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>

arch/arm/include/asm/arch-aspeed/scu_ast2500.h

@@ -31,6 +31,34 @@
 
 #define SCU_MISC_UARTCLK_DIV13		(1 << 12)
 
+/*
+ * SYSRESET is actually more like a Power register,
+ * except that corresponding bit set to 1 means that
+ * the peripheral is off.
+ */
+#define SCU_SYSRESET_XDMA		(1 << 25)
+#define SCU_SYSRESET_MCTP		(1 << 24)
+#define SCU_SYSRESET_ADC		(1 << 23)
+#define SCU_SYSRESET_JTAG		(1 << 22)
+#define SCU_SYSRESET_MIC		(1 << 18)
+#define SCU_SYSRESET_SDIO		(1 << 16)
+#define SCU_SYSRESET_USB11HOST		(1 << 15)
+#define SCU_SYSRESET_USBHUB		(1 << 14)
+#define SCU_SYSRESET_CRT		(1 << 13)
+#define SCU_SYSRESET_MAC2		(1 << 12)
+#define SCU_SYSRESET_MAC1		(1 << 11)
+#define SCU_SYSRESET_PECI		(1 << 10)
+#define SCU_SYSRESET_PWM		(1 << 9)
+#define SCU_SYSRESET_PCI_VGA		(1 << 8)
+#define SCU_SYSRESET_2D			(1 << 7)
+#define SCU_SYSRESET_VIDEO		(1 << 6)
+#define SCU_SYSRESET_LPC		(1 << 5)
+#define SCU_SYSRESET_HAC		(1 << 4)
+#define SCU_SYSRESET_USBHID		(1 << 3)
+#define SCU_SYSRESET_I2C		(1 << 2)
+#define SCU_SYSRESET_AHB		(1 << 1)
+#define SCU_SYSRESET_SDRAM_WDT		(1 << 0)
+
 #ifndef __ASSEMBLY__
 
 struct ast2500_clk_priv {

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

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

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),
+};