Re: [PATCH] drm/i915: CPT/PPT pch dp transcoder workaround

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Thu,  1 Nov 2012 09:15:30 +0100
Daniel Vetter <daniel.vetter@ffwll.ch> wrote:

> We need to set the timing override chicken bit after fdi link training
> has completed and before we enable the dp transcoder. We also have to
> clear that bit again after disabling the pch dp transcoder.
> 
> See "Graphics BSpec: vol4g North Display Engine Registers [IVB],
> Display Mode Set Sequence" and "Graphics BSpec: vol4h South Display
> Engine Registers [CPT, PPT], South Display Engine Transcoder and FDI
> Control, Transcoder Debug and DFT, TRANS_CHICKEN_2" bit 31:
> 
> "Workaround : Enable the override prior to enabling the transcoder.
> Disable the override after disabling the transcoder."
> 
> While at it, use the _PIPE macro for the other TRANS_DP register.
> 
> v2: Keep the w/a as-is, but kill the original (but wrongly placed)
> workaround introduced in
> 
> commit 3bcf603f6d5d18bd9d076dc280de71f48add4101
> Author: Jesse Barnes <jbarnes@virtuousgeek.org>
> Date:   Wed Jul 27 11:51:40 2011 -0700
> 
>     drm/i915: apply timing generator bug workaround on CPT and PPT
> 
> and
> 
> commit d4270e57efe9e2536798c59e1ed2fd0a1e5cdfcf
> Author: Jesse Barnes <jbarnes@virtuousgeek.org>
> Date:   Tue Oct 11 10:43:02 2011 -0700
> 
>     drm/i915: export a CPT mode set verification function
> 
> Note that this old code has unconditionally set the w/a, which might
> explain why fdi link training sometimes silently fails, and especially
> why the auto-train did not seem to work properly.
> 
> v3: Paulo Zanoni pointed out that this workaround is also required on
> the LPT PCH. And Arthur Ranyan confirmed that this workaround is
> requierd for all ports on the pch, not just DP: The important part
> is that the bit is set whenever the pch transcoder is enabled, and
> that it is _not_ set while the fdi link is trained. It is also
> important that the pch transcoder is fully disabled, i.e. we have to
> wait for bit 30 to clear before clearing the w/a bit.
> 
> Hence move to workaround into enable/disable_transcoder, where the pch
> transcoder gets enabled/disabled.
> 
> v4: Whitespace changes dropped.
> 
> v5: Don't run the w/a on IBX, we only need it on CPT/PPT and LPT.
> 
> Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
> Cc: Paulo Zanoni <przanoni@gmail.com>
> Cc: Arthur Ranyan <arthur.j.runyan@intel.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>  drivers/gpu/drm/i915/i915_reg.h      |  5 +++--
>  drivers/gpu/drm/i915/intel_display.c | 32 +++++++++++++++++++++++---------
>  drivers/gpu/drm/i915/intel_pm.c      |  4 ----
>  3 files changed, 26 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 2dd880f..f1fe3a0 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -3806,7 +3806,8 @@
>  #define _TRANSA_CHICKEN2	 0xf0064
>  #define _TRANSB_CHICKEN2	 0xf1064
>  #define TRANS_CHICKEN2(pipe) _PIPE(pipe, _TRANSA_CHICKEN2, _TRANSB_CHICKEN2)
> -#define   TRANS_AUTOTRAIN_GEN_STALL_DIS	(1<<31)
> +#define  TRANS_CHICKEN2_TIMING_OVERRIDE		(1<<31)
> +
>  
>  #define SOUTH_CHICKEN1		0xc2000
>  #define  FDIA_PHASE_SYNC_SHIFT_OVR	19
> @@ -4064,7 +4065,7 @@
>  #define TRANS_DP_CTL_A		0xe0300
>  #define TRANS_DP_CTL_B		0xe1300
>  #define TRANS_DP_CTL_C		0xe2300
> -#define TRANS_DP_CTL(pipe)	(TRANS_DP_CTL_A + (pipe) * 0x01000)
> +#define TRANS_DP_CTL(pipe)	_PIPE(pipe, TRANS_DP_CTL_A, TRANS_DP_CTL_B)
>  #define  TRANS_DP_OUTPUT_ENABLE	(1<<31)
>  #define  TRANS_DP_PORT_SEL_B	(0<<29)
>  #define  TRANS_DP_PORT_SEL_C	(1<<29)
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 129059b..675079a 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -1673,9 +1673,9 @@ static void intel_disable_pch_pll(struct intel_crtc *intel_crtc)
>  static void intel_enable_transcoder(struct drm_i915_private *dev_priv,
>  				    enum pipe pipe)
>  {
> -	int reg;
> -	u32 val, pipeconf_val;
> +	struct drm_device *dev = dev_priv->dev;
>  	struct drm_crtc *crtc = dev_priv->pipe_to_crtc_mapping[pipe];
> +	uint32_t reg, val, pipeconf_val;
>  
>  	/* PCH only available on ILK+ */
>  	BUG_ON(dev_priv->info->gen < 5);
> @@ -1693,6 +1693,16 @@ static void intel_enable_transcoder(struct drm_i915_private *dev_priv,
>  		DRM_ERROR("Attempting to enable transcoder on Haswell with pipe > 0\n");
>  		return;
>  	}
> +
> +	if (!HAS_PCH_IBX(dev)) {
> +		/* Workaround: Set the timing override bit before enabling the
> +		 * pch transcoder. */
> +		reg = TRANS_CHICKEN2(pipe);
> +		val = I915_READ(reg);
> +		val |= TRANS_CHICKEN2_TIMING_OVERRIDE;
> +		I915_WRITE(reg, val);
> +	}

I'd like this better if it were HAS_PCH_CPT; we use that as a synonym
for PPT elsehwere, and it shouldn't apply to LPT right?  I see LPT has
the bit, but I don't know if it's needed (the changelong and summary
are misleading if so).


> +
>  	reg = TRANSCONF(pipe);
>  	val = I915_READ(reg);
>  	pipeconf_val = I915_READ(PIPECONF(pipe));
> @@ -1724,8 +1734,8 @@ static void intel_enable_transcoder(struct drm_i915_private *dev_priv,
>  static void intel_disable_transcoder(struct drm_i915_private *dev_priv,
>  				     enum pipe pipe)
>  {
> -	int reg;
> -	u32 val;
> +	struct drm_device *dev = dev_priv->dev;
> +	uint32_t reg, val;
>  
>  	/* FDI relies on the transcoder */
>  	assert_fdi_tx_disabled(dev_priv, pipe);
> @@ -1741,6 +1751,14 @@ static void intel_disable_transcoder(struct drm_i915_private *dev_priv,
>  	/* wait for PCH transcoder off, transcoder state */
>  	if (wait_for((I915_READ(reg) & TRANS_STATE_ENABLE) == 0, 50))
>  		DRM_ERROR("failed to disable transcoder %d\n", pipe);
> +
> +	if (!HAS_PCH_IBX(dev)) {
> +		/* Workaround: Clear the timing override chicken bit again. */
> +		reg = TRANS_CHICKEN2(pipe);
> +		val = I915_READ(reg);
> +		val &= ~TRANS_CHICKEN2_TIMING_OVERRIDE;
> +		I915_WRITE(reg, val);
> +	}


>  }
>  
>  /**
> @@ -3217,16 +3235,12 @@ prepare: /* separate function? */
>  void intel_cpt_verify_modeset(struct drm_device *dev, int pipe)
>  {
>  	struct drm_i915_private *dev_priv = dev->dev_private;
> -	int dslreg = PIPEDSL(pipe), tc2reg = TRANS_CHICKEN2(pipe);
> +	int dslreg = PIPEDSL(pipe);
>  	u32 temp;
>  
>  	temp = I915_READ(dslreg);
>  	udelay(500);
>  	if (wait_for(I915_READ(dslreg) != temp, 5)) {
> -		/* Without this, mode sets may fail silently on FDI */
> -		I915_WRITE(tc2reg, TRANS_AUTOTRAIN_GEN_STALL_DIS);
> -		udelay(250);
> -		I915_WRITE(tc2reg, 0);
>  		if (wait_for(I915_READ(dslreg) != temp, 5))
>  			DRM_ERROR("mode set failed: pipe %d stuck\n", pipe);
>  	}

Note this was an older version of the workaround.  "wrongly placed"
indeed.

-- 
Jesse Barnes, Intel Open Source Technology Center