Re: [PATCH 14/20] drm: Implement timings adjustments for frame packing

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Damien Lespiau <damien.lespiau@intel.com>
Cc: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org
Subject: Re: [PATCH 14/20] drm: Implement timings adjustments for frame packing
Date: Fri, 20 Sep 2013 16:47:53 +0300	[thread overview]
Message-ID: <20130920134753.GP4531@intel.com> (raw)
In-Reply-To: <1379608835-11760-15-git-send-email-damien.lespiau@intel.com>

On Thu, Sep 19, 2013 at 05:40:29PM +0100, Damien Lespiau wrote:
> When using the frame packing and a single big framebuffer, some hardware
> requires that we do everything like if we were scanning out the big
> buffer itself. Let's instrument drm_mode_set_crtcinfo() to be able to do
> this adjustement if the driver is asking for it.
> 
> Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
> ---
>  drivers/gpu/drm/drm_modes.c | 51 ++++++++++++++++++++++++++++++++++++++++++++-
>  include/drm/drm_crtc.h      |  3 ++-
>  2 files changed, 52 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
> index ef26eb2..d9c5a34 100644
> --- a/drivers/gpu/drm/drm_modes.c
> +++ b/drivers/gpu/drm/drm_modes.c
> @@ -704,15 +704,47 @@ int drm_mode_vrefresh(const struct drm_display_mode *mode)
>  }
>  EXPORT_SYMBOL(drm_mode_vrefresh);
>  
> +static bool drm_mode_is_ntsc(const struct drm_display_mode *mode)
> +{
> +	int ntsc_clock;
> +
> +	ntsc_clock = DIV_ROUND_UP(mode->vtotal * mode->htotal * mode->vrefresh,
> +				  1001);
> +
> +	if (ntsc_clock == mode->clock)
> +		return true;
> +
> +	return false;
> +}
> +
> +static void drm_mode_reconstruct_crtc_clock(struct drm_display_mode *mode)
> +{
> +	int clock;
> +
> +	clock = mode->crtc_vtotal * mode->crtc_htotal *
> +		drm_mode_vrefresh(mode) / 1000;
> +
> +	if (drm_mode_is_ntsc(mode))
> +		mode->crtc_clock = DIV_ROUND_UP(clock * 1000, 1001);
> +	else
> +		mode->crtc_clock = clock;
> +}
> +
>  /**
>   * drm_mode_set_crtcinfo - set CRTC modesetting parameters
>   * @p: mode
> - * @adjust_flags: unused? (FIXME)
> + * @adjust_flags: a combination of adjustment flags
>   *
>   * LOCKING:
>   * None.
>   *
>   * Setup the CRTC modesetting parameters for @p, adjusting if necessary.
> + *
> + * - The CRTC_INTERLACE_HALVE_V flag can be used to halve vertical timings of
> + *   interlaced modes.
> + * - The CRTC_STEREO_DOUBLE flag can be used to compute the timings for
> + *   buffers containing two eyes (only adjust the timings when needed, eg. for
> + *   "frame packing" or "side by side full").
>   */
>  void drm_mode_set_crtcinfo(struct drm_display_mode *p, int adjust_flags)
>  {
> @@ -753,6 +785,23 @@ void drm_mode_set_crtcinfo(struct drm_display_mode *p, int adjust_flags)
>  		p->crtc_vtotal *= p->vscan;
>  	}
>  
> +	if (adjust_flags & CRTC_STEREO_DOUBLE) {
> +		unsigned int layout = p->flags & DRM_MODE_FLAG_3D_MASK;
> +		int vactive_space;
> +
> +		switch (layout) {
> +		case DRM_MODE_FLAG_3D_FRAME_PACKING:
> +			vactive_space = p->vtotal - p->vdisplay;
> +
> +			p->crtc_vdisplay += p->vdisplay + vactive_space;
> +			p->crtc_vsync_start += p->vdisplay + vactive_space;
> +			p->crtc_vsync_end += p->vdisplay + vactive_space;
> +			p->crtc_vtotal += p->vdisplay + vactive_space;

All of these are just '+= votal'. Maybe just write it that way and add a
comment to help the uninformed.

In fact it should be crtc_vtotal to maintain the CRTC_INTERLACE_HALVE_V
etc. adjustments already done. So even if you don't take my suggestion
of using just += crtc_vtotal, you should at least switch to
'vactive_space = p->crtc_vtotal - p->crtc_vdisplay;'

> +			drm_mode_reconstruct_crtc_clock(p);

This thing loses precision and shouldn't even be needed. Just double
crtc_clock.

> +			break;
> +		}
> +	}
> +
>  	p->crtc_vblank_start = min(p->crtc_vsync_start, p->crtc_vdisplay);
>  	p->crtc_vblank_end = max(p->crtc_vsync_end, p->crtc_vtotal);
>  	p->crtc_hblank_start = min(p->crtc_hsync_start, p->crtc_hdisplay);
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index 73478bc..b2d08ca 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -125,7 +125,8 @@ enum drm_mode_status {
>  	.vscan = (vs), .flags = (f), \
>  	.base.type = DRM_MODE_OBJECT_MODE
>  
> -#define CRTC_INTERLACE_HALVE_V 0x1 /* halve V values for interlacing */
> +#define CRTC_INTERLACE_HALVE_V	(1 << 0) /* halve V values for interlacing */
> +#define CRTC_STEREO_DOUBLE	(1 << 1) /* adjust timings for stereo modes */
>  
>  struct drm_display_mode {
>  	/* Header */
> -- 
> 1.8.3.1
> 
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-- 
Ville Syrjälä
Intel OTC