sandbox: use nvmem on top of stickypage for reset reason

Watchdog and system reset driver use a byte in the sticky page to
persist reset reason over reexec. So far, this was a byte outside
partitioned space. With the new nvmem-cells binding, a partition can be
dedicated to holding nvmem cells. Use that instead.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.barebox.org/20210619034516.6737-6-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

3 files changed, 45 insertions, 28 deletions

diff --git a/arch/sandbox/board/power.c b/arch/sandbox/board/power.c
index 3cc9447958..57801c8c3d 100644
--- a/arch/sandbox/board/power.c
+++ b/arch/sandbox/board/power.c
@@ -4,11 +4,11 @@
 #include <restart.h>
 #include <mach/linux.h>
 #include <reset_source.h>
-#include <mfd/syscon.h>
+#include <linux/nvmem-consumer.h>
 
 struct sandbox_power {
 	struct restart_handler rst_hang, rst_reexec;
-	struct regmap *src;
+	struct nvmem_cell *reset_source_cell;
 	u32 src_offset;
 };
 
@@ -24,16 +24,20 @@ static void sandbox_rst_hang(struct restart_handler *rst)
 
 static void sandbox_rst_reexec(struct restart_handler *rst)
 {
+	u8 reason = RESET_RST;
 	struct sandbox_power *power = container_of(rst, struct sandbox_power, rst_reexec);
-	regmap_update_bits(power->src, power->src_offset, 0xff, RESET_RST);
+
+	if (!IS_ERR(power->reset_source_cell))
+		WARN_ON(nvmem_cell_write(power->reset_source_cell, &reason, 1) <= 0);
+
 	linux_reexec();
 }
 
 static int sandbox_power_probe(struct device_d *dev)
 {
 	struct sandbox_power *power = xzalloc(sizeof(*power));
-	unsigned int rst;
-	int ret;
+	size_t len = 1;
+	u8 *rst;
 
 	poweroff_handler_register_fn(sandbox_poweroff);
 
@@ -52,20 +56,21 @@ static int sandbox_power_probe(struct device_d *dev)
 	if (IS_ENABLED(CONFIG_SANDBOX_REEXEC))
 		restart_handler_register(&power->rst_reexec);
 
-	power->src = syscon_regmap_lookup_by_phandle(dev->device_node, "barebox,reset-source");
-	if (IS_ERR(power->src))
+	power->reset_source_cell = of_nvmem_cell_get(dev->device_node, "reset-source");
+	if (IS_ERR(power->reset_source_cell)) {
+		dev_warn(dev, "No reset source info available: %pe\n", power->reset_source_cell);
 		return 0;
+	}
 
-	ret = of_property_read_u32_index(dev->device_node, "barebox,reset-source", 1,
-					 &power->src_offset);
-	if (ret)
-		return 0;
+	rst = nvmem_cell_read(power->reset_source_cell, &len);
+	if (!IS_ERR(rst)) {
+		if (*rst == 0)
+			*rst = RESET_POR;
+		reset_source_set_prinst(*rst, RESET_SOURCE_DEFAULT_PRIORITY, 0);
 
-	ret = regmap_read(power->src, power->src_offset, &rst);
-	if (ret == 0 && rst == 0)
-		rst = RESET_POR;
+		free(rst);
+	}
 
-	reset_source_set_prinst(rst, RESET_SOURCE_DEFAULT_PRIORITY, 0);
 	return 0;
 }
 
diff --git a/arch/sandbox/board/watchdog.c b/arch/sandbox/board/watchdog.c
index e1cff7a0bf..ff26a2019f 100644
--- a/arch/sandbox/board/watchdog.c
+++ b/arch/sandbox/board/watchdog.c
@@ -6,7 +6,7 @@
 #include <mach/linux.h>
 #include <of.h>
 #include <watchdog.h>
-#include <mfd/syscon.h>
+#include <linux/nvmem-consumer.h>
 #include <reset_source.h>
 
 struct sandbox_watchdog {
@@ -36,10 +36,9 @@ static int sandbox_watchdog_set_timeout(struct watchdog *wdd, unsigned int timeo
 static int sandbox_watchdog_probe(struct device_d *dev)
 {
 	struct device_node *np = dev->device_node;
+	struct nvmem_cell *reset_source_cell;
 	struct sandbox_watchdog *wd;
 	struct watchdog *wdd;
-	struct regmap *src;
-	u32 src_offset;
 	int ret;
 
 	wd = xzalloc(sizeof(*wd));
@@ -57,16 +56,17 @@ static int sandbox_watchdog_probe(struct device_d *dev)
 		return ret;
 	}
 
-	src = syscon_regmap_lookup_by_phandle(np, "barebox,reset-source");
-	if (IS_ERR(src))
-		return 0;
+	reset_source_cell = of_nvmem_cell_get(dev->device_node, "reset-source");
+	if (IS_ERR(reset_source_cell)) {
+		dev_warn(dev, "No reset source info available: %pe\n", reset_source_cell);
+		goto out;
+	}
 
-	ret = of_property_read_u32_index(np, "barebox,reset-source", 1, &src_offset);
-	if (ret)
-		return 0;
+	nvmem_cell_write(reset_source_cell, &(u8) { RESET_WDG }, 1);
 
-	regmap_update_bits(src, src_offset, 0xff, RESET_WDG);
+	nvmem_cell_put(reset_source_cell);
 
+out:
 	dev_info(dev, "probed\n");
 	return 0;
 }
diff --git a/arch/sandbox/dts/sandbox.dts b/arch/sandbox/dts/sandbox.dts
index e99986bb90..7f8f1964e4 100644
--- a/arch/sandbox/dts/sandbox.dts
+++ b/arch/sandbox/dts/sandbox.dts
@@ -71,7 +71,17 @@
 			#address-cells = <1>;
 			#size-cells = <1>;
 
-			/* 0x00+4 reserved for syscon use */
+			part_nvmem: nvmem@300 {
+				compatible = "nvmem-cells";
+				reg = <0x300 0x100>;
+				label = "nvmem";
+				#address-cells = <1>;
+				#size-cells = <1>;
+
+				reset_source: reset-source@0 {
+					reg = <0x0 0x1>;
+				};
+			};
 
 			part_env: env@400 {
 				reg = <0x400 0x800>;
@@ -87,12 +97,14 @@
 
 	power {
 		compatible = "barebox,sandbox-power";
-		barebox,reset-source = <&stickypage 0>;
+		nvmem-cell-names = "reset-source";
+		nvmem-cells = <&reset_source>;
 	};
 
 	watchdog {
 		compatible = "barebox,sandbox-watchdog";
-		barebox,reset-source = <&stickypage 0>;
+		nvmem-cell-names = "reset-source";
+		nvmem-cells = <&reset_source>;
 	};
 
 	sound {