timer: npcm: Add NPCM timer support

Add Nuvoton BMC NPCM7xx/NPCM8xx timer driver.

Signed-off-by: Jim Liu <JJLIU0@nuvoton.com>
Signed-off-by: Stanley Chu <yschu@nuvoton.com>

drivers/timer/Kconfig

@@ -172,6 +172,15 @@ config NOMADIK_MTU_TIMER
 	  The MTU provides 4 decrementing free-running timers.
 	  At the moment, only the first timer is used by the driver.
 
+config NPCM_TIMER
+	bool "Nuvoton NPCM timer support"
+	depends on TIMER
+	help
+	  Select this to enable a timer on Nuvoton NPCM SoCs.
+	  NPCM timer module has 5 down-counting timers, only the first timer
+	  is used to implement timer ops. No support for early timer and
+	  boot timer.
+
 config OMAP_TIMER
 	bool "Omap timer support"
 	depends on TIMER

drivers/timer/Makefile

@@ -14,6 +14,7 @@ obj-$(CONFIG_CADENCE_TTC_TIMER)	+= cadence-ttc.o
 obj-$(CONFIG_DESIGNWARE_APB_TIMER)	+= dw-apb-timer.o
 obj-$(CONFIG_MPC83XX_TIMER) += mpc83xx_timer.o
 obj-$(CONFIG_NOMADIK_MTU_TIMER)	+= nomadik-mtu-timer.o
+obj-$(CONFIG_NPCM_TIMER)        += npcm-timer.o
 obj-$(CONFIG_OMAP_TIMER)	+= omap-timer.o
 obj-$(CONFIG_RENESAS_OSTM_TIMER) += ostm_timer.o
 obj-$(CONFIG_RISCV_TIMER) += riscv_timer.o

drivers/timer/npcm-timer.c

@@ -0,0 +1,115 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2022 Nuvoton Technology Corp.
+ */
+
+#include <common.h>
+#include <clk.h>
+#include <dm.h>
+#include <timer.h>
+#include <asm/io.h>
+
+#define NPCM_TIMER_CLOCK_RATE	1000000UL		/* 1MHz timer */
+#define NPCM_TIMER_INPUT_RATE	25000000UL		/* Rate of input clock */
+#define NPCM_TIMER_TDR_MASK	GENMASK(23, 0)
+#define NPCM_TIMER_MAX_VAL	NPCM_TIMER_TDR_MASK	/* max counter value */
+
+/* Register offsets */
+#define TCR0	0x0	/* Timer Control and Status Register */
+#define TICR0	0x8	/* Timer Initial Count Register */
+#define TDR0	0x10	/* Timer Data Register */
+
+/* TCR fields */
+#define TCR_MODE_PERIODIC	BIT(27)
+#define TCR_EN			BIT(30)
+#define TCR_PRESCALE		(NPCM_TIMER_INPUT_RATE / NPCM_TIMER_CLOCK_RATE - 1)
+
+enum input_clock_type {
+	INPUT_CLOCK_FIXED,	/* input clock rate is fixed */
+	INPUT_CLOCK_NON_FIXED
+};
+
+/**
+ * struct npcm_timer_priv - private data for npcm timer driver
+ * npcm timer is a 24-bits down-counting timer.
+ *
+ * @last_count: last hw counter value
+ * @counter: the value to be returned for get_count ops
+ */
+struct npcm_timer_priv {
+	void __iomem *base;
+	u32 last_count;
+	u64 counter;
+};
+
+static u64 npcm_timer_get_count(struct udevice *dev)
+{
+	struct npcm_timer_priv *priv = dev_get_priv(dev);
+	u32 val;
+
+	/* The timer is counting down */
+	val = readl(priv->base + TDR0) & NPCM_TIMER_TDR_MASK;
+	if (val <= priv->last_count)
+		priv->counter += priv->last_count - val;
+	else
+		priv->counter += priv->last_count + (NPCM_TIMER_MAX_VAL + 1 - val);
+	priv->last_count = val;
+
+	return priv->counter;
+}
+
+static int npcm_timer_probe(struct udevice *dev)
+{
+	struct timer_dev_priv *uc_priv = dev_get_uclass_priv(dev);
+	struct npcm_timer_priv *priv = dev_get_priv(dev);
+	enum input_clock_type type = dev_get_driver_data(dev);
+	struct clk clk;
+	int ret;
+
+	priv->base = dev_read_addr_ptr(dev);
+	if (!priv->base)
+		return -EINVAL;
+	uc_priv->clock_rate = NPCM_TIMER_CLOCK_RATE;
+
+	if (type == INPUT_CLOCK_NON_FIXED) {
+		ret = clk_get_by_index(dev, 0, &clk);
+		if (ret < 0)
+			return ret;
+
+		ret = clk_set_rate(&clk, NPCM_TIMER_INPUT_RATE);
+		if (ret < 0)
+			return ret;
+	}
+
+	/*
+	 * Configure timer and start
+	 * periodic mode
+	 * timer clock rate = input clock / prescale
+	 */
+	writel(0, priv->base + TCR0);
+	writel(NPCM_TIMER_MAX_VAL, priv->base + TICR0);
+	writel(TCR_EN | TCR_MODE_PERIODIC | TCR_PRESCALE,
+	       priv->base + TCR0);
+
+	return 0;
+}
+
+static const struct timer_ops npcm_timer_ops = {
+	.get_count = npcm_timer_get_count,
+};
+
+static const struct udevice_id npcm_timer_ids[] = {
+	{ .compatible = "nuvoton,npcm845-timer", .data = INPUT_CLOCK_FIXED},
+	{ .compatible = "nuvoton,npcm750-timer", .data = INPUT_CLOCK_NON_FIXED},
+	{}
+};
+
+U_BOOT_DRIVER(npcm_timer) = {
+	.name	= "npcm_timer",
+	.id	= UCLASS_TIMER,
+	.of_match = npcm_timer_ids,
+	.priv_auto = sizeof(struct npcm_timer_priv),
+	.probe = npcm_timer_probe,
+	.ops	= &npcm_timer_ops,
+	.flags = DM_FLAG_PRE_RELOC,
+};