[U-Boot] [PATCH] mx6: Add IOMUX_CONFIG_SION flag to all GPIO pins

[Eric Nelson]

Hi Benoît,

On 10/01/2013 12:50 PM, Benoît Thébaudeau wrote:
> On Tuesday, October 1, 2013 6:17:06 PM, Eric Nelson wrote:
>> On 10/01/2013 09:10 AM, Stefano Babic wrote:
>>> On 01/10/2013 17:56, Eric Nelson wrote:
>>>> On 10/01/2013 07:49 AM, Stefano Babic wrote:
>>>>> On 01/10/2013 16:26, Eric Nelson wrote:
>>>>
...
>>>> Did I miss something in this thread that does actually require
>>>> that ability? It seems a pretty obscure thing in the normal case
>>>> to drive an output without confidence that it will succeed.
>>>
>>> Yes, it seems quite strange, but it helps to debug the hardware. It is
>>> not the first time we see that, even driving the output, the signal does
>>> not go to the expected value, due for example to a conflict (another
>>> peripheral driving the signal) or to a wrong pull up resistor. As U-Boot
>>> is a great tool for hardware debugging, reading the signal back let
>>> check that the output is set to the desired value.
>>>
>>
>> I agree with all of that, though this only covers the case of a
>> pin set up as a GPIO output, and that same debugging approach
>> is often used for other functions (display data pins, clock inputs
>> and outputs, et cetera).
>>
>> You probably wouldn't just set SION on all pins, right? I suspect
>> that there'd be some ramification in terms of power consumption if
>> nothing else.
>
> Right. Well, instead of adding SION to the pin definition header files, then we
> could just add SION where needed on a per-pin basis, e.g.:
> ---
> imx_iomux_v3_setup_pad(MX6_PAD_NANDF_D1__GPIO_2_1 |
> 			IOMUX_CONFIG_SION << MUX_MODE_SHIFT);
> ---
>
> A helper macro could be defined in arch/arm/include/asm/imx-common/iomux-v3.h in
> order to simplify the writing, e.g.:
> ---
> #define MUX_MODE_SION	(IOMUX_CONFIG_SION << MUX_MODE_SHIFT)
> ---
> imx_iomux_v3_setup_pad(MX6_PAD_NANDF_D1__GPIO_2_1 | MUX_MODE_SION);
> ---
>

I like this approach much better since it lets the reader know there's
something special about the pin.

Regards,


Eric