
+	return 0;
+}
+
+static ssize_t rescan_store(struct bus_type *bus,
+			    const char *buf, size_t count)
+{
+	unsigned long val;
+
+	if (kstrtoul(buf, 0, &val) < 0)
+		return -EINVAL;
+
+	if (val)
+		bus_for_each_dev(bus, NULL, NULL, scan_fsl_mc_bus);
+
+	return count;
+}
+static BUS_ATTR_WO(rescan);
+
+static struct attribute *fsl_mc_bus_attrs[] = {
+	&bus_attr_rescan.attr,
+	NULL,
+};
+
+ATTRIBUTE_GROUPS(fsl_mc_bus);
+
 struct bus_type fsl_mc_bus_type = {
 	.name = "fsl-mc",
 	.match = fsl_mc_bus_match,
 	.uevent = fsl_mc_bus_uevent,
 	.dma_configure  = fsl_mc_dma_configure,
 	.dev_groups = fsl_mc_dev_groups,
+	.bus_groups = fsl_mc_bus_groups,
 };
 EXPORT_SYMBOL_GPL(fsl_mc_bus_type);
 

drivers/bus/fsl-mc/fsl-mc-private.h

@@ -594,6 +594,9 @@ int __init dprc_driver_init(void);
 
 void dprc_driver_exit(void);
 
+int dprc_scan_objects(struct fsl_mc_device *mc_bus_dev,
+		      bool alloc_interrupts);
+
 int __init fsl_mc_allocator_driver_init(void);
 
 void fsl_mc_allocator_driver_exit(void);