drm/i915: Upscale scaler max scale for NV12

drm/i915: Upscale scaler max scale for NV12

This patch updates scaler max limit support for NV12

v2: Rebased (me)

v3: Rebased (me)

v4: Missed the Tested-by/Reviewed-by in the previous series
Adding the same to commit message in this version.

v5: Addressed review comments from Ville and rebased
- calculation of max_scale to be made
less convoluted by splitting it up a bit
- Indentation errors to be fixed in the series

v6: Rebased (me)
Fixed review comments from Paauwe, Bob J
Previous version, where a split of calculation
was done, was wrong. Fixed that issue here.

v7: Rebased (me)

v8: Rebased (me)

v9: Rebased (me)

v10: Rebased (me)

v11: Addressed review comments from Shashank Sharma
Alignment issues fixed.
When call to skl_update_scaler is made, 0 was being
sent instead of pixel_format.
When crtc update scaler is called, we dont have the
fb to derive the pixel format. Added the function
parameter bool plane_scaler_check to account for this.

v12: Fixed failure in IGT debugfs_test.
fb is NULL in skl_update_scaler_plane
Due to this, accessing fb->format caused failure.
Patch checks fb before using.

v13: In the previous version there was a flaw.
In skl_update_scaler during plane_scaler_check
if the format was non-NV12, it would set need_scaling
to false. This could reset the previously set need_scaling
from a previous condition check. Patch fixes this.
Patch also adds minimum src height for YUV 420 formats
to 16 (as defined in BSpec) and adds for checking this
range.

v14: Addressed review comments from Maarten
Just add a check for NV12 min src height in
skl_update_scaler and retain the remaining checks
as is. Added Reviewed By from Juha-Pekka Heikkila.

v15: Rebased the series.

v16: Changed fb height restriction to be >= 16 as per
Bspec. Earlier it was > 16.

v17: Adding src width and height to be mult of 4 restriction
to avoid pipe fifo underruns for NV12.

Credits-to: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Tested-by: Clinton Taylor <clinton.a.taylor@intel.com>
Reviewed-by: Clinton Taylor <clinton.a.taylor@intel.com>
Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Signed-off-by: Chandra Konduru <chandra.konduru@intel.com>
Signed-off-by: Nabendu Maiti <nabendu.bikash.maiti@intel.com>
Signed-off-by: Vidya Srinivas <vidya.srinivas@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1523245273-30264-15-git-send-email-vidya.srinivas@intel.com