On 13 October 2011 06:31, Grant Likely <grant.likely@xxxxxxxxxxxx> wrote: > On Wed, Oct 12, 2011 at 09:45:25PM +0530, Thomas Abraham wrote: >> On 12 October 2011 20:41, Rob Herring <robherring2@xxxxxxxxx> wrote: >> > On 10/11/2011 11:06 AM, Thomas Abraham wrote: >> >> On 11 October 2011 21:00, Rob Herring <robherring2@xxxxxxxxx> wrote: >> >>> On 10/11/2011 10:19 AM, Thomas Abraham wrote: >> >>>> Hi Rob, >> >>>> >> >>>> On 11 October 2011 20:41, Rob Herring <robherring2@xxxxxxxxx> 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@xxxxxxxxxx> >> >>>>>> --- >> >>>>>> 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. >> > >> > Linux should provide clues about what's needed in a binding, but the >> > binding should not be defined based on current Linux code. Doing the >> > binding one way and changing it later is not a good plan. >> >> Ok. When starting on this, two compatible values where used for the >> gpio controllers, one was "samsung,exynos4-gpio" and another was >> "samsung,exynos4-gpio-<ctrl_name>". And when the gpio dt support would >> mature, the second compatible value could be dropped. Non-linux >> platforms could always use the generic "samsung,exynos4-gpio" >> compatible value to match. I moved to using only >> "samsung,exynos4-gpio-<ctrl_name>" just before sending this patch >> because I was not sure of the right approach. >> >> > >> > I think you need to convert all users of gpio over as well so you can >> > move to dynamic gpio_chip creation and gpio numbering. Or maybe you can >> > match based on base address? This is going to be a common problem as >> > gpio is converted over to DT. Perhaps Grant or others have suggestions >> > on the approach to use. >> >> Yes, I agree with you about the dynamic gpio_chip creation and gpio >> numbering. Probably, I should have focussed more on this before moving >> to dt support for other controllers. >> >> But matching based on base address is still an option if that is >> better than matching with compatible values as defined currently. The >> 'struct samsung_gpio_chip' which encapsulates 'struct gpio_chip' has >> information about the base address of the gpio controller. The match >> of gpio device node with 'struct gpio_chip' can be quickly moved over >> to base address matching. Would this be better than the current >> approach? > > That's what I would do. Thanks Grant. I will modify the patch to match against the base address of the controller. Regards, Thomas. > > g. > > -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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