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

[Thomas Zimmermann <tzimmermann@xxxxxxx>]

Hi

Am 12.07.23 um 17:05 schrieb Sui Jingfeng:
> 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 the info.

Best regards
Thomas

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

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

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