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

[Vishwanath Sripathy <vishwanath.bs@ti.com>]

Kooi,

> -----Original Message-----
> From: Nishanth Menon [mailto:nm@ti.com]
> Sent: Tuesday, January 18, 2011 10:19 PM
> To: Koen Kooi
> Cc: Sanjeev Premi; l-o List; thara@ti.com; Vishwanath Sripathy
> Subject: Re: [PATCH] omap3: Add basic support for 720MHz part
>
> 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
Yes, this is a limitation with the current set of DVFS patches.
With the next version of DVFS patches (will be out soon) this feature is
going to be supported. That means you can have 2 opps with the same
voltage but with different frequency. The device will be configured based
on user requested frequency.

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