Re: [PATCH v4 2/2] drm/ast: report connection status on Display Port.

From: Thomas Zimmermann <tzimmermann@suse.de>
To: Jocelyn Falempe <jfalempe@redhat.com>,
	airlied@redhat.com, kuohsiang_chou@aspeedtech.com,
	jammy_huang@aspeedtech.com, jani.nikula@linux.intel.com,
	dianders@chromium.org
Cc: dri-devel@lists.freedesktop.org
Subject: Re: [PATCH v4 2/2] drm/ast: report connection status on Display Port.
Date: Wed, 12 Jul 2023 16:51:30 +0200	[thread overview]
Message-ID: <b3357699-174a-394d-0595-a636cca75057@suse.de> (raw)
In-Reply-To: <af5ab6ed-2f8f-f02e-bc5d-9d13d9e8c87a@redhat.com>

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Hi

Am 12.07.23 um 16:39 schrieb Jocelyn Falempe:
> On 12/07/2023 15:55, Thomas Zimmermann wrote:
>> Hi
>>
>> Am 12.07.23 um 15:27 schrieb Jocelyn Falempe:
>>> Aspeed always report the display port as "connected", because it
>>> doesn't set a .detect callback.
>>> Fix this by providing the proper detect callback for astdp and dp501.
>>>
>>> This also fixes the following regression:
>>> 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 BMC resolution to 640x480, which is
>>> inconvenient, and breaks the anaconda installer.
>>
>> The formatting of these paragraphs still looks off.
> 
> ok, I think it's because I start a new line in the middle of the 
> sentence, before "The default resolution ..." ?
> I will fix that.
>>
>> It just occured to me that you probably want output polling to make 
>> detection work dynamically. See an old patch of mine on how that works:
>>
>> https://patchwork.freedesktop.org/patch/488460/
> 
> So, if I understand well, I just need to add:
> 
> connector->polled = DRM_CONNECTOR_POLL_CONNECT | 
> DRM_CONNECTOR_POLL_DISCONNECT;
> 
> and call drm_kms_helper_poll_init() ?

That's it, I think. The flags tell what to poll for and the call starts 
the polling timeout. It worked when I tested it with vga back then.

Best regards
Thomas

>>
>> We also get an interrupt when the connector state changes, but IDK how 
>> that has to be handled. So polling is the next best thing. Sorry for 
>> missing this in the earlier reviews.
> 
> Yes, there is no irq configured in the ast driver, so let's fallback to 
> polling.
> 

-- 
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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