linux-kernel - Re: [PATCH] ARM: dts: sun8i: h2+: Enable optional SPI flash on Orange Pi Zero board

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Message-ID: <20201008171454.qixrcjmhzko766su@gilmour.lan>
Date:   Thu, 8 Oct 2020 19:14:54 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     Michal Suchánek <msuchanek@...e.de>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Rob Herring <robh+dt@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: dts: sun8i: h2+: Enable optional SPI flash on
 Orange Pi Zero board

On Thu, Oct 08, 2020 at 06:02:19PM +0200, Michal Suchánek wrote:
> On Thu, Oct 08, 2020 at 05:13:15PM +0200, Maxime Ripard wrote:
> > Hi,
> > 
> > On Tue, Sep 29, 2020 at 10:30:25AM +0200, Michal Suchanek wrote:
> > > The flash is present on all new boards and users went out of their way
> > > to add it on the old ones.
> > > 
> > > Enabling it makes a more reasonable default.
> > > 
> > > Signed-off-by: Michal Suchanek <msuchanek@...e.de>
> > > ---
> > >  arch/arm/boot/dts/sun8i-h2-plus-orangepi-zero.dts | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/arch/arm/boot/dts/sun8i-h2-plus-orangepi-zero.dts b/arch/arm/boot/dts/sun8i-h2-plus-orangepi-zero.dts
> > > index f19ed981da9d..061d295bbba7 100644
> > > --- a/arch/arm/boot/dts/sun8i-h2-plus-orangepi-zero.dts
> > > +++ b/arch/arm/boot/dts/sun8i-h2-plus-orangepi-zero.dts
> > > @@ -163,8 +163,8 @@ &ohci1 {
> > >  };
> > >  
> > >  &spi0 {
> > > -	/* Disable SPI NOR by default: it optional on Orange Pi Zero boards */
> > > -	status = "disabled";
> > > +	/* Enable optional SPI NOR by default */
> > > +	status = "okay";
> > >  
> > >  	flash@0 {
> > >  		#address-cells = <1>;
> > 
> > Unfortunately, it's optional, so there's really no reason to enable it
> > all the time. If it's troublesome to users, then the distros or vendors
> > should make the changes necessary to the hardware, bootloader or their
> > documentation to make it easier for those users.
> 
> I don't understand the reasoning. Why must it be disabled when optional?

Think about it the other way around. If we enable everything that is
optional, we're going to have a multitude of conflicts everywhere, and
without a clear decision as to who is "best" and thus how we should
resolve it.

On a separate platform, recently I've been using a VGA bridge for the
RaspberryPi that takes the UART pins as well. It's definitely optional,
should I enable it by default? At the same time, enabling by default the
UART is just as arbitrary and will result in people using the VGA bridge
to complain about their regression (rightfully so).

So, really, if it's optional, it means that it not always there. If it's
not always there, it's meant to be supported by an overlay.

> By the same reasoning there is no reason to disable it all the time.

I'm not sure I follow you here. The least common denominator is that
it's not there, so it's not enabled.

> Also the boards that do not have the flsh are either broken or
> obsolete.

Making general statements without arguments doesn't really make it true
though. Plenty of boards to have flash and are neither broken nor
obsolete.

> So most of the time enabling the flash chip is the right thing.
> 
> Or do we need two DTBs like sun8i-h2-plus-orangepi-zero.dts and
> sun8i-h2-plus-orangepi-zero-no-spi-nor.dts

No, you need sun8i-h2-plus-orangepi-zero plus an overlay for the
SPI-NOR.

> There is no way to change the setting on a runnig system, the pins are
> routed to the flash pads anyway so are not usable for anything else. The
> only thing that happens on boards that do not have the flash is kernel
> probing it and complaining that the ID 00 00 00 is not valid SPI NOR
> flash memory ID.

We have people reporting bugs about completely innocuous error messages
without any side effects already. An error about a missing or broken
storage device will surely raise some eyebrows.

Maxime

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