| From 57f85874d565b7a4fe62c748c033e91a91743a11 Mon Sep 17 00:00:00 2001 |
| From: Paulo Zanoni <paulo.r.zanoni@intel.com> |
| Date: Thu, 19 Sep 2013 17:03:06 -0300 |
| Subject: drm/i915: wait for IPS_ENABLE when enabling IPS |
| |
| At the end of haswell_crtc_enable we have an intel_wait_for_vblank |
| with a big comment, and the message suggests it's a workaround for |
| something we don't really understand. So I removed that wait and |
| started getting HW state readout error messages saying that the IPS |
| state is not what we expected. |
| |
| I investigated and concluded that after you write IPS_ENABLE to |
| IPS_CTL, the bit will only actually become 1 on the next vblank. So |
| add code to wait for the IPS_ENABLE bit. We don't really need this |
| wait right now due to the wait I already mentioned, but at least this |
| one has a reason to be there, while the other one is just to |
| workaround some problem: we may remove it in the future. |
| |
| The wait also acts as a POSTING_READ which we missed. |
| |
| Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com> |
| Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> |
| Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> |
| (cherry picked from commit 5ade2c2f5813733f23bbb2f21e8ba5c3f8474a2b) |
| Signed-off-by: Darren Hart <dvhart@linux.intel.com> |
| --- |
| drivers/gpu/drm/i915/intel_display.c | 8 ++++++++ |
| 1 file changed, 8 insertions(+) |
| |
| diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c |
| index 3bd2dc39cfc0..6418b8aa95a9 100644 |
| --- a/drivers/gpu/drm/i915/intel_display.c |
| +++ b/drivers/gpu/drm/i915/intel_display.c |
| @@ -3346,6 +3346,14 @@ void hsw_enable_ips(struct intel_crtc *crtc) |
| * for a vblank, so all we need to do here is to enable the IPS bit. */ |
| assert_plane_enabled(dev_priv, crtc->plane); |
| I915_WRITE(IPS_CTL, IPS_ENABLE); |
| + |
| + /* The bit only becomes 1 in the next vblank, so this wait here is |
| + * essentially intel_wait_for_vblank. If we don't have this and don't |
| + * wait for vblanks until the end of crtc_enable, then the HW state |
| + * readout code will complain that the expected IPS_CTL value is not the |
| + * one we read. */ |
| + if (wait_for(I915_READ_NOTRACE(IPS_CTL) & IPS_ENABLE, 50)) |
| + DRM_ERROR("Timed out waiting for IPS enable\n"); |
| } |
| |
| void hsw_disable_ips(struct intel_crtc *crtc) |
| -- |
| 1.8.5.rc3 |
| |
