Messages in this thread | | | From | Mike Turquette <> | Subject | Re: [PATCH 6/6 v6] cpufreq, highbank: add support for highbank cpufreq | Date | Wed, 28 Nov 2012 13:05:52 -0800 |
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Quoting Mark Langsdorf (2012-11-28 08:18:35) > On 11/28/2012 10:01 AM, Mike Turquette wrote: > > Quoting Shawn Guo (2012-11-28 07:17:44) > >> On Wed, Nov 28, 2012 at 10:58:02PM +0800, Shawn Guo wrote: > >>> On Wed, Nov 28, 2012 at 07:16:12AM -0600, Mark Langsdorf wrote: > >>>> I'd > >>>> have to move most of the logic of hb_set_target() into > >>>> clk_highbank.c:clk_pll_set_rate() and then add extra logic for when > >>>> cpufreq is not enabled/loaded. > >>> > >>> You only need to move hb_voltage_change() into cpu clock's .set_rate() > >>> hook with no need of checking if cpufreq is enabled or not. > >>> > >> Need to also check whether frequency or voltage should be changed first > >> in .set_rate() though. > >> > >> Shawn > >> > > > > The notifiers in the clk framework might be a better place for this than > > just simply hacking the logic into the .set_rate callback. > > Unless the clk notifiers are different than the cpufreq notifiers, they > don't handle returning error conditions very well. And given that the > voltage change operation can fail (though it almost always succeeds on a > retry) I need to be able to handle and detect that error condition. >
The notifier handler can handle the case where the transition fails (and needs to be retried).
Also you should check out the clk notifiers. I think they handle failure decently. If a notifer returns an error code then everything unrolls and the clk_set_rate operation aborts.
Regards, Mike
> > I haven't looked at the definition of hb_voltage_change but does the > > call graph make any clk api calls? Are you talking over i2c to a > > regulator? If so then you'll probably hit the same reentrancy problem I > > hit when trying to make a general solution. > > I'm talking over a pl320 Interprocessor Communication Mailbox to a > separate core running it's own RTOS. The RTOS might speak i2c to a > regulator but it's a black box to me. > > hb_voltage_change() doesn't make any clk api calls. It changes the > voltages, and then hb_set_target() makes clk api calls to change the > frequency. > > --Mark Langsdorf > Calxeda, Inc.
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