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Wysocki" , Viresh Kumar , devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Subject: Re: [PATCH v3 2/2] ARM: dts: sun8i-r40: Add "cpu-supply" node for sun8i-r40 based board Message-ID: <20220513081556.knd3tf6pangfblh3@houat> References: <20220512071858.10805-1-qianfanguijin@163.com> <20220512071858.10805-2-qianfanguijin@163.com> <20220513073849.cu4jzykefat2sepg@houat> <1352b9d7-5219-af09-948b-6462def39ea5@163.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="ocbjtkvxhxhj7iii" Content-Disposition: inline In-Reply-To: <1352b9d7-5219-af09-948b-6462def39ea5@163.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --ocbjtkvxhxhj7iii Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, May 13, 2022 at 03:48:50PM +0800, qianfan wrote: >=20 >=20 > =E5=9C=A8 2022/5/13 15:38, Maxime Ripard =E5=86=99=E9=81=93: > > Hi, > >=20 > > On Thu, May 12, 2022 at 03:18:58PM +0800, qianfanguijin@163.com wrote: > > > From: qianfan Zhao > > >=20 > > > sun8i-r40 actived cpufreq feature now, let's add "cpu-supply" node on > > > board. > > >=20 > > > Signed-off-by: qianfan Zhao > > > --- > > > arch/arm/boot/dts/sun8i-r40-bananapi-m2-ultra.dts | 4 ++++ > > > arch/arm/boot/dts/sun8i-r40-feta40i.dtsi | 4 ++++ > > > arch/arm/boot/dts/sun8i-t3-cqa3t-bv3.dts | 4 ++++ > > > arch/arm/boot/dts/sun8i-v40-bananapi-m2-berry.dts | 4 ++++ > > > 4 files changed, 16 insertions(+) > > >=20 > > > diff --git a/arch/arm/boot/dts/sun8i-r40-bananapi-m2-ultra.dts b/arch= /arm/boot/dts/sun8i-r40-bananapi-m2-ultra.dts > > > index a6a1087a0c9b..4f30018ec4a2 100644 > > > --- a/arch/arm/boot/dts/sun8i-r40-bananapi-m2-ultra.dts > > > +++ b/arch/arm/boot/dts/sun8i-r40-bananapi-m2-ultra.dts > > > @@ -113,6 +113,10 @@ &ahci { > > > status =3D "okay"; > > > }; > > > +&cpu0 { > > > + cpu-supply =3D <®_dcdc2>; > > > +}; > > > + > > This will break bisection on those boards. Indeed, you added the OPPs on > > the first patch, and if you only apply that patch, the boards in the > > second patch will be missing their CPU regulator. The kernel will then > > ramp up the frequency to the highest OPP, but will not change the > > voltage, resulting in a crash. > > This is a good point and I will merge those two patch. That's not what I meant to say. Those two patches are great separated. You can invert them though. > > There's a similar issue for all the boards that don't have a regulator > > in the first place. > >=20 > > The way we worked around this for the other SoCs is to have a DTSI with > > the OPPs with a frequency higher than what U-Boot boots with (1008MHz?), > > and only include that DTSI on boards that have a CPU regulator hooked i= n. > > Is this really necessary? It seems like every board based on sun8i-r40 > have a cpu regulator. This probably won't be the case whenever someone starts a new design, and then they'll face random crashes for no apparent reason, and waste a lot of time in the process. Whereas the alternative is that you would be missing some OPPs, something that is fairly easy to figure out. Maxime --ocbjtkvxhxhj7iii Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQRcEzekXsqa64kGDp7j7w1vZxhRxQUCYn4TvAAKCRDj7w1vZxhR xXVzAQCYS/y6GVik1wq99/10xFtsQVwNbQDTafNgKQRW8bpSxwD+Ohmf/aYmi5JZ QfgJA4DF5q5bvX0nina8Y7KiVSMVSQ0= =x+9H -----END PGP SIGNATURE----- --ocbjtkvxhxhj7iii--