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SubjectRe: [PATCH] drm: mali-dp: Add CTM support
+Daniel to weigh in on the coefficient conversion.

On Wed, Feb 01, 2017 at 12:05:03PM +0000, Mihail Atanassov wrote:
>All DPs have a COLORADJ matrix which is applied prior to output gamma.
>Attach that to the CTM property. Also, ensure the input CTM's coefficients
>can fit in the DP registers' Q3.12 format.
>
>Signed-off-by: Mihail Atanassov <mihail.atanassov@arm.com>
>---
>
>This patch depends on "[PATCH 2/2] drm: mali-dp: enable gamma support", sent
>out earlier (https://lkml.org/lkml/2017/2/1/201).
>
> drivers/gpu/drm/arm/malidp_crtc.c | 59 +++++++++++++++++++++++++++++++++++++--
> drivers/gpu/drm/arm/malidp_drv.c | 35 +++++++++++++++++++++++
> drivers/gpu/drm/arm/malidp_drv.h | 1 +
> drivers/gpu/drm/arm/malidp_regs.h | 2 ++
> 4 files changed, 95 insertions(+), 2 deletions(-)
>
>diff --git a/drivers/gpu/drm/arm/malidp_crtc.c b/drivers/gpu/drm/arm/malidp_crtc.c
>index 10f79b6..2f366e4 100644
>--- a/drivers/gpu/drm/arm/malidp_crtc.c
>+++ b/drivers/gpu/drm/arm/malidp_crtc.c
>@@ -190,6 +190,55 @@ static int malidp_crtc_atomic_check_gamma(struct drm_crtc *crtc,
> return 0;
> }
>
>+/*
>+ * Check if there is a new CTM and if it contains valid input. Valid here means
>+ * that the number is inside the representable range for a Q3.12 number,
>+ * excluding truncating the fractional part of the input data.
>+ *
>+ * The COLORADJ registers can be changed atomically.
>+ */
>+static int malidp_crtc_atomic_check_ctm(struct drm_crtc *crtc,
>+ struct drm_crtc_state *state)
>+{
>+ struct malidp_crtc_state *mc = to_malidp_crtc_state(state);
>+ struct drm_color_ctm *ctm;
>+ int i;
>+
>+ if (!state->color_mgmt_changed)
>+ return 0;
>+
>+ if (!state->ctm)
>+ return 0;
>+
>+ if (crtc->state->ctm && (crtc->state->ctm->base.id ==
>+ state->ctm->base.id))
>+ return 0;
>+
>+ /*
>+ * The size of the ctm is checked in
>+ * drm_atomic_replace_property_blob_from_id.
>+ */
>+ ctm = (struct drm_color_ctm *)state->ctm->data;
>+ for (i = 0; i < ARRAY_SIZE(ctm->matrix); ++i) {
>+ /* Convert from S31.32 to Q3.12. */
>+ s64 val = ctm->matrix[i];
>+ u64 mag = ((((u64)val) & ~BIT_ULL(63)) >> 20) &
>+ GENMASK_ULL(14, 0);

nitpick: You don't need 64 bits for mag.

Daniel was suggesting implementing a helper to change the S31.32 into
something more useful (presumably Q32.32), as probably the
sign+magnitude format isn't really useful to most drivers.

I'm not sure what he had in mind exactly; whether we should convert
the whole matrix up-front into a new copy, or just provide a helper
for drivers to use when reading the matrix.

>+
>+ /* Check the destination's top bit for overflow. */

... and also convert to two's complement.

For the overflow check though I think it would be more obvious to look
at bit 34 in the original S31.32 value (or bit 14 before you mask it).
There's no trickiness around inverting then.
-Brian

>+ if (val & BIT_ULL(63)) {
>+ mag = ~mag + 1;
>+ if (!(mag & BIT_ULL(14)))
>+ return -EINVAL;
>+ } else if (mag & BIT_ULL(14)) {
>+ return -EINVAL;
>+ }
>+ mc->coloradj_coeffs[i] = mag;
>+ }
>+
>+ return 0;
>+}
>+
> static int malidp_crtc_atomic_check(struct drm_crtc *crtc,
> struct drm_crtc_state *state)
> {
>@@ -270,6 +319,10 @@ static int malidp_crtc_atomic_check(struct drm_crtc *crtc,
> if (ret)
> return ret;
>
>+ ret = malidp_crtc_atomic_check_ctm(crtc, state);
>+ if (ret)
>+ return ret;
>+
> return 0;
> }
>
>@@ -289,6 +342,8 @@ static struct drm_crtc_state *malidp_crtc_duplicate_state(struct drm_crtc *crtc)
> __drm_atomic_helper_crtc_duplicate_state(crtc, &state->base);
> memcpy(state->gamma_coeffs, cs->gamma_coeffs,
> sizeof(state->gamma_coeffs));
>+ memcpy(state->coloradj_coeffs, cs->coloradj_coeffs,
>+ sizeof(state->coloradj_coeffs));
>
> return &state->base;
> }
>@@ -359,10 +414,10 @@ int malidp_crtc_init(struct drm_device *drm)
>
> drm_crtc_helper_add(&malidp->crtc, &malidp_crtc_helper_funcs);
> drm_mode_crtc_set_gamma_size(&malidp->crtc, 4096);
>- /* No inverse-gamma and color adjustments yet. */
>+ /* No inverse-gamma: it is per-plane. */
> drm_crtc_enable_color_mgmt(&malidp->crtc,
> 0,
>- false,
>+ true,
> 4096);
> return 0;
>
>diff --git a/drivers/gpu/drm/arm/malidp_drv.c b/drivers/gpu/drm/arm/malidp_drv.c
>index a9f787d..682901a 100644
>--- a/drivers/gpu/drm/arm/malidp_drv.c
>+++ b/drivers/gpu/drm/arm/malidp_drv.c
>@@ -78,6 +78,37 @@ static void malidp_atomic_commit_update_gamma(struct drm_crtc *crtc,
> }
> }
>
>+static
>+void malidp_atomic_commit_update_coloradj(struct drm_crtc *crtc,
>+ struct drm_crtc_state *old_state)
>+{
>+ struct malidp_drm *malidp = crtc_to_malidp_device(crtc);
>+ struct malidp_hw_device *hwdev = malidp->dev;
>+ int i;
>+
>+ if (!crtc->state->color_mgmt_changed)
>+ return;
>+
>+ if (!crtc->state->ctm) {
>+ malidp_hw_clearbits(hwdev, MALIDP_DISP_FUNC_CADJ,
>+ MALIDP_DE_DISPLAY_FUNC);
>+ } else {
>+ struct malidp_crtc_state *mc =
>+ to_malidp_crtc_state(crtc->state);
>+
>+ if (!old_state->ctm || (crtc->state->ctm->base.id !=
>+ old_state->ctm->base.id))
>+ for (i = 0; i < MALIDP_COLORADJ_NUM_COEFFS; ++i)
>+ malidp_hw_write(hwdev,
>+ mc->coloradj_coeffs[i],
>+ hwdev->map.coeffs_base +
>+ MALIDP_COLOR_ADJ_COEF + 4 * i);
>+
>+ malidp_hw_setbits(hwdev, MALIDP_DISP_FUNC_CADJ,
>+ MALIDP_DE_DISPLAY_FUNC);
>+ }
>+}
>+
> /*
> * set the "config valid" bit and wait until the hardware acts on it
> */
>@@ -144,6 +175,10 @@ static void malidp_atomic_commit_tail(struct drm_atomic_state *state)
> malidp_atomic_commit_update_gamma(crtc, old_crtc_state);
>
> drm_atomic_helper_commit_modeset_enables(drm, state);
>+
>+ for_each_crtc_in_state(state, crtc, old_crtc_state, i)
>+ malidp_atomic_commit_update_coloradj(crtc, old_crtc_state);
>+
> drm_atomic_helper_commit_planes(drm, state, 0);
>
> malidp_atomic_commit_hw_done(state);
>diff --git a/drivers/gpu/drm/arm/malidp_drv.h b/drivers/gpu/drm/arm/malidp_drv.h
>index 374d43e..55b0f8b 100644
>--- a/drivers/gpu/drm/arm/malidp_drv.h
>+++ b/drivers/gpu/drm/arm/malidp_drv.h
>@@ -50,6 +50,7 @@ struct malidp_plane_state {
> struct malidp_crtc_state {
> struct drm_crtc_state base;
> u32 gamma_coeffs[MALIDP_COEFFTAB_NUM_COEFFS];
>+ u32 coloradj_coeffs[MALIDP_COLORADJ_NUM_COEFFS];
> };
>
> #define to_malidp_crtc_state(x) container_of(x, struct malidp_crtc_state, base)
>diff --git a/drivers/gpu/drm/arm/malidp_regs.h b/drivers/gpu/drm/arm/malidp_regs.h
>index 2e213c3..b15ef50 100644
>--- a/drivers/gpu/drm/arm/malidp_regs.h
>+++ b/drivers/gpu/drm/arm/malidp_regs.h
>@@ -64,6 +64,7 @@
> /* bit masks that are common between products */
> #define MALIDP_CFG_VALID (1 << 0)
> #define MALIDP_DISP_FUNC_GAM (1 << 0)
>+#define MALIDP_DISP_FUNC_CADJ (1 << 4)
> #define MALIDP_DISP_FUNC_ILACED (1 << 8)
>
> /* register offsets for IRQ management */
>@@ -93,6 +94,7 @@
> #define MALIDP_DE_H_ACTIVE(x) (((x) & 0x1fff) << 0)
> #define MALIDP_DE_V_ACTIVE(x) (((x) & 0x1fff) << 16)
>
>+#define MALIDP_COLORADJ_NUM_COEFFS 12
> #define MALIDP_COEFFTAB_NUM_COEFFS 64
> /* register offsets relative to MALIDP5x0_COEFFS_BASE */
> #define MALIDP_COLOR_ADJ_COEF 0x00000
>--
>1.9.1
>

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