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Subject: Re: [PATCH] MIPS: DTS: CI20: Raise VDDCORE voltage to 1.125 volts
From:   "H. Nikolaus Schaller" <hns@goldelico.com>
In-Reply-To: <20230623130938.GC11636@alpha.franken.de>
Date:   Fri, 23 Jun 2023 15:23:48 +0200
Cc:     Paul Cercueil <paul@crapouillou.net>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>, linux-mips@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        list@opendingux.net
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Message-Id: <8024618C-BB30-46CD-8B2F-299C04308974@goldelico.com>
References: <20230622175934.71601-1-paul@crapouillou.net>
 <20230623130938.GC11636@alpha.franken.de>
To:     Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Precedence: bulk

Hi Thomas,
you are again too fast. Please let people enough time to test and =
comment patches.

I have started ca. 1 hour ago to do more tests on this topic and am =
currently in the middle of testing this.

At the moment it looks as if I would recommend not to apply it now. =
Since I have no problems with 1.10V with the letux-os distribution =
kernel (which adds some other patches and uses a different defconfig) =
but only with upstream and ci20_defconfig. So a proper solution may be =
completely different.

Best regards,
Nikolaus


> Am 23.06.2023 um 15:09 schrieb Thomas Bogendoerfer =
<tsbogend@alpha.franken.de>:
>=20
> On Thu, Jun 22, 2023 at 07:59:34PM +0200, Paul Cercueil wrote:
>> Commit 08384e80a70f ("MIPS: DTS: CI20: Fix ACT8600 regulator node
>> names") caused the VDDCORE power supply (regulated by the ACT8600's
>> DCDC1 output) to drop from a voltage of 1.2V configured by the
>> bootloader, to the 1.1V set in the Device Tree.
>>=20
>> According to the documentation, the VDDCORE supply should be between
>> 0.99V and 1.21V; both values are therefore within the supported =
range.
>>=20
>> However, VDDCORE being 1.1V results in the CI20 being very unstable,
>> with corrupted memory, failures to boot, or reboots at random. The
>> reason might be succint drops of the voltage below the minimum =
required.
>>=20
>> Raising the minimum voltage to 1.125 volts seems to be enough to =
address
>> this issue, while still keeping a relatively low core voltage which
>> helps for power consumption and thermals.
>>=20
>> Fixes: 08384e80a70f ("MIPS: DTS: CI20: Fix ACT8600 regulator node =
names")
>> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
>>=20
>> ---
>> Cc: H. Nikolaus Schaller <hns@goldelico.com>
>> ---
>> arch/mips/boot/dts/ingenic/ci20.dts | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>=20
>> diff --git a/arch/mips/boot/dts/ingenic/ci20.dts =
b/arch/mips/boot/dts/ingenic/ci20.dts
>> index cec0caa2350c..a141a699b790 100644
>> --- a/arch/mips/boot/dts/ingenic/ci20.dts
>> +++ b/arch/mips/boot/dts/ingenic/ci20.dts
>> @@ -298,8 +298,8 @@ act8600: act8600@5a {
>>=20
>> 		regulators {
>> 			vddcore: DCDC1 {
>> -				regulator-min-microvolt =3D <1100000>;
>> -				regulator-max-microvolt =3D <1100000>;
>> +				regulator-min-microvolt =3D <1125000>;
>> +				regulator-max-microvolt =3D <1125000>;
>> 				vp1-supply =3D <&vcc_33v>;
>> 				regulator-always-on;
>> 			};
>> --=20
>> 2.40.1
>=20
> applied to mips-next.
>=20
> Thomas.
>=20
> --=20
> Crap can work. Given enough thrust pigs will fly, but it's not =
necessarily a
> good idea.                                                [ RFC1925, =
2.3 ]