On Fri, May 30, 2014 at 07:05:43PM +0100, Thomas Abraham wrote: > Hi Mark, > > On Fri, May 30, 2014 at 6:38 PM, Mark Rutland <mark.rutland@xxxxxxx> wrote: > > Hi, > > > > Apologies for being somewhat late w.r.t. review on this. > > > > On Fri, May 30, 2014 at 10:01:17AM +0100, Thomas Abraham wrote: > >> From: Thomas Abraham <thomas.ab@xxxxxxxxxxx> > >> > >> Add a new optional boost-frequency binding for specifying the frequencies > >> usable in boost mode. > >> > >> Cc: Rob Herring <robh+dt@xxxxxxxxxx> > >> Cc: Pawel Moll <pawel.moll@xxxxxxx> > >> Cc: Mark Rutland <mark.rutland@xxxxxxx> > >> Cc: Ian Campbell <ijc+devicetree@xxxxxxxxxxxxxx> > >> Cc: Kumar Gala <galak@xxxxxxxxxxxxxx> > >> Signed-off-by: Thomas Abraham <thomas.ab@xxxxxxxxxxx> > >> Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx> > >> Acked-by: Nishanth Menon <nm@xxxxxx> > >> Acked-by: Lukasz Majewski <l.majewski@xxxxxxxxxxx> > >> --- > >> .../devicetree/bindings/cpufreq/cpufreq-boost.txt | 38 ++++++++++++++++++++ > >> 1 file changed, 38 insertions(+) > >> create mode 100644 Documentation/devicetree/bindings/cpufreq/cpufreq-boost.txt > >> > >> diff --git a/Documentation/devicetree/bindings/cpufreq/cpufreq-boost.txt b/Documentation/devicetree/bindings/cpufreq/cpufreq-boost.txt > >> new file mode 100644 > >> index 0000000..63ed0fc > >> --- /dev/null > >> +++ b/Documentation/devicetree/bindings/cpufreq/cpufreq-boost.txt > >> @@ -0,0 +1,38 @@ > >> +* Device tree binding for CPU boost frequency (aka over-clocking) > >> + > >> +Certain CPU's can be operated in optional 'boost' mode (or sometimes referred as > > > > Nit: CPUs (we're not greengrocers [1]) > > > >> +overclocking) in which the CPU can operate at frequencies which are not > >> +specified by the manufacturer as CPU's operating frequency. > >> + > >> +Optional Properties: > >> +- boost-frequencies: list of frequencies in KHz to be used only in boost mode. > >> + This list should be a subset of frequencies listed in "operating-points" > >> + property. Refer to Documentation/devicetree/bindings/power/opp.txt for > >> + details about "operating-points" property. > > > > What is 'boost-mode'? > > boost-mode activates additional one or more cpu clock speeds (which > are not specified as operating frequency of the cpu by the > manufacturer). The cpu is allowed to operate in these boost mode > speeds when the boost mode is active. The boost mode speeds are > usually undocumented. Some of the chip samples could be clocked in > boost mode speeds and only such samples can be safely operated in > boost mode. > > The mechanism of entry into and exit out of boost mode is outside the > scope of this documentation. > > > > > What are the limitations on boost frequencies? When is a CPU expected to > > go to these frequencies and for now long? When should I as a dt author > > place elements in boost-frequencies? > > I will add these details in the next revision of this patch. Cheers. > > > > Why are these in both operating-points and boost-frequencies? It'll be > > really easy to accidentally forget to mark something as a > > boost-frequency this way. Why not have a boost-points instead? > > Does boost-points mean a set of clock speeds which are not listed as > part of operating-points property? If yes, that also is a possible > implementation (it was implemented in one of the earlier version of > this series). Could you confirm that you want the boost mode speeds to > be exclusive of the speeds listed in operating-points? If these boost mode operating points are not generally advisable for use as the other operating-points are, then they should IMO been in an entirely separate property exclusive of (but in the same format as) the operating-points property, e.g. operating points = <A B>, <C D>; boost-points = <E F>; Otherwise, without boost-mode support we have to parse the boost mode table to figure out which points to avoid. Or if someone typos a value in either table we might go into a boost mode when we didn't want to! Cheers, Mark. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
