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

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Date:	Tue, 29 Jul 2014 18:07:36 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Grant Likely <grant.likely@...aro.org>
CC:	Stanimir Varbanov <svarbanov@...sol.com>,
	Arnd Bergmann <arnd@...db.de>,
	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,
	Mark Brown <broonie@...aro.org>
Subject: Re: use IORESOURCE_REG resource type for non-translatable addresses
 in DT

On 07/29/14 16:45, Grant Likely wrote:
> On Tue, 29 Jul 2014 17:06:42 +0300, Stanimir Varbanov <svarbanov@...sol.com> wrote:
>>
>> This was just an example. Of course it has many issues and probaly it is
>> wrong:) The main goal was to understand does IORESOURCE_REG resource
>> type and parsing the *reg* properties for non-translatable addresses are
>> feasible. And also does it acceptable by community and OF platform
>> maintainers.
> The use case is actually very different from of_address_to_resource or
> of_get_address() because those APIs explicitly return physical memory
> addresses from the CPU perspective. It makes more sense to create a new
> API that doesn't attempt to translate the reg address. Alternately, a
> new API that only translates upto a given parent node.

The most important thing is that platform_get_resource{_by_name}(&pdev,
IORESOURCE_REG, n) returns the reg property and optional size encoded
into a struct resource. I think Rob is suggesting we circumvent the
entire of_address_to_resource() path and do some if
(IS_ENABLED(CONFIG_OF) && type == IORESOURCE_REG) check in
platform_get_resource() to package up the reg property into a struct
resource. That should work.

It sounds like you think partially translating addresses is risky
though. Fair enough. Perhaps we should call WARN() if someone tries to
call platform_get_resource() with IORESOURCE_REG and the parent node has
a ranges property that isn't a one-to-one conversion. That way if we
want to do something like this we can.

pmic@0 {
    #address-cells = <1>;
    #size-cells = <0>;
    reg = <0>;

    regulators {
        ranges;
        #address-cells = <1>;
        #size-cells = <0>;

        regulator@40 {
            reg = <0x40>;
        };

        regulator@50 {
            reg = <0x50>;
        }
    };
};

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