OMAP2/3 GPTIMER: allow system tick GPTIMER to be changed in board-*.c files

Add a function omap2_gp_clockevent_set_gptimer() for board-*.c files
to use in .init_irq functions to configure the system tick GPTIMER.
Practical choices at this point are GPTIMER1 or GPTIMER12.  Both of
these timers are in the WKUP powerdomain, and so are unaffected by
chip power management.  GPTIMER1 can use sys_clk as a source, for
applications where a high-resolution timer is more important than
power management.  GPTIMER12 has the special property that it has the
secure 32kHz oscillator as its source clock, which may be less prone
to glitches than the off-chip 32kHz oscillator.  But on HS devices, it
may not be available for Linux use.

It appears that most boards are fine with GPTIMER1, but BeagleBoard
should use GPTIMER12 when using a 32KiHz timer source, due to hardware bugs
in revisions B4 and below.  Modify board-omap3beagle.c to use GPTIMER12.

This patch originally used a Kbuild config option to select the GPTIMER,
but was changed to allow this to be specified in board-*.c files, per
Tony's request.

Kalle Vallo <kalle.valo@nokia.com> found a bug in an earlier version of
this patch - thanks Kalle.

Tested on Beagle rev B4 ES2.1, with and without CONFIG_OMAP_32K_TIMER, and
3430SDP.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Cc: Kalle Valo <kalle.valo@nokia.com>

1 files changed, 45 insertions, 3 deletions

diff --git a/arch/arm/mach-omap2/timer-gp.c b/arch/arm/mach-omap2/timer-gp.c
index 9fc13a2cc3f..7835048041e 100644
--- a/arch/arm/mach-omap2/timer-gp.c
+++ b/arch/arm/mach-omap2/timer-gp.c
@@ -3,6 +3,8 @@
  *
  * OMAP2 GP timer support.
  *
+ * Copyright (C) 2009 Nokia Corporation
+ *
  * Update to use new clocksource/clockevent layers
  * Author: Kevin Hilman, MontaVista Software, Inc. <source@mvista.com>
  * Copyright (C) 2007 MontaVista Software, Inc.
@@ -36,8 +38,13 @@
 #include <asm/mach/time.h>
 #include <mach/dmtimer.h>
 
+/* MAX_GPTIMER_ID: number of GPTIMERs on the chip */
+#define MAX_GPTIMER_ID		12
+
 static struct omap_dm_timer *gptimer;
 static struct clock_event_device clockevent_gpt;
+static u8 __initdata gptimer_id = 1;
+static u8 __initdata inited;
 
 static irqreturn_t omap2_gp_timer_interrupt(int irq, void *dev_id)
 {
@@ -95,20 +102,53 @@ static struct clock_event_device clockevent_gpt = {
 	.set_mode	= omap2_gp_timer_set_mode,
 };
 
+/**
+ * omap2_gp_clockevent_set_gptimer - set which GPTIMER is used for clockevents
+ * @id: GPTIMER to use (1..MAX_GPTIMER_ID)
+ *
+ * Define the GPTIMER that the system should use for the tick timer.
+ * Meant to be called from board-*.c files in the event that GPTIMER1, the
+ * default, is unsuitable.  Returns -EINVAL on error or 0 on success.
+ */
+int __init omap2_gp_clockevent_set_gptimer(u8 id)
+{
+	if (id < 1 || id > MAX_GPTIMER_ID)
+		return -EINVAL;
+
+	BUG_ON(inited);
+
+	gptimer_id = id;
+
+	return 0;
+}
+
 static void __init omap2_gp_clockevent_init(void)
 {
 	u32 tick_rate;
+	int src;
+
+	inited = 1;
 
-	gptimer = omap_dm_timer_request_specific(1);
+	gptimer = omap_dm_timer_request_specific(gptimer_id);
 	BUG_ON(gptimer == NULL);
 
 #if defined(CONFIG_OMAP_32K_TIMER)
-	omap_dm_timer_set_source(gptimer, OMAP_TIMER_SRC_32_KHZ);
+	src = OMAP_TIMER_SRC_32_KHZ;
 #else
-	omap_dm_timer_set_source(gptimer, OMAP_TIMER_SRC_SYS_CLK);
+	src = OMAP_TIMER_SRC_SYS_CLK;
+	WARN(gptimer_id == 12, "WARNING: GPTIMER12 can only use the "
+	     "secure 32KiHz clock source\n");
 #endif
+
+	if (gptimer_id != 12)
+		WARN(IS_ERR_VALUE(omap_dm_timer_set_source(gptimer, src)),
+		     "timer-gp: omap_dm_timer_set_source() failed\n");
+
 	tick_rate = clk_get_rate(omap_dm_timer_get_fclk(gptimer));
 
+	pr_info("OMAP clockevent source: GPTIMER%d at %u Hz\n",
+		gptimer_id, tick_rate);
+
 	omap2_gp_timer_irq.dev_id = (void *)gptimer;
 	setup_irq(omap_dm_timer_get_irq(gptimer), &omap2_gp_timer_irq);
 	omap_dm_timer_set_int_enable(gptimer, OMAP_TIMER_INT_OVERFLOW);
@@ -125,6 +165,8 @@ static void __init omap2_gp_clockevent_init(void)
 	clockevents_register_device(&clockevent_gpt);
 }
 
+/* Clocksource code */
+
 #ifdef CONFIG_OMAP_32K_TIMER
 /* 
  * When 32k-timer is enabled, don't use GPTimer for clocksource