Re: [PATCH 1/3] drm/i915: add PWM and BLC assertion checks

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

On Tue, 01 Apr 2014, Jani Nikula <jani.nikula@linux.intel.com> wrote:
> On Mon, 31 Mar 2014, Jesse Barnes <jbarnes@virtuousgeek.org> wrote:
>> To make sure we properly follow the enable/disable sequences.
>>
>> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
>> ---
>>  drivers/gpu/drm/i915/intel_dp.c    | 62 ++++++++++++++++++++++++++++++++++++--
>>  drivers/gpu/drm/i915/intel_drv.h   |  1 +
>>  drivers/gpu/drm/i915/intel_panel.c |  5 ++-
>>  3 files changed, 65 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
>> index bf73771..b6f7087 100644
>> --- a/drivers/gpu/drm/i915/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/intel_dp.c
>> @@ -301,6 +301,20 @@ static u32 _pp_stat_reg(struct intel_dp *intel_dp)
>>  		return VLV_PIPE_PP_STATUS(vlv_power_sequencer_pipe(intel_dp));
>>  }
>>  
>> +static void assert_pwm(struct intel_connector *connector,
>> +		       bool expected_state)
>> +{
>> +	bool state;
>> +
>> +	state = intel_panel_get_backlight(connector);
>
> If the duty cycle is regarded as a binary on/off, I'd rather add an
> additional "is enabled" call to intel_panel.c. Especially so because the
> duty cycle value returned by intel_panel_get_backlight is meaningless
> without the max value.
>
>> +
>> +	WARN(state != expected_state, "pwm state failure, expected %d, found "
>> +	     "%d\n", expected_state, state);
>> +}
>> +
>> +#define assert_pwm_enabled(c) assert_pwm((c), true)
>> +#define assert_pwm_disabled(c) assert_pwm((c), false)
>> +
>>  static bool edp_have_panel_power(struct intel_dp *intel_dp)
>>  {
>>  	struct drm_device *dev = intel_dp_to_dev(intel_dp);
>> @@ -884,6 +898,8 @@ static void intel_dp_mode_set(struct intel_encoder *encoder)
>>  	struct intel_crtc *crtc = to_intel_crtc(encoder->base.crtc);
>>  	struct drm_display_mode *adjusted_mode = &crtc->config.adjusted_mode;
>>  
>> +	assert_pwm_disabled(intel_dp->attached_connector);
>> +
>>  	/*
>>  	 * There are four kinds of DP registers:
>>  	 *
>> @@ -1167,6 +1183,23 @@ static void edp_panel_vdd_off(struct intel_dp *intel_dp, bool sync)
>>  	}
>>  }
>>  
>> +/*
>> + * For this and the disable sequence below, Google for actual eDP LCD timing
>> + * diagrams or check the eDP spec.  Below is for reference on asserts and
>> + * does not contain Tx values for delays between steps.
>> + *
>> + * For panel on, the sequence should be:
>> + * - LCD power supply on (PP regs or VDD AUX)
>> + *   - eDP should display black at this point
>> + * - HPD (if present) should go high
>> + * - AUX channel becomes available
>> + * - link training begins
>> + * - LED backlight power on
>> + * - LED PWM_EN goes high, duty cycle >min (PWM regs)
>> + * - link training completes
>> + * - LED_EN goes high (PP BLC_EN bit)
>> + */
>> +
>>  void intel_edp_panel_on(struct intel_dp *intel_dp)
>>  {
>>  	struct drm_device *dev = intel_dp_to_dev(intel_dp);
>> @@ -1212,6 +1245,19 @@ void intel_edp_panel_on(struct intel_dp *intel_dp)
>>  	}
>>  }
>>  
>> +/*
>> + * For panel off the sequence should be:
>> + * - LED_EN goes low (BLC_EN in our PP regs)
>> + * - LED PWM_EN goes low (PWM duty cycle 0 and PWM enable = 0)
>> + *   - eDP should display black video at this point
>> + * - LED VCCS goes low (power for backlight)
>> + * - DP link goes to idle or off
>> + * - AUX goes down
>> + * - HPD line (if present) drops to low
>> + * - eDP black video stops
>> + * - LCD power supply shuts down (PP regs and VDD AUX)
>> + */
>> +
>>  void intel_edp_panel_off(struct intel_dp *intel_dp)
>>  {
>>  	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
>> @@ -1231,11 +1277,17 @@ void intel_edp_panel_off(struct intel_dp *intel_dp)
>>  
>>  	WARN(!intel_dp->want_panel_vdd, "Need VDD to turn off panel\n");
>>  
>> +	/* By this time the PWM and BLC bits should be off already */
>> +	assert_pwm_disabled(intel_dp->attached_connector);
>> +
>>  	pp = ironlake_get_pp_control(intel_dp);
>> +
>> +	WARN(pp & EDP_BLC_ENABLE,
>> +	     "backlight controller still on at panel off time\n");
>> +
>>  	/* We need to switch off panel power _and_ force vdd, for otherwise some
>>  	 * panels get very unhappy and cease to work. */
>> -	pp &= ~(POWER_TARGET_ON | PANEL_POWER_RESET | EDP_FORCE_VDD |
>> -		EDP_BLC_ENABLE);
>> +	pp &= ~(POWER_TARGET_ON | PANEL_POWER_RESET | EDP_FORCE_VDD);
>>  
>>  	pp_ctrl_reg = _pp_ctrl_reg(intel_dp);
>>  
>> @@ -1271,6 +1323,9 @@ void intel_edp_backlight_on(struct intel_dp *intel_dp)
>>  	 * allowing it to appear.
>>  	 */
>>  	wait_backlight_on(intel_dp);
>> +
>> +	assert_pwm_enabled(intel_dp->attached_connector);
>> +
>>  	pp = ironlake_get_pp_control(intel_dp);
>>  	pp |= EDP_BLC_ENABLE;
>>  
>> @@ -1292,6 +1347,9 @@ void intel_edp_backlight_off(struct intel_dp *intel_dp)
>>  	if (!is_edp(intel_dp))
>>  		return;
>>  
>> +	/* PWM must still be enabled here */
>> +	assert_pwm_enabled(intel_dp->attached_connector);
>> +
>>  	intel_panel_disable_backlight(intel_dp->attached_connector);
>>  
>>  	DRM_DEBUG_KMS("\n");
>> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
>> index 9002e77..0e91c40 100644
>> --- a/drivers/gpu/drm/i915/intel_drv.h
>> +++ b/drivers/gpu/drm/i915/intel_drv.h
>> @@ -861,6 +861,7 @@ void intel_gmch_panel_fitting(struct intel_crtc *crtc,
>>  			      int fitting_mode);
>>  void intel_panel_set_backlight(struct intel_connector *connector, u32 level,
>>  			       u32 max);
>> +u32 intel_panel_get_backlight(struct intel_connector *connector);
>>  int intel_panel_setup_backlight(struct drm_connector *connector);
>>  void intel_panel_enable_backlight(struct intel_connector *connector);
>>  void intel_panel_disable_backlight(struct intel_connector *connector);
>> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
>> index cb05840..21c5e6f 100644
>> --- a/drivers/gpu/drm/i915/intel_panel.c
>> +++ b/drivers/gpu/drm/i915/intel_panel.c
>> @@ -384,6 +384,9 @@ static u32 _vlv_get_backlight(struct drm_device *dev, enum pipe pipe)
>>  {
>>  	struct drm_i915_private *dev_priv = dev->dev_private;
>>  
>> +	if (I915_READ(VLV_BLC_PWM_CTL2(pipe) & BLM_PWM_ENABLE))
>> +		return 0;
>> +
>
> If our internal state is consistent, I don't think this should be
> necessary. And if our internal state isn't consistent, we should fix
> that and maybe add internal asserts within intel_panel.c.

I wrote this with the bigger picture in mind, but your check above is
also doubly wrong!

BR,
Jani.


>
>>  	return I915_READ(VLV_BLC_PWM_CTL(pipe)) & BACKLIGHT_DUTY_CYCLE_MASK;
>>  }
>>  
>> @@ -395,7 +398,7 @@ static u32 vlv_get_backlight(struct intel_connector *connector)
>>  	return _vlv_get_backlight(dev, pipe);
>>  }
>>  
>> -static u32 intel_panel_get_backlight(struct intel_connector *connector)
>> +u32 intel_panel_get_backlight(struct intel_connector *connector)
>>  {
>>  	struct drm_device *dev = connector->base.dev;
>>  	struct drm_i915_private *dev_priv = dev->dev_private;
>> -- 
>> 1.8.4.2
>>
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>
> -- 
> Jani Nikula, Intel Open Source Technology Center
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> Intel-gfx@lists.freedesktop.org
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-- 
Jani Nikula, Intel Open Source Technology Center