On Wed, 16 Oct 2013, Jani Nikula <jani.nikula@xxxxxxxxx> wrote: > This isn't a real fix to the problem, but rather a stopgap measure while > trying to find a proper solution. > > There are several laptops out there that fail to light up the eDP panel > in UEFI boot mode. They seem to be mostly IVB machines, including but > apparently not limited to Dell XPS 13, Asus TX300, Asus UX31A, Asus > UX32VD, Acer Aspire S7. They seem to work in CSM or legacy boot. > > The difference between UEFI and CSM is that the BIOS provides a > different VBT to the kernel. The UEFI VBT typically specifies 18 bpp and > 1.62 GHz link for eDP, while CSM VBT has 24 bpp and 2.7 GHz link. We end > up clamping to 18 bpp in UEFI mode, which we can fit in the 1.62 Ghz > link, and for reasons yet unknown fail to light up the panel. > > Dithering from 24 to 18 bpp itself seems to work; if we use 18 bpp with > 2.7 GHz link, the eDP panel lights up. So essentially this is a link > speed issue, and *not* a bpp clamping issue. > > The bug raised its head since > commit 657445fe8660100ad174600ebfa61536392b7624 > Author: Daniel Vetter <daniel.vetter@xxxxxxxx> > Date: Sat May 4 10:09:18 2013 +0200 > > Revert "drm/i915: revert eDP bpp clamping code changes" > > which started clamping bpp *before* computing the link requirements, and > thus affecting the required bandwidth. Clamping after the computations > kept the link at 2.7 GHz. > > Even though the BIOS tells us to use 18 bpp through the VBT, it happily > boots up at 24 bpp and 2.7 GHz itself! Use this information to > selectively ignore the VBT provided value. > > We can't ignore the VBT eDP bpp altogether, as there are other laptops > that do require the clamping to be used due to EDID reporting higher bpp > than the panel can support. > > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=59841 > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=67950 > CC: stable@xxxxxxxxxxxxxxx > Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx> Tested-by: Ulf Winkelvos <ulf@xxxxxxxxxxxx> Tested-by: jkp <jkp@xxxxxx> and I also have another machine on loan this fixes. Jani. > > --- > > For backporting to v3.12, you also need > commit 84a44adc16ab118cf7e0518861216cbc91cee6e4 > Author: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > Date: Fri Sep 6 23:29:00 2013 +0300 > > drm/i915: Add support for pipe_bpp readout > --- > drivers/gpu/drm/i915/intel_dp.c | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) > > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c > index f63aa8c..cb895d8 100644 > --- a/drivers/gpu/drm/i915/intel_dp.c > +++ b/drivers/gpu/drm/i915/intel_dp.c > @@ -1476,6 +1476,27 @@ static void intel_dp_get_config(struct intel_encoder *encoder, > ironlake_check_encoder_dotclock(pipe_config, dotclock); > > pipe_config->adjusted_mode.crtc_clock = dotclock; > + > + if (is_edp(intel_dp) && dev_priv->vbt.edp_bpp && > + pipe_config->pipe_bpp > dev_priv->vbt.edp_bpp) { > + /* > + * This is a big fat ugly hack. > + * > + * Some machines in UEFI boot mode provide us a VBT that has 18 > + * bpp and 1.62 GHz link bandwidth for eDP, which for reasons > + * unknown we fail to light up. Yet the same BIOS boots up with > + * 24 bpp and 2.7 GHz link. Use the same bpp as the BIOS uses as > + * max, not what it tells us to use. > + * > + * Note: This will still be broken if the eDP panel is not lit > + * up by the BIOS, and thus we can't get the mode at module > + * load. > + */ > + DRM_DEBUG_KMS("pipe has %d bpp for eDP panel, overriding BIOS-provided max %d bpp\n", > + pipe_config->pipe_bpp, dev_priv->vbt.edp_bpp); > + dev_priv->vbt.edp_bpp = pipe_config->pipe_bpp; > + } > + > } > > static bool is_edp_psr(struct drm_device *dev) > -- > 1.7.9.5 > -- Jani Nikula, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
