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

[Thomas Zimmermann <tzimmermann@xxxxxxx>]

Hi

Am 06.07.23 um 11:16 schrieb Jocelyn Falempe:
> On 04/07/2023 18:45, Jocelyn Falempe wrote:
> > On 04/07/2023 16:54, Jani Nikula wrote:
> > > On Fri, 23 Jun 2023, Jocelyn Falempe <jfalempe@xxxxxxxxxx> wrote:
> > > > Since commit fae7d186403e ("drm/probe-helper: Default to 640x480 if no
> > > >   EDID on DP")
> > > > The default resolution is now 640x480 when no monitor is connected.
> > > > But Aspeed graphics is mostly used in servers, where no monitor
> > > > is attached. This also affects the "remote" resolution to 640x480, 
> > > > which is
> > > > inconvenient, and breaks the anaconda installer.
> > > > So when no EDID is present, set 1024x768 as preferred resolution.
> > >
> > > This conflates "monitor connected" and "EDID present", which are not
> > > necessarily the same thing.
> > >
> > > The fallback in drm_helper_probe_single_connector_modes() is for no
> > > modes, but connector status is connected or unknown.
> >
> > When debugging the issue, I found it surprising that the status is 
> > "connected" when nothing is plugged in the DP port.
> > > You could add a connector ->detect callback that returns disconnected
> > > when there's no display, and the problem should go away. If there's no
> > > ->detect callback, it'll default to connected.
> >
> > ok, I'll try that. I don't know how the hardware detect something is 
> > connected, but looking at the dp code, maybe checking 
> > "AST_IO_CRTC_PORT,0xDC, ASTDP_LINK_SUCCESS" would be good enough.
>
> I've tested this approach, and it works. But on the server I'm testing, 
> there are VGA and DP output. I think on a server that has only one DP 
> output, if no monitor is connected, then no modes will be reported to 
> userspace, and the remote BMC may not work ?

You could out-comment the VGA code in the ast driver for testing.

Best regards
Thomas

> Also I don't have physical access to the server, so I only tested when 
> no monitor is plugged.
>
> I will send shortly a v2 with this change, so others can help me test 
> this case.
>
> 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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