Re: [PATCH] drm/TODO: Add vrefresh replacement to the todo

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

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
> 
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-- 
Ville Syrjälä
Intel