[Intel-gfx] [PATCH] drm/i915/dsb: Enable lmem for dsb

[Ville Syrjälä]

On Fri, Jan 31, 2020 at 05:12:58PM +0530, Animesh Manna wrote:
> If lmem is supported DSB should use local memeory instead
> of system memory. Using local memory surely bring performance
> improvement as local memory is close to gpu. Also want to avoid
> multiple gpu using system memory.
> 
> Used LMEM api to create gem object needed for DSB command buffer.

The whole point of the dsb is to avoid doing mmio.a Now you're
replacing the nice dma with mmio again. Granted lmem is probably
wc so maybe not as slow as direct mmio register access, and also
we can do this ahead of time so not as time critical as direct
mmio during the the vblank.

> 
> v1: Initial patch.
> 
> Cc: Jani Nikula <jani.nikula at linux.intel.com>
> Cc: Matthew Auld <matthew.auld at intel.com>
> Cc: Ramalingam C <ramalingam.c at intel.com>
> Signed-off-by: Animesh Manna <animesh.manna at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dsb.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c b/drivers/gpu/drm/i915/display/intel_dsb.c
> index 9dd18144a664..d67b6a764ba0 100644
> --- a/drivers/gpu/drm/i915/display/intel_dsb.c
> +++ b/drivers/gpu/drm/i915/display/intel_dsb.c
> @@ -6,6 +6,7 @@
>  
>  #include "i915_drv.h"
>  #include "intel_display_types.h"
> +#include "gem/i915_gem_lmem.h"
>  
>  #define DSB_BUF_SIZE    (2 * PAGE_SIZE)
>  
> @@ -113,7 +114,11 @@ intel_dsb_get(struct intel_crtc *crtc)
>  
>  	wakeref = intel_runtime_pm_get(&i915->runtime_pm);
>  
> -	obj = i915_gem_object_create_internal(i915, DSB_BUF_SIZE);
> +	if (HAS_LMEM(i915))
> +		obj = i915_gem_object_create_lmem(i915, DSB_BUF_SIZE, 0);
> +	else
> +		obj = i915_gem_object_create_internal(i915, DSB_BUF_SIZE);
> +
>  	if (IS_ERR(obj)) {
>  		DRM_ERROR("Gem object creation failed\n");
>  		goto out;
> -- 
> 2.24.0
> 
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-- 
Ville Syrjälä
Intel