drm/vc4: Add CTM support

The hardware has a single block for applying a CTM prior to gamma lut.
It can be fed with pixels from one of our CRTC at a time and uses a
matrix with S0.9 scalars. Use private atomic state to reject attempts
from userland to apply CTM for more than one CRTC at a time and reject
matrices with scalars that we can't approximate without integer bits.

Signed-off-by: Stefan Schake <stschake@gmail.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/218067/

4 files changed, 215 insertions, 1 deletions

diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
index 08fe8dd7d8df..83d3b7912fc2 100644
--- a/drivers/gpu/drm/vc4/vc4_crtc.c
+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
@@ -1018,6 +1018,11 @@ static int vc4_crtc_bind(struct device *dev, struct device *master, void *data)
 	drm_mode_crtc_set_gamma_size(crtc, ARRAY_SIZE(vc4_crtc->lut_r));
 	drm_crtc_enable_color_mgmt(crtc, 0, false, crtc->gamma_size);
 
+	/* We support CTM, but only for one CRTC at a time. It's therefore
+	 * implemented as private driver state in vc4_kms, not here.
+	 */
+	drm_crtc_enable_color_mgmt(crtc, 0, true, crtc->gamma_size);
+
 	/* Set up some arbitrary number of planes.  We're not limited
 	 * by a set number of physical registers, just the space in
 	 * the HVS (16k) and how small an plane can be (28 bytes).
diff --git a/drivers/gpu/drm/vc4/vc4_drv.c b/drivers/gpu/drm/vc4/vc4_drv.c
index af9515ae0e0a..40ddeaafd65f 100644
--- a/drivers/gpu/drm/vc4/vc4_drv.c
+++ b/drivers/gpu/drm/vc4/vc4_drv.c
@@ -319,6 +319,7 @@ dev_unref:
 static void vc4_drm_unbind(struct device *dev)
 {
 	struct drm_device *drm = dev_get_drvdata(dev);
+	struct vc4_dev *vc4 = to_vc4_dev(drm);
 
 	drm_dev_unregister(drm);
 
@@ -326,6 +327,8 @@ static void vc4_drm_unbind(struct device *dev)
 
 	drm_mode_config_cleanup(drm);
 
+	drm_atomic_private_obj_fini(&vc4->ctm_manager);
+
 	drm_dev_unref(drm);
 }
 
diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
index 4288615b66a2..22589d39083c 100644
--- a/drivers/gpu/drm/vc4/vc4_drv.h
+++ b/drivers/gpu/drm/vc4/vc4_drv.h
@@ -10,6 +10,7 @@
 #include <drm/drmP.h>
 #include <drm/drm_encoder.h>
 #include <drm/drm_gem_cma_helper.h>
+#include <drm/drm_atomic.h>
 
 #include "uapi/drm/vc4_drm.h"
 
@@ -193,6 +194,9 @@ struct vc4_dev {
 	} hangcheck;
 
 	struct semaphore async_modeset;
+
+	struct drm_modeset_lock ctm_state_lock;
+	struct drm_private_obj ctm_manager;
 };
 
 static inline struct vc4_dev *
diff --git a/drivers/gpu/drm/vc4/vc4_kms.c b/drivers/gpu/drm/vc4/vc4_kms.c
index e791e498a3dd..8a411e5f8776 100644
--- a/drivers/gpu/drm/vc4/vc4_kms.c
+++ b/drivers/gpu/drm/vc4/vc4_kms.c
@@ -23,6 +23,117 @@
 #include <drm/drm_fb_cma_helper.h>
 #include <drm/drm_gem_framebuffer_helper.h>
 #include "vc4_drv.h"
+#include "vc4_regs.h"
+
+struct vc4_ctm_state {
+	struct drm_private_state base;
+	struct drm_color_ctm *ctm;
+	int fifo;
+};
+
+static struct vc4_ctm_state *to_vc4_ctm_state(struct drm_private_state *priv)
+{
+	return container_of(priv, struct vc4_ctm_state, base);
+}
+
+static struct vc4_ctm_state *vc4_get_ctm_state(struct drm_atomic_state *state,
+					       struct drm_private_obj *manager)
+{
+	struct drm_device *dev = state->dev;
+	struct vc4_dev *vc4 = dev->dev_private;
+	struct drm_private_state *priv_state;
+	int ret;
+
+	ret = drm_modeset_lock(&vc4->ctm_state_lock, state->acquire_ctx);
+	if (ret)
+		return ERR_PTR(ret);
+
+	priv_state = drm_atomic_get_private_obj_state(state, manager);
+	if (IS_ERR(priv_state))
+		return ERR_CAST(priv_state);
+
+	return to_vc4_ctm_state(priv_state);
+}
+
+static struct drm_private_state *
+vc4_ctm_duplicate_state(struct drm_private_obj *obj)
+{
+	struct vc4_ctm_state *state;
+
+	state = kmemdup(obj->state, sizeof(*state), GFP_KERNEL);
+	if (!state)
+		return NULL;
+
+	__drm_atomic_helper_private_obj_duplicate_state(obj, &state->base);
+
+	return &state->base;
+}
+
+static void vc4_ctm_destroy_state(struct drm_private_obj *obj,
+				  struct drm_private_state *state)
+{
+	struct vc4_ctm_state *ctm_state = to_vc4_ctm_state(state);
+
+	kfree(ctm_state);
+}
+
+static const struct drm_private_state_funcs vc4_ctm_state_funcs = {
+	.atomic_duplicate_state = vc4_ctm_duplicate_state,
+	.atomic_destroy_state = vc4_ctm_destroy_state,
+};
+
+/* Converts a DRM S31.32 value to the HW S0.9 format. */
+static u16 vc4_ctm_s31_32_to_s0_9(u64 in)
+{
+	u16 r;
+
+	/* Sign bit. */
+	r = in & BIT_ULL(63) ? BIT(9) : 0;
+
+	if ((in & GENMASK_ULL(62, 32)) > 0) {
+		/* We have zero integer bits so we can only saturate here. */
+		r |= GENMASK(8, 0);
+	} else {
+		/* Otherwise take the 9 most important fractional bits. */
+		r |= (in >> 23) & GENMASK(8, 0);
+	}
+
+	return r;
+}
+
+static void
+vc4_ctm_commit(struct vc4_dev *vc4, struct drm_atomic_state *state)
+{
+	struct vc4_ctm_state *ctm_state = to_vc4_ctm_state(vc4->ctm_manager.state);
+	struct drm_color_ctm *ctm = ctm_state->ctm;
+
+	if (ctm_state->fifo) {
+		HVS_WRITE(SCALER_OLEDCOEF2,
+			  VC4_SET_FIELD(vc4_ctm_s31_32_to_s0_9(ctm->matrix[0]),
+					SCALER_OLEDCOEF2_R_TO_R) |
+			  VC4_SET_FIELD(vc4_ctm_s31_32_to_s0_9(ctm->matrix[3]),
+					SCALER_OLEDCOEF2_R_TO_G) |
+			  VC4_SET_FIELD(vc4_ctm_s31_32_to_s0_9(ctm->matrix[6]),
+					SCALER_OLEDCOEF2_R_TO_B));
+		HVS_WRITE(SCALER_OLEDCOEF1,
+			  VC4_SET_FIELD(vc4_ctm_s31_32_to_s0_9(ctm->matrix[1]),
+					SCALER_OLEDCOEF1_G_TO_R) |
+			  VC4_SET_FIELD(vc4_ctm_s31_32_to_s0_9(ctm->matrix[4]),
+					SCALER_OLEDCOEF1_G_TO_G) |
+			  VC4_SET_FIELD(vc4_ctm_s31_32_to_s0_9(ctm->matrix[7]),
+					SCALER_OLEDCOEF1_G_TO_B));
+		HVS_WRITE(SCALER_OLEDCOEF0,
+			  VC4_SET_FIELD(vc4_ctm_s31_32_to_s0_9(ctm->matrix[2]),
+					SCALER_OLEDCOEF0_B_TO_R) |
+			  VC4_SET_FIELD(vc4_ctm_s31_32_to_s0_9(ctm->matrix[5]),
+					SCALER_OLEDCOEF0_B_TO_G) |
+			  VC4_SET_FIELD(vc4_ctm_s31_32_to_s0_9(ctm->matrix[8]),
+					SCALER_OLEDCOEF0_B_TO_B));
+	}
+
+	HVS_WRITE(SCALER_OLEDOFFS,
+		  VC4_SET_FIELD(ctm_state->fifo, SCALER_OLEDOFFS_DISPFIFO));
+}
 
 static void
 vc4_atomic_complete_commit(struct drm_atomic_state *state)
@@ -36,6 +147,8 @@ vc4_atomic_complete_commit(struct drm_atomic_state *state)
 
 	drm_atomic_helper_commit_modeset_disables(dev, state);
 
+	vc4_ctm_commit(vc4, state);
+
 	drm_atomic_helper_commit_planes(dev, state, 0);
 
 	drm_atomic_helper_commit_modeset_enables(dev, state);
@@ -207,9 +320,89 @@ static struct drm_framebuffer *vc4_fb_create(struct drm_device *dev,
 	return drm_gem_fb_create(dev, file_priv, mode_cmd);
 }
 
+/* Our CTM has some peculiar limitations: we can only enable it for one CRTC
+ * at a time and the HW only supports S0.9 scalars. To account for the latter,
+ * we don't allow userland to set a CTM that we have no hope of approximating.
+ */
+static int
+vc4_ctm_atomic_check(struct drm_device *dev, struct drm_atomic_state *state)
+{
+	struct vc4_dev *vc4 = to_vc4_dev(dev);
+	struct vc4_ctm_state *ctm_state = NULL;
+	struct drm_crtc *crtc;
+	struct drm_crtc_state *old_crtc_state, *new_crtc_state;
+	struct drm_color_ctm *ctm;
+	int i;
+
+	for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
+		/* CTM is being disabled. */
+		if (!new_crtc_state->ctm && old_crtc_state->ctm) {
+			ctm_state = vc4_get_ctm_state(state, &vc4->ctm_manager);
+			if (IS_ERR(ctm_state))
+				return PTR_ERR(ctm_state);
+			ctm_state->fifo = 0;
+		}
+	}
+
+	for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
+		if (new_crtc_state->ctm == old_crtc_state->ctm)
+			continue;
+
+		if (!ctm_state) {
+			ctm_state = vc4_get_ctm_state(state, &vc4->ctm_manager);
+			if (IS_ERR(ctm_state))
+				return PTR_ERR(ctm_state);
+		}
+
+		/* CTM is being enabled or the matrix changed. */
+		if (new_crtc_state->ctm) {
+			/* fifo is 1-based since 0 disables CTM. */
+			int fifo = to_vc4_crtc(crtc)->channel + 1;
+
+			/* Check userland isn't trying to turn on CTM for more
+			 * than one CRTC at a time.
+			 */
+			if (ctm_state->fifo && ctm_state->fifo != fifo) {
+				DRM_DEBUG_DRIVER("Too many CTM configured\n");
+				return -EINVAL;
+			}
+
+			/* Check we can approximate the specified CTM.
+			 * We disallow scalars |c| > 1.0 since the HW has
+			 * no integer bits.
+			 */
+			ctm = new_crtc_state->ctm->data;
+			for (i = 0; i < ARRAY_SIZE(ctm->matrix); i++) {
+				u64 val = ctm->matrix[i];
+
+				val &= ~BIT_ULL(63);
+				if (val > BIT_ULL(32))
+					return -EINVAL;
+			}
+
+			ctm_state->fifo = fifo;
+			ctm_state->ctm = ctm;
+		}
+	}
+
+	return 0;
+}
+
+static int
+vc4_atomic_check(struct drm_device *dev, struct drm_atomic_state *state)
+{
+	int ret;
+
+	ret = vc4_ctm_atomic_check(dev, state);
+	if (ret < 0)
+		return ret;
+
+	return drm_atomic_helper_check(dev, state);
+}
+
 static const struct drm_mode_config_funcs vc4_mode_funcs = {
 	.output_poll_changed = drm_fb_helper_output_poll_changed,
-	.atomic_check = drm_atomic_helper_check,
+	.atomic_check = vc4_atomic_check,
 	.atomic_commit = vc4_atomic_commit,
 	.fb_create = vc4_fb_create,
 };
@@ -217,6 +410,7 @@ static const struct drm_mode_config_funcs vc4_mode_funcs = {
 int vc4_kms_load(struct drm_device *dev)
 {
 	struct vc4_dev *vc4 = to_vc4_dev(dev);
+	struct vc4_ctm_state *ctm_state;
 	int ret;
 
 	sema_init(&vc4->async_modeset, 1);
@@ -237,6 +431,14 @@ int vc4_kms_load(struct drm_device *dev)
 	dev->mode_config.async_page_flip = true;
 	dev->mode_config.allow_fb_modifiers = true;
 
+	drm_modeset_lock_init(&vc4->ctm_state_lock);
+
+	ctm_state = kzalloc(sizeof(*ctm_state), GFP_KERNEL);
+	if (!ctm_state)
+		return -ENOMEM;
+	drm_atomic_private_obj_init(&vc4->ctm_manager, &ctm_state->base,
+				    &vc4_ctm_state_funcs);
+
 	drm_mode_config_reset(dev);
 
 	if (dev->mode_config.num_connector)