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 <rfoss@xxxxxxxxxx> > Signed-off-by: Marek Vasut <marex@xxxxxxx> > --- > Cc: Adam Ford <aford173@xxxxxxxxx> > Cc: Alexander Stein <alexander.stein@xxxxxxxxxxxxxxx> > Cc: Andrzej Hajda <andrzej.hajda@xxxxxxxxx> > Cc: Daniel Vetter <daniel@xxxxxxxx> > Cc: David Airlie <airlied@xxxxxxxxx> > Cc: Frieder Schrempf <frieder.schrempf@xxxxxxxxxx> > Cc: Jernej Skrabec <jernej.skrabec@xxxxxxxxx> > Cc: Jonas Karlman <jonas@xxxxxxxxx> > Cc: Laurent Pinchart <Laurent.pinchart@xxxxxxxxxxxxxxxx> > Cc: Lucas Stach <l.stach@xxxxxxxxxxxxxx> > Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx> > Cc: Maxime Ripard <mripard@xxxxxxxxxx> > Cc: Michael Walle <mwalle@xxxxxxxxxx> > Cc: Neil Armstrong <neil.armstrong@xxxxxxxxxx> > Cc: Robert Foss <rfoss@xxxxxxxxxx> > Cc: Thomas Zimmermann <tzimmermann@xxxxxxx> > Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx > Cc: kernel@xxxxxxxxxxxxxxxxxx > --- > 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.baryshkov@xxxxxxxxxx> -- With best wishes Dmitry
