soc: microchip: mpfs: enable access to the system controller's flash

The system controller has a flash that contains images used to reprogram
the FPGA using IAP (In-Application Programming).
Introduce a function that allows a driver with a reference to the system
controller to get one to a flash device attached to it.
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>

drivers/soc/microchip/Kconfig

 config POLARFIRE_SOC_SYS_CTRL
 	tristate "POLARFIRE_SOC_SYS_CTRL"
 	depends on POLARFIRE_SOC_MAILBOX
+	depends on MTD
 	help
 	  This driver adds support for the PolarFire SoC (MPFS) system controller.
 

drivers/soc/microchip/mpfs-sys-controller.c

@@ -12,6 +12,8 @@
 #include <linux/kref.h>
 #include <linux/module.h>
 #include <linux/jiffies.h>
+#include <linux/mtd/mtd.h>
+#include <linux/spi/spi.h>
 #include <linux/interrupt.h>
 #include <linux/of.h>
 #include <linux/mailbox_client.h>
@@ -30,6 +32,7 @@ struct mpfs_sys_controller {
 	struct mbox_client client;
 	struct mbox_chan *chan;
 	struct completion c;
+	struct mtd_info *flash;
 	struct kref consumers;
 };
 
@@ -99,6 +102,12 @@ static void mpfs_sys_controller_put(void *data)
 	kref_put(&sys_controller->consumers, mpfs_sys_controller_delete);
 }
 
+struct mtd_info *mpfs_sys_controller_get_flash(struct mpfs_sys_controller *mpfs_client)
+{
+	return mpfs_client->flash;
+}
+EXPORT_SYMBOL(mpfs_sys_controller_get_flash);
+
 static struct platform_device subdevs[] = {
 	{
 		.name		= "mpfs-rng",
@@ -114,12 +123,23 @@ static int mpfs_sys_controller_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct mpfs_sys_controller *sys_controller;
+	struct device_node *np;
 	int i, ret;
 
 	sys_controller = kzalloc(sizeof(*sys_controller), GFP_KERNEL);
 	if (!sys_controller)
 		return -ENOMEM;
 
+	np = of_parse_phandle(dev->of_node, "microchip,bitstream-flash", 0);
+	if (!np)
+		goto no_flash;
+
+	sys_controller->flash = of_get_mtd_device_by_node(np);
+	of_node_put(np);
+	if (IS_ERR(sys_controller->flash))
+		return dev_err_probe(dev, PTR_ERR(sys_controller->flash), "Failed to get flash\n");
+
+no_flash:
 	sys_controller->client.dev = dev;
 	sys_controller->client.rx_callback = mpfs_sys_controller_rx_callback;
 	sys_controller->client.tx_block = 1U;

include/soc/microchip/mpfs.h

@@ -38,6 +38,8 @@ int mpfs_blocking_transaction(struct mpfs_sys_controller *mpfs_client, struct mp
 
 struct mpfs_sys_controller *mpfs_sys_controller_get(struct device *dev);
 
+struct mtd_info *mpfs_sys_controller_get_flash(struct mpfs_sys_controller *mpfs_client);
+
 #endif /* if IS_ENABLED(CONFIG_POLARFIRE_SOC_SYS_CTRL) */
 
 #if IS_ENABLED(CONFIG_MCHP_CLK_MPFS)