* Duration of mdelay and udelay depends on MPU frequency in SMP
@ 2011-05-05 6:49 Saquib
2011-05-05 6:53 ` Saquib
0 siblings, 1 reply; 6+ messages in thread
From: Saquib @ 2011-05-05 6:49 UTC (permalink / raw)
To: linux-arm-kernel
Hi All,
Can anyone please help me to understand and fix this issue?
When CPU frequency is "1008MHz", duration of delay was close to theoretical
value, however, when "300MHz", it was close to about 4 times the theoretical
value.
Please find the log as attachments. I tested it on OMAP4(SMP) blaze board.
--
Thanks & regards,
Saquib
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* Duration of mdelay and udelay depends on MPU frequency in SMP
2011-05-05 6:49 Duration of mdelay and udelay depends on MPU frequency in SMP Saquib
@ 2011-05-05 6:53 ` Saquib
2011-05-12 6:42 ` Santosh Shilimkar
0 siblings, 1 reply; 6+ messages in thread
From: Saquib @ 2011-05-05 6:53 UTC (permalink / raw)
To: linux-arm-kernel
Hi All,
Can anyone please help me to understand and fix this issue?
When CPU frequency is "1008MHz", duration of delay was close to theoretical
value, however, when "300MHz", it was close to about 4 times the theoretical
value.
I tested it on OMAP4(SMP) blaze board.
--
Thanks & regards,
Saquib
-------------- next part --------------
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* Duration of mdelay and udelay depends on MPU frequency in SMP
2011-05-05 6:53 ` Saquib
@ 2011-05-12 6:42 ` Santosh Shilimkar
2011-06-10 22:19 ` Menon, Nishanth
0 siblings, 1 reply; 6+ messages in thread
From: Santosh Shilimkar @ 2011-05-12 6:42 UTC (permalink / raw)
To: linux-arm-kernel
On 5/5/2011 12:23 PM, Saquib wrote:
> Hi All,
>
> Can anyone please help me to understand and fix this issue?
>
> When CPU frequency is "1008MHz", duration of delay was close to
> theoretical value, however, when "300MHz", it was close to about 4 times
> the theoretical value.
>
> I tested it on OMAP4(SMP) blaze board.
>
It's a well known problem if the udelay() is based of global lpj.
You can read more here [1]
Regards
Santosh
[1] http://eeek.borgchat.net/lists/arm-kernel/msg120702.html
^ permalink raw reply [flat|nested] 6+ messages in thread
* Duration of mdelay and udelay depends on MPU frequency in SMP
2011-05-12 6:42 ` Santosh Shilimkar
@ 2011-06-10 22:19 ` Menon, Nishanth
2011-06-14 3:24 ` Stephen Boyd
0 siblings, 1 reply; 6+ messages in thread
From: Menon, Nishanth @ 2011-06-10 22:19 UTC (permalink / raw)
To: linux-arm-kernel
On Thu, May 12, 2011 at 01:42, Santosh Shilimkar
<santosh.shilimkar@ti.com> wrote:
> On 5/5/2011 12:23 PM, Saquib wrote:
>> Can anyone please help me to understand and fix this issue?
>>
>> When CPU frequency is "1008MHz", duration of delay was close to
>> theoretical value, however, when "300MHz", it was close to about 4 times
>> the theoretical value.
>>
>> I tested it on OMAP4(SMP) blaze board.
>
>>
> It's a well known problem if the udelay() is based of global lpj.
> You can read more here [1]
>
> Regards
> Santosh
> [1] http://eeek.borgchat.net/lists/arm-kernel/msg120702.html
I am curious about this topic now.
Searching Russel's patchworks for this:
http://www.arm.linux.org.uk/developer/patches/search.php?summary=udelay
I see nothing queued. What is the recommendation for udelay?
Regards,
Nishanth Menon
^ permalink raw reply [flat|nested] 6+ messages in thread
* Duration of mdelay and udelay depends on MPU frequency in SMP
2011-06-10 22:19 ` Menon, Nishanth
@ 2011-06-14 3:24 ` Stephen Boyd
2011-06-14 4:19 ` Menon, Nishanth
0 siblings, 1 reply; 6+ messages in thread
From: Stephen Boyd @ 2011-06-14 3:24 UTC (permalink / raw)
To: linux-arm-kernel
On 06/10/2011 03:19 PM, Menon, Nishanth wrote:
> On Thu, May 12, 2011 at 01:42, Santosh Shilimkar
> <santosh.shilimkar@ti.com> wrote:
>>
>> It's a well known problem if the udelay() is based of global lpj.
>> You can read more here [1]
>>
>> Regards
>> Santosh
>> [1] http://eeek.borgchat.net/lists/arm-kernel/msg120702.html
> I am curious about this topic now.
> Searching Russel's patchworks for this:
> http://www.arm.linux.org.uk/developer/patches/search.php?summary=udelay
> I see nothing queued. What is the recommendation for udelay?
The patches are sitting in Russell's patch tracker, waiting for him to
accept/reject them.
http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=6874/1
http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=6875/1
http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=6873/1
--
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Duration of mdelay and udelay depends on MPU frequency in SMP
2011-06-14 3:24 ` Stephen Boyd
@ 2011-06-14 4:19 ` Menon, Nishanth
0 siblings, 0 replies; 6+ messages in thread
From: Menon, Nishanth @ 2011-06-14 4:19 UTC (permalink / raw)
To: linux-arm-kernel
On Mon, Jun 13, 2011 at 22:24, Stephen Boyd <sboyd@codeaurora.org> wrote:
> On 06/10/2011 03:19 PM, Menon, Nishanth wrote:
>> On Thu, May 12, 2011 at 01:42, Santosh Shilimkar
>> <santosh.shilimkar@ti.com> wrote:
>>>
>>> It's a well known problem if the udelay() is based of global lpj.
>>> You can read more here [1]
>>>
>>> Regards
>>> Santosh
>>> [1] http://eeek.borgchat.net/lists/arm-kernel/msg120702.html
>> I am curious about this topic now.
>> Searching Russel's patchworks for this:
>> http://www.arm.linux.org.uk/developer/patches/search.php?summary=udelay
>> I see nothing queued. What is the recommendation for udelay?
>
> The patches are sitting in Russell's patch tracker, waiting for him to
> accept/reject them.
>
> http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=6874/1
> http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=6875/1
> http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=6873/1
thanks for the same and hope these do get through :)
Regards,
Nishanth Menon
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2011-05-05 6:49 Duration of mdelay and udelay depends on MPU frequency in SMP Saquib
2011-05-05 6:53 ` Saquib
2011-05-12 6:42 ` Santosh Shilimkar
2011-06-10 22:19 ` Menon, Nishanth
2011-06-14 3:24 ` Stephen Boyd
2011-06-14 4:19 ` Menon, Nishanth
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