| Message ID | 20190129161611.241599-1-sean@poorly.run (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/TODO: Add vrefresh replacement to the todo | expand |
On Tue, Jan 29, 2019 at 11:15:51AM -0500, Sean Paul wrote: > From: Sean Paul <seanpaul@chromium.org> > > Suggested-by: Daniel Vetter <daniel@ffwll.ch> > Signed-off-by: Sean Paul <seanpaul@chromium.org> Reviewed-by: Sam Ravnborg <sam@ravnborg.org> > --- > Documentation/gpu/todo.rst | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst > index 38360ede12215..7fc30380eaf6c 100644 > --- a/Documentation/gpu/todo.rst > +++ b/Documentation/gpu/todo.rst > @@ -262,6 +262,21 @@ As a reference, take a look at the conversions already completed in drm core. > > Contact: Sean Paul, respective driver maintainers > > +Convert direct mode.vrefresh accesses to use drm_mode_vrefresh() > +---------------------------------------------------------------- > + > +drm_display_mode.vrefresh isn't guaranteed to be populated. As such, using it > +is risky and has been known to cause div-by-zero bugs. Fortunately, drm core > +has helper which will use mode.vrefresh if it's !0 and will calculate it from > +the timings when it's 0. > + > +Use simple search/replace, or (more fun) cocci to replace instances of direct > +vrefresh access with a call to the helper. Check out > +https://lists.freedesktop.org/archives/dri-devel/2019-January/205186.html for > +inspiration. Bonus points for the link! Sam
On Tue, Jan 29, 2019 at 11:15:51AM -0500, Sean Paul wrote: > From: Sean Paul <seanpaul@chromium.org> > > Suggested-by: Daniel Vetter <daniel@ffwll.ch> > Signed-off-by: Sean Paul <seanpaul@chromium.org> > --- > Documentation/gpu/todo.rst | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst > index 38360ede12215..7fc30380eaf6c 100644 > --- a/Documentation/gpu/todo.rst > +++ b/Documentation/gpu/todo.rst > @@ -262,6 +262,21 @@ As a reference, take a look at the conversions already completed in drm core. > > Contact: Sean Paul, respective driver maintainers > > +Convert direct mode.vrefresh accesses to use drm_mode_vrefresh() > +---------------------------------------------------------------- > + > +drm_display_mode.vrefresh isn't guaranteed to be populated. As such, using it > +is risky and has been known to cause div-by-zero bugs. Fortunately, drm core > +has helper which will use mode.vrefresh if it's !0 and will calculate it from > +the timings when it's 0. > + > +Use simple search/replace, or (more fun) cocci to replace instances of direct > +vrefresh access with a call to the helper. Check out > +https://lists.freedesktop.org/archives/dri-devel/2019-January/205186.html for > +inspiration. I would suggest just nuking mode.vrefresh entirely because we don't want to risk drm_mode_vrefresh() returning some stale value. > + > +Contact: Sean Paul > + > Core refactorings > ================= > > -- > Sean Paul, Software Engineer, Google / Chromium OS > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel
diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst index 38360ede12215..7fc30380eaf6c 100644 --- a/Documentation/gpu/todo.rst +++ b/Documentation/gpu/todo.rst @@ -262,6 +262,21 @@ As a reference, take a look at the conversions already completed in drm core. Contact: Sean Paul, respective driver maintainers +Convert direct mode.vrefresh accesses to use drm_mode_vrefresh() +---------------------------------------------------------------- + +drm_display_mode.vrefresh isn't guaranteed to be populated. As such, using it +is risky and has been known to cause div-by-zero bugs. Fortunately, drm core +has helper which will use mode.vrefresh if it's !0 and will calculate it from +the timings when it's 0. + +Use simple search/replace, or (more fun) cocci to replace instances of direct +vrefresh access with a call to the helper. Check out +https://lists.freedesktop.org/archives/dri-devel/2019-January/205186.html for +inspiration. + +Contact: Sean Paul + Core refactorings =================