<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_NEW " title="NEW - [AMD tahiti XT] displayport broken" href="https://bugs.freedesktop.org/show_bug.cgi?id=107784#c20">Comment # 20</a> on <a class="bz_bug_link bz_status_NEW " title="NEW - [AMD tahiti XT] displayport broken" href="https://bugs.freedesktop.org/show_bug.cgi?id=107784">bug 107784</a> from <a class="email" href="mailto:sylvain.bertrand@gmail.com" title="Sylvain BERTRAND <sylvain.bertrand@gmail.com>"> Sylvain BERTRAND</a> <pre>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 <<a href="mailto:pasha.tatashin@oracle.com">pasha.tatashin@oracle.com</a>> 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.</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the assignee for the bug.</li> </ul> </body> </html>