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From: Lucas Stach <l.stach@pengutronix.de>
To: Heiko Thiery <heiko.thiery@gmail.com>,
	Frieder Schrempf <frieder.schrempf@kontron.de>
Cc: devicetree@vger.kernel.org, "Guido Günther" <agx@sigxcpu.org>,
	"Fabio Estevam" <festevam@gmail.com>,
	"Shengjiu Wang" <shengjiu.wang@nxp.com>,
	"Angus Ainslie (Purism)" <angus@akkea.ca>,
	linux-kernel@vger.kernel.org,
	"Krzysztof Kozlowski" <krzk@kernel.org>,
	"Joakim Zhang" <qiangqing.zhang@nxp.com>,
	"Michael Walle" <michael@walle.cc>,
	"Rob Herring" <robh+dt@kernel.org>,
	"NXP Linux Team" <linux-imx@nxp.com>,
	"Pengutronix Kernel Team" <kernel@pengutronix.de>,
	"Shawn Guo" <shawnguo@kernel.org>,
	"Sascha Hauer" <s.hauer@pengutronix.de>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm64: dts: imx8mm-kontron-n801x-som: do not allow to switch off buck2
Date: Fri, 17 Sep 2021 13:44:04 +0200	[thread overview]
Message-ID: <9bcf7b749dca57d42aa2e7afd88b5a26f3eeff2a.camel@pengutronix.de> (raw)
In-Reply-To: <CAEyMn7ZbJr0_2Phc2rW7sDYQu4AABWPZ1F7xDgaS5U7ha7iqzA@mail.gmail.com>

Am Freitag, dem 17.09.2021 um 09:28 +0200 schrieb Heiko Thiery:
> Hi Frieder,
> 
> Am Mi., 15. Sept. 2021 um 14:09 Uhr schrieb Frieder Schrempf
> <frieder.schrempf@kontron.de>:
> > 
> > On 15.09.21 14:05, Michael Walle wrote:
> > > Am 2021-09-15 14:03, schrieb Heiko Thiery:
> > > > The buck2 output of the PMIC is the VDD core voltage of the cpu.
> > > > Switching off this will poweroff the CPU. Add the 'regulator-always-on'
> > > > property to avoid this.
> > > 
> > > Mh, have this ever worked? Is there a commit which introduced a regression?
> > 
> > Yes, this did work before, even without 'regulator-always-on'. I
> > currently don't understand why this is needed. The regulator is
> > referenced in the CPU nodes as 'cpu-supply'. This should be enough to
> > not disable it as long as the CPU is up.
> 
> I rechecked that with 5.11, 5.10 and 5.9 and I see on all of them the
> same issue:
> 
> [ 31.716031] vdd-5v: disabling
> [ 31.719032] rst-usb-eth2: disabling
> [ 31.722553] buck2: disabling
> 
> While on that I tried to compare with other boards and see that they
> also have the cpu-voltage marked as "regulator-always-on". The only
> exception in dts/freescale is in imx8mq-librem5-devkit.dts [1] that
> has not set this property.
> 
> I agree with you and don't understand why this is happening. Has
> anyone else an explanation?
> 
> [1] https://elixir.bootlin.com/linux/latest/source/arch/arm64/boot/dts/freescale/imx8mq-librem5-devkit.dts#L319
> 
Maybe your kernel config is missing the cpufreq driver, so you don't
have a consumer of the regulator?

Marking the regulator as always-on seems like the right thing to do,
you don't want to depend on a consumer showing up to make sure that
your CPU voltage isn't cut...

Regards,
Lucas


WARNING: multiple messages have this Message-ID
From: Lucas Stach <l.stach@pengutronix.de>
To: Heiko Thiery <heiko.thiery@gmail.com>,
	Frieder Schrempf <frieder.schrempf@kontron.de>
Cc: devicetree@vger.kernel.org, "Guido Günther" <agx@sigxcpu.org>,
	"Fabio Estevam" <festevam@gmail.com>,
	"Shengjiu Wang" <shengjiu.wang@nxp.com>,
	"Angus Ainslie (Purism)" <angus@akkea.ca>,
	linux-kernel@vger.kernel.org,
	"Krzysztof Kozlowski" <krzk@kernel.org>,
	"Joakim Zhang" <qiangqing.zhang@nxp.com>,
	"Michael Walle" <michael@walle.cc>,
	"Rob Herring" <robh+dt@kernel.org>,
	"NXP Linux Team" <linux-imx@nxp.com>,
	"Pengutronix Kernel Team" <kernel@pengutronix.de>,
	"Shawn Guo" <shawnguo@kernel.org>,
	"Sascha Hauer" <s.hauer@pengutronix.de>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm64: dts: imx8mm-kontron-n801x-som: do not allow to switch off buck2
Date: Fri, 17 Sep 2021 13:44:04 +0200	[thread overview]
Message-ID: <9bcf7b749dca57d42aa2e7afd88b5a26f3eeff2a.camel@pengutronix.de> (raw)
In-Reply-To: <CAEyMn7ZbJr0_2Phc2rW7sDYQu4AABWPZ1F7xDgaS5U7ha7iqzA@mail.gmail.com>

Am Freitag, dem 17.09.2021 um 09:28 +0200 schrieb Heiko Thiery:
> Hi Frieder,
> 
> Am Mi., 15. Sept. 2021 um 14:09 Uhr schrieb Frieder Schrempf
> <frieder.schrempf@kontron.de>:
> > 
> > On 15.09.21 14:05, Michael Walle wrote:
> > > Am 2021-09-15 14:03, schrieb Heiko Thiery:
> > > > The buck2 output of the PMIC is the VDD core voltage of the cpu.
> > > > Switching off this will poweroff the CPU. Add the 'regulator-always-on'
> > > > property to avoid this.
> > > 
> > > Mh, have this ever worked? Is there a commit which introduced a regression?
> > 
> > Yes, this did work before, even without 'regulator-always-on'. I
> > currently don't understand why this is needed. The regulator is
> > referenced in the CPU nodes as 'cpu-supply'. This should be enough to
> > not disable it as long as the CPU is up.
> 
> I rechecked that with 5.11, 5.10 and 5.9 and I see on all of them the
> same issue:
> 
> [ 31.716031] vdd-5v: disabling
> [ 31.719032] rst-usb-eth2: disabling
> [ 31.722553] buck2: disabling
> 
> While on that I tried to compare with other boards and see that they
> also have the cpu-voltage marked as "regulator-always-on". The only
> exception in dts/freescale is in imx8mq-librem5-devkit.dts [1] that
> has not set this property.
> 
> I agree with you and don't understand why this is happening. Has
> anyone else an explanation?
> 
> [1] https://elixir.bootlin.com/linux/latest/source/arch/arm64/boot/dts/freescale/imx8mq-librem5-devkit.dts#L319
> 
Maybe your kernel config is missing the cpufreq driver, so you don't
have a consumer of the regulator?

Marking the regulator as always-on seems like the right thing to do,
you don't want to depend on a consumer showing up to make sure that
your CPU voltage isn't cut...

Regards,
Lucas


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  parent reply	other threads:[~2021-09-17 11:44 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-15 12:03 Heiko Thiery
2021-09-15 12:03 ` Heiko Thiery
2021-09-15 12:05 ` Michael Walle
2021-09-15 12:05   ` Michael Walle
2021-09-15 12:09   ` Frieder Schrempf
2021-09-15 12:09     ` Frieder Schrempf
2021-09-17  7:28     ` Heiko Thiery
2021-09-17  7:28       ` Heiko Thiery
2021-09-17  8:21       ` Michael Walle
2021-09-17  8:21         ` Michael Walle
2021-09-17  8:51         ` Heiko Thiery
2021-09-17  8:51           ` Heiko Thiery
2021-09-17 11:44       ` Lucas Stach [this message]
2021-09-17 11:44         ` Lucas Stach
2021-09-17 16:10         ` Heiko Thiery
2021-09-17 16:10           ` Heiko Thiery
2021-09-20  7:31           ` Frieder Schrempf
2021-09-20  7:31             ` Frieder Schrempf
2021-09-20  7:43             ` Michael Walle
2021-09-20  7:43               ` Michael Walle
2021-09-20  8:10               ` Lucas Stach
2021-09-20  8:10                 ` Lucas Stach
2021-10-04 12:39 ` Shawn Guo
2021-10-04 12:39   ` Shawn Guo

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