Re: [PATCH] drm/i915: Add BXT Sprite plane fractional scalings

["Maiti, Nabendu Bikash" <nabendu.bikash.maiti@intel.com>]

On 11/18/2015 5:41 PM, Ville Syrjälä wrote:
> On Wed, Nov 18, 2015 at 05:13:01PM +0530, Nabendu Maiti wrote:
>> On older platforms scalers/cliping used to provide destination size an
>> exact multiple of src size.
>> Gen-9 and above support fractional ratio of dst/src so that source is
>> not manipulated to meet the exact multiple factor.
>>
>> Signed-off-by: Nabendu Maiti <nabendu.bikash.maiti@intel.com>
>> ---
>>   drivers/gpu/drm/i915/intel_sprite.c | 48 +++++++++++++++++++++----------------
>>   1 file changed, 28 insertions(+), 20 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c
>> index 2b96f33..e8c17ae 100644
>> --- a/drivers/gpu/drm/i915/intel_sprite.c
>> +++ b/drivers/gpu/drm/i915/intel_sprite.c
>> @@ -813,29 +813,37 @@ intel_check_sprite_plane(struct drm_plane *plane,
>>   	crtc_h = drm_rect_height(dst);
>>   
>>   	if (state->visible) {
>> -		/* check again in case clipping clamped the results */
>> -		hscale = drm_rect_calc_hscale(src, dst, min_scale, max_scale);
>> -		if (hscale < 0) {
>> -			DRM_DEBUG_KMS("Horizontal scaling factor out of limits\n");
>> -			drm_rect_debug_print("src: ", src, true);
>> -			drm_rect_debug_print("dst: ", dst, false);
>> -
>> -			return hscale;
>> -		}
>>   
>> -		vscale = drm_rect_calc_vscale(src, dst, min_scale, max_scale);
>> -		if (vscale < 0) {
>> -			DRM_DEBUG_KMS("Vertical scaling factor out of limits\n");
>> -			drm_rect_debug_print("src: ", src, true);
>> -			drm_rect_debug_print("dst: ", dst, false);
>> +		/* Gen 9 and above has fractional scaling support */
>> +		if (INTEL_INFO(plane->dev)->gen < 9) {
>>   
>> -			return vscale;
>> -		}
>> +			/* check again in case clipping clamped the results */
>> +			hscale = drm_rect_calc_hscale(src, dst, min_scale, max_scale);
>> +			if (hscale < 0) {
>> +				DRM_DEBUG_KMS("Horizontal scaling factor out of limits\n");
>> +				drm_rect_debug_print("src: ", src, true);
>> +				drm_rect_debug_print("dst: ", dst, false);
>> +
>> +				return hscale;
>> +			}
>> +
>> +			vscale = drm_rect_calc_vscale(src, dst, min_scale, max_scale);
>> +			if (vscale < 0) {
>> +				DRM_DEBUG_KMS("Vertical scaling factor out of limits\n");
>> +				drm_rect_debug_print("src: ", src, true);
>> +				drm_rect_debug_print("dst: ", dst, false);
>>   
>> -		/* Make the source viewport size an exact multiple of the scaling factors. */
>> -		drm_rect_adjust_size(src,
>> -				     drm_rect_width(dst) * hscale - drm_rect_width(src),
>> -				     drm_rect_height(dst) * vscale - drm_rect_height(src));
>> +				return vscale;
>> +			}
>> +
>> +			/*
>> +			 * Make the source viewport size an exact
>> +			 * multiple of the scaling factors.
>> +			 */
>> +			drm_rect_adjust_size(src,
>> +					     drm_rect_width(dst) * hscale - drm_rect_width(src),
>> +					     drm_rect_height(dst) * vscale - drm_rect_height(src));
>> +		}
> NAK. This code just makes sure the actual scaling ratio matches what we
> calculated. As in there may have been some amount of rounding involved
> etc.
>
> The part you actually want to change is what comes after this where we
> throw away the fractional part of the coordinates. And then you need to
> change the actual hw programming so that we actually feed the sub-pixel
> coordinates to the hardware.

In line

drm_rect_adjust_size(src,
+					     drm_rect_width(dst) * hscale - drm_rect_width(src),
+					     drm_rect_height(dst) * vscale - drm_rect_height(src));

I think we throw away the fractional part, which modifies the src,rectangle. In commit we use the modified state->src size.

>>   
>>   		drm_rect_rotate_inv(src, fb->width << 16, fb->height << 16,
>>   				    state->base.rotation);
>> -- 
>> 1.9.1
>>
>> _______________________________________________
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>> Intel-gfx@lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

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