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From: sylvain.bertrand@gmail.com
To: bugzilla-daemon@freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Subject: Re: [Bug 107784] [AMD tahiti XT] displayport broken
Date: Sun, 9 Sep 2018 03:45:49 +0000	[thread overview]
Message-ID: <20180909034549.GA451@freedom> (raw)
In-Reply-To: <bug-107784-502-s985ubzvG2@http.bugs.freedesktop.org/>

Found the bug, very probably.

It seems to be an upstream bug: a 32bits multiplication overflow on TSC
frequency introduced in recent TSC cleanup:

--------------------------------------------------------------------------------
commit cf7a63ef4e0203f6f33284c69e8188d91422de83
Author: Pavel Tatashin <pasha.tatashin@oracle.com>
Date:   Thu Jul 19 16:55:38 2018 -0400

    x86/tsc: Calibrate tsc only once
    
    During boot tsc is calibrated twice: once in tsc_early_delay_calibrate(),
    and the second time in tsc_init().
    
    Rename tsc_early_delay_calibrate() to tsc_early_init(), and rework it so
    the calibration is done only early, and make tsc_init() to use the values
    already determined in tsc_early_init().
    
    Sometimes it is not possible to determine tsc early, as the subsystem that
    is required is not yet initialized, in such case try again later in
    tsc_init().
--------------------------------------------------------------------------------

One nasty thing: this commit is broken, it does not compile, hence it's a
bisect "skipped" commit.

Roughly, if you have a cpu with a frequency above 4.2GHz (max unsigned 32bits),
linux time subsystem gets broken leading to the timeouts in displayport
programming. Ofc, my cpu runs at 4.7GHz.
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  reply	other threads:[~2018-09-09  3:46 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-02 17:22 [Bug 107784] [AMD tahiti XT] displayport broken bugzilla-daemon
2018-09-02 17:28 ` bugzilla-daemon
2018-09-03  9:17 ` bugzilla-daemon
2018-09-03 10:30 ` bugzilla-daemon
2018-09-03 14:55 ` bugzilla-daemon
2018-09-05  7:19 ` bugzilla-daemon
2018-09-05 11:50 ` bugzilla-daemon
2018-09-05 12:28 ` bugzilla-daemon
2018-09-05 12:33 ` bugzilla-daemon
2018-09-05 13:38   ` sylvain.bertrand
2018-09-05 13:38 ` bugzilla-daemon
2018-09-05 17:44 ` bugzilla-daemon
2018-09-05 21:48   ` sylvain.bertrand
2018-09-05 21:48 ` bugzilla-daemon
2018-09-05 21:52 ` bugzilla-daemon
2018-09-05 21:54 ` bugzilla-daemon
2018-09-06 10:04 ` bugzilla-daemon
2018-09-06 12:31   ` sylvain.bertrand
2018-09-06 12:31 ` bugzilla-daemon
2018-09-06 14:22 ` bugzilla-daemon
2018-09-06 16:20   ` sylvain.bertrand
2018-09-06 16:20 ` bugzilla-daemon
2018-09-06 21:10   ` sylvain.bertrand
2018-09-07 21:48     ` sylvain.bertrand
2018-09-06 21:10 ` bugzilla-daemon
2018-09-07 21:48 ` bugzilla-daemon
2018-09-09  3:45   ` sylvain.bertrand [this message]
2018-09-09  3:46 ` bugzilla-daemon
2018-09-09  5:57 ` bugzilla-daemon
2018-09-09 13:05 ` bugzilla-daemon
2018-09-09 13:11 ` bugzilla-daemon
2018-09-09 14:59   ` sylvain.bertrand
2018-09-09 14:59 ` bugzilla-daemon
2018-09-10  5:20 ` bugzilla-daemon
2018-09-10  9:15 ` bugzilla-daemon

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