On Thu, Jan 14, 2016 at 02:39:42PM +0000, John Keeping wrote: > Signed-off-by: John Keeping <john at metanate.com> > --- > drivers/gpu/drm/rockchip/rockchip_drm_fb.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c > index 679d23a..b267ce4 100644 > --- a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c > +++ b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c > @@ -177,6 +177,12 @@ static void rockchip_crtc_wait_for_update(struct drm_crtc *crtc) > crtc_funcs->wait_for_update(crtc); > } > > +/* > + * We can't use drm_atomic_helper_wait_for_vblanks() because rk3288 and rk3066 > + * have hardware counters for neither vblanks nor scanlines. This function is > + * equivalent but uses rockchip_crtc_wait_for_update() instead of waiting for > + * vblank_count to change. > + */ This is kind of misleading. From reading earlier parts of the thread the reason why drm_atomic_helper_wait_for_vblanks() won't work is because it has a potential race condition that can't be detected unless you also have a vblank counter. However, the above comment makes it work like drm_atomic_helper_wait_for_vblanks() doesn't work in the absence of a vblank counter, which isn't quite true. Perhaps also the drm_atomic_helper_wait_for_vblanks() kerneldoc needs to be updated with these restrictions on its use? Thierry -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: not available URL: <http://lists.infradead.org/pipermail/linux-rockchip/attachments/20160114/20fef853/attachment-0001.sig>
