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

[Michal Simek <michal.simek@xilinx.com>]

On 13. 07. 20 18:08, Maarten Brock wrote:
> On 2020-07-13 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.
> 
> What if you also have a 16550 (in the PL) and give it the serial0 alias?
> Or a UARTlite? The serialN alias is inappropriate to set the number for
> ttyPSn. How are you supposed to create all of ttyPS0, ttyS0 and ttyUL0
> using a single serial0 alias?

yes this combination is not possible and I don't think this is xilinx
specific issue.
I expect the same problem you have with ttyAMA, ttyS and others.


>>> 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.
>>
>>> All of these above are just not setting any console= on bootargs.
>>
>> We usually set the console= assignment on bootargs.
>>
>>> 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?
>>
>> Helmut
> 
> I think that it would be better if u-boot used a "console" alias.

console is defined in bootargs which is OS specific feature. U-Boot has
no idea what ttyPS, ttyS, etc means. That's why I don't think there is
something wrong in this in u-boot. But please elaborate more on this
because I am not aware about any issue on u-boot configuration.

Thanks,
Michal