Hi Clément,
On Tue, Apr 28, 2020 at 04:26:29PM +0200, Clément Péron wrote:
> Tanix TX6 has a fixed regulator. As DVFS is instructed to change
> voltage to meet OPP table, the DVFS is not working as expected.
>
> Avoid to introduce a new dedicated OPP Table where voltage are
> equals to the fixed regulator as it will only duplicate all the OPPs.
> Instead remove the fixed regulator so the DVFS framework will create
> dummy regulator and will have the same behavior.
>
> Add some comments to explain this in the device-tree.
>
> Reported-by: Piotr Oniszczuk
> Fixes: add1e27fb703 ("arm64: dts: allwinner: h6: Enable CPU opp tables for
> Tanix TX6")
> Signed-off-by: Clément Péron
> ---
> .../boot/dts/allwinner/sun50i-h6-tanix-tx6.dts | 18 --
> 1 file changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/boot/dts/allwinner/sun50i-h6-tanix-tx6.dts
> b/arch/arm64/boot/dts/allwinner/sun50i-h6-tanix-tx6.dts
> index be81330db14f..3e96fcb317ea 100644
> --- a/arch/arm64/boot/dts/allwinner/sun50i-h6-tanix-tx6.dts
> +++ b/arch/arm64/boot/dts/allwinner/sun50i-h6-tanix-tx6.dts
> @@ -48,7 +48,15 @@
> };
>
> {
> - cpu-supply = <_vdd_cpu_gpu>;
> + /*
> + * Don't specify the CPU regulator, as it's a fixed
> + * regulator DVFS will not work as it is intructed
> + * to reach a voltage which can't be reached.
> + * Not specifying a regulator will create a dummy
> + * regulator allowing all OPPs.
> + *
> + * cpu-supply = <_vdd_cpu_gpu>;
> + */
reg_vdd_cpu_gpu has
regulator-min-microvolt = <1135000>;
regulator-max-microvolt = <1135000>;
top OPP is:
opp@18 {
clock-latency-ns = <244144>; /* 8 32k periods */
opp-hz = /bits/ 64 <18>;
opp-microvolt-speed0 = <116>;
opp-microvolt-speed1 = <110>;
opp-microvolt-speed2 = <110>;
};
So I guess ignoring the voltage and not disabling this OPP may or may not work
based on SoC bin.
On Orange Pi One, there's a regulator that supports two voltages (that can't
support all the listed OPPs for H3), and cpufreq-dt can deal with that
automagically, if you specify OPP voltages via a tripplet of [prefered min max].
Kernell will log this in dmesg on boot:
[0.672440] core: _opp_supported_by_regulators: OPP minuV: 132 maxuV:
132, not supported by regulator
[0.672454] cpu cpu0: _opp_add: OPP not supported by regulators (110400)
[0.672523] core: _opp_supported_by_regulators: OPP minuV: 132 maxuV:
132, not supported by regulator
[0.672530] cpu cpu0: _opp_add: OPP not supported by regulators (12)
[0.672621] core: _opp_supported_by_regulators: OPP minuV: 134 maxuV:
134, not supported by regulator
[0.672628] cpu cpu0: _opp_add: OPP not supported by regulators (129600)
[0.672712] core: _opp_supported_by_regulators: OPP minuV: 140 maxuV:
140, not supported by regulator
[0.672719] cpu cpu0: _opp_add: OPP not supported by regulators (136800)
And the list of available OPPs will be reduced at runtime to a supportable
set by the CPU regulator.
If you look at:
https://megous.com/git/linux/commit/?h=ths-5.7=d231770195913cf543c0cf9539deee2ecec06680
you'll see a bunch of OPPs for H3 that are specified as a range. So
for example if you want 480MHz, and your regulator can't produce
1.04V exactly, cpufreq will set the voltage to something supportable
in the range.
I think the proper fix is to fix the OPP table for H6, so that it uses
voltage ranges for each OPP and not a single fixed voltage, to support
boards that don't have the standard PMIC that goes with H6.
regards,
o.
> };
>
> {
> @@ -68,7 +76,13 @@
> };
>
> {
> - mali-supply = <_vdd_cpu_gpu>;
> + /*
> + * Don't specify the GPU regulator, see comment
> + * above for the CPU supply.
> + *
> + * mali-supply = <_vdd_cpu_gpu>;
> + */
> +
> status = "okay";
> };
>
> --
> 2.20.1
>
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