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 <[email protected]> > Signed-off-by: Marek Vasut <[email protected]> > --- > Cc: Adam Ford <[email protected]> > Cc: Alexander Stein <[email protected]> > Cc: Andrzej Hajda <[email protected]> > Cc: Daniel Vetter <[email protected]> > Cc: David Airlie <[email protected]> > Cc: Frieder Schrempf <[email protected]> > Cc: Jernej Skrabec <[email protected]> > Cc: Jonas Karlman <[email protected]> > Cc: Laurent Pinchart <[email protected]> > Cc: Lucas Stach <[email protected]> > Cc: Maarten Lankhorst <[email protected]> > Cc: Maxime Ripard <[email protected]> > Cc: Michael Walle <[email protected]> > Cc: Neil Armstrong <[email protected]> > Cc: Robert Foss <[email protected]> > Cc: Thomas Zimmermann <[email protected]> > Cc: [email protected] > Cc: [email protected] > --- > 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 <[email protected]> -- With best wishes Dmitry
