Re: [PATCH] omap3: Add basic support for 720MHz part

Nishanth Menon
2011-01-18T16:49:06Z

Koen Kooi wrote, on 01/18/2011 05:38 PM:
>
> Op 18 jan 2011, om 08:49 heeft Sanjeev Premi het volgende geschreven:
>
>> This patch adds support for new speed enhanced parts with ARM
>> and IVA running at 720MHz and 520MHz respectively. These parts
>> can be probed at run-time by reading PRODID.SKUID[3:0] at
>> 0x4830A20C [1].
>>
>> This patch specifically does following:
>> * Detect devices capable of 720MHz.
>> * Add new OPP
>> * Ensure that OPP is conditionally enabled.
>> * Check for presence of IVA before attempting to enable
>> the corresponding OPP.
>
> Thanks for the updated patch!
>
> I'm still having problem using this together with DVFS, the kernel won't scale beyond 600MHz because 600MHz and 720MHz share the same voltage. Thara, Nishant, do you have any suggestions on how to convince the kernel that 2 frequencies can share the same voltage settings?
+ Vishwa

>
> If that isn't possible, should we lower the voltages for the lower opps when detecting a 720MHz capable SoC? It would make sense that if 720MHz works at X volt that 600MHz would work at less than X volt. (I don't have a PDF reader at hand to check the TRM at the moment).
>
> Complete tree at http://dominion.thruhere.net/git/cgit.cgi/linux-omap/log/?h=koen/beagle-next but this can be reproduced as well by merging Thara's dvfs branch and applying Sanjeevs patch.
I suspect the problem lies here:

http://dominion.thruhere.net/git/cgit.cgi/linux-omap/tree/arch/arm/mach-omap2/voltage.c?h=koen/beagle-next#n1847
if two OPP frequencies have same voltage, the api introduced in
http://dominion.thruhere.net/git/cgit.cgi/linux-omap/commit/?h=koen/beagle-next&id=fd2991c20a8f770c7b8f5a29b3cbb17b9fca4768

will return back the first OPP entry which matches, which would be the
lower frequency as OPPs are organized in the OPP layer in increasing order.

--
Regards,
Nishanth Menon