aspeed: Reset Driver

Add Reset Driver for ast2500 SoC. This driver uses Watchdog Timer to
perform resets and thus depends on it. The actual Watchdog device used
needs to be configured in Device Tree using "aspeed,wdt" property, which
must be WDT phandle, for example:

rst: reset-controller {
    compatible = "aspeed,ast2500-reset";
    aspeed,wdt = <&wdt1>;
}

Signed-off-by: Maxim Sloyko <maxims@google.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

3 files changed, 117 insertions, 0 deletions

diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
index fa77ee4..80f4646 100644
--- a/drivers/reset/Kconfig
+++ b/drivers/reset/Kconfig
@@ -51,4 +51,14 @@ config RESET_UNIPHIER
 	  Say Y if you want to control reset signals provided by System Control
 	  block, Media I/O block, Peripheral Block.
 
+config AST2500_RESET
+	bool "Reset controller driver for AST2500 SoCs"
+	depends on DM_RESET && WDT_ASPEED
+	default y if ASPEED_AST2500
+	help
+	  Support for reset controller on AST2500 SoC. This controller uses
+	  watchdog to reset different peripherals and thus only supports
+	  resets that are supported by watchdog. The main limitation though
+	  is that some reset signals, like I2C or MISC reset multiple devices.
+
 endmenu
diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
index 2b96396..630b4b4 100644
--- a/drivers/reset/Makefile
+++ b/drivers/reset/Makefile
@@ -9,3 +9,4 @@ obj-$(CONFIG_STI_RESET) += sti-reset.o
 obj-$(CONFIG_TEGRA_CAR_RESET) += tegra-car-reset.o
 obj-$(CONFIG_TEGRA186_RESET) += tegra186-reset.o
 obj-$(CONFIG_RESET_UNIPHIER) += reset-uniphier.o
+obj-$(CONFIG_AST2500_RESET) += ast2500-reset.o
diff --git a/drivers/reset/ast2500-reset.c b/drivers/reset/ast2500-reset.c
new file mode 100644
index 0000000..b2c89e1
--- /dev/null
+++ b/drivers/reset/ast2500-reset.c
@@ -0,0 +1,106 @@
+/*
+ * Copyright 2017 Google, Inc
+ *
+ * SPDX-License-Identifier: GPL-2.0
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <misc.h>
+#include <reset.h>
+#include <reset-uclass.h>
+#include <wdt.h>
+#include <asm/io.h>
+#include <asm/arch/scu_ast2500.h>
+#include <asm/arch/wdt.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+struct ast2500_reset_priv {
+	/* WDT used to perform resets. */
+	struct udevice *wdt;
+	struct ast2500_scu *scu;
+};
+
+static int ast2500_ofdata_to_platdata(struct udevice *dev)
+{
+	struct ast2500_reset_priv *priv = dev_get_priv(dev);
+	int ret;
+
+	ret = uclass_get_device_by_phandle(UCLASS_WDT, dev, "aspeed,wdt",
+					   &priv->wdt);
+	if (ret) {
+		debug("%s: can't find WDT for reset controller", __func__);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int ast2500_reset_assert(struct reset_ctl *reset_ctl)
+{
+	struct ast2500_reset_priv *priv = dev_get_priv(reset_ctl->dev);
+	u32 reset_mode, reset_mask;
+	bool reset_sdram;
+	int ret;
+
+	/*
+	 * To reset SDRAM, a specifal flag in SYSRESET register
+	 * needs to be enabled first
+	 */
+	reset_mode = ast_reset_mode_from_flags(reset_ctl->id);
+	reset_mask = ast_reset_mask_from_flags(reset_ctl->id);
+	reset_sdram = reset_mode == WDT_CTRL_RESET_SOC &&
+		(reset_mask & WDT_RESET_SDRAM);
+
+	if (reset_sdram) {
+		ast_scu_unlock(priv->scu);
+		setbits_le32(&priv->scu->sysreset_ctrl1,
+			     SCU_SYSRESET_SDRAM_WDT);
+		ret = wdt_expire_now(priv->wdt, reset_ctl->id);
+		clrbits_le32(&priv->scu->sysreset_ctrl1,
+			     SCU_SYSRESET_SDRAM_WDT);
+		ast_scu_lock(priv->scu);
+	} else {
+		ret = wdt_expire_now(priv->wdt, reset_ctl->id);
+	}
+
+	return ret;
+}
+
+static int ast2500_reset_request(struct reset_ctl *reset_ctl)
+{
+	debug("%s(reset_ctl=%p) (dev=%p, id=%lu)\n", __func__, reset_ctl,
+	      reset_ctl->dev, reset_ctl->id);
+
+	return 0;
+}
+
+static int ast2500_reset_probe(struct udevice *dev)
+{
+	struct ast2500_reset_priv *priv = dev_get_priv(dev);
+
+	priv->scu = ast_get_scu();
+
+	return 0;
+}
+
+static const struct udevice_id ast2500_reset_ids[] = {
+	{ .compatible = "aspeed,ast2500-reset" },
+	{ }
+};
+
+struct reset_ops ast2500_reset_ops = {
+	.rst_assert = ast2500_reset_assert,
+	.request = ast2500_reset_request,
+};
+
+U_BOOT_DRIVER(ast2500_reset) = {
+	.name		= "ast2500_reset",
+	.id		= UCLASS_RESET,
+	.of_match = ast2500_reset_ids,
+	.probe = ast2500_reset_probe,
+	.ops = &ast2500_reset_ops,
+	.ofdata_to_platdata = ast2500_ofdata_to_platdata,
+	.priv_auto_alloc_size = sizeof(struct ast2500_reset_priv),
+};