Re: [PATCH 05/10] drm/i915/psr: Ensure SFF/CFF bits are not written at their sample point

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Dec 13, 2024 at 08:35:23AM +0200, Jouni Högander wrote:
> Bspec says this for SFF/CFF:
> 
> "Hardware samples this bit on the start of every V. Blank Guardband
> region. For deterministic behavior, Software should ensure it is not
> changing this bit around the sample point."
> 
> This can be achieved by using intel_vblank_evade.
> 
> Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_psr.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
> index c074de6b6c12..8aa2574ba5c9 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.c
> +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> @@ -26,6 +26,7 @@
>  #include <drm/drm_atomic_helper.h>
>  #include <drm/drm_damage_helper.h>
>  #include <drm/drm_debugfs.h>
> +#include <drm/drm_vblank.h>
>  
>  #include "i915_drv.h"
>  #include "i915_reg.h"
> @@ -44,6 +45,7 @@
>  #include "intel_psr.h"
>  #include "intel_psr_regs.h"
>  #include "intel_snps_phy.h"
> +#include "intel_vblank.h"
>  #include "skl_universal_plane.h"
>  
>  /**
> @@ -3114,16 +3116,31 @@ static void intel_psr_configure_full_frame_update(struct intel_dp *intel_dp)
>  {
>  	struct intel_display *display = to_intel_display(intel_dp);
>  	enum transcoder cpu_transcoder = intel_dp->psr.transcoder;
> +	struct intel_crtc *crtc = intel_crtc_for_pipe(display, intel_dp->psr.pipe);
> +	struct intel_crtc_state *crtc_state = to_intel_crtc_state(crtc->base.state);

You can't use that without proper locking.

> +	struct intel_vblank_evade_ctx evade;
>  
>  	if (!intel_dp->psr.psr2_sel_fetch_enabled)
>  		return;
>  
> +	intel_vblank_evade_init(crtc_state, crtc_state, &evade);
> +
> +	drm_crtc_vblank_get(&crtc->base);
> +
> +	local_irq_disable();
> +
> +	intel_vblank_evade(&evade);
> +
> +	drm_crtc_vblank_put(&crtc->base);
> +
>  	intel_de_write(display,
>  		       PSR2_MAN_TRK_CTL(display, cpu_transcoder),
>  		       man_trk_ctl_enable_bit_get(display) |
>  		       man_trk_ctl_partial_frame_bit_get(display) |
>  		       man_trk_ctl_single_full_frame_bit_get(display) |
>  		       man_trk_ctl_continuos_full_frame(display));
> +
> +	local_irq_enable();
>  }
>  
>  static void _psr_invalidate_handle(struct intel_dp *intel_dp)
> -- 
> 2.34.1

-- 
Ville Syrjälä
Intel