timer: atmel_tcb_timer: add atmel_tcb driver

Add a driver for the timer counter block that can be found on sama5d2.
This driver will be used when booting under OP-TEE since the pit timer
which is part of the SYSC is secured. Channel 1 & 2 are configured to
be chained together which allows to have a 64bits counter.

Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Clément Léger <clement.leger@bootlin.com>

MAINTAINERS

@@ -352,6 +352,7 @@ F:	arch/arm/mach-at91/
 F:	board/atmel/
 F:	drivers/cpu/at91_cpu.c
 F:	drivers/misc/microchip_flexcom.c
+F:	drivers/timer/atmel_tcb_timer.c
 F:	include/dt-bindings/mfd/atmel-flexcom.h
 F:	drivers/timer/mchp-pit64b-timer.c
 

arch/arm/mach-at91/armv7/Makefile

@@ -14,9 +14,11 @@ obj-y += cpu.o
 ifndef CONFIG_$(SPL_TPL_)SYSRESET
 obj-y	+= reset.o
 endif
+ifneq ($(CONFIG_ATMEL_TCB_TIMER),y)
 ifneq ($(CONFIG_ATMEL_PIT_TIMER),y)
 ifneq ($(CONFIG_MCHP_PIT64B_TIMER),y)
 # old non-DM timer driver
 obj-y += timer.o
 endif
 endif
+endif

drivers/timer/Kconfig

@@ -96,6 +96,14 @@ config ATMEL_PIT_TIMER
 	  it is designed to offer maximum accuracy and efficient management,
 	  even for systems with long response time.
 
+config ATMEL_TCB_TIMER
+	bool "Atmel timer counter support"
+	depends on TIMER
+	depends on ARCH_AT91
+	help
+	  Select this to enable the use of the timer counter as a monotonic
+	  counter.
+
 config CADENCE_TTC_TIMER
 	bool "Cadence TTC (Triple Timer Counter)"
 	depends on TIMER

drivers/timer/Makefile

@@ -10,6 +10,7 @@ obj-$(CONFIG_ARC_TIMER)	+= arc_timer.o
 obj-$(CONFIG_AST_TIMER)	+= ast_timer.o
 obj-$(CONFIG_ATCPIT100_TIMER) += atcpit100_timer.o
 obj-$(CONFIG_ATMEL_PIT_TIMER) += atmel_pit_timer.o
+obj-$(CONFIG_ATMEL_TCB_TIMER) += atmel_tcb_timer.o
 obj-$(CONFIG_CADENCE_TTC_TIMER)	+= cadence-ttc.o
 obj-$(CONFIG_DESIGNWARE_APB_TIMER)	+= dw-apb-timer.o
 obj-$(CONFIG_MPC83XX_TIMER) += mpc83xx_timer.o

drivers/timer/atmel_tcb_timer.c

@@ -0,0 +1,161 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2022 Microchip Corporation
+ *
+ * Author: Clément Léger <clement.leger@bootlin.com>
+ */
+
+#include <common.h>
+#include <clk.h>
+#include <dm.h>
+#include <timer.h>
+#include <asm/io.h>
+#include <linux/bitops.h>
+
+#define TCB_CHAN(chan)		((chan) * 0x40)
+
+#define TCB_CCR(chan)		(0x0 + TCB_CHAN(chan))
+#define  TCB_CCR_CLKEN		(1 << 0)
+
+#define TCB_CMR(chan)		(0x4 + TCB_CHAN(chan))
+#define  TCB_CMR_WAVE		(1 << 15)
+#define  TCB_CMR_TIMER_CLOCK2	1
+#define  TCB_CMR_XC1		6
+#define  TCB_CMR_ACPA_SET	(1 << 16)
+#define  TCB_CMR_ACPC_CLEAR	(2 << 18)
+
+#define TCB_CV(chan)		(0x10 + TCB_CHAN(chan))
+
+#define TCB_RA(chan)		(0x14 + TCB_CHAN(chan))
+#define TCB_RC(chan)		(0x1c + TCB_CHAN(chan))
+
+#define TCB_IDR(chan)		(0x28 + TCB_CHAN(chan))
+
+#define TCB_BCR			0xc0
+#define  TCB_BCR_SYNC		(1 << 0)
+
+#define TCB_BMR			0xc4
+#define  TCB_BMR_TC1XC1S_TIOA0	(2 << 2)
+
+#define TCB_WPMR		0xe4
+#define  TCB_WPMR_WAKEY		0x54494d
+
+#define TCB_CLK_DIVISOR		8
+struct atmel_tcb_plat {
+	void __iomem *base;
+};
+
+static u64 atmel_tcb_get_count(struct udevice *dev)
+{
+	struct atmel_tcb_plat *plat = dev_get_plat(dev);
+	u64 cv0 = 0;
+	u64 cv1 = 0;
+
+	do {
+		cv1 = readl(plat->base + TCB_CV(1));
+		cv0 = readl(plat->base + TCB_CV(0));
+	} while (readl(plat->base + TCB_CV(1)) != cv1);
+
+	cv0 |= cv1 << 32;
+
+	return cv0;
+}
+
+static void atmel_tcb_configure(void __iomem *base)
+{
+	/* Disable write protection */
+	writel(TCB_WPMR_WAKEY, base + TCB_WPMR);
+
+	/* Disable all irqs for both channel 0 & 1 */
+	writel(0xff, base + TCB_IDR(0));
+	writel(0xff, base + TCB_IDR(1));
+
+	/*
+	 * In order to avoid wrapping, use a 64 bit counter by chaining
+	 * two channels.
+	 * Channel 0 is configured to generate a clock on TIOA0 which is cleared
+	 * when reaching 0x80000000 and set when reaching 0.
+	 */
+	writel(TCB_CMR_TIMER_CLOCK2 | TCB_CMR_WAVE | TCB_CMR_ACPA_SET
+		   | TCB_CMR_ACPC_CLEAR, base + TCB_CMR(0));
+	writel(0x80000000, base + TCB_RC(0));
+	writel(0x1, base + TCB_RA(0));
+	writel(TCB_CCR_CLKEN, base + TCB_CCR(0));
+
+	/* Channel 1 is configured to use TIOA0 as input */
+	writel(TCB_CMR_XC1 | TCB_CMR_WAVE, base + TCB_CMR(1));
+	writel(TCB_CCR_CLKEN, base + TCB_CCR(1));
+
+	/* Set XC1 input to be TIOA0 (ie output of Channel 0) */
+	writel(TCB_BMR_TC1XC1S_TIOA0, base + TCB_BMR);
+
+	/* Sync & start all timers */
+	writel(TCB_BCR_SYNC, base + TCB_BCR);
+}
+
+static int atmel_tcb_probe(struct udevice *dev)
+{
+	struct atmel_tcb_plat *plat = dev_get_plat(dev);
+	struct timer_dev_priv *uc_priv = dev_get_uclass_priv(dev);
+	struct clk clk;
+	ulong clk_rate;
+	int ret;
+
+	if (!device_is_compatible(dev->parent, "atmel,sama5d2-tcb"))
+		return -EINVAL;
+
+	/* Currently, we only support channel 0 and 1 to be chained */
+	if (dev_read_addr_index(dev, 0) != 0 &&
+	    dev_read_addr_index(dev, 1) != 1) {
+		printf("Error: only chained timers 0 and 1 are supported\n");
+		return -EINVAL;
+	}
+
+	ret = clk_get_by_name(dev->parent, "t0_clk", &clk);
+	if (ret)
+		return -EINVAL;
+
+	ret = clk_enable(&clk);
+	if (ret)
+		return ret;
+
+	clk_rate = clk_get_rate(&clk);
+	if (!clk_rate) {
+		clk_disable(&clk);
+		return -EINVAL;
+	}
+
+	uc_priv->clock_rate = clk_rate / TCB_CLK_DIVISOR;
+
+	atmel_tcb_configure(plat->base);
+
+	return 0;
+}
+
+static int atmel_tcb_of_to_plat(struct udevice *dev)
+{
+	struct atmel_tcb_plat *plat = dev_get_plat(dev);
+
+	plat->base = dev_read_addr_ptr(dev->parent);
+
+	return 0;
+}
+
+static const struct timer_ops atmel_tcb_ops = {
+	.get_count = atmel_tcb_get_count,
+};
+
+static const struct udevice_id atmel_tcb_ids[] = {
+	{ .compatible = "atmel,tcb-timer" },
+	{ }
+};
+
+U_BOOT_DRIVER(atmel_tcb) = {
+	.name = "atmel_tcb",
+	.id = UCLASS_TIMER,
+	.of_match = atmel_tcb_ids,
+	.of_to_plat = atmel_tcb_of_to_plat,
+	.plat_auto = sizeof(struct atmel_tcb_plat),
+	.probe = atmel_tcb_probe,
+	.ops = &atmel_tcb_ops,
+};