linux-kernel - Re: [PATCH v4 4/6] reset: sunxi: Add Allwinner H3 bus resets

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Message-ID: <20151104163014.GB6114@lukather>
Date:	Wed, 4 Nov 2015 08:30:14 -0800
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Jens Kuske <jenskuske@...il.com>, Chen-Yu Tsai <wens@...e.org>,
	Michael Turquette <mturquette@...libre.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Emilio López <emilio@...pez.com.ar>,
	devicetree@...r.kernel.org,
	Vishnu Patekar <vishnupatekar0510@...il.com>,
	linux-kernel@...r.kernel.org, Hans de Goede <hdegoede@...hat.com>,
	linux-sunxi@...glegroups.com
Subject: Re: [PATCH v4 4/6] reset: sunxi: Add Allwinner H3 bus resets

Hi Arnd,

On Fri, Oct 30, 2015 at 09:27:03AM +0100, Arnd Bergmann wrote:
> On Tuesday 27 October 2015 17:50:24 Jens Kuske wrote:
> > 
> > +static int sun8i_h3_bus_reset_xlate(struct reset_controller_dev *rcdev,
> > +                                   const struct of_phandle_args *reset_spec)
> > +{
> > +       unsigned int index = reset_spec->args[0];
> > +
> > +       if (index < 96)
> > +               return index;
> > +       else if (index < 128)
> > +               return index + 32;
> > +       else if (index < 160)
> > +               return index + 64;
> > +       else
> > +               return -EINVAL;
> > +}
> > +
> > 
> 
> This looks like you are doing something wrong and should either
> put the actual number into DT,

This is the actual number, except that there's some useless registers
in between. Allwinner documents it like that:

0x0	Reset 0
0x4	Reset 1
0xc	Reset 2

So we have to adjust the offset to account with the blank register in
between (0x8).

> or use a two-cell representation, with the first cell indicating the
> block (0, 1 or 2), and the second cell the index.

And the missing register is not a block either.

That would also imply either changing the bindings of that driver (and
all the current DTS that are using it), or introducing a whole new
driver just to deal with some extraordinary offset calculation.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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