+Nishanth
Tero Kristo <t-kristo@xxxxxx> writes:
> On Thu, 2012-03-01 at 14:07 -0800, Kevin Hilman wrote:
>> +Tero
>>
>> Kevin Hilman <khilman@xxxxxx> writes:
>>
>> > Afzal Mohammed <afzal@xxxxxx> writes:
>> >
>> >> Specify voltage in ranges for regulator. Range
>> >> used is tolerance specified for OPP.
>> >>
>> >> This helps to achieve DVFS with a wider range of
>> >> regulators.
>> >>
>> >> Cc: Kevin Hilman <khilman@xxxxxx>
>> >> Cc: Sekhar Nori <nsekhar@xxxxxx>
>> >> Signed-off-by: Afzal Mohammed <afzal@xxxxxx>
>> >
>> > Thanks, will queue this with the CPUfreq changes for MPU DVFS.
>>
>> Actually, not quite yet...
>>
>> After some testing with the SMPS regulators, this won't quite work with
>> the current SMPS regulators. Does this actually work with the
>> regulators you're using?
>>
>> For OMAPs using VC/VP for voltage scaling, the TWL regulator passes on
>> the voltage requested directly to the voltage layer. When using voltage
>> - tolerance, this results in voltages that the voltage layer doesn't
>> know about because they do not match any of the voltages from the known
>> OPPs.
>>
>> The problem that we have is that while the regulators can support a
>> broad range of voltages (from min to max with a some step), the on-chip
>> voltage domains cannot, which is why we have defined the OPPs which are
>> known to work.
>>
>> Tero, for the SMPS regulators, would it be possible to configure the
>> regulators so that only a discrete set voltages are availble to pick
>> from? These should be initialied from the OPP layer.
>
> I guess this would be possible. Looking at this patch, I guess what we
> want to do is that we just use the current API we have at the SMPS
> regulator layer to pass the min_uV as target_uV for the regulator, and
> just get the next opp voltage that is >= than the target_uV.
Yeah, this should work.
However, after discussing this on IRC with Nishanth, instead of enforcing
this in the TWL glue layer, I think we need to enforce using OPP
voltages in the voltage layer itself. Patch below[1].
I've now added that patch to my for_3.4/pm/smps-regulator branch (and
will post to the list shortly.)
I've also added $SUBJECT patch (back) to my for_3.4/cpufreq branch.
I'd appreciate some testing of these two branches together. With those
two, I've tested MPU DVFS on 3530/Overo, 3630/Zoom3 and 4430/Panda, but
would appreciate any additional testing.
Kevin
>From 212024af641266c3de8b55764f84d923f238315c Mon Sep 17 00:00:00 2001
From: Kevin Hilman <khilman@xxxxxx>
Date: Fri, 2 Mar 2012 14:08:57 -0800
Subject: [PATCH] ARM: OMAP2+: voltage: ensure voltage used is exact voltage
from OPP table
When using the SMPS regulators to scale voltages, the regulator
framework may pass a minimum voltage that is not an exact OPP voltage.
For the VC/VP controlled voltage domains, we must ensure that the
voltage requested is the exact voltage from the OPP table. This is
especially critical when using SR.
To fix, voltdm_scale() uses the target voltage passed to walk through
the OPP voltages until it finds a voltage that is >= one of the OPP
voltages.
Cc: Tero Kristo <t-kristo@xxxxxx>
Cc: Nishanth Menon <nm@xxxxxx>
Signed-off-by: Kevin Hilman <khilman@xxxxxx>
---
arch/arm/mach-omap2/voltage.c | 21 ++++++++++++++++++---
1 file changed, 18 insertions(+), 3 deletions(-)
diff --git a/arch/arm/mach-omap2/voltage.c b/arch/arm/mach-omap2/voltage.c
index 8a36342..4dc60e8 100644
--- a/arch/arm/mach-omap2/voltage.c
+++ b/arch/arm/mach-omap2/voltage.c
@@ -73,7 +73,8 @@ unsigned long voltdm_get_voltage(struct voltagedomain *voltdm)
int voltdm_scale(struct voltagedomain *voltdm,
unsigned long target_volt)
{
- int ret;
+ int ret, i;
+ unsigned long volt = 0;
if (!voltdm || IS_ERR(voltdm)) {
pr_warning("%s: VDD specified does not exist!\n", __func__);
@@ -86,9 +87,23 @@ int voltdm_scale(struct voltagedomain *voltdm,
return -ENODATA;
}
- ret = voltdm->scale(voltdm, target_volt);
+ /* Adjust voltage to the exact voltage from the OPP table */
+ for (i = 0; voltdm->volt_data[i].volt_nominal != 0; i++) {
+ if (voltdm->volt_data[i].volt_nominal >= target_volt) {
+ volt = voltdm->volt_data[i].volt_nominal;
+ break;
+ }
+ }
+
+ if (!volt) {
+ pr_warning("%s: not scaling. OPP voltage for %lu, not found.\n",
+ __func__, target_volt);
+ return -EINVAL;
+ }
+
+ ret = voltdm->scale(voltdm, volt);
if (!ret)
- voltdm->nominal_volt = target_volt;
+ voltdm->nominal_volt = volt;
return ret;
}
--
1.7.9.2
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