sysreset: Add support for Microblaze soft reset jump

Microblaze is storing reset vector at address 0x0.
It means soft reset can be done by just jumping to this address.
This code was in platform code but sysreset interface is providing
enough capabilities to have more options how to reset the system. It can
go from gpio reset through watchdog reset till soft reset.

The driver has not compatible string because this is cpu specific and DM
core is not able to detect compatible string in DT root that's why this
driver will be instantiated from platform code by calling
device_bind_driver(gd->dm_root, "mb_soft_reset", "reset_soft",
NULL);
It should be bind as the last reset method to ensure that hw reset is
called before this.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>

drivers/sysreset/Kconfig

@@ -23,6 +23,12 @@ config SYSRESET_GPIO
 	  example on Microblaze where reset logic can be controlled via GPIO
 	  pin which triggers cpu reset.
 
+config SYSRESET_MICROBLAZE
+	bool "Enable support for Microblaze soft reset"
+	depends on MICROBLAZE
+	help
+	  This is soft reset on Microblaze which does jump to 0x0 address.
+
 config SYSRESET_PSCI
 	bool "Enable support for PSCI System Reset"
 	depends on ARM_PSCI_FW

drivers/sysreset/Makefile

@@ -4,6 +4,7 @@
 
 obj-$(CONFIG_SYSRESET) += sysreset-uclass.o
 obj-$(CONFIG_SYSRESET_GPIO) += sysreset_gpio.o
+obj-$(CONFIG_SYSRESET_MICROBLAZE) += sysreset_microblaze.o
 obj-$(CONFIG_SYSRESET_PSCI) += sysreset_psci.o
 obj-$(CONFIG_SYSRESET_SYSCON) += sysreset_syscon.o
 obj-$(CONFIG_SYSRESET_WATCHDOG) += sysreset_watchdog.o

drivers/sysreset/sysreset_microblaze.c

@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2018 Xilinx, Inc. - Michal Simek
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <sysreset.h>
+#include <linux/err.h>
+
+static int microblaze_sysreset_request(struct udevice *dev,
+				       enum sysreset_t type)
+{
+	puts("Microblaze soft reset sysreset\n");
+	__asm__ __volatile__ ("	mts rmsr, r0;" \
+				"bra r0");
+
+	return -EINPROGRESS;
+}
+
+static struct sysreset_ops microblaze_sysreset = {
+	.request = microblaze_sysreset_request,
+};
+
+U_BOOT_DRIVER(sysreset_microblaze) = {
+	.id	= UCLASS_SYSRESET,
+	.name	= "mb_soft_reset",
+	.ops	= &microblaze_sysreset,
+};