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From: =?UTF-8?B?6buD56uL6YqY?= <orbit.huang@gmail.com>
Date: Mon, 1 Apr 2024 10:20:48 +0800
Message-ID: <CAOj9kT3=UA-5wkVXb8Rk2h3D=vtZDbhzxe4MY=Nwzod96DeppA@mail.gmail.com>
Subject: Re: [PATCH] drm/ast: Fix soft lockup
To: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Jocelyn Falempe <jfalempe@redhat.com>, maarten.lankhorst@linux.intel.com, 
	mripard@kernel.org, airlied@redhat.com, airlied@gmail.com, daniel@ffwll.ch, 
	dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, 
	Jammy Huang <jammy_huang@aspeedtech.com>, stable@vger.kernel.org
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Hi Thomas and Jocelyn,

What we do in ast_dp_set_on_off() is a handshake between host driver
and bmc-fw to confirm
the operation, on/off, is completed.

We use some scratch registers in bmc to handshake with host. This
handshake only work if
BMC's scu-lock is opened. If scu-lock is opened too late, then it
could lead to this issue.

Best regards
Jammy

Thomas Zimmermann <tzimmermann@suse.de> =E6=96=BC 2024=E5=B9=B43=E6=9C=8828=
=E6=97=A5 =E9=80=B1=E5=9B=9B =E4=B8=8A=E5=8D=884:28=E5=AF=AB=E9=81=93=EF=BC=
=9A
>
> Hi
>
> Am 27.03.24 um 09:53 schrieb Jocelyn Falempe:
> > Hi,
> >
> > Thanks for your patch.
> > I'm wondering how you can trigger this infinite loop ?
>
> Yeah, a bit more context for this bug would be welcome. It's hard to
> judge the fix without.
>
> Best regards
> Thomas
>
> >
> > Also this looks like a simple fix, that can be easily backported, so
> > I'm adding stable in Cc.
> >
> > If Thomas has no objections, I can push it to drm-misc-fixes.
> >
> > Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
> >
>
>
>
> --
> --
> 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)
>