On 2/11/22 11:46, Raphaël Gallais-Pou wrote:
From: Raphael Gallais-Pou <raphael.gallais-...@foss.st.com>

This patch adds the CRC hashing feature supported by some recent hardware
versions of the LTDC. This is useful for test suite such as IGT-GPU-tools
[1] where a CRTC output frame can be compared to a test reference frame
thanks to their respective CRC hash.

[1] https://cgit.freedesktop.org/drm/igt-gpu-tools

Signed-off-by: Raphael Gallais-Pou <raphael.gallais-...@foss.st.com>

Applied on drm-misc-next.
Many thanks for your patch,
Philippe :-)

---
  drivers/gpu/drm/stm/ltdc.c | 104 +++++++++++++++++++++++++++++++++++--
  drivers/gpu/drm/stm/ltdc.h |   3 ++
  2 files changed, 104 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
index 5eeb32c9c9ce..b29476aec3a1 100644
--- a/drivers/gpu/drm/stm/ltdc.c
+++ b/drivers/gpu/drm/stm/ltdc.c
@@ -77,6 +77,7 @@
  #define LTDC_CPSR     0x0044          /* Current Position Status */
  #define LTDC_CDSR     0x0048          /* Current Display Status */
  #define LTDC_EDCR     0x0060          /* External Display Control */
+#define LTDC_CCRCR     0x007C          /* Computed CRC value */
  #define LTDC_FUT      0x0090          /* Fifo underrun Threshold */
/* Layer register offsets */
@@ -121,6 +122,7 @@
#define GCR_LTDCEN BIT(0) /* LTDC ENable */
  #define GCR_DEN               BIT(16)         /* Dither ENable */
+#define GCR_CRCEN      BIT(19)         /* CRC ENable */
  #define GCR_PCPOL     BIT(28)         /* Pixel Clock POLarity-Inverted */
  #define GCR_DEPOL     BIT(29)         /* Data Enable POLarity-High */
  #define GCR_VSPOL     BIT(30)         /* Vertical Synchro POLarity-High */
@@ -227,6 +229,13 @@
#define NB_PF 8 /* Max nb of HW pixel format */ +/*
+ * Skip the first value and the second in case CRC was enabled during
+ * the thread irq. This is to be sure CRC value is relevant for the
+ * frame.
+ */
+#define CRC_SKIP_FRAMES 2
+
  enum ltdc_pix_fmt {
        PF_NONE,
        /* RGB formats */
@@ -664,6 +673,26 @@ static inline void ltdc_set_ycbcr_coeffs(struct drm_plane 
*plane)
                     ltdc_ycbcr2rgb_coeffs[enc][ran][1]);
  }
+static inline void ltdc_irq_crc_handle(struct ltdc_device *ldev,
+                                      struct drm_crtc *crtc)
+{
+       u32 crc;
+       int ret;
+
+       if (ldev->crc_skip_count < CRC_SKIP_FRAMES) {
+               ldev->crc_skip_count++;
+               return;
+       }
+
+       /* Get the CRC of the frame */
+       ret = regmap_read(ldev->regmap, LTDC_CCRCR, &crc);
+       if (ret)
+               return;
+
+       /* Report to DRM the CRC (hw dependent feature) */
+       drm_crtc_add_crc_entry(crtc, true, drm_crtc_accurate_vblank_count(crtc), 
&crc);
+}
+
  static irqreturn_t ltdc_irq_thread(int irq, void *arg)
  {
        struct drm_device *ddev = arg;
@@ -671,9 +700,14 @@ static irqreturn_t ltdc_irq_thread(int irq, void *arg)
        struct drm_crtc *crtc = drm_crtc_from_index(ddev, 0);
/* Line IRQ : trigger the vblank event */
-       if (ldev->irq_status & ISR_LIF)
+       if (ldev->irq_status & ISR_LIF) {
                drm_crtc_handle_vblank(crtc);
+ /* Early return if CRC is not active */
+               if (ldev->crc_active)
+                       ltdc_irq_crc_handle(ldev, crtc);
+       }
+
        /* Save FIFO Underrun & Transfer Error status */
        mutex_lock(&ldev->err_lock);
        if (ldev->irq_status & ISR_FUIF)
@@ -1079,6 +1113,48 @@ static void ltdc_crtc_disable_vblank(struct drm_crtc 
*crtc)
        regmap_clear_bits(ldev->regmap, LTDC_IER, IER_LIE);
  }
+static int ltdc_crtc_set_crc_source(struct drm_crtc *crtc, const char *source)
+{
+       struct ltdc_device *ldev = crtc_to_ltdc(crtc);
+       int ret;
+
+       DRM_DEBUG_DRIVER("\n");
+
+       if (!crtc)
+               return -ENODEV;
+
+       if (source && strcmp(source, "auto") == 0) {
+               ldev->crc_active = true;
+               ret = regmap_set_bits(ldev->regmap, LTDC_GCR, GCR_CRCEN);
+       } else if (!source) {
+               ldev->crc_active = false;
+               ret = regmap_clear_bits(ldev->regmap, LTDC_GCR, GCR_CRCEN);
+       } else {
+               ret = -EINVAL;
+       }
+
+       ldev->crc_skip_count = 0;
+       return ret;
+}
+
+static int ltdc_crtc_verify_crc_source(struct drm_crtc *crtc,
+                                      const char *source, size_t *values_cnt)
+{
+       DRM_DEBUG_DRIVER("\n");
+
+       if (!crtc)
+               return -ENODEV;
+
+       if (source && strcmp(source, "auto") != 0) {
+               DRM_DEBUG_DRIVER("Unknown CRC source %s for %s\n",
+                                source, crtc->name);
+               return -EINVAL;
+       }
+
+       *values_cnt = 1;
+       return 0;
+}
+
  static const struct drm_crtc_funcs ltdc_crtc_funcs = {
        .destroy = drm_crtc_cleanup,
        .set_config = drm_atomic_helper_set_config,
@@ -1091,6 +1167,20 @@ static const struct drm_crtc_funcs ltdc_crtc_funcs = {
        .get_vblank_timestamp = drm_crtc_vblank_helper_get_vblank_timestamp,
  };
+static const struct drm_crtc_funcs ltdc_crtc_with_crc_support_funcs = {
+       .destroy = drm_crtc_cleanup,
+       .set_config = drm_atomic_helper_set_config,
+       .page_flip = drm_atomic_helper_page_flip,
+       .reset = drm_atomic_helper_crtc_reset,
+       .atomic_duplicate_state = drm_atomic_helper_crtc_duplicate_state,
+       .atomic_destroy_state = drm_atomic_helper_crtc_destroy_state,
+       .enable_vblank = ltdc_crtc_enable_vblank,
+       .disable_vblank = ltdc_crtc_disable_vblank,
+       .get_vblank_timestamp = drm_crtc_vblank_helper_get_vblank_timestamp,
+       .set_crc_source = ltdc_crtc_set_crc_source,
+       .verify_crc_source = ltdc_crtc_verify_crc_source,
+};
+
  /*
   * DRM_PLANE
   */
@@ -1478,8 +1568,13 @@ static int ltdc_crtc_init(struct drm_device *ddev, 
struct drm_crtc *crtc)
drm_plane_create_zpos_immutable_property(primary, 0); - ret = drm_crtc_init_with_planes(ddev, crtc, primary, NULL,
-                                       &ltdc_crtc_funcs, NULL);
+       /* Init CRTC according to its hardware features */
+       if (ldev->caps.crc)
+               ret = drm_crtc_init_with_planes(ddev, crtc, primary, NULL,
+                                               
&ltdc_crtc_with_crc_support_funcs, NULL);
+       else
+               ret = drm_crtc_init_with_planes(ddev, crtc, primary, NULL,
+                                               &ltdc_crtc_funcs, NULL);
        if (ret) {
                DRM_ERROR("Can not initialize CRTC\n");
                goto cleanup;
@@ -1629,6 +1724,7 @@ static int ltdc_get_caps(struct drm_device *ddev)
                ldev->caps.ycbcr_input = false;
                ldev->caps.ycbcr_output = false;
                ldev->caps.plane_reg_shadow = false;
+               ldev->caps.crc = false;
                break;
        case HWVER_20101:
                ldev->caps.layer_ofs = LAY_OFS_0;
@@ -1643,6 +1739,7 @@ static int ltdc_get_caps(struct drm_device *ddev)
                ldev->caps.ycbcr_input = false;
                ldev->caps.ycbcr_output = false;
                ldev->caps.plane_reg_shadow = false;
+               ldev->caps.crc = false;
                break;
        case HWVER_40100:
                ldev->caps.layer_ofs = LAY_OFS_1;
@@ -1657,6 +1754,7 @@ static int ltdc_get_caps(struct drm_device *ddev)
                ldev->caps.ycbcr_input = true;
                ldev->caps.ycbcr_output = true;
                ldev->caps.plane_reg_shadow = true;
+               ldev->caps.crc = true;
                break;
        default:
                return -ENODEV;
diff --git a/drivers/gpu/drm/stm/ltdc.h b/drivers/gpu/drm/stm/ltdc.h
index 6968d1ca5149..59fc5d1bbbab 100644
--- a/drivers/gpu/drm/stm/ltdc.h
+++ b/drivers/gpu/drm/stm/ltdc.h
@@ -27,6 +27,7 @@ struct ltdc_caps {
        bool ycbcr_input;       /* ycbcr input converter supported */
        bool ycbcr_output;      /* ycbcr output converter supported */
        bool plane_reg_shadow;  /* plane shadow registers ability */
+       bool crc;               /* cyclic redundancy check supported */
  };
#define LTDC_MAX_LAYER 4
@@ -46,6 +47,8 @@ struct ltdc_device {
        u32 irq_status;
        struct fps_info plane_fpsi[LTDC_MAX_LAYER];
        struct drm_atomic_state *suspend_state;
+       int crc_skip_count;
+       bool crc_active;
  };
int ltdc_load(struct drm_device *ddev);

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