On Tue, May 14, 2024 at 02:47:24AM +0200, Marek Vasut wrote: > TC9595 datasheet Video Path0 Control (VPCTRL0) Register bit FRMSYNC > description > says "This bit should be disabled only in video mode transmission where Host > transmits video timing together with video data and where pixel clock source > is from DSI clock." . This driver always sources pixel clock from external > xtal, > therefore the FRMSYNC bit must always be enabled, enable it. > > This fixes an actual issue with DSI-to-DPI mode, where the display would > randomly show subtle pixel flickering, or wobble, or shimmering. This is > visible on solid gray color, but the degree of the shimmering differs > between boots, which makes it hard to debug. > > There is a caveat to the FRMSYNC and this bridge pixel PLL, which can only > generate pixel clock with limited accuracy, it may therefore be necessary > to reduce the HFP to fit into line length of input pixel data, to avoid any > possible overflows, which make the output video look striped horizontally. > > Reviewed-by: Robert Foss <rf...@kernel.org> > Signed-off-by: Marek Vasut <ma...@denx.de> > --- > Cc: Adam Ford <aford...@gmail.com> > Cc: Alexander Stein <alexander.st...@ew.tq-group.com> > Cc: Andrzej Hajda <andrzej.ha...@intel.com> > Cc: Daniel Vetter <dan...@ffwll.ch> > Cc: David Airlie <airl...@gmail.com> > Cc: Frieder Schrempf <frieder.schre...@kontron.de> > Cc: Jernej Skrabec <jernej.skra...@gmail.com> > Cc: Jonas Karlman <jo...@kwiboo.se> > Cc: Laurent Pinchart <laurent.pinch...@ideasonboard.com> > Cc: Lucas Stach <l.st...@pengutronix.de> > Cc: Maarten Lankhorst <maarten.lankho...@linux.intel.com> > Cc: Maxime Ripard <mrip...@kernel.org> > Cc: Michael Walle <mwa...@kernel.org> > Cc: Neil Armstrong <neil.armstr...@linaro.org> > Cc: Robert Foss <rf...@kernel.org> > Cc: Thomas Zimmermann <tzimmerm...@suse.de> > Cc: dri-devel@lists.freedesktop.org > Cc: ker...@dh-electronics.com > --- > V2: - Use plain DIV_ROUND_UP() instead of custom local one > - Add RB from Robert > --- > drivers/gpu/drm/bridge/tc358767.c | 18 +++++++++++++++--- > 1 file changed, 15 insertions(+), 3 deletions(-) >
Reviewed-by: Dmitry Baryshkov <dmitry.barysh...@linaro.org> -- With best wishes Dmitry
