* [PATCH] ARM: TWD: fix the clock calculation for TWD
@ 2011-01-20 6:33 Chao Xie
2011-01-20 14:08 ` Russell King - ARM Linux
0 siblings, 1 reply; 6+ messages in thread
From: Chao Xie @ 2011-01-20 6:33 UTC (permalink / raw)
To: linux-arm-kernel
The original code will do count * (HZ /5). It will make the twd
timer rate decreased if HZ can not be excatly divided. For
example HZ=128.
Signed-off-by: Chao Xie <chao.xie@marvell.com>
---
arch/arm/kernel/smp_twd.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
index 35882fb..ca6405b 100644
--- a/arch/arm/kernel/smp_twd.c
+++ b/arch/arm/kernel/smp_twd.c
@@ -111,7 +111,8 @@ static void __cpuinit twd_calibrate_rate(void)
count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
- twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
+ twd_timer_rate = ((unsigned long)(0xFFFFFFFFU - count))
+ * HZ / 5;
printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
(twd_timer_rate / 100000) % 100);
--
1.6.3.3
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH] ARM: TWD: fix the clock calculation for TWD
2011-01-20 6:33 [PATCH] ARM: TWD: fix the clock calculation for TWD Chao Xie
@ 2011-01-20 14:08 ` Russell King - ARM Linux
2011-01-20 14:44 ` Jamie Iles
0 siblings, 1 reply; 6+ messages in thread
From: Russell King - ARM Linux @ 2011-01-20 14:08 UTC (permalink / raw)
To: linux-arm-kernel
On Thu, Jan 20, 2011 at 02:33:57PM +0800, Chao Xie wrote:
> The original code will do count * (HZ /5). It will make the twd
> timer rate decreased if HZ can not be excatly divided. For
> example HZ=128.
>
> Signed-off-by: Chao Xie <chao.xie@marvell.com>
> ---
> arch/arm/kernel/smp_twd.c | 3 ++-
> 1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
> index 35882fb..ca6405b 100644
> --- a/arch/arm/kernel/smp_twd.c
> +++ b/arch/arm/kernel/smp_twd.c
> @@ -111,7 +111,8 @@ static void __cpuinit twd_calibrate_rate(void)
>
> count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
>
> - twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
> + twd_timer_rate = ((unsigned long)(0xFFFFFFFFU - count))
> + * HZ / 5;
>
> printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
> (twd_timer_rate / 100000) % 100);
I don't think this patch has any effect what so ever, so I just tried:
#define HZ 128
unsigned long twd_timer_rate;
void calc1(unsigned long count)
{
twd_timer_rate = (0xffffffffU - count) * (HZ / 5);
}
void calc2(unsigned long count)
{
twd_timer_rate = ((unsigned long)(0xffffffffU - count)) * (HZ / 5);
}
calc1:
@ args = 0, pretend = 0, frame = 0
@ frame_needed = 0, uses_anonymous_args = 0
@ link register save eliminated.
mvn r0, r0
add r0, r0, r0, asl #2
ldr r3, .L2
add r0, r0, r0, asl #2
@ lr needed for prologue
str r0, [r3, #0]
mov pc, lr
calc2:
@ args = 0, pretend = 0, frame = 0
@ frame_needed = 0, uses_anonymous_args = 0
@ link register save eliminated.
mvn r0, r0
add r0, r0, r0, asl #2
ldr r3, .L5
add r0, r0, r0, asl #2
@ lr needed for prologue
str r0, [r3, #0]
mov pc, lr
The code looks identical to me, so the patch appears to have no effect.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH] ARM: TWD: fix the clock calculation for TWD
2011-01-20 14:08 ` Russell King - ARM Linux
@ 2011-01-20 14:44 ` Jamie Iles
2011-01-20 16:38 ` Russell King - ARM Linux
0 siblings, 1 reply; 6+ messages in thread
From: Jamie Iles @ 2011-01-20 14:44 UTC (permalink / raw)
To: linux-arm-kernel
On Thu, Jan 20, 2011 at 02:08:11PM +0000, Russell King - ARM Linux wrote:
> On Thu, Jan 20, 2011 at 02:33:57PM +0800, Chao Xie wrote:
> > The original code will do count * (HZ /5). It will make the twd
> > timer rate decreased if HZ can not be excatly divided. For
> > example HZ=128.
> >
> > Signed-off-by: Chao Xie <chao.xie@marvell.com>
> > ---
> > arch/arm/kernel/smp_twd.c | 3 ++-
> > 1 files changed, 2 insertions(+), 1 deletions(-)
> >
> > diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
> > index 35882fb..ca6405b 100644
> > --- a/arch/arm/kernel/smp_twd.c
> > +++ b/arch/arm/kernel/smp_twd.c
> > @@ -111,7 +111,8 @@ static void __cpuinit twd_calibrate_rate(void)
> >
> > count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
> >
> > - twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
> > + twd_timer_rate = ((unsigned long)(0xFFFFFFFFU - count))
> > + * HZ / 5;
> >
> > printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
> > (twd_timer_rate / 100000) % 100);
>
> I don't think this patch has any effect what so ever, so I just tried:
>
> #define HZ 128
> unsigned long twd_timer_rate;
> void calc1(unsigned long count)
> {
> twd_timer_rate = (0xffffffffU - count) * (HZ / 5);
> }
> void calc2(unsigned long count)
> {
> twd_timer_rate = ((unsigned long)(0xffffffffU - count)) * (HZ / 5);
> }
Hi Russell,
In Chao's patch the parentheses around (HZ / 5) have been removed so its
now dowing the multiplication before the division (if I remember the
precedences correctly!). I don't think the cast to unsigned long is
needed though.
Jamie
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH] ARM: TWD: fix the clock calculation for TWD
2011-01-20 14:44 ` Jamie Iles
@ 2011-01-20 16:38 ` Russell King - ARM Linux
2011-01-20 18:10 ` Jamie Iles
0 siblings, 1 reply; 6+ messages in thread
From: Russell King - ARM Linux @ 2011-01-20 16:38 UTC (permalink / raw)
To: linux-arm-kernel
On Thu, Jan 20, 2011 at 02:44:09PM +0000, Jamie Iles wrote:
> On Thu, Jan 20, 2011 at 02:08:11PM +0000, Russell King - ARM Linux wrote:
> > On Thu, Jan 20, 2011 at 02:33:57PM +0800, Chao Xie wrote:
> > > The original code will do count * (HZ /5). It will make the twd
> > > timer rate decreased if HZ can not be excatly divided. For
> > > example HZ=128.
> > >
> > > Signed-off-by: Chao Xie <chao.xie@marvell.com>
> > > ---
> > > arch/arm/kernel/smp_twd.c | 3 ++-
> > > 1 files changed, 2 insertions(+), 1 deletions(-)
> > >
> > > diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
> > > index 35882fb..ca6405b 100644
> > > --- a/arch/arm/kernel/smp_twd.c
> > > +++ b/arch/arm/kernel/smp_twd.c
> > > @@ -111,7 +111,8 @@ static void __cpuinit twd_calibrate_rate(void)
> > >
> > > count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
> > >
> > > - twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
> > > + twd_timer_rate = ((unsigned long)(0xFFFFFFFFU - count))
> > > + * HZ / 5;
> > >
> > > printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
> > > (twd_timer_rate / 100000) % 100);
> >
> > I don't think this patch has any effect what so ever, so I just tried:
> >
> > #define HZ 128
> > unsigned long twd_timer_rate;
> > void calc1(unsigned long count)
> > {
> > twd_timer_rate = (0xffffffffU - count) * (HZ / 5);
> > }
> > void calc2(unsigned long count)
> > {
> > twd_timer_rate = ((unsigned long)(0xffffffffU - count)) * (HZ / 5);
> > }
>
> Hi Russell,
>
> In Chao's patch the parentheses around (HZ / 5) have been removed so its
> now dowing the multiplication before the division (if I remember the
> precedences correctly!). I don't think the cast to unsigned long is
> needed though.
Hmm. That means the maximum twd timer rate we can support is about
860MHz. Is that enough?
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH] ARM: TWD: fix the clock calculation for TWD
2011-01-20 16:38 ` Russell King - ARM Linux
@ 2011-01-20 18:10 ` Jamie Iles
2011-01-24 1:35 ` Chao Xie
0 siblings, 1 reply; 6+ messages in thread
From: Jamie Iles @ 2011-01-20 18:10 UTC (permalink / raw)
To: linux-arm-kernel
On Thu, Jan 20, 2011 at 04:38:36PM +0000, Russell King - ARM Linux wrote:
> On Thu, Jan 20, 2011 at 02:44:09PM +0000, Jamie Iles wrote:
> > On Thu, Jan 20, 2011 at 02:08:11PM +0000, Russell King - ARM Linux wrote:
> > > On Thu, Jan 20, 2011 at 02:33:57PM +0800, Chao Xie wrote:
> > > > The original code will do count * (HZ /5). It will make the twd
> > > > timer rate decreased if HZ can not be excatly divided. For
> > > > example HZ=128.
> > > >
> > > > Signed-off-by: Chao Xie <chao.xie@marvell.com>
> > > > ---
> > > > arch/arm/kernel/smp_twd.c | 3 ++-
> > > > 1 files changed, 2 insertions(+), 1 deletions(-)
> > > >
> > > > diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
> > > > index 35882fb..ca6405b 100644
> > > > --- a/arch/arm/kernel/smp_twd.c
> > > > +++ b/arch/arm/kernel/smp_twd.c
> > > > @@ -111,7 +111,8 @@ static void __cpuinit twd_calibrate_rate(void)
> > > >
> > > > count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
> > > >
> > > > - twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
> > > > + twd_timer_rate = ((unsigned long)(0xFFFFFFFFU - count))
> > > > + * HZ / 5;
> > > >
> > > > printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
> > > > (twd_timer_rate / 100000) % 100);
> > >
> > > I don't think this patch has any effect what so ever, so I just tried:
> > >
> > > #define HZ 128
> > > unsigned long twd_timer_rate;
> > > void calc1(unsigned long count)
> > > {
> > > twd_timer_rate = (0xffffffffU - count) * (HZ / 5);
> > > }
> > > void calc2(unsigned long count)
> > > {
> > > twd_timer_rate = ((unsigned long)(0xffffffffU - count)) * (HZ / 5);
> > > }
> >
> > Hi Russell,
> >
> > In Chao's patch the parentheses around (HZ / 5) have been removed so its
> > now dowing the multiplication before the division (if I remember the
> > precedences correctly!). I don't think the cast to unsigned long is
> > needed though.
>
> Hmm. That means the maximum twd timer rate we can support is about
> 860MHz. Is that enough?
I'm not familiar with any ARM SMP systems so I wouldn't like to commit
to that! If the answer is no, then I guess could we do something like
the (untested in a kernel) patch below to get a few more bits and we
should then be able to support rates of up to ~4294MHz.
Jamie
8<----
diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
index fd91566..334ad95 100644
--- a/arch/arm/kernel/smp_twd.c
+++ b/arch/arm/kernel/smp_twd.c
@@ -89,6 +89,8 @@ static void __cpuinit twd_calibrate_rate(void)
* the timer ticks
*/
if (twd_timer_rate == 0) {
+ u64 rate64;
+
printk(KERN_INFO "Calibrating local timer... ");
/* Wait for a tick to start */
@@ -111,7 +113,9 @@ static void __cpuinit twd_calibrate_rate(void)
count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
- twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
+ rate64 = (0xFFFFFFFFLLU - count) * (u64)HZ;
+ do_div(rate64, 5);
+ twd_timer_rate = rate64;
printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
(twd_timer_rate / 1000000) % 100);
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH] ARM: TWD: fix the clock calculation for TWD
2011-01-20 18:10 ` Jamie Iles
@ 2011-01-24 1:35 ` Chao Xie
0 siblings, 0 replies; 6+ messages in thread
From: Chao Xie @ 2011-01-24 1:35 UTC (permalink / raw)
To: linux-arm-kernel
Your patch is better. 64bit is enough, I think.
-----Original Message-----
From: Jamie Iles [mailto:jamie at jamieiles.com]
Sent: Friday, January 21, 2011 2:11 AM
To: Russell King - ARM Linux
Cc: Jamie Iles; Chao Xie; linux-arm-kernel at lists.infradead.org
Subject: Re: [PATCH] ARM: TWD: fix the clock calculation for TWD
On Thu, Jan 20, 2011 at 04:38:36PM +0000, Russell King - ARM Linux wrote:
> On Thu, Jan 20, 2011 at 02:44:09PM +0000, Jamie Iles wrote:
> > On Thu, Jan 20, 2011 at 02:08:11PM +0000, Russell King - ARM Linux wrote:
> > > On Thu, Jan 20, 2011 at 02:33:57PM +0800, Chao Xie wrote:
> > > > The original code will do count * (HZ /5). It will make the twd
> > > > timer rate decreased if HZ can not be excatly divided. For
> > > > example HZ=128.
> > > >
> > > > Signed-off-by: Chao Xie <chao.xie@marvell.com>
> > > > ---
> > > > arch/arm/kernel/smp_twd.c | 3 ++-
> > > > 1 files changed, 2 insertions(+), 1 deletions(-)
> > > >
> > > > diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
> > > > index 35882fb..ca6405b 100644
> > > > --- a/arch/arm/kernel/smp_twd.c
> > > > +++ b/arch/arm/kernel/smp_twd.c
> > > > @@ -111,7 +111,8 @@ static void __cpuinit twd_calibrate_rate(void)
> > > >
> > > > count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
> > > >
> > > > - twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
> > > > + twd_timer_rate = ((unsigned long)(0xFFFFFFFFU - count))
> > > > + * HZ / 5;
> > > >
> > > > printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
> > > > (twd_timer_rate / 100000) % 100);
> > >
> > > I don't think this patch has any effect what so ever, so I just tried:
> > >
> > > #define HZ 128
> > > unsigned long twd_timer_rate;
> > > void calc1(unsigned long count)
> > > {
> > > twd_timer_rate = (0xffffffffU - count) * (HZ / 5);
> > > }
> > > void calc2(unsigned long count)
> > > {
> > > twd_timer_rate = ((unsigned long)(0xffffffffU - count)) * (HZ / 5);
> > > }
> >
> > Hi Russell,
> >
> > In Chao's patch the parentheses around (HZ / 5) have been removed so its
> > now dowing the multiplication before the division (if I remember the
> > precedences correctly!). I don't think the cast to unsigned long is
> > needed though.
>
> Hmm. That means the maximum twd timer rate we can support is about
> 860MHz. Is that enough?
I'm not familiar with any ARM SMP systems so I wouldn't like to commit
to that! If the answer is no, then I guess could we do something like
the (untested in a kernel) patch below to get a few more bits and we
should then be able to support rates of up to ~4294MHz.
Jamie
8<----
diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
index fd91566..334ad95 100644
--- a/arch/arm/kernel/smp_twd.c
+++ b/arch/arm/kernel/smp_twd.c
@@ -89,6 +89,8 @@ static void __cpuinit twd_calibrate_rate(void)
* the timer ticks
*/
if (twd_timer_rate == 0) {
+ u64 rate64;
+
printk(KERN_INFO "Calibrating local timer... ");
/* Wait for a tick to start */
@@ -111,7 +113,9 @@ static void __cpuinit twd_calibrate_rate(void)
count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
- twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
+ rate64 = (0xFFFFFFFFLLU - count) * (u64)HZ;
+ do_div(rate64, 5);
+ twd_timer_rate = rate64;
printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
(twd_timer_rate / 1000000) % 100);
^ permalink raw reply related [flat|nested] 6+ messages in thread
end of thread, other threads:[~2011-01-24 1:35 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2011-01-20 6:33 [PATCH] ARM: TWD: fix the clock calculation for TWD Chao Xie
2011-01-20 14:08 ` Russell King - ARM Linux
2011-01-20 14:44 ` Jamie Iles
2011-01-20 16:38 ` Russell King - ARM Linux
2011-01-20 18:10 ` Jamie Iles
2011-01-24 1:35 ` Chao Xie
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