Il 01/03/23 05:53, Chen-Yu Tsai ha scritto:
> On Tue, Feb 28, 2023 at 6:47 PM AngeloGioacchino Del Regno
> <angelogioacchino.delregno@collabora.com> wrote:
>>
>> Add coupling for these regulators, as VSRAM_OTHER is used to power the
>> GPU SRAM, and they have a strict voltage output relation to satisfy in
>> order to ensure GPU stable operation.
>> While at it, also add voltage constraint overrides for the GPU SRAM
>> regulator "mt6359_vsram_others", but don't touch mt6315's vbuck1 as
>> its constraints are fine.
>
> The minimum voltage on vbuck1 matches the lowest OPP. However the maximum
> voltage is set to the maximum of the regulator itself. The MT8192 datasheet
> says the absolute maximum for the GPU is 0.8V, and the recommended range
> for 0.8V is 0.72V ~ 0.88V. The highest OPP we have is 0.8V, so I would
> just set the maximum voltage to that?
>
The point was that we'd never get vbuck1 at more than vsram+10mV because
of the constraints that are set with regulator-coupled-max-spread, but
thinking about it again, relying on that is *highly* suboptimal.
Yes, you're right, let's change the constraints on vbuck1 to 800mV: that's
going to be for v4.
Thanks!
Angelo
> ChenYu
>
>> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
>> ---
>> arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi | 9 +++++++++
>> 1 file changed, 9 insertions(+)
>>
>> diff --git a/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi b/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi
>> index df477eb89f21..c8b6e1a9605b 100644
>> --- a/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi
>> +++ b/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi
>> @@ -447,6 +447,13 @@ &mt6359_vrf12_ldo_reg {
>> regulator-always-on;
>> };
>>
>> +&mt6359_vsram_others_ldo_reg {
>> + regulator-min-microvolt = <750000>;
>> + regulator-max-microvolt = <850000>;
>> + regulator-coupled-with = <&mt6315_7_vbuck1>;
>> + regulator-coupled-max-spread = <10000>;
>> +};
>> +
>> &mt6359_vufs_ldo_reg {
>> regulator-always-on;
>> };
>> @@ -1411,6 +1418,8 @@ mt6315_7_vbuck1: vbuck1 {
>> regulator-max-microvolt = <1193750>;
>> regulator-enable-ramp-delay = <256>;
>> regulator-allowed-modes = <0 1 2>;
>> + regulator-coupled-with = <&mt6359_vsram_others_ldo_reg>;
>> + regulator-coupled-max-spread = <10000>;
>> };
>> };
>> };
>> --
>> 2.39.2
>>