drm/sun4i: Add support for HW scaling to DE2

Scaling is currently supported only for RGB framebuffers

Coefficients and algorithm which coefficients to select are taken
from BSP driver.
Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171201060550.10392-22-jernej.skrabec@siol.net

drivers/gpu/drm/sun4i/Makefile

@@ -10,7 +10,8 @@ sun4i-drm-hdmi-y		+= sun4i_hdmi_i2c.o
 sun4i-drm-hdmi-y		+= sun4i_hdmi_tmds_clk.o
 
 sun8i-mixer-y			+= sun8i_mixer.o sun8i_ui_layer.o \
-				   sun8i_vi_layer.o
+				   sun8i_vi_layer.o sun8i_ui_scaler.o \
+				   sun8i_vi_scaler.o
 
 sun4i-tcon-y			+= sun4i_crtc.o
 sun4i-tcon-y			+= sun4i_dotclock.o

drivers/gpu/drm/sun4i/sun8i_mixer.h

@@ -77,10 +77,6 @@
  * These sub-engines are still unknown now, the EN registers are here only to
  * be used to disable these sub-engines.
  */
-#define SUN8I_MIXER_VSU_EN			0x20000
-#define SUN8I_MIXER_GSU1_EN			0x30000
-#define SUN8I_MIXER_GSU2_EN			0x40000
-#define SUN8I_MIXER_GSU3_EN			0x50000
 #define SUN8I_MIXER_FCE_EN			0xa0000
 #define SUN8I_MIXER_BWS_EN			0xa2000
 #define SUN8I_MIXER_LTI_EN			0xa4000

drivers/gpu/drm/sun4i/sun8i_ui_layer.c

@@ -24,6 +24,7 @@
 
 #include "sun8i_ui_layer.h"
 #include "sun8i_mixer.h"
+#include "sun8i_ui_scaler.h"
 
 static void sun8i_ui_layer_enable(struct sun8i_mixer *mixer, int channel,
 				  int overlay, bool enable)
@@ -56,29 +57,35 @@ static int sun8i_ui_layer_update_coord(struct sun8i_mixer *mixer, int channel,
 				       int overlay, struct drm_plane *plane)
 {
 	struct drm_plane_state *state = plane->state;
-	u32 width, height, size;
+	u32 src_w, src_h, dst_w, dst_h;
+	u32 outsize, insize;
+	u32 hphase, vphase;
 
-	DRM_DEBUG_DRIVER("Updating channel %d overlay %d\n", channel, overlay);
+	DRM_DEBUG_DRIVER("Updating UI channel %d overlay %d\n",
+			 channel, overlay);
 
-	/*
-	 * Same source and destination width and height are guaranteed
-	 * by atomic check function.
-	 */
-	width = drm_rect_width(&state->dst);
-	height = drm_rect_height(&state->dst);
-	size = SUN8I_MIXER_SIZE(width, height);
+	src_w = drm_rect_width(&state->src) >> 16;
+	src_h = drm_rect_height(&state->src) >> 16;
+	dst_w = drm_rect_width(&state->dst);
+	dst_h = drm_rect_height(&state->dst);
+
+	hphase = state->src.x1 & 0xffff;
+	vphase = state->src.y1 & 0xffff;
+
+	insize = SUN8I_MIXER_SIZE(src_w, src_h);
+	outsize = SUN8I_MIXER_SIZE(dst_w, dst_h);
 
 	if (plane->type == DRM_PLANE_TYPE_PRIMARY) {
 		bool interlaced = false;
 		u32 val;
 
 		DRM_DEBUG_DRIVER("Primary layer, updating global size W: %u H: %u\n",
-				 width, height);
+				 dst_w, dst_h);
 		regmap_write(mixer->engine.regs,
 			     SUN8I_MIXER_GLOBAL_SIZE,
-			     size);
+			     outsize);
 		regmap_write(mixer->engine.regs, SUN8I_MIXER_BLEND_OUTSIZE,
-			     size);
+			     outsize);
 
 		if (state->crtc)
 			interlaced = state->crtc->state->adjusted_mode.flags
@@ -99,23 +106,42 @@ static int sun8i_ui_layer_update_coord(struct sun8i_mixer *mixer, int channel,
 	}
 
 	/* Set height and width */
-	DRM_DEBUG_DRIVER("Layer size W: %u H: %u\n", width, height);
+	DRM_DEBUG_DRIVER("Layer source offset X: %d Y: %d\n",
+			 state->src.x1 >> 16, state->src.y1 >> 16);
+	DRM_DEBUG_DRIVER("Layer source size W: %d H: %d\n", src_w, src_h);
 	regmap_write(mixer->engine.regs,
 		     SUN8I_MIXER_CHAN_UI_LAYER_SIZE(channel, overlay),
-		     size);
+		     insize);
 	regmap_write(mixer->engine.regs,
 		     SUN8I_MIXER_CHAN_UI_OVL_SIZE(channel),
-		     size);
+		     insize);
+
+	if (insize != outsize || hphase || vphase) {
+		u32 hscale, vscale;
+
+		DRM_DEBUG_DRIVER("HW scaling is enabled\n");
+
+		hscale = state->src_w / state->crtc_w;
+		vscale = state->src_h / state->crtc_h;
+
+		sun8i_ui_scaler_setup(mixer, channel, src_w, src_h, dst_w,
+				      dst_h, hscale, vscale, hphase, vphase);
+		sun8i_ui_scaler_enable(mixer, channel, true);
+	} else {
+		DRM_DEBUG_DRIVER("HW scaling is not needed\n");
+		sun8i_ui_scaler_enable(mixer, channel, false);
+	}
 
 	/* Set base coordinates */
-	DRM_DEBUG_DRIVER("Layer coordinates X: %d Y: %d\n",
+	DRM_DEBUG_DRIVER("Layer destination coordinates X: %d Y: %d\n",
 			 state->dst.x1, state->dst.y1);
+	DRM_DEBUG_DRIVER("Layer destination size W: %d H: %d\n", dst_w, dst_h);
 	regmap_write(mixer->engine.regs,
 		     SUN8I_MIXER_BLEND_ATTR_COORD(channel),
 		     SUN8I_MIXER_COORD(state->dst.x1, state->dst.y1));
 	regmap_write(mixer->engine.regs,
 		     SUN8I_MIXER_BLEND_ATTR_INSIZE(channel),
-		     size);
+		     outsize);
 
 	return 0;
 }
@@ -181,8 +207,10 @@ static int sun8i_ui_layer_update_buffer(struct sun8i_mixer *mixer, int channel,
 static int sun8i_ui_layer_atomic_check(struct drm_plane *plane,
 				       struct drm_plane_state *state)
 {
+	struct sun8i_ui_layer *layer = plane_to_sun8i_ui_layer(plane);
 	struct drm_crtc *crtc = state->crtc;
 	struct drm_crtc_state *crtc_state;
+	int min_scale, max_scale;
 	struct drm_rect clip;
 
 	if (!crtc)
@@ -197,9 +225,16 @@ static int sun8i_ui_layer_atomic_check(struct drm_plane *plane,
 	clip.x2 = crtc_state->adjusted_mode.hdisplay;
 	clip.y2 = crtc_state->adjusted_mode.vdisplay;
 
+	min_scale = DRM_PLANE_HELPER_NO_SCALING;
+	max_scale = DRM_PLANE_HELPER_NO_SCALING;
+
+	if (layer->mixer->cfg->scaler_mask & BIT(layer->channel)) {
+		min_scale = SUN8I_UI_SCALER_SCALE_MIN;
+		max_scale = SUN8I_UI_SCALER_SCALE_MAX;
+	}
+
 	return drm_atomic_helper_check_plane_state(state, crtc_state, &clip,
-						   DRM_PLANE_HELPER_NO_SCALING,
-						   DRM_PLANE_HELPER_NO_SCALING,
+						   min_scale, max_scale,
 						   true, true);
 }
 

drivers/gpu/drm/sun4i/sun8i_ui_scaler.c

+/*
+ * Copyright (C) 2017 Jernej Skrabec <jernej.skrabec@siol.net>
+ *
+ * Coefficients are taken from BSP driver, which is:
+ * Copyright (C) 2014-2015 Allwinner
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2.  This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include "sun8i_ui_scaler.h"
+
+static const u32 lan2coefftab16[240] = {
+	0x00004000, 0x00033ffe, 0x00063efc, 0x000a3bfb,
+	0xff0f37fb, 0xfe1433fb, 0xfd192ffb, 0xfd1f29fb,
+	0xfc2424fc, 0xfb291ffd, 0xfb2f19fd, 0xfb3314fe,
+	0xfb370fff, 0xfb3b0a00, 0xfc3e0600, 0xfe3f0300,
+
+	0xff053804, 0xff083801, 0xff0a3700, 0xff0e34ff,
+	0xff1232fd, 0xfe162ffd, 0xfd1b2cfc, 0xfd1f28fc,
+	0xfd2323fd, 0xfc281ffd, 0xfc2c1bfd, 0xfd2f16fe,
+	0xfd3212ff, 0xff340eff, 0x00360a00, 0x02370700,
+
+	0xff083207, 0xff0a3205, 0xff0d3103, 0xfe113001,
+	0xfe142e00, 0xfe182bff, 0xfe1b29fe, 0xfe1f25fe,
+	0xfe2222fe, 0xfe251ffe, 0xfe291bfe, 0xff2b18fe,
+	0x002e14fe, 0x013010ff, 0x03310dff, 0x05310a00,
+
+	0xff0a2e09, 0xff0c2e07, 0xff0f2d05, 0xff122c03,
+	0xfe152b02, 0xfe182901, 0xfe1b2700, 0xff1e24ff,
+	0xff2121ff, 0xff241eff, 0x00261bff, 0x012818ff,
+	0x022a15ff, 0x032c12ff, 0x052d0fff, 0x072d0c00,
+
+	0xff0c2a0b, 0xff0e2a09, 0xff102a07, 0xff132905,
+	0xff162803, 0xff182702, 0xff1b2501, 0xff1e2300,
+	0x00202000, 0x01221d00, 0x01251bff, 0x032618ff,
+	0x042815ff, 0x052913ff, 0x072a10ff, 0x092a0d00,
+
+	0xff0d280c, 0xff0f280a, 0xff112808, 0xff142706,
+	0xff162605, 0xff192503, 0x001b2302, 0x001d2201,
+	0x011f1f01, 0x01221d00, 0x02231b00, 0x04241800,
+	0x052616ff, 0x072713ff, 0x08271100, 0x0a280e00,
+
+	0xff0e260d, 0xff10260b, 0xff122609, 0xff142508,
+	0x00152506, 0x00182305, 0x001b2203, 0x011d2002,
+	0x011f1f01, 0x02201d01, 0x03221b00, 0x04231801,
+	0x06241600, 0x08251300, 0x09261100, 0x0b260f00,
+
+	0xff0e250e, 0xff10250c, 0x0011250a, 0x00142408,
+	0x00162307, 0x00182206, 0x011a2104, 0x011c2003,
+	0x021e1e02, 0x03201c01, 0x04211a01, 0x05221801,
+	0x07231600, 0x08241400, 0x0a241200, 0x0c241000,
+
+	0x000e240e, 0x0010240c, 0x0013230a, 0x00142309,
+	0x00162208, 0x01182106, 0x011a2005, 0x021b1f04,
+	0x031d1d03, 0x041e1c02, 0x05201a01, 0x06211801,
+	0x07221601, 0x09231400, 0x0a231300, 0x0c231100,
+
+	0x000f220f, 0x0011220d, 0x0013220b, 0x0015210a,
+	0x01162108, 0x01182007, 0x02191f06, 0x031a1e05,
+	0x041c1c04, 0x051d1b03, 0x061f1902, 0x07201801,
+	0x08211601, 0x0a211500, 0x0b221300, 0x0d221100,
+
+	0x0010210f, 0x0011210e, 0x0013210c, 0x0114200b,
+	0x01161f0a, 0x02171f08, 0x03181e07, 0x031a1d06,
+	0x041c1c04, 0x051d1a04, 0x071d1903, 0x081e1802,
+	0x091f1602, 0x0b1f1501, 0x0c211300, 0x0e201200,
+
+	0x00102010, 0x0012200e, 0x0013200d, 0x01151f0b,
+	0x01161f0a, 0x02171e09, 0x03191d07, 0x041a1c06,
+	0x051b1b05, 0x061c1a04, 0x071d1903, 0x081e1703,
+	0x0a1f1601, 0x0b1f1501, 0x0d201300, 0x0e201200,
+
+	0x00102010, 0x00121f0f, 0x00141f0d, 0x01141f0c,
+	0x02161e0a, 0x03171d09, 0x03181d08, 0x041a1c06,
+	0x051b1b05, 0x061c1a04, 0x081c1903, 0x091d1703,
+	0x0a1e1602, 0x0c1e1501, 0x0d1f1400, 0x0e1f1201,
+
+	0x00111e11, 0x00131e0f, 0x01131e0e, 0x02151d0c,
+	0x02161d0b, 0x03171c0a, 0x04181b09, 0x05191b07,
+	0x061a1a06, 0x071b1905, 0x091b1804, 0x0a1c1703,
+	0x0b1d1602, 0x0c1d1502, 0x0e1d1401, 0x0f1e1300,
+
+	0x00111e11, 0x00131d10, 0x01141d0e, 0x02151c0d,
+	0x03161c0b, 0x04171b0a, 0x05171b09, 0x06181a08,
+	0x07191907, 0x081a1806, 0x091a1805, 0x0a1b1704,
+	0x0b1c1603, 0x0d1c1502, 0x0e1d1401, 0x0f1d1301,
+};
+
+static int sun8i_ui_scaler_coef_index(unsigned int step)
+{
+	unsigned int scale, int_part, float_part;
+
+	scale = step >> (SUN8I_UI_SCALER_SCALE_FRAC - 3);
+	int_part = scale >> 3;
+	float_part = scale & 0x7;
+
+	switch (int_part) {
+	case 0:
+		return 0;
+	case 1:
+		return float_part;
+	case 2:
+		return 8 + (float_part >> 1);
+	case 3:
+		return 12;
+	case 4:
+		return 13;
+	default:
+		return 14;
+	}
+}
+
+void sun8i_ui_scaler_enable(struct sun8i_mixer *mixer, int layer, bool enable)
+{
+	int vi_cnt = mixer->cfg->vi_num;
+	u32 val;
+
+	if (WARN_ON(layer < vi_cnt))
+		return;
+
+	if (enable)
+		val = SUN8I_SCALER_GSU_CTRL_EN |
+		      SUN8I_SCALER_GSU_CTRL_COEFF_RDY;
+	else
+		val = 0;
+
+	regmap_write(mixer->engine.regs,
+		     SUN8I_SCALER_GSU_CTRL(vi_cnt, layer - vi_cnt), val);
+}
+
+void sun8i_ui_scaler_setup(struct sun8i_mixer *mixer, int layer,
+			   u32 src_w, u32 src_h, u32 dst_w, u32 dst_h,
+			   u32 hscale, u32 vscale, u32 hphase, u32 vphase)
+{
+	int vi_cnt = mixer->cfg->vi_num;
+	u32 insize, outsize;
+	int i, offset;
+
+	if (WARN_ON(layer < vi_cnt))
+		return;
+
+	hphase <<= SUN8I_UI_SCALER_PHASE_FRAC - 16;
+	vphase <<= SUN8I_UI_SCALER_PHASE_FRAC - 16;
+	hscale <<= SUN8I_UI_SCALER_SCALE_FRAC - 16;
+	vscale <<= SUN8I_UI_SCALER_SCALE_FRAC - 16;
+
+	insize = SUN8I_UI_SCALER_SIZE(src_w, src_h);
+	outsize = SUN8I_UI_SCALER_SIZE(dst_w, dst_h);
+
+	layer -= vi_cnt;
+
+	regmap_write(mixer->engine.regs,
+		     SUN8I_SCALER_GSU_OUTSIZE(vi_cnt, layer), outsize);
+	regmap_write(mixer->engine.regs,
+		     SUN8I_SCALER_GSU_INSIZE(vi_cnt, layer), insize);
+	regmap_write(mixer->engine.regs,
+		     SUN8I_SCALER_GSU_HSTEP(vi_cnt, layer), hscale);
+	regmap_write(mixer->engine.regs,
+		     SUN8I_SCALER_GSU_VSTEP(vi_cnt, layer), vscale);
+	regmap_write(mixer->engine.regs,
+		     SUN8I_SCALER_GSU_HPHASE(vi_cnt, layer), hphase);
+	regmap_write(mixer->engine.regs,
+		     SUN8I_SCALER_GSU_VPHASE(vi_cnt, layer), vphase);
+	offset = sun8i_ui_scaler_coef_index(hscale) *
+			SUN8I_UI_SCALER_COEFF_COUNT;
+	for (i = 0; i < SUN8I_UI_SCALER_COEFF_COUNT; i++)
+		regmap_write(mixer->engine.regs,
+			     SUN8I_SCALER_GSU_HCOEFF(vi_cnt, layer, i),
+			     lan2coefftab16[offset + i]);
+}

drivers/gpu/drm/sun4i/sun8i_ui_scaler.h

+/*
+ * Copyright (C) 2017 Jernej Skrabec <jernej.skrabec@siol.net>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2.  This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#ifndef _SUN8I_UI_SCALER_H_
+#define _SUN8I_UI_SCALER_H_
+
+#include "sun8i_mixer.h"
+
+/* this two macros assumes 16 fractional bits which is standard in DRM */
+#define SUN8I_UI_SCALER_SCALE_MIN		1
+#define SUN8I_UI_SCALER_SCALE_MAX		((1UL << 20) - 1)
+
+#define SUN8I_UI_SCALER_SCALE_FRAC		20
+#define SUN8I_UI_SCALER_PHASE_FRAC		20
+#define SUN8I_UI_SCALER_COEFF_COUNT		16
+#define SUN8I_UI_SCALER_SIZE(w, h)		(((h) - 1) << 16 | ((w) - 1))
+
+#define SUN8I_SCALER_GSU_CTRL(vi_cnt, ui_idx) \
+	(0x20000 + 0x20000 * (vi_cnt) + 0x10000 * (ui_idx) + 0x0)
+#define SUN8I_SCALER_GSU_OUTSIZE(vi_cnt, ui_idx) \
+	(0x20000 + 0x20000 * (vi_cnt) + 0x10000 * (ui_idx) + 0x40)
+#define SUN8I_SCALER_GSU_INSIZE(vi_cnt, ui_idx) \
+	(0x20000 + 0x20000 * (vi_cnt) + 0x10000 * (ui_idx) + 0x80)
+#define SUN8I_SCALER_GSU_HSTEP(vi_cnt, ui_idx) \
+	(0x20000 + 0x20000 * (vi_cnt) + 0x10000 * (ui_idx) + 0x88)
+#define SUN8I_SCALER_GSU_VSTEP(vi_cnt, ui_idx) \
+	(0x20000 + 0x20000 * (vi_cnt) + 0x10000 * (ui_idx) + 0x8c)
+#define SUN8I_SCALER_GSU_HPHASE(vi_cnt, ui_idx) \
+	(0x20000 + 0x20000 * (vi_cnt) + 0x10000 * (ui_idx) + 0x90)
+#define SUN8I_SCALER_GSU_VPHASE(vi_cnt, ui_idx) \
+	(0x20000 + 0x20000 * (vi_cnt) + 0x10000 * (ui_idx) + 0x98)
+#define SUN8I_SCALER_GSU_HCOEFF(vi_cnt, ui_idx, index) \
+	(0x20000 + 0x20000 * (vi_cnt) + 0x10000 * (ui_idx) + 0x200 + \
+	0x4 * (index))
+
+#define SUN8I_SCALER_GSU_CTRL_EN		BIT(0)
+#define SUN8I_SCALER_GSU_CTRL_COEFF_RDY		BIT(4)
+
+void sun8i_ui_scaler_enable(struct sun8i_mixer *mixer, int layer, bool enable);
+void sun8i_ui_scaler_setup(struct sun8i_mixer *mixer, int layer,
+			   u32 src_w, u32 src_h, u32 dst_w, u32 dst_h,
+			   u32 hscale, u32 vscale, u32 hphase, u32 vphase);
+
+#endif

drivers/gpu/drm/sun4i/sun8i_vi_layer.c

@@ -18,6 +18,7 @@
 
 #include "sun8i_vi_layer.h"
 #include "sun8i_mixer.h"
+#include "sun8i_vi_scaler.h"
 
 static void sun8i_vi_layer_enable(struct sun8i_mixer *mixer, int channel,
 				  int overlay, bool enable)
@@ -50,36 +51,61 @@ static int sun8i_vi_layer_update_coord(struct sun8i_mixer *mixer, int channel,
 				       int overlay, struct drm_plane *plane)
 {
 	struct drm_plane_state *state = plane->state;
-	u32 width, height, size;
+	u32 src_w, src_h, dst_w, dst_h;
+	u32 outsize, insize;
+	u32 hphase, vphase;
 
 	DRM_DEBUG_DRIVER("Updating VI channel %d overlay %d\n",
 			 channel, overlay);
-	/*
-	 * Same source and destination width and height are guaranteed
-	 * by atomic check function.
-	 */
-	width = drm_rect_width(&state->dst);
-	height = drm_rect_height(&state->dst);
-	size = SUN8I_MIXER_SIZE(width, height);
+
+	src_w = drm_rect_width(&state->src) >> 16;
+	src_h = drm_rect_height(&state->src) >> 16;
+	dst_w = drm_rect_width(&state->dst);
+	dst_h = drm_rect_height(&state->dst);
+
+	hphase = state->src.x1 & 0xffff;
+	vphase = state->src.y1 & 0xffff;
+
+	insize = SUN8I_MIXER_SIZE(src_w, src_h);
+	outsize = SUN8I_MIXER_SIZE(dst_w, dst_h);
 
 	/* Set height and width */
-	DRM_DEBUG_DRIVER("Layer size W: %u H: %u\n", width, height);
+	DRM_DEBUG_DRIVER("Layer source offset X: %d Y: %d\n",
+			 state->src.x1 >> 16, state->src.y1 >> 16);
+	DRM_DEBUG_DRIVER("Layer source size W: %d H: %d\n", src_w, src_h);
 	regmap_write(mixer->engine.regs,
 		     SUN8I_MIXER_CHAN_VI_LAYER_SIZE(channel, overlay),
-		     size);
+		     insize);
 	regmap_write(mixer->engine.regs,
 		     SUN8I_MIXER_CHAN_VI_OVL_SIZE(channel),
-		     size);
+		     insize);
+
+	if (insize != outsize || hphase || vphase) {
+		u32 hscale, vscale;
+
+		DRM_DEBUG_DRIVER("HW scaling is enabled\n");
+
+		hscale = state->src_w / state->crtc_w;
+		vscale = state->src_h / state->crtc_h;
+
+		sun8i_vi_scaler_setup(mixer, channel, src_w, src_h, dst_w,
+				      dst_h, hscale, vscale, hphase, vphase);
+		sun8i_vi_scaler_enable(mixer, channel, true);
+	} else {
+		DRM_DEBUG_DRIVER("HW scaling is not needed\n");
+		sun8i_vi_scaler_enable(mixer, channel, false);
+	}
 
 	/* Set base coordinates */
-	DRM_DEBUG_DRIVER("Layer coordinates X: %d Y: %d\n",
+	DRM_DEBUG_DRIVER("Layer destination coordinates X: %d Y: %d\n",
 			 state->dst.x1, state->dst.y1);
+	DRM_DEBUG_DRIVER("Layer destination size W: %d H: %d\n", dst_w, dst_h);
 	regmap_write(mixer->engine.regs,
 		     SUN8I_MIXER_BLEND_ATTR_COORD(channel),
 		     SUN8I_MIXER_COORD(state->dst.x1, state->dst.y1));
 	regmap_write(mixer->engine.regs,
 		     SUN8I_MIXER_BLEND_ATTR_INSIZE(channel),
-		     size);
+		     outsize);
 
 	return 0;
 }
@@ -147,8 +173,10 @@ static int sun8i_vi_layer_update_buffer(struct sun8i_mixer *mixer, int channel,
 static int sun8i_vi_layer_atomic_check(struct drm_plane *plane,
 				       struct drm_plane_state *state)
 {
+	struct sun8i_vi_layer *layer = plane_to_sun8i_vi_layer(plane);
 	struct drm_crtc *crtc = state->crtc;
 	struct drm_crtc_state *crtc_state;
+	int min_scale, max_scale;
 	struct drm_rect clip;
 
 	if (!crtc)
@@ -163,9 +191,13 @@ static int sun8i_vi_layer_atomic_check(struct drm_plane *plane,
 	clip.x2 = crtc_state->adjusted_mode.hdisplay;
 	clip.y2 = crtc_state->adjusted_mode.vdisplay;
 
+	if (layer->mixer->cfg->scaler_mask & BIT(layer->channel)) {
+		min_scale = SUN8I_VI_SCALER_SCALE_MIN;
+		max_scale = SUN8I_VI_SCALER_SCALE_MAX;
+	}
+
 	return drm_atomic_helper_check_plane_state(state, crtc_state, &clip,
-						   DRM_PLANE_HELPER_NO_SCALING,
-						   DRM_PLANE_HELPER_NO_SCALING,
+						   min_scale, max_scale,
 						   true, true);
 }
 

drivers/gpu/drm/sun4i/sun8i_vi_scaler.h

+/*
+ * Copyright (C) 2017 Jernej Skrabec <jernej.skrabec@siol.net>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2.  This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#ifndef _SUN8I_VI_SCALER_H_
+#define _SUN8I_VI_SCALER_H_
+
+#include "sun8i_mixer.h"
+
+/* this two macros assumes 16 fractional bits which is standard in DRM */
+#define SUN8I_VI_SCALER_SCALE_MIN		1
+#define SUN8I_VI_SCALER_SCALE_MAX		((1UL << 20) - 1)
+
+#define SUN8I_VI_SCALER_SCALE_FRAC		20
+#define SUN8I_VI_SCALER_PHASE_FRAC		20
+#define SUN8I_VI_SCALER_COEFF_COUNT		32
+#define SUN8I_VI_SCALER_SIZE(w, h)		(((h) - 1) << 16 | ((w) - 1))
+
+#define SUN8I_SCALER_VSU_CTRL(ch)	(0x20000 + 0x20000 * (ch) + 0x0)
+#define SUN8I_SCALER_VSU_OUTSIZE(ch)	(0x20000 + 0x20000 * (ch) + 0x40)
+#define SUN8I_SCALER_VSU_YINSIZE(ch)	(0x20000 + 0x20000 * (ch) + 0x80)
+#define SUN8I_SCALER_VSU_YHSTEP(ch)	(0x20000 + 0x20000 * (ch) + 0x88)
+#define SUN8I_SCALER_VSU_YVSTEP(ch)	(0x20000 + 0x20000 * (ch) + 0x8c)
+#define SUN8I_SCALER_VSU_YHPHASE(ch)	(0x20000 + 0x20000 * (ch) + 0x90)
+#define SUN8I_SCALER_VSU_YVPHASE(ch)	(0x20000 + 0x20000 * (ch) + 0x98)
+#define SUN8I_SCALER_VSU_CINSIZE(ch)	(0x20000 + 0x20000 * (ch) + 0xc0)
+#define SUN8I_SCALER_VSU_CHSTEP(ch)	(0x20000 + 0x20000 * (ch) + 0xc8)
+#define SUN8I_SCALER_VSU_CVSTEP(ch)	(0x20000 + 0x20000 * (ch) + 0xcc)
+#define SUN8I_SCALER_VSU_CHPHASE(ch)	(0x20000 + 0x20000 * (ch) + 0xd0)
+#define SUN8I_SCALER_VSU_CVPHASE(ch)	(0x20000 + 0x20000 * (ch) + 0xd8)
+#define SUN8I_SCALER_VSU_YHCOEFF0(ch, i) \
+	(0x20000 + 0x20000 * (ch) + 0x200 + 0x4 * (i))
+#define SUN8I_SCALER_VSU_YHCOEFF1(ch, i) \
+	(0x20000 + 0x20000 * (ch) + 0x300 + 0x4 * (i))
+#define SUN8I_SCALER_VSU_YVCOEFF(ch, i) \
+	(0x20000 + 0x20000 * (ch) + 0x400 + 0x4 * (i))
+#define SUN8I_SCALER_VSU_CHCOEFF0(ch, i) \
+	(0x20000 + 0x20000 * (ch) + 0x600 + 0x4 * (i))
+#define SUN8I_SCALER_VSU_CHCOEFF1(ch, i) \
+	(0x20000 + 0x20000 * (ch) + 0x700 + 0x4 * (i))
+#define SUN8I_SCALER_VSU_CVCOEFF(ch, i) \
+	(0x20000 + 0x20000 * (ch) + 0x800 + 0x4 * (i))
+
+#define SUN8I_SCALER_VSU_CTRL_EN		BIT(0)
+#define SUN8I_SCALER_VSU_CTRL_COEFF_RDY		BIT(4)
+
+void sun8i_vi_scaler_enable(struct sun8i_mixer *mixer, int layer, bool enable);
+void sun8i_vi_scaler_setup(struct sun8i_mixer *mixer, int layer,
+			   u32 src_w, u32 src_h, u32 dst_w, u32 dst_h,
+			   u32 hscale, u32 vscale, u32 hphase, u32 vphase);
+
+#endif