RE: [PATCH 3/5] ARM: twd: Add context save restore support

[Santosh Shilimkar <santosh.shilimkar@ti.com>]

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Russell, Thomas
> -----Original Message-----
> From: Russell King - ARM Linux [mailto:linux@arm.linux.org.uk]
> Sent: Tuesday, January 25, 2011 7:08 PM
> To: Thomas Gleixner
> Cc: Colin Cross; Santosh Shilimkar; catalin.marinas@arm.com;
> linus.ml.walleij@gmail.com; linux-omap@vger.kernel.org; linux-arm-
> kernel@lists.infradead.org
> Subject: Re: [PATCH 3/5] ARM: twd: Add context save restore support
>
[...]
>
> I can't say because these patches only add the hooks, there's no
> implementation yet which uses the hooks.
>
> Given the description about _why_ those hooks are necessary, it
> seems
> that something is required.  Either we start adding custom hacks to
> each clockevent driver as is done with this patch, or we get some
> generic help in place.
>
> I'm not thrilled by the custom hack approach - and I thought the
> clockevent stuff was created to stop this kind of thing happening.
>
> I suggest we defer this until there's a visible use case available.
Got some time to debug this issue. OMAP idle code already has the
broad-cast notifiers working for sometime. So I removed the existing
save restore twd code and just used the below patch which Russell
posted on this thread.
And things just work and I guess we are done with this issue !!
Timer framework is doing all right things with notifiers.

Am going to use this patch for my further work and drop the
save/restore patch. Will update you if there is any other
issue on this. I should have validated this patch on my own
earlier :(

Thanks for the discussion.

-----------------
>From 9084dd3e68a8528172d97fb49c42437ae873af43 Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@arm.linux.org.uk>
Date: Tue, 25 Jan 2011 14:26:41 +0530
Subject: [PATCH] ARM: smp_twd: Always program the loadvalue when switching
to periodic mode.

Always program the load value when switching to periodic mode so that
we don't need to save restore twd load register.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
 arch/arm/kernel/smp_twd.c |    7 ++-----
 1 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
index fd91566..60636f4 100644
--- a/arch/arm/kernel/smp_twd.c
+++ b/arch/arm/kernel/smp_twd.c
@@ -36,6 +36,7 @@ static void twd_set_mode(enum clock_event_mode mode,
 		/* timer load already set up */
 		ctrl = TWD_TIMER_CONTROL_ENABLE |
TWD_TIMER_CONTROL_IT_ENABLE
 			| TWD_TIMER_CONTROL_PERIODIC;
+		__raw_writel(twd_timer_rate / HZ, twd_base +
TWD_TIMER_LOAD);
 		break;
 	case CLOCK_EVT_MODE_ONESHOT:
 		/* period set, and timer enabled in 'next_event' hook */
@@ -81,7 +82,7 @@ int twd_timer_ack(void)

 static void __cpuinit twd_calibrate_rate(void)
 {
-	unsigned long load, count;
+	unsigned long count;
 	u64 waitjiffies;

 	/*
@@ -116,10 +117,6 @@ static void __cpuinit twd_calibrate_rate(void)
 		printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
 			(twd_timer_rate / 1000000) % 100);
 	}
-
-	load = twd_timer_rate / HZ;
-
-	__raw_writel(load, twd_base + TWD_TIMER_LOAD);
 }

 /*
-- 
1.6.0.4

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From 9084dd3e68a8528172d97fb49c42437ae873af43 Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@arm.linux.org.uk>
Date: Tue, 25 Jan 2011 14:26:41 +0530
Subject: [PATCH] ARM: smp_twd: Always program the loadvalue when switching to periodic mode.

Always program the load value when switching to periodic mode so that
we don't need to save restore twd load register.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
 arch/arm/kernel/smp_twd.c |    7 ++-----
 1 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
index fd91566..60636f4 100644
--- a/arch/arm/kernel/smp_twd.c
+++ b/arch/arm/kernel/smp_twd.c
@@ -36,6 +36,7 @@ static void twd_set_mode(enum clock_event_mode mode,
 		/* timer load already set up */
 		ctrl = TWD_TIMER_CONTROL_ENABLE | TWD_TIMER_CONTROL_IT_ENABLE
 			| TWD_TIMER_CONTROL_PERIODIC;
+		__raw_writel(twd_timer_rate / HZ, twd_base + TWD_TIMER_LOAD);
 		break;
 	case CLOCK_EVT_MODE_ONESHOT:
 		/* period set, and timer enabled in 'next_event' hook */
@@ -81,7 +82,7 @@ int twd_timer_ack(void)
 
 static void __cpuinit twd_calibrate_rate(void)
 {
-	unsigned long load, count;
+	unsigned long count;
 	u64 waitjiffies;
 
 	/*
@@ -116,10 +117,6 @@ static void __cpuinit twd_calibrate_rate(void)
 		printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
 			(twd_timer_rate / 1000000) % 100);
 	}
-
-	load = twd_timer_rate / HZ;
-
-	__raw_writel(load, twd_base + TWD_TIMER_LOAD);
 }
 
 /*
-- 
1.6.0.4


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