Re: [PATCH v5 1/5] drm/i915: Add enable/disable flip done and flip done handler

[Paulo Zanoni <paulo.r.zanoni@intel.com>]

Em seg, 2020-07-20 às 17:01 +0530, Karthik B S escreveu:
> Add enable/disable flip done functions and the flip done handler
> function which handles the flip done interrupt.
> 
> Enable the flip done interrupt in IER.
> 
> Enable flip done function is called before writing the
> surface address register as the write to this register triggers
> the flip done interrupt
> 
> Flip done handler is used to send the page flip event as soon as the
> surface address is written as per the requirement of async flips.
> The interrupt is disabled after the event is sent.
> 
> v2: -Change function name from icl_* to skl_* (Paulo)
>     -Move flip handler to this patch (Paulo)
>     -Remove vblank_put() (Paulo)
>     -Enable flip done interrupt for gen9+ only (Paulo)
>     -Enable flip done interrupt in power_well_post_enable hook (Paulo)
>     -Removed the event check in flip done handler to handle async
>      flips without pageflip events.
> 
> v3: -Move skl_disable_flip_done out of interrupt handler (Paulo)
>     -Make the pending vblank event NULL in the beginning of
>      flip_done_handler to remove sporadic WARN_ON that is seen.
> 
> v4: -Calculate timestamps using flip done time stamp and current
>      timestamp for async flips (Ville)
> 
> v5: -Fix the sparse warning by making the function 'g4x_get_flip_counter'
>      static.(Reported-by: kernel test robot <lkp@intel.com>)
>     -Fix the typo in commit message.
> 
> Signed-off-by: Karthik B S <karthik.b.s@intel.com>
> Signed-off-by: Vandita Kulkarni <vandita.kulkarni@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display.c | 10 +++
>  drivers/gpu/drm/i915/i915_irq.c              | 83 ++++++++++++++++++--
>  drivers/gpu/drm/i915/i915_irq.h              |  2 +
>  drivers/gpu/drm/i915/i915_reg.h              |  4 +-
>  4 files changed, 91 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index db2a5a1a9b35..b8ff032195d9 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -15562,6 +15562,13 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
>  
>  	intel_dbuf_pre_plane_update(state);
>  
> +	for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i) {
> +		if (new_crtc_state->uapi.async_flip) {
> +			skl_enable_flip_done(&crtc->base);
> +			break;

Do we really want the break here? What if more than one CRTC wants an
async flip?

Perhaps you could extend IGT to try this.

> +		}
> +	}
> +
>  	/* Now enable the clocks, plane, pipe, and connectors that we set up. */
>  	dev_priv->display.commit_modeset_enables(state);
>  
> @@ -15583,6 +15590,9 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
>  	drm_atomic_helper_wait_for_flip_done(dev, &state->base);
>  
>  	for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i) {
> +		if (new_crtc_state->uapi.async_flip)
> +			skl_disable_flip_done(&crtc->base);

Here we don't break in the first found, so at least there's an
inconsistency.

> +
>  		if (new_crtc_state->hw.active &&
>  		    !needs_modeset(new_crtc_state) &&
>  		    !new_crtc_state->preload_luts &&
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index 1fa67700d8f4..95953b393941 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -697,14 +697,24 @@ u32 i915_get_vblank_counter(struct drm_crtc *crtc)
>  	return (((high1 << 8) | low) + (pixel >= vbl_start)) & 0xffffff;
>  }
>  
> +static u32 g4x_get_flip_counter(struct drm_crtc *crtc)
> +{
> +	struct drm_i915_private *dev_priv = to_i915(crtc->dev);
> +	enum pipe pipe = to_intel_crtc(crtc)->pipe;
> +
> +	return I915_READ(PIPE_FLIPCOUNT_G4X(pipe));
> +}
> +
>  u32 g4x_get_vblank_counter(struct drm_crtc *crtc)
>  {
>  	struct drm_i915_private *dev_priv = to_i915(crtc->dev);
>  	enum pipe pipe = to_intel_crtc(crtc)->pipe;
>  
> +	if (crtc->state->async_flip)
> +		return g4x_get_flip_counter(crtc);
> +
>  	return I915_READ(PIPE_FRMCOUNT_G4X(pipe));

I don't understand the intention behind this, can you please clarify?
This goes back to my reply of the cover letter. It seems that here
we're going to alternate between two different counters in our vblank
count. So if user space alternates between sometimes using async flips
and sometimes using normal flip it's going to get some very weird
deltas, isn't it? At least this is what I remember from when I played
with these registers: FLIPCOUNT drifts away from FRMCOUNT when we start
using async flips.

IMHO we really need our IGT to exercise this possibility.

>  }
> -

Don't remove this blank line, please.

>  /*
>   * On certain encoders on certain platforms, pipe
>   * scanline register will not work to get the scanline,
> @@ -737,17 +747,24 @@ static u32 __intel_get_crtc_scanline_from_timestamp(struct intel_crtc *crtc)
>  		 * pipe frame time stamp. The time stamp value
>  		 * is sampled at every start of vertical blank.
>  		 */
> -		scan_prev_time = intel_de_read_fw(dev_priv,
> -						  PIPE_FRMTMSTMP(crtc->pipe));
> -
> +		if (!crtc->config->uapi.async_flip)
> +			scan_prev_time = intel_de_read_fw(dev_priv,
> +							  PIPE_FRMTMSTMP(crtc->pipe));
> +		else
> +			scan_prev_time = intel_de_read_fw(dev_priv,
> +							  PIPE_FLIPTMSTMP(crtc->pipe));
>  		/*
>  		 * The TIMESTAMP_CTR register has the current
>  		 * time stamp value.
>  		 */
>  		scan_curr_time = intel_de_read_fw(dev_priv, IVB_TIMESTAMP_CTR);
>  
> -		scan_post_time = intel_de_read_fw(dev_priv,
> -						  PIPE_FRMTMSTMP(crtc->pipe));
> +		if (!crtc->config->uapi.async_flip)
> +			scan_post_time = intel_de_read_fw(dev_priv,
> +							  PIPE_FRMTMSTMP(crtc->pipe));
> +		else
> +			scan_post_time = intel_de_read_fw(dev_priv,
> +							  PIPE_FLIPTMSTMP(crtc->pipe));
>  	} while (scan_post_time != scan_prev_time);
>  
>  	scanline = div_u64(mul_u32_u32(scan_curr_time - scan_prev_time,
> @@ -937,7 +954,6 @@ static bool i915_get_crtc_scanoutpos(struct drm_crtc *_crtc,
>  		*vpos = position / htotal;
>  		*hpos = position - (*vpos * htotal);
>  	}
> -

Please don't remove random blank lines.

>  	return true;
>  }
>  
> @@ -1295,6 +1311,24 @@ display_pipe_crc_irq_handler(struct drm_i915_private *dev_priv,
>  			     u32 crc4) {}
>  #endif
>  
> +static void flip_done_handler(struct drm_i915_private *dev_priv,
> +			      unsigned int pipe)
> +{
> +	struct intel_crtc *crtc = intel_get_crtc_for_pipe(dev_priv, pipe);
> +	struct drm_crtc_state *crtc_state = crtc->base.state;
> +	struct drm_pending_vblank_event *e = crtc_state->event;
> +	struct drm_device *dev = &dev_priv->drm;
> +	unsigned long irqflags;
> +
> +	crtc_state->event = NULL;
> +
> +	drm_crtc_accurate_vblank_count(&crtc->base);
> +	spin_lock_irqsave(&dev->event_lock, irqflags);
> +
> +	drm_crtc_send_vblank_event(&crtc->base, e);

Can you please explain why we need this pair of functions instead of
relying on intel_handle_vblank() like the handler for the 'real' vblank
interrupt? I'm not saying this is wrong, I'm just trying to understand
the code in order to review it properly.


> +
> +	spin_unlock_irqrestore(&dev->event_lock, irqflags);
> +}
>  
>  static void hsw_pipe_crc_irq_handler(struct drm_i915_private *dev_priv,
>  				     enum pipe pipe)
> @@ -2389,6 +2423,9 @@ gen8_de_irq_handler(struct drm_i915_private *dev_priv, u32 master_ctl)
>  		if (iir & GEN8_PIPE_VBLANK)
>  			intel_handle_vblank(dev_priv, pipe);
>  
> +		if (iir & GEN9_PIPE_PLANE1_FLIP_DONE)
> +			flip_done_handler(dev_priv, pipe);
> +
>  		if (iir & GEN8_PIPE_CDCLK_CRC_DONE)
>  			hsw_pipe_crc_irq_handler(dev_priv, pipe);
>  
> @@ -2710,6 +2747,19 @@ int bdw_enable_vblank(struct drm_crtc *crtc)
>  	return 0;
>  }
>  
> +void skl_enable_flip_done(struct drm_crtc *crtc)
> +{
> +	struct drm_i915_private *dev_priv = to_i915(crtc->dev);
> +	enum pipe pipe = to_intel_crtc(crtc)->pipe;
> +	unsigned long irqflags;
> +
> +	spin_lock_irqsave(&dev_priv->irq_lock, irqflags);
> +
> +	bdw_enable_pipe_irq(dev_priv, pipe, GEN9_PIPE_PLANE1_FLIP_DONE);
> +
> +	spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);
> +}
> +
>  /* Called from drm generic code, passed 'crtc' which
>   * we use as a pipe index
>   */
> @@ -2770,6 +2820,19 @@ void bdw_disable_vblank(struct drm_crtc *crtc)
>  	spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);
>  }
>  
> +void skl_disable_flip_done(struct drm_crtc *crtc)
> +{
> +	struct drm_i915_private *dev_priv = to_i915(crtc->dev);
> +	enum pipe pipe = to_intel_crtc(crtc)->pipe;
> +	unsigned long irqflags;
> +
> +	spin_lock_irqsave(&dev_priv->irq_lock, irqflags);
> +
> +	bdw_disable_pipe_irq(dev_priv, pipe, GEN9_PIPE_PLANE1_FLIP_DONE);
> +
> +	spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);
> +}
> +
>  static void ibx_irq_reset(struct drm_i915_private *dev_priv)
>  {
>  	struct intel_uncore *uncore = &dev_priv->uncore;
> @@ -2980,6 +3043,9 @@ void gen8_irq_power_well_post_enable(struct drm_i915_private *dev_priv,
>  	u32 extra_ier = GEN8_PIPE_VBLANK | GEN8_PIPE_FIFO_UNDERRUN;
>  	enum pipe pipe;
>  
> +	if (INTEL_GEN(dev_priv) >= 9)
> +		extra_ier |= GEN9_PIPE_PLANE1_FLIP_DONE;
> +
>  	spin_lock_irq(&dev_priv->irq_lock);
>  
>  	if (!intel_irqs_enabled(dev_priv)) {
> @@ -3458,6 +3524,9 @@ static void gen8_de_irq_postinstall(struct drm_i915_private *dev_priv)
>  	de_pipe_enables = de_pipe_masked | GEN8_PIPE_VBLANK |
>  					   GEN8_PIPE_FIFO_UNDERRUN;
>  
> +	if (INTEL_GEN(dev_priv) >= 9)
> +		de_pipe_enables |= GEN9_PIPE_PLANE1_FLIP_DONE;
> +
>  	de_port_enables = de_port_masked;
>  	if (IS_GEN9_LP(dev_priv))
>  		de_port_enables |= BXT_DE_PORT_HOTPLUG_MASK;
> diff --git a/drivers/gpu/drm/i915/i915_irq.h b/drivers/gpu/drm/i915/i915_irq.h
> index 25f25cd95818..2f10c8135116 100644
> --- a/drivers/gpu/drm/i915/i915_irq.h
> +++ b/drivers/gpu/drm/i915/i915_irq.h
> @@ -112,11 +112,13 @@ int i915gm_enable_vblank(struct drm_crtc *crtc);
>  int i965_enable_vblank(struct drm_crtc *crtc);
>  int ilk_enable_vblank(struct drm_crtc *crtc);
>  int bdw_enable_vblank(struct drm_crtc *crtc);
> +void skl_enable_flip_done(struct drm_crtc *crtc);
>  void i8xx_disable_vblank(struct drm_crtc *crtc);
>  void i915gm_disable_vblank(struct drm_crtc *crtc);
>  void i965_disable_vblank(struct drm_crtc *crtc);
>  void ilk_disable_vblank(struct drm_crtc *crtc);
>  void bdw_disable_vblank(struct drm_crtc *crtc);
> +void skl_disable_flip_done(struct drm_crtc *crtc);
>  
>  void gen2_irq_reset(struct intel_uncore *uncore);
>  void gen3_irq_reset(struct intel_uncore *uncore, i915_reg_t imr,
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index a0d31f3bf634..8cee06314d5d 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -11144,9 +11144,11 @@ enum skl_power_gate {
>  #define  GEN9_TIMESTAMP_OVERRIDE_US_COUNTER_DENOMINATOR_MASK	(0xf << 12)
>  
>  #define _PIPE_FRMTMSTMP_A		0x70048
> +#define _PIPE_FLIPTMSTMP_A		0x7004C
>  #define PIPE_FRMTMSTMP(pipe)		\
>  			_MMIO_PIPE2(pipe, _PIPE_FRMTMSTMP_A)
> -
> +#define PIPE_FLIPTMSTMP(pipe)		\
> +			_MMIO_PIPE2(pipe, _PIPE_FLIPTMSTMP_A)
>  /* BXT MIPI clock controls */
>  #define BXT_MAX_VAR_OUTPUT_KHZ			39500
>  

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