drivers: timer: add timer driver for ARMv7 based Tegra devices

Add timer support for T20/T30/T114 and T124 based devices.
Driver is based on DM, has device tree support and can be
used on SPL and early boot stage.

Tested-by: Andreas Westman Dorcsak <hedmoo@yahoo.com> # ASUS TF600T T30
Tested-by: Jonas Schwöbel <jonasschwoebel@yahoo.de> # Surface RT T30
Tested-by: Robert Eckelmann <longnoserob@gmail.com> # ASUS TF101 T20
Tested-by: Svyatoslav Ryhel <clamor95@gmail.com> # LG P895 T30
Co-developed-by: Jonas Schwöbel <jonasschwoebel@yahoo.de>
Signed-off-by: Jonas Schwöbel <jonasschwoebel@yahoo.de>
Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>

Author: clamor-s

drivers/timer/Kconfig

@@ -252,6 +252,14 @@ config STM32_TIMER
 	  Select this to enable support for the timer found on
 	  STM32 devices.
 
+config TEGRA_TIMER
+	bool "Tegra timer support"
+	depends on TIMER
+	select TIMER_EARLY
+	help
+	  Select this to enable support for the timer found on
+	  Tegra devices.
+
 config X86_TSC_TIMER
 	bool "x86 Time-Stamp Counter (TSC) timer support"
 	depends on TIMER && X86

drivers/timer/Makefile

@@ -27,6 +27,7 @@ obj-$(CONFIG_SP804_TIMER)	+= sp804_timer.o
 obj-$(CONFIG_$(SPL_)SIFIVE_CLINT) += sifive_clint_timer.o
 obj-$(CONFIG_ARM_GLOBAL_TIMER)	+= arm_global_timer.o
 obj-$(CONFIG_STM32_TIMER)	+= stm32_timer.o
+obj-$(CONFIG_TEGRA_TIMER)	+= tegra-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/tegra-timer.c

@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2022 Svyatoslav Ryhel <clamor95@gmail.com>
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <timer.h>
+
+#include <asm/io.h>
+#include <asm/arch/clock.h>
+#include <asm/arch/tegra.h>
+
+#define TEGRA_OSC_CLK_ENB_L_SET		(NV_PA_CLK_RST_BASE + 0x320)
+#define TEGRA_OSC_SET_CLK_ENB_TMR	BIT(5)
+
+#define TEGRA_TIMER_USEC_CNTR		(NV_PA_TMRUS_BASE + 0)
+#define TEGRA_TIMER_USEC_CFG		(NV_PA_TMRUS_BASE + 4)
+
+#define TEGRA_TIMER_RATE		1000000 /* 1 MHz */
+
+u64 notrace timer_early_get_count(void)
+{
+	/* At this stage raw timer is used */
+	return readl(TEGRA_TIMER_USEC_CNTR);
+}
+
+unsigned long notrace timer_early_get_rate(void)
+{
+	return TEGRA_TIMER_RATE;
+}
+
+#if CONFIG_IS_ENABLED(BOOTSTAGE)
+ulong timer_get_boot_us(void)
+{
+	u64 ticks = 0;
+	int ret;
+
+	ret = dm_timer_init();
+	if (!ret)
+		timer_get_count(gd->timer, &ticks);
+	else
+		ticks = timer_early_get_count();
+
+	return ticks;
+}
+#endif
+
+static notrace u64 tegra_timer_get_count(struct udevice *dev)
+{
+	u32 val = timer_early_get_count();
+	return timer_conv_64(val);
+}
+
+static int tegra_timer_probe(struct udevice *dev)
+{
+	struct timer_dev_priv *uc_priv = dev_get_uclass_priv(dev);
+	u32 usec_config, value;
+
+	/* Timer rate has to be set unconditionally */
+	uc_priv->clock_rate = TEGRA_TIMER_RATE;
+
+	/*
+	 * Configure microsecond timers to have 1MHz clock
+	 * Config register is 0xqqww, where qq is "dividend", ww is "divisor"
+	 * Uses n+1 scheme
+	 */
+	switch (clock_get_osc_freq()) {
+	case CLOCK_OSC_FREQ_13_0:
+		usec_config = 0x000c; /* (12+1)/(0+1) */
+		break;
+	case CLOCK_OSC_FREQ_19_2:
+		usec_config = 0x045f; /* (95+1)/(4+1) */
+		break;
+	case CLOCK_OSC_FREQ_12_0:
+		usec_config = 0x000b; /* (11+1)/(0+1) */
+		break;
+	case CLOCK_OSC_FREQ_26_0:
+		usec_config = 0x0019; /* (25+1)/(0+1) */
+		break;
+	case CLOCK_OSC_FREQ_16_8:
+		usec_config = 0x0453; /* (83+1)/(4+1) */
+		break;
+	case CLOCK_OSC_FREQ_38_4:
+		usec_config = 0x04bf; /* (191+1)/(4+1) */
+		break;
+	case CLOCK_OSC_FREQ_48_0:
+		usec_config = 0x002f; /* (47+1)/(0+1) */
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	/* Enable clock to timer hardware */
+	value = readl_relaxed(TEGRA_OSC_CLK_ENB_L_SET);
+	writel_relaxed(value | TEGRA_OSC_SET_CLK_ENB_TMR,
+		       TEGRA_OSC_CLK_ENB_L_SET);
+
+	writel_relaxed(usec_config, TEGRA_TIMER_USEC_CFG);
+
+	return 0;
+}
+
+static const struct timer_ops tegra_timer_ops = {
+	.get_count = tegra_timer_get_count,
+};
+
+static const struct udevice_id tegra_timer_ids[] = {
+	{ .compatible = "nvidia,tegra20-timer" },
+	{ .compatible = "nvidia,tegra30-timer" },
+	{ .compatible = "nvidia,tegra114-timer" },
+	{ .compatible = "nvidia,tegra124-timer" },
+	{ }
+};
+
+U_BOOT_DRIVER(tegra_timer) = {
+	.name		= "tegra_timer",
+	.id		= UCLASS_TIMER,
+	.of_match	= tegra_timer_ids,
+	.probe		= tegra_timer_probe,
+	.ops		= &tegra_timer_ops,
+	.flags		= DM_FLAG_PRE_RELOC,
+};