Hi, On Tue, Sep 16, 2025 at 8:28 AM Emanuele Ghidoli <ghidoliemanu...@gmail.com> wrote: > > On 16/09/2025 16:45, Doug Anderson wrote: > > Hi, > > > > On Tue, Sep 16, 2025 at 7:22 AM Emanuele Ghidoli > > <ghidoliemanu...@gmail.com> wrote: > >> > >> From: Emanuele Ghidoli <emanuele.ghid...@toradex.com> > >> > >> The component datasheet recommends, to reduce power consumption, > >> transitioning to LP mode on every video line. > >> > >> Enable the MIPI_DSI_MODE_VIDEO_NO_HFP and MIPI_DSI_MODE_VIDEO_NO_HBP > >> flags so that the bridge can enter LP mode during the horizontal front > >> porch and back porch periods. > >> > >> Signed-off-by: Emanuele Ghidoli <emanuele.ghid...@toradex.com> > >> --- > >> Cc: Douglas Anderson <diand...@chromium.org> > >> Cc: Andrzej Hajda <andrzej.ha...@intel.com> > >> Cc: Neil Armstrong <neil.armstr...@linaro.org> > >> Cc: Robert Foss <rf...@kernel.org> > >> Cc: Laurent Pinchart <laurent.pinch...@ideasonboard.com> > >> Cc: Jonas Karlman <jo...@kwiboo.se> > >> Cc: Jernej Skrabec <jernej.skra...@gmail.com> > >> Cc: Maarten Lankhorst <maarten.lankho...@linux.intel.com> > >> Cc: Maxime Ripard <mrip...@kernel.org> > >> Cc: Thomas Zimmermann <tzimmerm...@suse.de> > >> Cc: David Airlie <airl...@gmail.com> > >> Cc: Simona Vetter <sim...@ffwll.ch> > >> Cc: Jayesh Choudhary <j-choudh...@ti.com> > >> Cc: <dri-devel@lists.freedesktop.org> > >> Cc: <linux-ker...@vger.kernel.org> > >> --- > >> drivers/gpu/drm/bridge/ti-sn65dsi86.c | 3 ++- > >> 1 file changed, 2 insertions(+), 1 deletion(-) > > > > I put this on a sc7180-trogdor based Chromebook and the display no > > longer comes up. I don't personally know the MIPI side of the spec too > > well so I have no idea why that would be. > > > > -Doug > > Hi Doug, > thanks for the test. > According to the datasheet, LP is recommended for the front porch and optional > for the back porch. > Could you please run another test by keeping only MIPI_DSI_MODE_VIDEO_NO_HFP > and removing MIPI_DSI_MODE_VIDEO_NO_HBP? > > dsi->mode_flags = MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_NO_HFP;
With just MIPI_DSI_MODE_VIDEO_NO_HFP: -> Display doesn't work With just MIPI_DSI_MODE_VIDEO_NO_HBP: -> Display doesn't work So if I set _either_ flag (or both) then the display doesn't work (it just comes up black). If I set neither flag then things are still OK. ...and, if it helps, when the screen isn't working I can still force the color bars to show up with: i2cset -f -y 2 0x2d 0x3c 0x10 ...so I know that the device has probed OK and the eDP side of things is OK. -Doug
