[PATCH] drm/ast: Fix default resolution when no monitor is connected on DP

[Jocelyn Falempe]

On 12/07/2023 17:05, Sui Jingfeng wrote:
> Hi,
> 
> 
> I'm here join to the discussion. Because I know a little about aspeed BMC.
> 
> 
> On 2023/7/10 16:07, Jocelyn Falempe wrote:
>> On 07/07/2023 09:30, Thomas Zimmermann wrote:
>>> Hi
>>>
>>> Am 06.07.23 um 18:37 schrieb Jocelyn Falempe:
>>> [...]
>>>>>>
>>>>>> You could out-comment the VGA code in the ast driver for testing.
>>>>>
>>>>> Oh, Thanks for the idea, I will try that.
>>>>>
>>>>
>>>> The result is that I get a black screen on the remote BMC. So maybe 
>>>> adding a remote/bmc connector will solve that.
>>>
>>> Could work. That would be a connector and encoder of type 'virtual'?
>>>
>>> Not all ast devices have a BMC. Do you know how to detect its presence?
>>
>> Hum, I though all ast devices have a BMC, 
> 
> No, Thomas is right, not all ast devices have a BMC.
> 
> I have two discrete AST BMC cards, see [1] for reference.
> 
> I generally using the ast2400 BMC cards to testing patches and study 
> drm/ast driver.
> 
> It seems that this two cards are pure 2D display card, because they 
> don't have a net interface(can not plug-in the net cable).
> 
> 
> [1] 
> https://github.com/loongson-gfx/loongson_boards/blob/main/ast_bmc_cards/ast1400_and_ast2400.jpg

Thanks for this picture, I didn't know about this discrete graphic 
cards, with PCIe connector.

> 
> 
>> and I don't see a way to detect that BMC is active or present.
> 
> I think we better find one, then if the BMC is active (present).
> 
> we could create a virtual encoder and connector safely.
> 
> 
>> (It would be even better to know the browser's size, and automatically 
>> resize, like when using a VM. But I'm not sure the hardware/firmware 
>> is able to do this).
>>
> 
> I think it is not difficult, it just that need the firmware of your 
> board to set a value to a register,
> 
> (a scratch register) or something like that.
> 
> But this really need you have the firmware (source code) to support this.

Yes, that's the difficult part.
> 
> Or you are luckily, if there somebody already done this for you.
> 
>> On the other hand, are there any drawback to present a BMC connector 
>> even when the hardware doesn't have it ?
> 
> If not properly setting up, I think you will create two encoder and two 
> connector in the system.

Yes, but I think it won't have any visible effect for the end-user.

-- 

Jocelyn

> 
>>>
>>> Best regards
>>> Thomas
>>>
>>>>
>>>>
>>>
>>
>> Best regards,
>>
>