[PATCH] drm/i915: rip out pre-production ilk cpu edp w/a

[PATCH] drm/i915: rip out pre-production ilk cpu edp w/a

[Daniel Vetter]

While reading docs I've noticed that this special workaround to select
the 1.6 GHz DP clock only applies to pre-production ilk machines.
Since the registers we're touching here are rather undocumented and
might be harmful on later chips, rip it out.

For the Bspec reference of this w/a look in "vol4g CPU Display
Registers [DevILK]", Section 4.1.7.1 "DP_A—DisplayPort A
Control Register", "DP_PLL_Frequency_Select".

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
 drivers/gpu/drm/i915/intel_dp.c | 22 +++-------------------
 1 file changed, 3 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 376ae28..e2794ca 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -818,27 +818,11 @@ static void ironlake_set_pll_edp(struct drm_crtc *crtc, int clock)
 	dpa_ctl = I915_READ(DP_A);
 	dpa_ctl &= ~DP_PLL_FREQ_MASK;
 
-	if (clock < 200000) {
-		u32 temp;
+	if (clock < 200000)
 		dpa_ctl |= DP_PLL_FREQ_160MHZ;
-		/* workaround for 160Mhz:
-		   1) program 0x4600c bits 15:0 = 0x8124
-		   2) program 0x46010 bit 0 = 1
-		   3) program 0x46034 bit 24 = 1
-		   4) program 0x64000 bit 14 = 1
-		   */
-		temp = I915_READ(0x4600c);
-		temp &= 0xffff0000;
-		I915_WRITE(0x4600c, temp | 0x8124);
-
-		temp = I915_READ(0x46010);
-		I915_WRITE(0x46010, temp | 1);
-
-		temp = I915_READ(0x46034);
-		I915_WRITE(0x46034, temp | (1 << 24));
-	} else {
+	else
 		dpa_ctl |= DP_PLL_FREQ_270MHZ;
-	}
+
 	I915_WRITE(DP_A, dpa_ctl);
 
 	POSTING_READ(DP_A);
-- 
1.7.11.2

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Re: [PATCH] drm/i915: rip out pre-production ilk cpu edp w/a

[Chris Wilson]

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On Thu, 13 Sep 2012 13:13:29 +0200, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> While reading docs I've noticed that this special workaround to select
> the 1.6 GHz DP clock only applies to pre-production ilk machines.
> Since the registers we're touching here are rather undocumented and
> might be harmful on later chips, rip it out.
> 
> For the Bspec reference of this w/a look in "vol4g CPU Display
> Registers [DevILK]", Section 4.1.7.1 "DP_A—DisplayPort A
> Control Register", "DP_PLL_Frequency_Select".
> 
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

The spec definitely says DevILK-A, are we sure it got excised in
production machines? Once a w/a is implemented by the Windows driver
they have a tendency to linger...

So can you instead replace the w/a with a message to remind us
about the possibilty of failure of the PLL to change frequencies.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre

[-- Attachment #2: Type: text/plain, Size: 159 bytes --]

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[PATCH] drm/i915: rip out pre-production ilk cpu edp w/a

[Daniel Vetter]

While reading docs I've noticed that this special workaround to select
the 1.6 GHz DP clock only applies to pre-production ilk machines.
Since the registers we're touching here are rather undocumented and
might be harmful on later chips, rip it out.

For the Bspec reference of this w/a look in "vol4g CPU Display
Registers [DevILK]", Section 4.1.7.1 "DP_A—DisplayPort A
Control Register", "DP_PLL_Frequency_Select".

v2: Keep a debug message as a hint in case something regresses.
Requested by Chris Wilson.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
 drivers/gpu/drm/i915/intel_dp.c | 21 +++++----------------
 1 file changed, 5 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 376ae28..1539c8c 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -819,26 +819,15 @@ static void ironlake_set_pll_edp(struct drm_crtc *crtc, int clock)
 	dpa_ctl &= ~DP_PLL_FREQ_MASK;
 
 	if (clock < 200000) {
-		u32 temp;
+		/* For a long time we've carried around a ILK-DevA w/a for the
+		 * 160MHz clock. If we're really unlucky, it's still required.
+		 */
+		DRM_DEBUG_KMS("160MHz cpu eDP clock, might need ilk devA w/a\n");
 		dpa_ctl |= DP_PLL_FREQ_160MHZ;
-		/* workaround for 160Mhz:
-		   1) program 0x4600c bits 15:0 = 0x8124
-		   2) program 0x46010 bit 0 = 1
-		   3) program 0x46034 bit 24 = 1
-		   4) program 0x64000 bit 14 = 1
-		   */
-		temp = I915_READ(0x4600c);
-		temp &= 0xffff0000;
-		I915_WRITE(0x4600c, temp | 0x8124);
-
-		temp = I915_READ(0x46010);
-		I915_WRITE(0x46010, temp | 1);
-
-		temp = I915_READ(0x46034);
-		I915_WRITE(0x46034, temp | (1 << 24));
 	} else {
 		dpa_ctl |= DP_PLL_FREQ_270MHZ;
 	}
+
 	I915_WRITE(DP_A, dpa_ctl);
 
 	POSTING_READ(DP_A);
-- 
1.7.11.2

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