[PATCH V2 2/4] ARM: Xilinx: Adding timer support to the platform

[John Linn]

The timer driver supports the Xilinx PS Timer Counter IP.

Signed-off-by: Kiran Sutariya <kiran.sutariya@xxxxxxxxxxxxxx>
Signed-off-by: John Linn <john.linn@xxxxxxxxxx>
---

V2 Changes

The timer code was changed quite a bit based on review inputs. It
got much smaller and cleaner I think.

Updates based on Russell King's comments	
	minor cleanups for documentation comments
	removed the name from the timer structure
	removed interrupt for clock source 
	moved to using clock functions provided in the kernel
		for calculating shift/mult values
	removed PM code as generic handles it

Updated based on Jamie Iles's comment
	cleaned up ENABLE_MASK which was confusing
	now using platform_add_devices() from platform code
	moved base_addr to void __iomem pointer
	removed stop of the event timer in one shot mode

 arch/arm/mach-xilinx/Makefile |    2 +-
 arch/arm/mach-xilinx/timer.c  |  301 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 302 insertions(+), 1 deletions(-)
 create mode 100644 arch/arm/mach-xilinx/timer.c

diff --git a/arch/arm/mach-xilinx/Makefile b/arch/arm/mach-xilinx/Makefile
index 783343b..194f9e4 100644
--- a/arch/arm/mach-xilinx/Makefile
+++ b/arch/arm/mach-xilinx/Makefile
@@ -3,4 +3,4 @@
 #
 
 # Common support
-obj-y := common.o board_ep107.o
+obj-y := common.o board_ep107.o timer.o
diff --git a/arch/arm/mach-xilinx/timer.c b/arch/arm/mach-xilinx/timer.c
new file mode 100644
index 0000000..31dcbfc
--- /dev/null
+++ b/arch/arm/mach-xilinx/timer.c
@@ -0,0 +1,301 @@
+/* arch/arm/mach-xilinx/timer.c
+ *
+ * This file contains driver for the Xilinx PS Timer Counter IP.
+ *
+ *  Copyright (C) 2011 Xilinx
+ *
+ * based on arch/mips/kernel/time.c timer driver
+ *
+ * This program is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License version 2 as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
+ * Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/types.h>
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <linux/io.h>
+
+#include <asm/mach/time.h>
+#include <mach/xilinx_soc.h>
+
+/*
+ * This driver configures the 2 16-bit count-up timers as follows:
+ *
+ * T1: Timer 1, clocksource for generic timekeeping
+ * T2: Timer 2, clockevent source for hrtimers
+ * T3: Timer 3, <unused>
+ *
+ * The input frequency to the timer module for emulation is 2.5MHz which is
+ * common to all the timer channels (T1, T2, and T3). With a pre-scaler of 32,
+ * the timers are clocked at 78.125KHz (12.8 us resolution).
+ *
+ * The input frequency to the timer module in silicon will be 200MHz. With the
+ * pre-scaler of 32, the timers are clocked at 6.25MHz (160ns resolution).
+ */
+#define XTTCPSS_CLOCKSOURCE	0	/* Timer 1 as a generic timekeeping */
+#define XTTCPSS_CLOCKEVENT	1	/* Timer 2 as a clock event */
+
+#define XTTCPSS_TIMER_BASE		TTC0_BASE
+#define XTTCPCC_EVENT_TIMER_IRQ		(IRQ_TIMERCOUNTER0 + 1)
+/*
+ * Timer Register Offset Definitions of Timer 1, Increment base address by 4
+ * and use same offsets for Timer 2
+ */
+#define XTTCPSS_CLK_CNTRL_OFFSET	0x00 /* Clock Control Reg, RW */
+#define XTTCPSS_CNT_CNTRL_OFFSET	0x0C /* Counter Control Reg, RW */
+#define XTTCPSS_COUNT_VAL_OFFSET	0x18 /* Counter Value Reg, RO */
+#define XTTCPSS_INTR_VAL_OFFSET		0x24 /* Interval Count Reg, RW */
+#define XTTCPSS_MATCH_1_OFFSET		0x30 /* Match 1 Value Reg, RW */
+#define XTTCPSS_MATCH_2_OFFSET		0x3C /* Match 2 Value Reg, RW */
+#define XTTCPSS_MATCH_3_OFFSET		0x48 /* Match 3 Value Reg, RW */
+#define XTTCPSS_ISR_OFFSET		0x54 /* Interrupt Status Reg, RO */
+#define XTTCPSS_IER_OFFSET		0x60 /* Interrupt Enable Reg, RW */
+
+#define XTTCPSS_CNT_CNTRL_DISABLE_MASK	0x1
+
+/**
+ * struct xttcpss_timer - This definition defines local timer structure
+ *
+ * @base_addr:	Base address of timer
+ * @timer_irq:	irqaction structure for the timer device
+ * @mode:       only valid for an clock event, periodic or one-shot
+ **/
+struct xttcpss_timer {
+	void __iomem *base_addr;
+	enum clock_event_mode mode;
+};
+
+static struct xttcpss_timer timers[2];
+static struct clock_event_device xttcpss_clockevent;
+
+/**
+ * xttcpss_set_interval - Set the timer interval value
+ *
+ * @timer:	Pointer to the timer instance
+ * @cycles:	Timer interval ticks
+ **/
+static void xttcpss_set_interval(struct xttcpss_timer *timer,
+					unsigned long cycles)
+{
+	u32 ctrl_reg;
+
+	/* Disable the counter, set the counter value  and re-enable counter */
+	ctrl_reg = __raw_readl(timer->base_addr + XTTCPSS_CNT_CNTRL_OFFSET);
+	ctrl_reg |= XTTCPSS_CNT_CNTRL_DISABLE_MASK;
+	__raw_writel(ctrl_reg, timer->base_addr + XTTCPSS_CNT_CNTRL_OFFSET);
+
+	__raw_writel(cycles, timer->base_addr + XTTCPSS_INTR_VAL_OFFSET);
+
+	/* Reset the counter (0x10) so that it starts from 0, one-shot
+	   mode makes this needed for timing to be right. */
+	ctrl_reg |= 0x10;
+	ctrl_reg &= ~XTTCPSS_CNT_CNTRL_DISABLE_MASK;
+	__raw_writel(ctrl_reg, timer->base_addr + XTTCPSS_CNT_CNTRL_OFFSET);
+}
+
+/**
+ * xttcpss_clock_event_interrupt - Clock event timer interrupt handler
+ *
+ * @irq:	IRQ number of the Timer
+ * @dev_id:	void pointer to the xttcpss_timer instance
+ *
+ * returns: Always IRQ_HANDLED - success
+ **/
+static irqreturn_t xttcpss_clock_event_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = &xttcpss_clockevent;
+	struct xttcpss_timer *timer = dev_id;
+
+	/* Acknowledge the interrupt and call event handler */
+	__raw_writel(__raw_readl(timer->base_addr + XTTCPSS_ISR_OFFSET),
+			timer->base_addr + XTTCPSS_ISR_OFFSET);
+
+	evt->event_handler(evt);
+
+	return IRQ_HANDLED;
+}
+
+static struct irqaction event_timer_irq = {
+	.name	= "xttcpss clockevent",
+	.flags	= IRQF_DISABLED | IRQF_TIMER,
+	.handler = xttcpss_clock_event_interrupt,
+};
+
+/**
+ * xttcpss_timer_hardware_init - Initialize the timer hardware
+ *
+ * Initialize the hardware to start the clock source, get the clock
+ * event timer ready to use, and hook up the interrupt.
+ **/
+static void __init xttcpss_timer_hardware_init(void)
+{
+	/* Setup the clock source counter to be an incrementing counter
+	 * with no interrupt and it rolls over at 0xFFFF. Pre-scale
+	   it by 32 also. Let it start running now.
+	 */
+	timers[XTTCPSS_CLOCKSOURCE].base_addr = XTTCPSS_TIMER_BASE;
+
+	__raw_writel(0x0, timers[XTTCPSS_CLOCKSOURCE].base_addr +
+				XTTCPSS_IER_OFFSET);
+	__raw_writel(0x9, timers[XTTCPSS_CLOCKSOURCE].base_addr +
+				XTTCPSS_CLK_CNTRL_OFFSET);
+	__raw_writel(0x10, timers[XTTCPSS_CLOCKSOURCE].base_addr +
+				XTTCPSS_CNT_CNTRL_OFFSET);
+
+	/* Setup the clock event timer to be an interval timer which
+	 * is prescaled by 32 using the interval interrupt. Leave it
+	 * disabled for now.
+	 */
+
+	timers[XTTCPSS_CLOCKEVENT].base_addr = XTTCPSS_TIMER_BASE + 4;
+
+	__raw_writel(0x23, timers[XTTCPSS_CLOCKEVENT].base_addr +
+			XTTCPSS_CNT_CNTRL_OFFSET);
+	__raw_writel(0x9, timers[XTTCPSS_CLOCKEVENT].base_addr +
+			XTTCPSS_CLK_CNTRL_OFFSET);
+	__raw_writel(0x1, timers[XTTCPSS_CLOCKEVENT].base_addr +
+			XTTCPSS_IER_OFFSET);
+
+	/* Setup IRQ the clock event timer */
+	event_timer_irq.dev_id = &timers[XTTCPSS_CLOCKEVENT];
+
+	if (event_timer_irq.handler != NULL)
+		setup_irq(XTTCPCC_EVENT_TIMER_IRQ, &event_timer_irq);
+}
+
+/**
+ * __raw_readl_cycles - Reads the timer counter register
+ *
+ * returns: Current timer counter register value
+ **/
+static cycle_t __raw_readl_cycles(struct clocksource *cs)
+{
+	struct xttcpss_timer *timer = &timers[XTTCPSS_CLOCKSOURCE];
+
+	return (cycle_t)__raw_readl(timer->base_addr +
+				XTTCPSS_COUNT_VAL_OFFSET);
+}
+
+
+/*
+ * Instantiate and initialize the clock source structure
+ */
+static struct clocksource clocksource_xttcpss = {
+	.name		= "xttcpss_timer1",
+	.rating		= 200,			/* Reasonable clock source */
+	.read		= __raw_readl_cycles,
+	.mask		= CLOCKSOURCE_MASK(16),
+	.shift		= 0,			/* Initialized to zero */
+	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+
+/**
+ * xttcpss_set_next_event - Sets the time interval for next event
+ *
+ * @cycles:	Timer interval ticks
+ * @evt:	Address of clock event instance
+ *
+ * returns: Always 0 - success
+ **/
+static int xttcpss_set_next_event(unsigned long cycles,
+					struct clock_event_device *evt)
+{
+	struct xttcpss_timer *timer = &timers[XTTCPSS_CLOCKEVENT];
+
+	xttcpss_set_interval(timer, cycles);
+	return 0;
+}
+
+/**
+ * xttcpss_set_mode - Sets the mode of timer
+ *
+ * @mode:	Mode to be set
+ * @evt:	Address of clock event instance
+ **/
+static void xttcpss_set_mode(enum clock_event_mode mode,
+					struct clock_event_device *evt)
+{
+	struct xttcpss_timer *timer = &timers[XTTCPSS_CLOCKEVENT];
+	u32 ctrl_reg;
+
+	timer->mode = mode;
+
+	switch (mode) {
+	case CLOCK_EVT_MODE_PERIODIC:
+		xttcpss_set_interval(timer, CLOCK_TICK_RATE / HZ);
+		break;
+	case CLOCK_EVT_MODE_ONESHOT:
+	case CLOCK_EVT_MODE_UNUSED:
+	case CLOCK_EVT_MODE_SHUTDOWN:
+		ctrl_reg = __raw_readl(timer->base_addr +
+					XTTCPSS_CNT_CNTRL_OFFSET);
+		ctrl_reg |= XTTCPSS_CNT_CNTRL_DISABLE_MASK;
+		__raw_writel(ctrl_reg,
+				timer->base_addr + XTTCPSS_CNT_CNTRL_OFFSET);
+		break;
+	case CLOCK_EVT_MODE_RESUME:
+		ctrl_reg = __raw_readl(timer->base_addr +
+					XTTCPSS_CNT_CNTRL_OFFSET);
+		ctrl_reg &= ~XTTCPSS_CNT_CNTRL_DISABLE_MASK;
+		__raw_writel(ctrl_reg,
+				timer->base_addr + XTTCPSS_CNT_CNTRL_OFFSET);
+		break;
+	}
+}
+
+/*
+ * Instantiate and initialize the clock event structure
+ */
+static struct clock_event_device xttcpss_clockevent = {
+	.name		= "xttcpss_timer2",
+	.features	= CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
+	.shift		= 0,		/* Initialized to zero */
+	.set_next_event	= xttcpss_set_next_event,
+	.set_mode	= xttcpss_set_mode,
+	.rating		= 200,
+};
+
+/**
+ * xttcpss_timer_init - Initialize the timer
+ *
+ * Initializes the timer hardware and register the clock source and clock event
+ * timers with Linux kernal timer framework
+ **/
+static void __init xttcpss_timer_init(void)
+{
+	xttcpss_timer_hardware_init();
+	clocksource_register_hz(&clocksource_xttcpss, CLOCK_TICK_RATE);
+
+	/* Calculate the parameters to allow the clockevent to operate using
+	   integer math
+	*/
+	clockevents_calc_mult_shift(&xttcpss_clockevent, CLOCK_TICK_RATE, 4);
+
+	xttcpss_clockevent.max_delta_ns =
+		clockevent_delta2ns(0xfffe, &xttcpss_clockevent);
+	xttcpss_clockevent.min_delta_ns =
+		clockevent_delta2ns(1, &xttcpss_clockevent);
+
+	/* Indicate that clock event can be used on any of the CPUs */
+
+	xttcpss_clockevent.cpumask = cpu_all_mask;
+	clockevents_register_device(&xttcpss_clockevent);
+}
+
+/*
+ * Instantiate and initialize the system timer structure
+ */
+struct sys_timer xttcpss_sys_timer = {
+	.init		= xttcpss_timer_init,
+};
-- 
1.6.2.1



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