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

[Thomas Zimmermann]

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 <jfale...@redhat.com> 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

inconvenient, and breaks the anaconda installer.
So when no EDID is present, set 1024x768 as preferred resolution.

is attached. This also affects the "remote" resolution to 640x480, which is

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

Best regards,

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.

--
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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