ARM: clocksource: Add asm9260_timer driver

In some cases asm9260 looks similar to iMX2x. One of exceptions is
timer controller. So this patch introduces new driver for this special case.

Signed-off-by: Oleksij Rempel <[e-mail]>
Acked-by: Daniel Lezcano <[e-mail]>
Signed-off-by: Daniel Lezcano <[e-mail]>

drivers/clocksource/Kconfig

···
 	depends on MIPS_GIC
 	select CLKSRC_OF
 
+config ASM9260_TIMER
+	bool "Alphascale ASM9260 timer driver"
+	depends on GENERIC_CLOCKEVENTS
+	select CLKSRC_MMIO
+	select CLKSRC_OF
+	default y if MACH_ASM9260
+	help
+	  This enables build of a clocksource and clockevent driver for
+	  the 32-bit System Timer hardware available on a Alphascale ASM9260.
+
 endmenu

drivers/clocksource/Makefile

···
 obj-$(CONFIG_ARCH_INTEGRATOR_AP)	+= timer-integrator-ap.o
 obj-$(CONFIG_CLKSRC_VERSATILE)		+= versatile.o
 obj-$(CONFIG_CLKSRC_MIPS_GIC)		+= mips-gic-timer.o
+obj-$(CONFIG_ASM9260_TIMER)		+= asm9260_timer.o

drivers/clocksource/asm9260_timer.c

···
+/*
+ * Copyright (C) 2014 Oleksij Rempel <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <linux/clk.h>
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/bitops.h>
+
+#define DRIVER_NAME	"asm9260-timer"
+
+/*
+ * this device provide 4 offsets for each register:
+ * 0x0 - plain read write mode
+ * 0x4 - set mode, OR logic.
+ * 0x8 - clr mode, XOR logic.
+ * 0xc - togle mode.
+ */
+#define SET_REG 4
+#define CLR_REG 8
+
+#define HW_IR           0x0000 /* RW. Interrupt */
+#define BM_IR_CR0	BIT(4)
+#define BM_IR_MR3	BIT(3)
+#define BM_IR_MR2	BIT(2)
+#define BM_IR_MR1	BIT(1)
+#define BM_IR_MR0	BIT(0)
+
+#define HW_TCR		0x0010 /* RW. Timer controller */
+/* BM_C*_RST
+ * Timer Counter and the Prescale Counter are synchronously reset on the
+ * next positive edge of PCLK. The counters remain reset until TCR[1] is
+ * returned to zero. */
+#define BM_C3_RST	BIT(7)
+#define BM_C2_RST	BIT(6)
+#define BM_C1_RST	BIT(5)
+#define BM_C0_RST	BIT(4)
+/* BM_C*_EN
+ * 1 - Timer Counter and Prescale Counter are enabled for counting
+ * 0 - counters are disabled */
+#define BM_C3_EN	BIT(3)
+#define BM_C2_EN	BIT(2)
+#define BM_C1_EN	BIT(1)
+#define BM_C0_EN	BIT(0)
+
+#define HW_DIR		0x0020 /* RW. Direction? */
+/* 00 - count up
+ * 01 - count down
+ * 10 - ?? 2^n/2 */
+#define BM_DIR_COUNT_UP		0
+#define BM_DIR_COUNT_DOWN	1
+#define BM_DIR0_SHIFT	0
+#define BM_DIR1_SHIFT	4
+#define BM_DIR2_SHIFT	8
+#define BM_DIR3_SHIFT	12
+#define BM_DIR_DEFAULT		(BM_DIR_COUNT_UP << BM_DIR0_SHIFT | \
+				 BM_DIR_COUNT_UP << BM_DIR1_SHIFT | \
+				 BM_DIR_COUNT_UP << BM_DIR2_SHIFT | \
+				 BM_DIR_COUNT_UP << BM_DIR3_SHIFT)
+
+#define HW_TC0		0x0030 /* RO. Timer counter 0 */
+/* HW_TC*. Timer counter owerflow (0xffff.ffff to 0x0000.0000) do not generate
+ * interrupt. This registers can be used to detect overflow */
+#define HW_TC1          0x0040
+#define HW_TC2		0x0050
+#define HW_TC3		0x0060
+
+#define HW_PR		0x0070 /* RW. prescaler */
+#define BM_PR_DISABLE	0
+#define HW_PC		0x0080 /* RO. Prescaler counter */
+#define HW_MCR		0x0090 /* RW. Match control */
+/* enable interrupt on match */
+#define BM_MCR_INT_EN(n)	(1 << (n * 3 + 0))
+/* enable TC reset on match */
+#define BM_MCR_RES_EN(n)	(1 << (n * 3 + 1))
+/* enable stop TC on match */
+#define BM_MCR_STOP_EN(n)	(1 << (n * 3 + 2))
+
+#define HW_MR0		0x00a0 /* RW. Match reg */
+#define HW_MR1		0x00b0
+#define HW_MR2		0x00C0
+#define HW_MR3		0x00D0
+
+#define HW_CTCR		0x0180 /* Counter control */
+#define BM_CTCR0_SHIFT	0
+#define BM_CTCR1_SHIFT	2
+#define BM_CTCR2_SHIFT	4
+#define BM_CTCR3_SHIFT	6
+#define BM_CTCR_TM	0	/* Timer mode. Every rising PCLK edge. */
+#define BM_CTCR_DEFAULT	(BM_CTCR_TM << BM_CTCR0_SHIFT | \
+			 BM_CTCR_TM << BM_CTCR1_SHIFT | \
+			 BM_CTCR_TM << BM_CTCR2_SHIFT | \
+			 BM_CTCR_TM << BM_CTCR3_SHIFT)
+
+static struct asm9260_timer_priv {
+	void __iomem *base;
+	unsigned long ticks_per_jiffy;
+} priv;
+
+static int asm9260_timer_set_next_event(unsigned long delta,
+					 struct clock_event_device *evt)
+{
+	/* configure match count for TC0 */
+	writel_relaxed(delta, priv.base + HW_MR0);
+	/* enable TC0 */
+	writel_relaxed(BM_C0_EN, priv.base + HW_TCR + SET_REG);
+	return 0;
+}
+
+static void asm9260_timer_set_mode(enum clock_event_mode mode,
+				    struct clock_event_device *evt)
+{
+	/* stop timer0 */
+	writel_relaxed(BM_C0_EN, priv.base + HW_TCR + CLR_REG);
+
+	switch (mode) {
+	case CLOCK_EVT_MODE_PERIODIC:
+		/* disable reset and stop on match */
+		writel_relaxed(BM_MCR_RES_EN(0) | BM_MCR_STOP_EN(0),
+				priv.base + HW_MCR + CLR_REG);
+		/* configure match count for TC0 */
+		writel_relaxed(priv.ticks_per_jiffy, priv.base + HW_MR0);
+		/* enable TC0 */
+		writel_relaxed(BM_C0_EN, priv.base + HW_TCR + SET_REG);
+		break;
+	case CLOCK_EVT_MODE_ONESHOT:
+		/* enable reset and stop on match */
+		writel_relaxed(BM_MCR_RES_EN(0) | BM_MCR_STOP_EN(0),
+				priv.base + HW_MCR + SET_REG);
+		break;
+	default:
+		break;
+	}
+}
+
+static struct clock_event_device event_dev = {
+	.name		= DRIVER_NAME,
+	.rating		= 200,
+	.features       = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
+	.set_next_event	= asm9260_timer_set_next_event,
+	.set_mode	= asm9260_timer_set_mode,
+};
+
+static irqreturn_t asm9260_timer_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = dev_id;
+
+	evt->event_handler(evt);
+
+	writel_relaxed(BM_IR_MR0, priv.base + HW_IR);
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * ---------------------------------------------------------------------------
+ * Timer initialization
+ * ---------------------------------------------------------------------------
+ */
+static void __init asm9260_timer_init(struct device_node *np)
+{
+	int irq;
+	struct clk *clk;
+	int ret;
+	unsigned long rate;
+
+	priv.base = of_io_request_and_map(np, 0, np->name);
+	if (!priv.base)
+		panic("%s: unable to map resource", np->name);
+
+	clk = of_clk_get(np, 0);
+
+	ret = clk_prepare_enable(clk);
+	if (ret)
+		panic("Failed to enable clk!\n");
+
+	irq = irq_of_parse_and_map(np, 0);
+	ret = request_irq(irq, asm9260_timer_interrupt, IRQF_TIMER,
+			DRIVER_NAME, &event_dev);
+	if (ret)
+		panic("Failed to setup irq!\n");
+
+	/* set all timers for count-up */
+	writel_relaxed(BM_DIR_DEFAULT, priv.base + HW_DIR);
+	/* disable divider */
+	writel_relaxed(BM_PR_DISABLE, priv.base + HW_PR);
+	/* make sure all timers use every rising PCLK edge. */
+	writel_relaxed(BM_CTCR_DEFAULT, priv.base + HW_CTCR);
+	/* enable interrupt for TC0 and clean setting for all other lines */
+	writel_relaxed(BM_MCR_INT_EN(0) , priv.base + HW_MCR);
+
+	rate = clk_get_rate(clk);
+	clocksource_mmio_init(priv.base + HW_TC1, DRIVER_NAME, rate,
+			200, 32, clocksource_mmio_readl_up);
+
+	/* Seems like we can't use counter without match register even if
+	 * actions for MR are disabled. So, set MR to max value. */
+	writel_relaxed(0xffffffff, priv.base + HW_MR1);
+	/* enable TC1 */
+	writel_relaxed(BM_C1_EN, priv.base + HW_TCR + SET_REG);
+
+	priv.ticks_per_jiffy = DIV_ROUND_CLOSEST(rate, HZ);
+	event_dev.cpumask = cpumask_of(0);
+	clockevents_config_and_register(&event_dev, rate, 0x2c00, 0xfffffffe);
+}
+CLOCKSOURCE_OF_DECLARE(asm9260_timer, "alphascale,asm9260-timer",
+		asm9260_timer_init);