On Mon, Jul 06, 2015 at 04:19:36PM +0300, Martin Peres wrote: > > > On 06/07/15 16:15, Martin Peres wrote: > >On 06/07/15 16:13, Chris Wilson wrote: > >>On Mon, Jul 06, 2015 at 03:10:48PM +0300, Martin Peres wrote: > >>>On 06/07/15 13:33, Chris Wilson wrote: > >>>>Move the query for the TIMESTAMP register from context init to the > >>>>screen, so that it is only queried once for all contexts. > >>>> > >>>>On 32bit systems, some old kernels trigger a hw bug resulting in the > >>>>TIMESTAMP register being shifted and the low bits always zero. Detect > >>>>this by repeating the read a few times and check the register is > >>>>incrementing. > >>>You do not do the latter. You only check for the low bits. > >>> > >>>I guess the counter is supposed to be monotonically increasing and > >>>with a resolution of a few microseconds which would make this > >>>perfectly valid. Could you confirm and make sure to add this > >>>information in the commit message please? > >>The counter should increment every 80ns. What's misleading in what I > >>wrote? It describes the hw bug and how to detect it. > > > >Well, it is not misleading, it just lacks this information. > > > >If it incremented every seconds, the patch would be stupid because > >the timestamp could be at 0 and polling 10 times at a few us of > >interval would always yield the same result. That's all :) > > Oh, forgot to say: With this information added in the commit message > and the commit message duplicated as a comment in > intel_detect_timestamp(), the patch is:
How about: On 32bit systems, some old kernels trigger a hw bug resulting in the TIMESTAMP register being shifted and the low 32bits always zero. Detect this by repeating the read a few times and check the register is incrementing every 80ns as expected and not stuck on zero (as would be the case with the buggy kernel/hw.). -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
