linux-kernel - Re: [PATCH 4/9] regulator: mt6358: Drop *

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Message-ID: <CAGXv+5FskpxjATk5aJA4CG0GyarO55XXYSYkvxWd-40d4ML8RQ@mail.gmail.com>
Date:   Mon, 12 Jun 2023 12:45:21 +0800
From:   Chen-Yu Tsai <wenst@...omium.org>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Gene Chen <gene_chen@...htek.com>,
        Johnson Wang <johnson.wang@...iatek.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/9] regulator: mt6358: Drop *_SSHUB regulators

On Fri, Jun 9, 2023 at 5:03 PM AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com> wrote:
>
> Il 09/06/23 10:30, Chen-Yu Tsai ha scritto:
> > The *_SSHUB regulators are actually alternate configuration interfaces
> > for their non *_SSHUB counterparts. They are not separate regulator
> > outputs. These registers are intended for the companion processor to
> > use to configure the power rails while the main processor is sleeping.
> > They are not intended for the main operating system to use.
> >
> > Since they are not real outputs they shouldn't be modeled separately.
> > Remove them. Luckily no device tree actually uses them.
> >
>
> I'm not sure that MT6358/6366 are used only on Chromebook SoCs, and that this SSHUB
> mechanism (companion processor) is the same across all firmwares.

AFAICT from Internet sources there's also the MT6771 and MT6781, which
are used on some phones.

But what part are you concerned about? The upstream regulator driver does
not actually have any code to switch to/from normal operation and SSHUB
mode.

In a downstream kernel I found that the SSHUB mode is only used if SCP is
doing DVFS [1]. In that same kernel, the regulator driver [2] doesn't even
list the *_SSHUB versions. So if SCP DVFS is used, the regulator driver
has no idea what's going on, and can't interfere either, which I think is
actually a good thing. Only one side should have complete control of one
output.

ChenYu

[1] https://github.com/nokia-dev/android_kernel_nokia_mt6771/blob/android-9.0/drivers/misc/mediatek/scp/mt6771/scp_dvfs.c
[2] https://github.com/nokia-dev/android_kernel_nokia_mt6771/blob/android-9.0/drivers/misc/mediatek/pmic/mt6358/v1/regulator_codegen.c

> I'd like someone from MediaTek to confirm that this is valid for both Chromebook
> and Smartphone firmwares.
>
> Regards,
> Angelo
>
> > Signed-off-by: Chen-Yu Tsai <wenst@...omium.org>
> > ---
> >   drivers/regulator/mt6358-regulator.c       | 14 --------------
> >   include/linux/regulator/mt6358-regulator.h |  4 ----
> >   2 files changed, 18 deletions(-)
> >
> > diff --git a/drivers/regulator/mt6358-regulator.c b/drivers/regulator/mt6358-regulator.c
> > index faf6b0757019..946a251a8b3a 100644
> > --- a/drivers/regulator/mt6358-regulator.c
> > +++ b/drivers/regulator/mt6358-regulator.c
> > @@ -505,9 +505,6 @@ static struct mt6358_regulator_info mt6358_regulators[] = {
> >       MT6358_BUCK("buck_vcore", VCORE, 500000, 1293750, 6250,
> >                   buck_volt_range1, 0x7f, MT6358_BUCK_VCORE_DBG0, 0x7f,
> >                   MT6358_VCORE_VGPU_ANA_CON0, 1),
> > -     MT6358_BUCK("buck_vcore_sshub", VCORE_SSHUB, 500000, 1293750, 6250,
> > -                 buck_volt_range1, 0x7f, MT6358_BUCK_VCORE_SSHUB_ELR0, 0x7f,
> > -                 MT6358_VCORE_VGPU_ANA_CON0, 1),
> >       MT6358_BUCK("buck_vpa", VPA, 500000, 3650000, 50000,
> >                   buck_volt_range3, 0x3f, MT6358_BUCK_VPA_DBG0, 0x3f,
> >                   MT6358_VPA_ANA_CON0, 3),
> > @@ -583,10 +580,6 @@ static struct mt6358_regulator_info mt6358_regulators[] = {
> >       MT6358_LDO1("ldo_vsram_others", VSRAM_OTHERS, 500000, 1293750, 6250,
> >                   buck_volt_range1, MT6358_LDO_VSRAM_OTHERS_DBG0, 0x7f00,
> >                   MT6358_LDO_VSRAM_CON2, 0x7f),
> > -     MT6358_LDO1("ldo_vsram_others_sshub", VSRAM_OTHERS_SSHUB, 500000,
> > -                 1293750, 6250, buck_volt_range1,
> > -                 MT6358_LDO_VSRAM_OTHERS_SSHUB_CON1, 0x7f,
> > -                 MT6358_LDO_VSRAM_OTHERS_SSHUB_CON1, 0x7f),
> >       MT6358_LDO1("ldo_vsram_gpu", VSRAM_GPU, 500000, 1293750, 6250,
> >                   buck_volt_range1, MT6358_LDO_VSRAM_GPU_DBG0, 0x7f00,
> >                   MT6358_LDO_VSRAM_CON3, 0x7f),
> > @@ -603,9 +596,6 @@ static struct mt6358_regulator_info mt6366_regulators[] = {
> >       MT6366_BUCK("buck_vcore", VCORE, 500000, 1293750, 6250,
> >                   buck_volt_range1, 0x7f, MT6358_BUCK_VCORE_DBG0, 0x7f,
> >                   MT6358_VCORE_VGPU_ANA_CON0, 1),
> > -     MT6366_BUCK("buck_vcore_sshub", VCORE_SSHUB, 500000, 1293750, 6250,
> > -                 buck_volt_range1, 0x7f, MT6358_BUCK_VCORE_SSHUB_ELR0, 0x7f,
> > -                 MT6358_VCORE_VGPU_ANA_CON0, 1),
> >       MT6366_BUCK("buck_vpa", VPA, 500000, 3650000, 50000,
> >                   buck_volt_range3, 0x3f, MT6358_BUCK_VPA_DBG0, 0x3f,
> >                   MT6358_VPA_ANA_CON0, 3),
> > @@ -670,10 +660,6 @@ static struct mt6358_regulator_info mt6366_regulators[] = {
> >       MT6366_LDO1("ldo_vsram_others", VSRAM_OTHERS, 500000, 1293750, 6250,
> >                   buck_volt_range1, MT6358_LDO_VSRAM_OTHERS_DBG0, 0x7f00,
> >                   MT6358_LDO_VSRAM_CON2, 0x7f),
> > -     MT6366_LDO1("ldo_vsram_others_sshub", VSRAM_OTHERS_SSHUB, 500000,
> > -                 1293750, 6250, buck_volt_range1,
> > -                 MT6358_LDO_VSRAM_OTHERS_SSHUB_CON1, 0x7f,
> > -                 MT6358_LDO_VSRAM_OTHERS_SSHUB_CON1, 0x7f),
> >       MT6366_LDO1("ldo_vsram_gpu", VSRAM_GPU, 500000, 1293750, 6250,
> >                   buck_volt_range1, MT6358_LDO_VSRAM_GPU_DBG0, 0x7f00,
> >                   MT6358_LDO_VSRAM_CON3, 0x7f),
> > diff --git a/include/linux/regulator/mt6358-regulator.h b/include/linux/regulator/mt6358-regulator.h
> > index a4307cd9edd6..c71a6a9fce7a 100644
> > --- a/include/linux/regulator/mt6358-regulator.h
> > +++ b/include/linux/regulator/mt6358-regulator.h
> > @@ -47,8 +47,6 @@ enum {
> >       MT6358_ID_VLDO28,
> >       MT6358_ID_VAUD28,
> >       MT6358_ID_VSIM2,
> > -     MT6358_ID_VCORE_SSHUB,
> > -     MT6358_ID_VSRAM_OTHERS_SSHUB,
> >       MT6358_ID_RG_MAX,
> >   };
> >
> > @@ -88,8 +86,6 @@ enum {
> >       MT6366_ID_VMC,
> >       MT6366_ID_VAUD28,
> >       MT6366_ID_VSIM2,
> > -     MT6366_ID_VCORE_SSHUB,
> > -     MT6366_ID_VSRAM_OTHERS_SSHUB,
> >       MT6366_ID_RG_MAX,
> >   };
> >
>