drm/mcde: Fix off by 10^3 in calculation

The calclulation of how many bytes we stuff into the
DSI pipeline for video mode panels is off by three
orders of magnitude because we did not account for the
fact that the DRM mode clock is in kilohertz rather
than hertz.

This used to be:
drm_mode_vrefresh(mode) * mode->htotal * mode->vtotal
which would become for example for s6e63m0:
60 x 514 x 831 = 25628040 Hz, but mode->clock is
25628 as it is in kHz.

This affects only the Samsung GT-I8190 "Golden" phone
right now since it is the only MCDE device with a video
mode display.

Curiously some specimen work with this code and wild
settings in the EOL and empty packets at the end of the
display, but I have noticed an eeire flicker until now.
Others were not so lucky and got black screens.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reported-by: Stephan Gerhold <stephan@gerhold.net>
Fixes: 920dd1b1425b ("drm/mcde: Use mode->clock instead of reverse calculating it from the vrefresh")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Stephan Gerhold <stephan@gerhold.net>
Reviewed-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20210608213318.3897858-1-linus.walleij@linaro.org

diff --git a/drivers/gpu/drm/mcde/mcde_dsi.c b/drivers/gpu/drm/mcde/mcde_dsi.c
index b3fd350..5275b27 100644 (file)
--- a/drivers/gpu/drm/mcde/mcde_dsi.c
+++ b/drivers/gpu/drm/mcde/mcde_dsi.c
@@ -577,7 +577,7 @@ static void mcde_dsi_setup_video_mode(struct mcde_dsi *d,
         * porches and sync.
         */
        /* (ps/s) / (pixels/s) = ps/pixels */
-       pclk = DIV_ROUND_UP_ULL(1000000000000, mode->clock);
+       pclk = DIV_ROUND_UP_ULL(1000000000000, (mode->clock * 1000));
        dev_dbg(d->dev, "picoseconds between two pixels: %llu\n",
                pclk);