linux-kernel - Re: [PATCH 09/14] regulator: dts: add full voltage range to LDO4 on the Lime2

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Date:   Tue, 27 Nov 2018 10:38:52 +0100
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Priit Laes <plaes@...es.org>
Cc:     Lee Jones <lee.jones@...aro.org>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Chen-Yu Tsai <wens@...e.org>,
        Sebastian Reichel <sre@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-pm@...r.kernel.org, Olliver Schinagl <oliver@...inagl.nl>
Subject: Re: [PATCH 09/14] regulator: dts: add full voltage range to LDO4 on
 the Lime2

On Mon, Nov 26, 2018 at 05:27:50PM +0200, Priit Laes wrote:
> From: Olliver Schinagl <oliver@...inagl.nl>
> 
> With commit b43776d65a33b46092 ("ARM: dts: sunxi: Use axp209.dtsi for
> Olinuxino Lime2") we force them an arbitrary 2.8 volts. Granted, for
> LDO3 this may be less arbitrary, but for LDO4 this is just wrong.
> 
> In the defense of LDO3, LDO3 is the regulator that feeds port bank E,
> which has no other purpose then a CSI/TS interface, however the case
> may still be, that the connected IO may be just as well be 3.3 volts.
> The big misnomer is however, that the schematic names GPIO-2 pin4
> LDO3_2.8V, rather then VDD-CSI0 or similar.
> 
> This is much worse for LDO4 however, which is not referenced on any
> pin, is now set to 2.8 volts, but port bank G can also support various
> other peripherals such as UARTS etc.
> 
> By having 2.8 volts however for LDO4, we thus now have peripherals that
> no longer function properly all of the time.
> 
> Ideally, we want to set a supply voltage for each port bank, but the
> monolithic nature of the sunxi pinctroller currently prevents this and
> as such, the board should at least configure the LDO4 with the proper
> ranges.
> 
> Until we can set the consumer at the port bank level, a child
> device-tree has to do something like:
> 
> &reg_ldo4 {
>     regulator-min-microvolt = <3300000>;
>     regulator-max-microvolt = <3300000>;
> };
> 
> While doing this the same way results in the same solution currently,
> we force the hack into the final devicetree rather then having it wrong
> at the board level.
> 
> Signed-off-by: Olliver Schinagl <oliver@...inagl.nl>
> Signed-off-by: Priit Laes <plaes@...es.org>
> ---
>  arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts b/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts
> index ffafe97..1b9867f 100644
> --- a/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts
> +++ b/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts
> @@ -250,9 +250,10 @@
>  };
>  
>  &reg_ldo4 {
> -	regulator-min-microvolt = <2800000>;
> -	regulator-max-microvolt = <2800000>;
> -	regulator-name = "vddio-csi1";
> +	regulator-always-on;
> +	regulator-min-microvolt = <1250000>;
> +	regulator-max-microvolt = <3300000>;
> +	regulator-name = "vdd-io-pg";

As we discussed on the U-Boot ML already, this shouldn't be made
always-on but tied to the consumer device (the pinctrl one) instead.

Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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