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Date: Mon, 13 Jun 2022 11:09:18 +0200
From: Greg KH <gregkh@linuxfoundation.org>
To: Yerong Li <yerong.li@outlook.com>
Cc: stable@vger.kernel.org, regressions@lists.linux.dev
Subject: Re: external monitor no signal with HDMI port apple-gmux.c
Message-ID: <Yqb+vtXP5DzVK+dz@kroah.com>
References: <SG2PR03MB41529020102E6D613A0E651CFFA69@SG2PR03MB4152.apcprd03.prod.outlook.com>
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On Fri, Jun 10, 2022 at 02:57:37PM -0500, Yerong Li wrote:
> Hi there:
> 
> I am using debian 11 linux with a macbook pro 2013 15-inch. i7-3740QM CPU
> (NIVIDIA-GPU switch)
> 
> I think on my macbook pro the HDMI port with external monitor is not working
> while the DP port /thunderbolt 2 is working. (Actually one of my 2 DP port
> is working the other is not) These three ports work under MacOS system:
> 
> https://forums.developer.nvidia.com/t/external-monitor-not-working-nvidia-optimus/216573/2
> 
> Many users met similar issues: HDMI got detected by xrandr while the
> external monitor got no signals. Could you help us?
> 
> https://forums.developer.nvidia.com/t/no-signal-with-hdmi-or-dp-0-ports-on-macbookpro10-1-gt-650m-only-dp-1-works/49777/5
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/platform/x86/apple-gmux.c#n311

I do not think this is a regression with the kernel as it never has
worked before.

Please contact the graphics developers so that they can help you out
with this.

Good luck!

greg k-h