Quoting Mika Kuoppala (2018-01-10 13:45:27) > Hans de Goede <hdegoede@xxxxxxxxxx> writes: > > > Hi, > > > > On 10-01-18 13:55, Chris Wilson wrote: > >> While we talk to the punit over its sideband, we need to prevent the cpu > >> from sleeping in order to prevent a potential machine hang. > >> > >> Note that by itself, it appears that pm_qos_update_request (via > >> intel_idle) doesn't provide a sufficient barrier to ensure that all core > >> are indeed awake (out of Cstate) and that the package is awake. To do so, > >> we need to supplement the pm_qos with a manual ping on_each_cpu. > >> > >> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=109051 > >> References: https://bugs.freedesktop.org/show_bug.cgi?id=102657 > >> References: https://bugzilla.kernel.org/show_bug.cgi?id=195255 > >> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > >> Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx> > >> Cc: Hans de Goede <hdegoede@xxxxxxxxxx> > > > > Interesting, I've added similar pm_qos code in > > drivers/i2c/busses/i2c-designware-baytrail.c quite a while ago because > > the CPU transitioning to higher C-state while accessing the i2c bus to > > the pmic (if it is shared) also causes the SoC to hang. > > > > I could reproduce this quite easily by doing "i2cdump" on the pmic, > > usually the system would hang in one or 2 i2cdump calls. > > > > Note IIRC this was on CHT. > > > > I see that you also block any pmic-i2c bus accesses while doing > > punit access by calling iosf_mbi_punit_acquire(); > > > > Maybe we need to move the pm_qos stuff out of > > drivers/i2c/busses/i2c-designware-baytrail.c > > > > And into iosf_mbi_punit_acquire? The i2c-designware-baytrail.c > > does its own pm_qos dance directly after calling > > iosf_mbi_punit_acquire / before calling iosf_mbi_punit_release(); > > > > Note the i2c-designware-baytrail.c version lacks the ping, but it > > should, probably have it too. > > The ping, if it deemed worthy, should find its way into intel_idle > parts. It's definitely the missing piece in the puzzle. Without the on_each_cpu(ping), the machine hangs remain a reoccuring nightmare. However, the max test runtime so far with these patches has been 12h on one j1900, not enough to be conclusive. -Chris _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
