> -----Original Message----- > From: Menon, Nishanth [mailto:nm@xxxxxx] > Sent: Wednesday, February 23, 2011 1:48 PM > To: Vishwanath Sripathy > Cc: linux-omap; Tony Lindgren; Kevin Hilman > Subject: Re: [PATCH 03/19] omap3+: voltage: remove initial voltage > > Wed, Feb 23, 2011 at 12:24, Vishwanath Sripathy > <vishwanath.bs@xxxxxx> wrote: > >> -----Original Message----- > >> From: Nishanth Menon [mailto:nm@xxxxxx] > >> Sent: Sunday, February 20, 2011 10:42 AM > >> To: Vishwanath Sripathy > >> Cc: linux-omap; Tony Lindgren; Kevin Hilman > >> Subject: Re: [PATCH 03/19] omap3+: voltage: remove initial voltage > >> > >> Vishwanath Sripathy wrote, on 02/19/2011 06:54 PM: > >> [..] > >> >> omap2_set_init_voltage should setup the curr_volt based on > which > >> OPP > >> >> the system is functioning at. Blindly setting a 1.2v setting in the > >> >> initial structure may not even match the default voltages stored > in > >> >> the voltage table which are supported for the domain. > >> >> > >> >> For example, OMAP3430 core domain does not use 1.2v and ends > up > >> >> generating a warning on the first transition. > >> >> > >> [..] > >> >> diff --git a/arch/arm/mach-omap2/voltage.c b/arch/arm/mach- > >> >> omap2/voltage.c > >> >> index 12be525..280ee12 100644 > >> >> --- a/arch/arm/mach-omap2/voltage.c > >> >> +++ b/arch/arm/mach-omap2/voltage.c > >> [..] > >> >> /* Generic voltage parameters */ > >> >> - vdd->curr_volt = 1200000; > >> > Where do you update this parameter upon initialization? Shouldn't > you > >> read > >> > the VP register and find the actual current voltage and update this > >> param? > >> > >> The sequence is as follows: > >> a) omapx_vdd_data configure is called as part of sr init sequence. > >> And the curr_volt with this patch is not updated at this stage. > >> b) somewhere down in the boot sequence, pm.c's > >> omap2_set_init_voltage > >> starts up. This looks up the current clk frequency from clock layer of > >> the parent device for the domain, picks up the nominal voltages > stored > >> in the opp layer, then does a omap_voltage_scale_vdd to that > voltage. In > >> omap_voltage_scale_vdd, The current voltage is merely picked off > the vp > >> (in _pre_volt_scale). the last step it does is to setup vdd->curr_volt. > >> This can then be used by dvfs layer etc to make appropriate > decisions. > >> > >> So, No, I dont think I need to update it here, it should happen as > part > >> of the pm init sequence. > >> > >> Could you explain what problem do you foresee by doing this? > > What if omap_voltage_scale_vdd fails when called from > > omap2_set_init_voltage? Or omap2_set_init_voltage returns error > even > > before calling omap_voltage_scale_vdd because it could not find the > > matching voltage for the frequency set by bootloader? > > > > Your assumption that curr_volt is always set by > omap2_set_init_voltage > > need not be true always. > > set_init_voltage's job is to set the initial voltage. if it is > incapable of doing it, I say fix that instead of hacking in some > random number as curr_volt. I never said to use random numbers. All I suggested was that instead of relying on some others function's behavior, read the VP register to fill in the right values. If set_init_voltage succeeds, it will anyway update with right voltage. Vishwa > > The logic involved for set_init_voltage is what we need for filling in > cur_volt. just replicating the logic makes no sense to me. > > Regards, > Nishanth Menon -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
