[PATCH] gpio: exynos4: Add device tree support

[Thomas Abraham]

On 11 October 2011 21:00, Rob Herring <robherring2 at gmail.com> wrote:
> On 10/11/2011 10:19 AM, Thomas Abraham wrote:
>> Hi Rob,
>>
>> On 11 October 2011 20:41, Rob Herring <robherring2 at gmail.com> wrote:
>>> Thomas,
>>>
>>> On 10/11/2011 03:16 AM, Thomas Abraham wrote:
>>>> As gpio chips get registered, a device tree node which represents the
>>>> gpio chip is searched and attached to it. A translate function is also
>>>> provided to convert the gpio specifier into actual platform settings
>>>> for pin function selection, pull up/down and driver strength settings.
>>>>
>>>> Signed-off-by: Thomas Abraham <thomas.abraham at linaro.org>
>>>> ---
>>>> This patch is based on the latest consolidated Samsung GPIO driver available
>>>> in the following tree:
>>>>   https://github.com/kgene/linux-samsung.git  branch: for-next
>>>>
>>>>  .../devicetree/bindings/gpio/gpio-samsung.txt      |   30 +++++++++++
>>>>  drivers/gpio/gpio-samsung.c                        |   53 ++++++++++++++++++++
>>>>  2 files changed, 83 insertions(+), 0 deletions(-)
>>>>  create mode 100644 Documentation/devicetree/bindings/gpio/gpio-samsung.txt
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/gpio/gpio-samsung.txt b/Documentation/devicetree/bindings/gpio/gpio-samsung.txt
>>>> new file mode 100644
>>>> index 0000000..883faeb
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/gpio/gpio-samsung.txt
>>>> @@ -0,0 +1,30 @@
>>>> +Samsung Exynos4 GPIO Controller
>>>> +
>>>> +Required properties:
>>>> +- compatible: Format of compatible property value should be
>>>> +  "samsung,exynos4-gpio-<controller_name>". Example: For GPA0 controller, the
>>>> +  compatible property value should be "samsung,exynos4-gpio-gpa0".
>>>
>>> Isn't gpa0 an instance of the h/w, not a version?
>>
>> GPA0 is a instance of the gpio controller. There are several such
>> instances and there could be differences in those instances such as
>> the number of GPIO lines managed by that gpio controller instance.
>>
>
> That doesn't seem like a reason to have different compatible strings.
> Does that affect the programming model of the controller? Unused lines
> whether at the board level or SOC level shouldn't really matter.


No, that does not affect the programming of the controller. The reason
for the instance name extension in compatible string is to match the
gpio_chip with a gpio controller node. When matched, the of_node
pointer of the gpio_chip is set to point to that controller node.

This might not be the best possible implementation but the device tree
support code in this patch is dictated by the structure of the
existing gpio driver code. As you suggested previously, I will look at
reworking the gpio driver a little later but for now, there was a need
for working gpio dt solution to make progress on dt support for other
controllers.

Thanks,
Thomas.

>
> Rob
>
>