timer: mchp-pit64b: add support for pit64b

Add support for Microchip PIT64B timer. The timer is 64 bit length and
is used as a free running counter (in continuous mode with highest values
for period registers). The clock feeding the timer would be no more
than 12.5MHz.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>

drivers/timer/Kconfig

@@ -213,4 +213,11 @@ config MTK_TIMER
 	  Select this to enable support for the timer found on
 	  MediaTek devices.
 
+config MCHP_PIT64B_TIMER
+	bool "Microchip 64-bit periodic interval timer support"
+	depends on TIMER
+	help
+	  Select this to enable support for Microchip 64-bit periodic
+	  interval timer.
+
 endmenu

drivers/timer/Makefile

@@ -22,3 +22,4 @@ obj-$(CONFIG_STI_TIMER)		+= sti-timer.o
 obj-$(CONFIG_STM32_TIMER)	+= stm32_timer.o
 obj-$(CONFIG_X86_TSC_TIMER)	+= tsc_timer.o
 obj-$(CONFIG_MTK_TIMER)		+= mtk_timer.o
+obj-$(CONFIG_MCHP_PIT64B_TIMER)	+= mchp-pit64b-timer.o

drivers/timer/mchp-pit64b-timer.c

@@ -0,0 +1,109 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * 64-bit Periodic Interval Timer driver
+ *
+ * Copyright (C) 2020 Microchip Technology Inc. and its subsidiaries
+ *
+ * Author: Claudiu Beznea <claudiu.beznea@microchip.com>
+ */
+
+#include <common.h>
+#include <clk.h>
+#include <dm.h>
+#include <timer.h>
+#include <asm/io.h>
+
+#define MCHP_PIT64B_CR			0x00	/* Control Register */
+#define		MCHP_PIT64B_CR_START	BIT(0)
+#define		MCHP_PIT64B_CR_SWRST	BIT(8)
+#define MCHP_PIT64B_MR			0x04	/* Mode Register */
+#define		MCHP_PIT64B_MR_CONT	BIT(0)
+#define MCHP_PIT64B_LSB_PR		0x08	/* LSB Period Register */
+#define MCHP_PIT64B_MSB_PR		0x0C	/* MSB Period Register */
+#define MCHP_PIT64B_TLSBR		0x20	/* Timer LSB Register */
+#define MCHP_PIT64B_TMSBR		0x24	/* Timer MSB Register */
+
+struct mchp_pit64b_priv {
+	void __iomem *base;
+};
+
+static int mchp_pit64b_get_count(struct udevice *dev, u64 *count)
+{
+	struct mchp_pit64b_priv *priv = dev_get_priv(dev);
+
+	u32 lsb = readl(priv->base + MCHP_PIT64B_TLSBR);
+	u32 msb = readl(priv->base + MCHP_PIT64B_TMSBR);
+
+	*count = ((u64)msb << 32) | lsb;
+
+	return 0;
+}
+
+static int mchp_pit64b_probe(struct udevice *dev)
+{
+	struct timer_dev_priv *uc_priv = dev_get_uclass_priv(dev);
+	struct mchp_pit64b_priv *priv = dev_get_priv(dev);
+	struct clk clk;
+	ulong rate;
+	int ret;
+
+	priv->base = dev_read_addr_ptr(dev);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	ret = clk_get_by_index(dev, 0, &clk);
+	if (ret)
+		return ret;
+
+	ret = clk_enable(&clk);
+	if (ret)
+		return ret;
+
+	rate = clk_get_rate(&clk);
+	if (!rate) {
+		clk_disable(&clk);
+		return -ENOTSUPP;
+	}
+
+	/* Reset the timer in case it was used by previous bootloaders. */
+	writel(MCHP_PIT64B_CR_SWRST, priv->base + MCHP_PIT64B_CR);
+
+	/*
+	 * Use highest prescaller (for a peripheral clock running at 200MHz
+	 * this will lead to the timer running at 12.5MHz) and continuous mode.
+	 */
+	writel((15 << 8) | MCHP_PIT64B_MR_CONT, priv->base + MCHP_PIT64B_MR);
+	uc_priv->clock_rate = rate / 16;
+
+	/*
+	 * Simulate free running counter by setting max values to period
+	 * registers.
+	 */
+	writel(~0UL, priv->base + MCHP_PIT64B_MSB_PR);
+	writel(~0UL, priv->base + MCHP_PIT64B_LSB_PR);
+
+	/* Start the timer. */
+	writel(MCHP_PIT64B_CR_START, priv->base + MCHP_PIT64B_CR);
+
+	return 0;
+}
+
+static const struct timer_ops mchp_pit64b_ops = {
+	.get_count = mchp_pit64b_get_count,
+};
+
+static const struct udevice_id mchp_pit64b_ids[] = {
+	{ .compatible = "microchip,sam9x60-pit64b", },
+	{ .compatible = "microchip,sama7g5-pit64b", },
+	{ }
+};
+
+U_BOOT_DRIVER(mchp_pit64b) = {
+	.name	= "mchp-pit64b",
+	.id	= UCLASS_TIMER,
+	.of_match = mchp_pit64b_ids,
+	.priv_auto_alloc_size = sizeof(struct mchp_pit64b_priv),
+	.probe	= mchp_pit64b_probe,
+	.ops	= &mchp_pit64b_ops,
+	.flags	= DM_FLAG_PRE_RELOC,
+};