linux-kernel - Re: use IORESOURCE_REG resource type for non-translatable addresses in DT

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Message-ID: <3794875.CZFbAag5Sv@wuerfel>
Date:	Tue, 29 Jul 2014 14:00:50 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Stanimir Varbanov <svarbanov@...sol.com>
Cc:	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...aro.org>,
	Rob Herring <robherring2@...il.com>,
	Lee Jones <lee.jones@...aro.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	linux-arm-kernel@...ts.infradead.org,
	Stephen Boyd <sboyd@...eaurora.org>,
	Mark Brown <broonie@...aro.org>
Subject: Re: use IORESOURCE_REG resource type for non-translatable addresses in DT

On Tuesday 29 July 2014 14:42:31 Stanimir Varbanov wrote:
>         taddr = of_translate_address(dev, addrp);
> -       if (taddr == OF_BAD_ADDR)
> -               return -EINVAL;
> +       /*
> +        * if the address is non-translatable to cpu physical address
> +        * fallback to a IORESOURCE_REG resource.
> +        */
> +       if (taddr == OF_BAD_ADDR) {
> +               memset(r, 0, sizeof(*r));
> +               taddr = of_read_number(addrp, 1);
> +               if (taddr == OF_BAD_ADDR)
> +                       return -EINVAL;
> +               r->start = taddr;
> +               r->end = taddr + size - 1;
> +               r->flags = IORESOURCE_REG;
> +               r->name = name ? name : dev->full_name;
> +               return 0;
> +       }
> +

I don't think that everything returning OF_BAD_ADDR makes sense
to turn into IORESOURCE_REG. It could be an e.g. invalid DT
representation, a node with #size-cells=<0>, or it could be
something that gets translated one or more nodes up in the
tree before it reaches a bus without a ranges property.

Also, you should not rely on #address-cells being hardcoded
to <1> above.

How about modifying of_get_address() rather than
__of_address_to_resource() instead? You could introduce
a new of_bus entry for each bus you expect to return
an IORESOURCE_REG, or you could change of_bus_default_get_flags
to return IORESOURCE_REG if the parent node has no ranges property
and is not the root node.

	Arnd
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