[U-Boot] [PATCH] py: test_gpio: Add support for GPIO pytest

[Stephen Warren]

On 09/21/2017 06:24 AM, Michal Simek wrote:
> Hi Stephen,
> 
> On 20.9.2017 19:05, Stephen Warren wrote:
>> On 09/20/2017 01:55 AM, Michal Simek wrote:
>>> From: Vipul Kumar <vipul.kumar at xilinx.com>
>>>
>>> This patch tests the gpio commands using the
>>> gpio data from boardenv file.
>>>
>>> Also one test will show the default status of all the gpio's
>>> supported by the processor.
>>
>> Nit: Wrap the commit description to something like 74 characters; the
>> text above is far too narrow.
>>
>> Nit: GPIO not gpio in any free-form text (here and in comments in the
>> source file)
>>
>> Ah, I'd briefly though about GPIO tests before, but was wondering how to
>> integrate e.g. a USB GPIO device to the host PC and interface that with
>> the target. Loopback GPIOs make this a lot easier:-)
> 
> good.
> 
>>
>>> diff --git a/test/py/tests/test_gpio.py b/test/py/tests/test_gpio.py
>>
>>> +"""
>>> +Note: This test relies on boardenv_* containing configuration values
>>> to define
>>> +which the gpio available for testing. Without this, this test will
>>> be  automat-
>>
>> Nit: Double space before automatically.
>>
>>> +For example:
>>> +
>>> +# A list of gpio's that are going to be tested in order to validate the
>>> +# test.
>>> +env__gpio_val = {
>>> +     "gpio": [0,1,2],
>>> +}
>>
>> Why is this a dictionary with only one key? Better to just assign the
>> array directly to env__gpio_val, or put both the "gpio" and
>> "list_of_gpios" into a single dictionary.
>>
>>> +# A list of gpio's that are shorted on the hardware board and first
>>> gpio of
>>> +# each group is configured as input and the other as output. If the
>>> pins are
>>> +# not shorted properly, then the test will be fail.
>>> +env__gpio_input_output = {
>>> +     "list_of_gpios": [ [36, 37], [38, 39]],
>>> +}
>>
>> Let's make the examples for env__gpio_val and env__gpio_input_output use
>> the same GPIO numbers so that they match, and it's obvious how the two
>> relate to each-other. I assume they're meant to?
> 
> The reason for two values is that you do that loopback between certain
> pins. It means you have to list pairs.
> I have tested this on the board where I can choose whatever
> configuration by external wires. Also this list is not the same with the
> above one because you are choosing which one is loopback but not all can
> be done as loopback.
> 
> Also I have tested that you can specify 36,37 as one pair and then 37,36
> pair which simply saying which pin is used as output and which as input.
> 
> I don't think it is right to say that both of them can bidirectional
> because at least in our chip with have some pins which are just output
> only and input only.

Sorry, I still don't understand why there are two lists. Certainly I see 
that there's different testing applied to each list, but I don't see any 
benefit from doing that. If you test just loopback pairs, then you've 
tested all the other APIs as part of that, so you don't need a separate 
test for a separate list of GPIOs.

Also, if the code was to include logic to test pairs of loopback GPIOs 
in both directions, the code would need to be careful to set both GPIOs 
to input after each test step. Without that, when setting up the output 
GPIO for the next round of testing, both GPIOs might be outputs for a 
while which could damage HW. I don't recall whether the current code is 
safe in this case or not.