Re: [PATCH 2/2] drm/i915: Use RCS flips on Ivybridge+

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Aug 26, 2013 at 08:58:12PM +0100, Chris Wilson wrote:
> RCS flips do work on Iybridge+ so long as we can unmask the messages
> through DERRMR. However, there are quite a few workarounds mentioned
> regarding unmasking more than one event or triggering more than one
> message through DERRMR. Those workarounds in principle prevent us from
> performing pipelined flips (and asynchronous flips across multiple
> planes) and equally apply to the "known good" BCS ring. Given that it
> already appears to work, and also appears to work with unmasking all 3
> planes at once (and queuing flips across multiple planes), be brave.
> 
> Bugzlla: https://bugs.freedesktop.org/show_bug.cgi?id=67600
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Lightly-tested-by: Stephane Marchesin <marchesin@icps.u-strasbg.fr>
> Cc: Stephane Marchesin <marchesin@icps.u-strasbg.fr>
> Cc: Ben Widawsky <ben@bwidawsk.net>

Both patches merged to dinq.
-Daniel

> ---
>  drivers/gpu/drm/i915/i915_reg.h      | 18 ++++++++++++++++
>  drivers/gpu/drm/i915/intel_display.c | 40 ++++++++++++++++++++++++++++--------
>  2 files changed, 49 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index c6f5009..df168f4 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -230,6 +230,7 @@
>   *   address/value pairs. Don't overdue it, though, x <= 2^4 must hold!
>   */
>  #define MI_LOAD_REGISTER_IMM(x)	MI_INSTR(0x22, 2*x-1)
> +#define MI_STORE_REGISTER_MEM(x) MI_INSTR(0x24, 2*x-1)
>  #define MI_FLUSH_DW		MI_INSTR(0x26, 1) /* for GEN6 */
>  #define   MI_FLUSH_DW_STORE_INDEX	(1<<21)
>  #define   MI_INVALIDATE_TLB		(1<<18)
> @@ -678,6 +679,23 @@
>  #define   FPGA_DBG_RM_NOCLAIM	(1<<31)
>  
>  #define DERRMR		0x44050
> +#define   DERRMR_PIPEA_SCANLINE		(1<<0)
> +#define   DERRMR_PIPEA_PRI_FLIP_DONE	(1<<1)
> +#define   DERRMR_PIPEA_SPR_FLIP_DONE	(1<<2)
> +#define   DERRMR_PIPEA_VBLANK		(1<<3)
> +#define   DERRMR_PIPEA_HBLANK		(1<<5)
> +#define   DERRMR_PIPEB_SCANLINE 	(1<<8)
> +#define   DERRMR_PIPEB_PRI_FLIP_DONE	(1<<9)
> +#define   DERRMR_PIPEB_SPR_FLIP_DONE	(1<<10)
> +#define   DERRMR_PIPEB_VBLANK		(1<<11)
> +#define   DERRMR_PIPEB_HBLANK		(1<<13)
> +/* Note that PIPEC is not a simple translation of PIPEA/PIPEB */
> +#define   DERRMR_PIPEC_SCANLINE		(1<<14)
> +#define   DERRMR_PIPEC_PRI_FLIP_DONE	(1<<15)
> +#define   DERRMR_PIPEC_SPR_FLIP_DONE	(1<<20)
> +#define   DERRMR_PIPEC_VBLANK		(1<<21)
> +#define   DERRMR_PIPEC_HBLANK		(1<<22)
> +
>  
>  /* GM45+ chicken bits -- debug workaround bits that may be required
>   * for various sorts of correct behavior.  The top 16 bits of each are
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 9748dce..ffbcbd1 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -7826,12 +7826,6 @@ err:
>  	return ret;
>  }
>  
> -/*
> - * On gen7 we currently use the blit ring because (in early silicon at least)
> - * the render ring doesn't give us interrpts for page flip completion, which
> - * means clients will hang after the first flip is queued.  Fortunately the
> - * blit ring generates interrupts properly, so use it instead.
> - */
>  static int intel_gen7_queue_flip(struct drm_device *dev,
>  				 struct drm_crtc *crtc,
>  				 struct drm_framebuffer *fb,
> @@ -7839,9 +7833,13 @@ static int intel_gen7_queue_flip(struct drm_device *dev,
>  {
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
> -	struct intel_ring_buffer *ring = &dev_priv->ring[BCS];
> +	struct intel_ring_buffer *ring;
>  	uint32_t plane_bit = 0;
> -	int ret;
> +	int len, ret;
> +
> +	ring = obj->ring;
> +	if (ring == NULL || ring->id != RCS)
> +		ring = &dev_priv->ring[BCS];
>  
>  	ret = intel_pin_and_fence_fb_obj(dev, obj, ring);
>  	if (ret)
> @@ -7863,10 +7861,34 @@ static int intel_gen7_queue_flip(struct drm_device *dev,
>  		goto err_unpin;
>  	}
>  
> -	ret = intel_ring_begin(ring, 4);
> +	len = 4;
> +	if (ring->id == RCS)
> +		len += 6;
> +
> +	ret = intel_ring_begin(ring, len);
>  	if (ret)
>  		goto err_unpin;
>  
> +	/* Unmask the flip-done completion message. Note that the bspec says that
> +	 * we should do this for both the BCS and RCS, and that we must not unmask
> +	 * more than one flip event at any time (or ensure that one flip message
> +	 * can be sent by waiting for flip-done prior to queueing new flips).
> +	 * Experimentation says that BCS works despite DERRMR masking all
> +	 * flip-done completion events and that unmasking all planes at once
> +	 * for the RCS also doesn't appear to drop events. Setting the DERRMR
> +	 * to zero does lead to lockups within MI_DISPLAY_FLIP.
> +	 */
> +	if (ring->id == RCS) {
> +		intel_ring_emit(ring, MI_LOAD_REGISTER_IMM(1));
> +		intel_ring_emit(ring, DERRMR);
> +		intel_ring_emit(ring, ~(DERRMR_PIPEA_PRI_FLIP_DONE |
> +					DERRMR_PIPEB_PRI_FLIP_DONE |
> +					DERRMR_PIPEC_PRI_FLIP_DONE));
> +		intel_ring_emit(ring, MI_STORE_REGISTER_MEM(1));
> +		intel_ring_emit(ring, DERRMR);
> +		intel_ring_emit(ring, ring->scratch.gtt_offset + 256);
> +	}
> +
>  	intel_ring_emit(ring, MI_DISPLAY_FLIP_I915 | plane_bit);
>  	intel_ring_emit(ring, (fb->pitches[0] | obj->tiling_mode));
>  	intel_ring_emit(ring, i915_gem_obj_ggtt_offset(obj) + intel_crtc->dspaddr_offset);
> -- 
> 1.8.4.rc3
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch