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From: Daniel Vetter <daniel.vetter@ffwll.ch>
To: Intel Graphics Development <intel-gfx@lists.freedesktop.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Subject: [PATCH] drm/i915: add comment about pch pll enabling rules
Date: Sat, 27 Oct 2012 18:46:14 +0200
Message-ID: <1351356374-1584-1-git-send-email-daniel.vetter@ffwll.ch> (raw)
In-Reply-To: <1351241899-7870-5-git-send-email-daniel.vetter@ffwll.ch>

Atm we have a few funny issues where we enable/disable shared
pll clocks. To make it clear that we are not required to enable/
disable the pch plls together with the other pch resources (and
so should keep it running when it's used by another pipe in
a shared pll configuration) add a comment.

This note is lifted from "Graphics BSpec: vol4g North Display Engine
Registers [IVB], Display Mode Set Sequence", step 9.d. of the enable
sequence:

"Configure and enable PCH DPLL, wait for PCH DPLL warmup (Can be
done anytime before enabling PCH transcoder)."

Since fixing the pll sharing code to no longer disable shared plls
if they're still in use is more involved, let's just stick with the
comment for now.

v2: Make the comment in the code clearer, to address questions raised
by Paulo Zanoni in review.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
 drivers/gpu/drm/i915/intel_display.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index b19e3bb..bf2356c 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -3007,6 +3007,13 @@ static void ironlake_pch_enable(struct drm_crtc *crtc)
 	/* For PCH output, training FDI link */
 	dev_priv->display.fdi_link_train(crtc);
 
+	/* XXX: pch pll's can be enabled any time before we enable the PCH
+	 * transcoder, and we actually should do this to not upset any PCH
+	 * transcoder that already use the clock when we share it.
+	 *
+	 * Note that enable_pch_pll tries to do the right thing, but get_pch_pll
+	 * unconditionally resets the pll - we need that to have the right LVDS
+	 * enable sequence. */
 	intel_enable_pch_pll(intel_crtc);
 
 	if (HAS_PCH_LPT(dev)) {
-- 
1.7.11.4

  parent reply index

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-10-26  8:58 [PATCH 0/9] some ivb fdi b/c fixes Daniel Vetter
2012-10-26  8:58 ` [PATCH 1/9] drm/i915: shut up spurious message in intel_dp_get_hw_state Daniel Vetter
2012-10-26 14:01   ` Paulo Zanoni
2012-10-26  8:58 ` [PATCH 2/9] drm/i915: Write the FDI RX TU size reg at the right time Daniel Vetter
2012-10-27 11:51   ` Paulo Zanoni
2012-10-27 12:59     ` Daniel Vetter
2012-10-27 13:03       ` Paulo Zanoni
2012-10-27 13:04         ` Daniel Vetter
2012-10-27 13:18           ` Paulo Zanoni
2012-10-27 13:50             ` Daniel Vetter
2012-10-27 13:20   ` [PATCH] " Daniel Vetter
2012-10-26  8:58 ` [PATCH 3/9] drm/i915: set FDI_RX_MISC to recommended values on CPT/PPT Daniel Vetter
2012-10-27 12:02   ` Paulo Zanoni
2012-10-26  8:58 ` [PATCH 4/9] drm/i915: add comment about pch pll enabling rules Daniel Vetter
2012-10-27 12:15   ` Paulo Zanoni
2012-10-27 12:57     ` Daniel Vetter
2012-10-27 16:46   ` Daniel Vetter [this message]
2012-10-29 12:02     ` [PATCH] " Paulo Zanoni
2012-10-26  8:58 ` [PATCH 5/9] drm/i915: CPT/PPT pch dp transcoder workaround Daniel Vetter
2012-10-26 14:21   ` Paulo Zanoni
2012-10-29 15:38     ` Daniel Vetter
2012-10-29 17:02       ` Paulo Zanoni
2012-10-29 17:14         ` Daniel Vetter
2012-10-31 17:41           ` Paulo Zanoni
2012-10-26  8:58 ` [PATCH 6/9] drm/i915: BUG on impossible pch dp port Daniel Vetter
2012-10-26 15:04   ` Paulo Zanoni
2012-10-26  8:58 ` [PATCH 7/9] drm/i915: drop unnecessary check from fdi_link_train code Daniel Vetter
2012-10-26 15:32   ` Paulo Zanoni
2012-10-26  8:58 ` [PATCH 8/9] drm/i915: add ->display.modeset_global_resources callback Daniel Vetter
2012-10-27 12:18   ` Paulo Zanoni
2012-10-26  8:58 ` [PATCH 9/9] drm/i915: check fdi B/C lane sharing constraint Daniel Vetter
2012-10-27 12:56   ` Paulo Zanoni
2012-10-27 13:03     ` Daniel Vetter
2012-10-27 13:58   ` [PATCH] " Daniel Vetter
2012-10-29 12:06     ` Paulo Zanoni
2012-10-29 17:42       ` Daniel Vetter

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