Re: [PATCH] drm/i915: Acquire dpio_lock for VLV sideband programming in DP/HDMI

[Jani Nikula <jani.nikula@linux.intel.com>]

On Fri, 26 Jul 2013, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> Otherwise we get flooded by the kernel warning us that we are doing
> long sequences of IO without serialisation. For example,
>
>  WARNING: CPU: 0 PID: 11136 at drivers/gpu/drm/i915/intel_sideband.c:40 vlv_sideband_rw+0x48/0x1ef()
>  Modules linked in:
>  CPU: 0 PID: 11136 Comm: kworker/u2:0 Tainted: G        W    3.11.0-rc2+ #4
>  Call Trace:
>   [<c2028564>] ?  warn_slowpath_common+0x63/0x78
>   [<c227ad43>] ?  vlv_sideband_rw+0x48/0x1ef
>   [<c20285dd>] ?  warn_slowpath_null+0xf/0x13
>   [<c227ad43>] ?  vlv_sideband_rw+0x48/0x1ef
>   [<c227b060>] ?  vlv_dpio_write+0x1c/0x21
>   [<c2262b3b>] ?  intel_dp_set_signal_levels+0x24a/0x385
>   [<c2264909>] ?  intel_dp_complete_link_train+0x25/0x1d1
>   [<c2264c55>] ?  intel_dp_check_link_status+0xf7/0x106
>   [<c2238ced>] ?  i915_hotplug_work_func+0x17b/0x221
>   [<c203a204>] ?  process_one_work+0x12e/0x210
>   [<c203a5e4>] ?  worker_thread+0x116/0x1ad
>   [<c203a4ce>] ?  rescuer_thread+0x1cb/0x1cb
>   [<c203d8f5>] ?  kthread+0x67/0x6c
>   [<c2457ebb>] ?  ret_from_kernel_thread+0x1b/0x30
>   [<c203d88e>] ?  init_completion+0x18/0x18
>
> v2: Retire the locking in vlv_crtc_enable() and do it close to the
> meat.

Grumble about throwing the fix and the refactoring together for no real
reason, and having a slightly misleading subject. But since we have the
warnings in place, the patch is small, and the end result is what we
want, I'll let it pass. Just this once. ;)

Reviewed-by: Jani Nikula <jani.nikula@intel.com>

> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 4 ----
>  drivers/gpu/drm/i915/intel_dp.c      | 6 ++++++
>  drivers/gpu/drm/i915/intel_hdmi.c    | 4 ++++
>  3 files changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index b3389d7..6bb9017 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -3653,8 +3653,6 @@ static void valleyview_crtc_enable(struct drm_crtc *crtc)
>  	intel_crtc->active = true;
>  	intel_update_watermarks(dev);
>  
> -	mutex_lock(&dev_priv->dpio_lock);
> -
>  	for_each_encoder_on_crtc(dev, crtc, encoder)
>  		if (encoder->pre_pll_enable)
>  			encoder->pre_pll_enable(encoder);
> @@ -3679,8 +3677,6 @@ static void valleyview_crtc_enable(struct drm_crtc *crtc)
>  	intel_crtc_update_cursor(crtc, true);
>  
>  	intel_update_fbc(dev);
> -
> -	mutex_unlock(&dev_priv->dpio_lock);
>  }
>  
>  static void i9xx_crtc_enable(struct drm_crtc *crtc)
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 4a7ba5e..2a455b8 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -1719,6 +1719,7 @@ static void intel_pre_enable_dp(struct intel_encoder *encoder)
>  		int pipe = intel_crtc->pipe;
>  		u32 val;
>  
> +		mutex_lock(&dev_priv->dpio_lock);
>  		val = vlv_dpio_read(dev_priv, DPIO_DATA_LANE_A(port));
>  		val = 0;
>  		if (pipe)
> @@ -1732,6 +1733,7 @@ static void intel_pre_enable_dp(struct intel_encoder *encoder)
>  				 0x00760018);
>  		vlv_dpio_write(dev_priv, DPIO_PCS_CLOCKBUF8(port),
>  				 0x00400888);
> +		mutex_unlock(&dev_priv->dpio_lock);
>  	}
>  }
>  
> @@ -1746,6 +1748,7 @@ static void intel_dp_pre_pll_enable(struct intel_encoder *encoder)
>  		return;
>  
>  	/* Program Tx lane resets to default */
> +	mutex_lock(&dev_priv->dpio_lock);
>  	vlv_dpio_write(dev_priv, DPIO_PCS_TX(port),
>  			 DPIO_PCS_TX_LANE2_RESET |
>  			 DPIO_PCS_TX_LANE1_RESET);
> @@ -1759,6 +1762,7 @@ static void intel_dp_pre_pll_enable(struct intel_encoder *encoder)
>  	vlv_dpio_write(dev_priv, DPIO_PCS_STAGGER1(port), 0x00750f00);
>  	vlv_dpio_write(dev_priv, DPIO_TX_CTL(port), 0x00001500);
>  	vlv_dpio_write(dev_priv, DPIO_TX_LANE(port), 0x40400000);
> +	mutex_unlock(&dev_priv->dpio_lock);
>  }
>  
>  /*
> @@ -1970,6 +1974,7 @@ static uint32_t intel_vlv_signal_levels(struct intel_dp *intel_dp)
>  		return 0;
>  	}
>  
> +	mutex_lock(&dev_priv->dpio_lock);
>  	vlv_dpio_write(dev_priv, DPIO_TX_OCALINIT(port), 0x00000000);
>  	vlv_dpio_write(dev_priv, DPIO_TX_SWING_CTL4(port), demph_reg_value);
>  	vlv_dpio_write(dev_priv, DPIO_TX_SWING_CTL2(port),
> @@ -1978,6 +1983,7 @@ static uint32_t intel_vlv_signal_levels(struct intel_dp *intel_dp)
>  	vlv_dpio_write(dev_priv, DPIO_PCS_STAGGER0(port), 0x00030000);
>  	vlv_dpio_write(dev_priv, DPIO_PCS_CTL_OVER1(port), preemph_reg_value);
>  	vlv_dpio_write(dev_priv, DPIO_TX_OCALINIT(port), 0x80000000);
> +	mutex_unlock(&dev_priv->dpio_lock);
>  
>  	return 0;
>  }
> diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
> index 044d11d..5fa3035 100644
> --- a/drivers/gpu/drm/i915/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> @@ -1033,6 +1033,7 @@ static void intel_hdmi_pre_enable(struct intel_encoder *encoder)
>  		return;
>  
>  	/* Enable clock channels for this port */
> +	mutex_lock(&dev_priv->dpio_lock);
>  	val = vlv_dpio_read(dev_priv, DPIO_DATA_LANE_A(port));
>  	val = 0;
>  	if (pipe)
> @@ -1063,6 +1064,7 @@ static void intel_hdmi_pre_enable(struct intel_encoder *encoder)
>  			 0x00760018);
>  	vlv_dpio_write(dev_priv, DPIO_PCS_CLOCKBUF8(port),
>  			 0x00400888);
> +	mutex_unlock(&dev_priv->dpio_lock);
>  }
>  
>  static void intel_hdmi_pre_pll_enable(struct intel_encoder *encoder)
> @@ -1076,6 +1078,7 @@ static void intel_hdmi_pre_pll_enable(struct intel_encoder *encoder)
>  		return;
>  
>  	/* Program Tx lane resets to default */
> +	mutex_lock(&dev_priv->dpio_lock);
>  	vlv_dpio_write(dev_priv, DPIO_PCS_TX(port),
>  			 DPIO_PCS_TX_LANE2_RESET |
>  			 DPIO_PCS_TX_LANE1_RESET);
> @@ -1094,6 +1097,7 @@ static void intel_hdmi_pre_pll_enable(struct intel_encoder *encoder)
>  			 0x00002000);
>  	vlv_dpio_write(dev_priv, DPIO_TX_OCALINIT(port),
>  			 DPIO_TX_OCALINIT_EN);
> +	mutex_lock(&dev_priv->dpio_lock);
>  }
>  
>  static void intel_hdmi_post_disable(struct intel_encoder *encoder)
> -- 
> 1.8.3.2
>
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-- 
Jani Nikula, Intel Open Source Technology Center