Re: [PATCH] tty: xilinx_uartps: Really fix id assignment

Michal Simek
2020-07-22T07:14:54Z

On 13. 07. 20 14:10, Helmut Grohne wrote:
> Hi Michal,
>
> On Mon, Jul 13, 2020 at 01:49:38PM +0200, Michal Simek wrote:
>> On 13. 07. 20 9:11, Helmut Grohne wrote:
>>> Let me try to enumerate those I know:
>>>
>>> uart0 | uart1 | console | remark
>>> ---------+----------+---------+----------
>>> serial0 | serial1 | ttyPS0 | regular case
>>> serial0 | serial1 | ttyPS1 | normal assignment, second console
>>> serial1 | serial0 | ttyPS0 | -> Jan Kiszka, broken since revert
>>> disabled | serial0 | ttyPS0 | use only uart1 as serial0
>>> serial0 | disabled | ttyPS0 | regular case with uart1 disabled
>>>
>>> Out of these, I'm actively using configurations 3 and 4.
>>>
>>> Which of these scenarios do you test already?
>>
>> For above we are missing also others
>> serial1 | serial0 | ttyPS1
>> disabled| serial1 | ttyPS1
>
> Is it actually possible to have ttyPS1, but no ttyPS0? I think I tried
> doing that earlier and it resulted in there being ttyPS0, but no ttyPS1.

serial1 alias should all the time create ttyPS1 device.
serial0 ttyPS0.

If there are no serial aliases driver should started numbering them from 0.

>> serial1 | disables | ttyPS0
>
> I'm not sure what this is supposed to mean. When there is no serial0
> alias, I'd expect ttyPS0 to be missing. However as indicated above that
> is not what happens in practice. So either of these two configurations
> seems invalid to me.

You are right on this one - this is not possible. It should be ttyPS1.

>
>> All of these above are just not setting any console= on bootargs.
>
> We usually set the console= assignment on bootargs.

I found some time ago that setting up console in bootargs was covering
issue reported by Jan but didn't have time to look at it in more details.

>
>> It means mix of these combinations is tested regularly but not all of
>> them. Do you see any other combination which is not supported?
>
> I'm not aware of further relevant combinations.
>
> Can we maybe trim down the matrix somehow? In my context, the need for
> swapping the serial aliases arises from a limitation in u-boot-xlnx and
> the desire to use one dtb for both linux and u-boot. It requires that
> the serial0 alias is the console. Are there other reasons to swap them?
> If not, maybe fixing u-boot would be an option?

I am not aware about any limitation in u-boot in this space. U-Boot is
working with aliases and also with stdout-patch selection.
Can you please elaborate more on this?

Thanks,
Michal