Commit af2eca53 authored by Eric Anholt's avatar Eric Anholt

drm/vc4: Avoid using vrefresh==0 mode in DSI htotal math.

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.
v3: Simplify math now that adjusted_mode->clock isn't padded.
v4: Drop some parens.
Signed-off-by: default avatarEric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20170815234722.20700-2-eric@anholt.netReviewed-by: default avatarAndrzej Hajda <a.hajda@samsung.com>
parent 9949b355
No related merge requests found
......@@ -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 = adjusted_mode->clock * mode->htotal /
mode->clock;
adjusted_mode->hsync_end += adjusted_mode->htotal - mode->htotal;
adjusted_mode->hsync_start += adjusted_mode->htotal - mode->htotal;
......
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