Messages in this thread | | | Date | Fri, 4 Aug 2017 10:53:04 +0200 | From | Boris Brezillon <> | Subject | Re: [PATCH v5 1/6] drm/vc4: Avoid using vrefresh==0 mode in DSI htotal math. |
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On Tue, 18 Jul 2017 14:05:05 -0700 Eric Anholt <eric@anholt.net> wrote:
> The incoming mode might have a missing vrefresh field if it came from > drmModeSetCrtc(), which the kernel is supposed to calculate using > drm_mode_vrefresh(). We could either use that or the adjusted_mode's > original vrefresh value. > > However, we can maintain a more exact vrefresh value (not just the > integer approximation), by scaling by the ratio of our clocks. > > v2: Use math suggested by Andrzej Hajda instead. > > Signed-off-by: Eric Anholt <eric@anholt.net> > --- > drivers/gpu/drm/vc4/vc4_dsi.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c > index 629d372633e6..57213f4e3c72 100644 > --- a/drivers/gpu/drm/vc4/vc4_dsi.c > +++ b/drivers/gpu/drm/vc4/vc4_dsi.c > @@ -866,7 +866,8 @@ static bool vc4_dsi_encoder_mode_fixup(struct drm_encoder *encoder, > adjusted_mode->clock = pixel_clock_hz / 1000 + 1; > > /* Given the new pixel clock, adjust HFP to keep vrefresh the same. */ > - adjusted_mode->htotal = pixel_clock_hz / (mode->vrefresh * mode->vtotal); > + adjusted_mode->htotal = (pixel_clock_hz / 1000 * mode->htotal / > + mode->clock);
Hm, I'm not sure I understand this. Shouldn't we have something like:
adjusted_mode->htotal = (adjusted_mode->clock * mode->htotal) / mode->clock;
Is there a reason for doing '+ 1' when you calculate the adjusted pixel clock rate but not here?
> adjusted_mode->hsync_end += adjusted_mode->htotal - mode->htotal; > adjusted_mode->hsync_start += adjusted_mode->htotal - mode->htotal; >
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