On Mon, Feb 09, 2015 at 03:15:56PM +0200, Jani Nikula wrote: > On Wed, 26 Nov 2014, Paulo Zanoni <przanoni@xxxxxxxxx> wrote: > > 2014-11-24 13:54 GMT-02:00 Daniel Vetter <daniel.vetter@xxxxxxxx>: > >> Nothing in Bspec seems to indicate that we actually needs this, and it > >> looks like can't work since by this point the pipe is off and so > >> vblanks won't really happen any more. > >> > >> Note that Bspec mentions that it takes a vblank for this bit to > >> change, but _only_ when enabling. > >> > >> Dropping this code quenches an annoying backtrace introduced by the > >> more anal checking since > >> > >> commit 51e31d49c89055299e34b8f44d13f70e19aaaad1 > >> Author: Daniel Vetter <daniel.vetter@xxxxxxxx> > >> Date: Mon Sep 15 12:36:02 2014 +0200 > >> > >> drm/i915: Use generic vblank wait > >> > >> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=86095 > >> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx> > >> --- > >> drivers/gpu/drm/i915/intel_dp.c | 17 +---------------- > >> 1 file changed, 1 insertion(+), 16 deletions(-) > >> > >> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c > >> index 46731da407c0..63fcdbf90652 100644 > >> --- a/drivers/gpu/drm/i915/intel_dp.c > >> +++ b/drivers/gpu/drm/i915/intel_dp.c > >> @@ -3514,8 +3514,6 @@ intel_dp_link_down(struct intel_dp *intel_dp) > >> enum port port = intel_dig_port->port; > >> struct drm_device *dev = intel_dig_port->base.base.dev; > >> struct drm_i915_private *dev_priv = dev->dev_private; > >> - struct intel_crtc *intel_crtc = > >> - to_intel_crtc(intel_dig_port->base.base.crtc); > >> uint32_t DP = intel_dp->DP; > >> > >> if (WARN_ON(HAS_DDI(dev))) > >> @@ -3540,8 +3538,6 @@ intel_dp_link_down(struct intel_dp *intel_dp) > >> > >> if (HAS_PCH_IBX(dev) && > >> I915_READ(intel_dp->output_reg) & DP_PIPEB_SELECT) { > >> - struct drm_crtc *crtc = intel_dig_port->base.base.crtc; > >> - > >> /* Hardware workaround: leaving our transcoder select > >> * set to transcoder B while it's off will prevent the > >> * corresponding HDMI output on transcoder A. > >> @@ -3552,18 +3548,7 @@ intel_dp_link_down(struct intel_dp *intel_dp) > >> */ > >> DP &= ~DP_PIPEB_SELECT; > >> I915_WRITE(intel_dp->output_reg, DP); > >> - > >> - /* Changes to enable or select take place the vblank > >> - * after being written. > >> - */ > >> - if (WARN_ON(crtc == NULL)) { > >> - /* We should never try to disable a port without a crtc > >> - * attached. For paranoia keep the code around for a > >> - * bit. */ > >> - POSTING_READ(intel_dp->output_reg); > >> - msleep(50); > >> - } else > >> - intel_wait_for_vblank(dev, intel_crtc->pipe); > > > > What I can guess is that we have the vblank wait here because the > > DP_PORT_EN bit is still enabled at this point. It would make some > > sense to have it if the pipe were not off... So removing the waits > > looks sane: Reviewed-by: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx> > > > > But when I read the spec, it makes me think that maybe doing the > > I915_WRITE above is also wrong, since the port is still enabled. Maybe > > we should only clear bit 30 in the same write as the one that clears > > bit 31? > > Ugh. So the spec says, "When disabling the port, software must > temporarily enable the port with transcoder select (bit #30) cleared to > ‘0’ after disabling the port." > > IIUC we should disable like we normally do, and do the w/a by enabling > and disabling the port with DP_PIPEB_SELECT cleared *after* that. I > think the current code is wrong, the patch is wrong, what Paulo suggests > is wrong, and also intel_disable_hdmi() is wrong. This code has been bugging me for a long time as well. IIRC I even had cooked up some patches to do the re-enable as you suggest since I read the spec the same way. But I never had enough time to test it. And in order to really test it I would first like to actually reproduce the problem that the workaround is supposed to fix. How else would you know if the workaround is correct after all. -- Ville Syrjälä Intel OTC _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
