Support a 1D gamma LUT with interpolation for each color channel on the
VKMS driver. Add a check for the LUT length by creating
vkms_atomic_check().
Tested with:
igt@kms_color@gamma
igt@kms_color@legacy-gamma
igt@kms_color@invalid-gamma-lut-sizes
v2:
- Add interpolation between the values of the LUT (Simon Ser)
v3:
- s/ratio/delta (Pekka)
- s/color_channel/channel_value (Pekka)
- s/lut_area/lut_channel
- Store the `drm_color_lut`, `lut_length`, and
`channel_value2index_ratio` inside a struct called `vkms_lut`
(Pekka)
- Pre-compute some constants values used through the LUT procedure
(Pekka)
- Change the switch statement to a cast to __u16* (Pekka)
- Make the apply_lut_to_channel_value return the computation result
(Pekka)
v4:
- Add a comment explaining that `enum lut_area` depends on the
layout of `struct drm_color_lut` (Pekka)
- Remove unused variable (kernel test robot)
Signed-off-by: Arthur Grillo <arthurgrillo@xxxxxxxxxx>
Acked-by: Pekka Paalanen <pekka.paalanen@xxxxxxxxxxxxx>
---
drivers/gpu/drm/vkms/vkms_composer.c | 86 ++++++++++++++++++++++++++++
drivers/gpu/drm/vkms/vkms_crtc.c | 3 +
drivers/gpu/drm/vkms/vkms_drv.c | 20 ++++++-
drivers/gpu/drm/vkms/vkms_drv.h | 9 +++
4 files changed, 117 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
index 906d3df40cdb..620c0bafbe56 100644
--- a/drivers/gpu/drm/vkms/vkms_composer.c
+++ b/drivers/gpu/drm/vkms/vkms_composer.c
@@ -6,6 +6,7 @@
#include <drm/drm_atomic_helper.h>
#include <drm/drm_blend.h>
#include <drm/drm_fourcc.h>
+#include <drm/drm_fixed.h>
#include <drm/drm_gem_framebuffer_helper.h>
#include <drm/drm_vblank.h>
#include <linux/minmax.h>
@@ -89,6 +90,73 @@ static void fill_background(const struct pixel_argb_u16 *background_color,
output_buffer->pixels[i] = *background_color;
}
+// lerp(a, b, t) = a + (b - a) * t
+static u16 lerp_u16(u16 a, u16 b, s64 t)
+{
+ s64 a_fp = drm_int2fixp(a);
+ s64 b_fp = drm_int2fixp(b);
+
+ s64 delta = drm_fixp_mul(b_fp - a_fp, t);
+
+ return drm_fixp2int(a_fp + delta);
+}
+
+static s64 get_lut_index(const struct vkms_color_lut *lut, u16 channel_value)
+{
+ s64 color_channel_fp = drm_int2fixp(channel_value);
+
+ return drm_fixp_mul(color_channel_fp, lut->channel_value2index_ratio);
+}
+
+/*
+ * This enum is related to the positions of the variables inside
+ * `struct drm_color_lut`, so the order of both needs to be the same.
+ */
+enum lut_channel {
+ LUT_RED = 0,
+ LUT_GREEN,
+ LUT_BLUE,
+ LUT_RESERVED
+};
+
+static u16 apply_lut_to_channel_value(const struct vkms_color_lut *lut, u16 channel_value,
+ enum lut_channel channel)
+{
+ s64 lut_index = get_lut_index(lut, channel_value);
+
+ /*
+ * This checks if `struct drm_color_lut` had any gap added by the compiler
+ * between the struct fields.
+ */
+ static_assert(sizeof(struct drm_color_lut) == sizeof(__u16) * 4);
+
+ u16 *floor_lut_value = (__u16 *)&lut->base[drm_fixp2int(lut_index)];
+ u16 *ceil_lut_value = (__u16 *)&lut->base[drm_fixp2int_ceil(lut_index)];
+
+ u16 floor_channel_value = floor_lut_value[channel];
+ u16 ceil_channel_value = ceil_lut_value[channel];
+
+ return lerp_u16(floor_channel_value, ceil_channel_value,
+ lut_index & DRM_FIXED_DECIMAL_MASK);
+}
+
+static void apply_lut(const struct vkms_crtc_state *crtc_state, struct line_buffer *output_buffer)
+{
+ if (!crtc_state->gamma_lut.base)
+ return;
+
+ if (!crtc_state->gamma_lut.lut_length)
+ return;
+
+ for (size_t x = 0; x < output_buffer->n_pixels; x++) {
+ struct pixel_argb_u16 *pixel = &output_buffer->pixels[x];
+
+ pixel->r = apply_lut_to_channel_value(&crtc_state->gamma_lut, pixel->r, LUT_RED);
+ pixel->g = apply_lut_to_channel_value(&crtc_state->gamma_lut, pixel->g, LUT_GREEN);
+ pixel->b = apply_lut_to_channel_value(&crtc_state->gamma_lut, pixel->b, LUT_BLUE);
+ }
+}
+
/**
* @wb_frame_info: The writeback frame buffer metadata
* @crtc_state: The crtc state
@@ -128,6 +196,8 @@ static void blend(struct vkms_writeback_job *wb,
output_buffer);
}
+ apply_lut(crtc_state, output_buffer);
+
*crc32 = crc32_le(*crc32, (void *)output_buffer->pixels, row_size);
if (wb)
@@ -242,6 +312,22 @@ void vkms_composer_worker(struct work_struct *work)
crtc_state->frame_start = 0;
crtc_state->frame_end = 0;
crtc_state->crc_pending = false;
+
+ if (crtc->state->gamma_lut) {
+ s64 max_lut_index_fp;
+ s64 u16_max_fp = drm_int2fixp(0xffff);
+
+ crtc_state->gamma_lut.base = (struct drm_color_lut *)crtc->state->gamma_lut->data;
+ crtc_state->gamma_lut.lut_length =
+ crtc->state->gamma_lut->length / sizeof(struct drm_color_lut);
+ max_lut_index_fp = drm_int2fixp(crtc_state->gamma_lut.lut_length - 1);
+ crtc_state->gamma_lut.channel_value2index_ratio = drm_fixp_div(max_lut_index_fp,
+ u16_max_fp);
+
+ } else {
+ crtc_state->gamma_lut.base = NULL;
+ }
+
spin_unlock_irq(&out->composer_lock);
/*
diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c
index 515f6772b866..61e500b8c9da 100644
--- a/drivers/gpu/drm/vkms/vkms_crtc.c
+++ b/drivers/gpu/drm/vkms/vkms_crtc.c
@@ -290,6 +290,9 @@ int vkms_crtc_init(struct drm_device *dev, struct drm_crtc *crtc,
drm_crtc_helper_add(crtc, &vkms_crtc_helper_funcs);
+ drm_mode_crtc_set_gamma_size(crtc, VKMS_LUT_SIZE);
+ drm_crtc_enable_color_mgmt(crtc, 0, false, VKMS_LUT_SIZE);
+
spin_lock_init(&vkms_out->lock);
spin_lock_init(&vkms_out->composer_lock);
diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
index e3c9c9571c8d..dd0af086e7fa 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.c
+++ b/drivers/gpu/drm/vkms/vkms_drv.c
@@ -120,9 +120,27 @@ static const struct drm_driver vkms_driver = {
.minor = DRIVER_MINOR,
};
+static int vkms_atomic_check(struct drm_device *dev, struct drm_atomic_state *state)
+{
+ struct drm_crtc *crtc;
+ struct drm_crtc_state *new_crtc_state;
+ int i;
+
+ for_each_new_crtc_in_state(state, crtc, new_crtc_state, i) {
+ if (!new_crtc_state->gamma_lut || !new_crtc_state->color_mgmt_changed)
+ continue;
+
+ if (new_crtc_state->gamma_lut->length / sizeof(struct drm_color_lut *)
+ > VKMS_LUT_SIZE)
+ return -EINVAL;
+ }
+
+ return drm_atomic_helper_check(dev, state);
+}
+
static const struct drm_mode_config_funcs vkms_mode_funcs = {
.fb_create = drm_gem_fb_create,
- .atomic_check = drm_atomic_helper_check,
+ .atomic_check = vkms_atomic_check,
.atomic_commit = drm_atomic_helper_commit,
};
diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
index 5f1a0a44a78c..f16b5d7b81ef 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.h
+++ b/drivers/gpu/drm/vkms/vkms_drv.h
@@ -23,6 +23,8 @@
#define NUM_OVERLAY_PLANES 8
+#define VKMS_LUT_SIZE 256
+
struct vkms_frame_info {
struct drm_framebuffer *fb;
struct drm_rect src, dst;
@@ -65,6 +67,12 @@ struct vkms_plane {
struct drm_plane base;
};
+struct vkms_color_lut {
+ struct drm_color_lut *base;
+ size_t lut_length;
+ s64 channel_value2index_ratio;
+};
+
/**
* vkms_crtc_state - Driver specific CRTC state
* @base: base CRTC state
@@ -80,6 +88,7 @@ struct vkms_crtc_state {
/* stack of active planes for crc computation, should be in z order */
struct vkms_plane_state **active_planes;
struct vkms_writeback_job *active_writeback;
+ struct vkms_color_lut gamma_lut;
/* below four are protected by vkms_output.composer_lock */
bool crc_pending;
--
2.41.0
