From 06c340cc854b1c8c275968c2830fbe8a5c3b0e4e Mon Sep 17 00:00:00 2001 From: Dave Stevenson Date: Fri, 18 Jun 2021 21:52:28 +0100 Subject: [PATCH] drm/vc4: Correct DSI divider calculations The divider calculations tried to find the divider just faster than the clock requested. However if it required a divider of 7 then the for loop aborted without handling the "error" case, and could end up with a clock lower than requested. Correct the loop so that we always have a clock greater than requested. Signed-off-by: Dave Stevenson --- drivers/gpu/drm/vc4/vc4_dsi.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) --- a/drivers/gpu/drm/vc4/vc4_dsi.c +++ b/drivers/gpu/drm/vc4/vc4_dsi.c @@ -850,11 +850,9 @@ static bool vc4_dsi_encoder_mode_fixup(s /* Find what divider gets us a faster clock than the requested * pixel clock. */ - for (divider = 1; divider < 8; divider++) { - if (parent_rate / divider < pll_clock) { - divider--; + for (divider = 1; divider < 7; divider++) { + if (parent_rate / (divider + 1) < pll_clock) break; - } } /* Now that we've picked a PLL divider, calculate back to its