[PATCH v1 3/5] drm/dp: add helpers for capture of frame CRCs

[Tomeu Vizoso]

Adds helpers for starting and stopping capture of frame CRCs through the
DPCD. When capture is on, a worker waits for vblanks and retrieves the
frame CRC to put it in the queue on the CRTC that is using the
eDP connector, so it's passed to userspace.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
---

 drivers/gpu/drm/drm_dp_helper.c | 133 ++++++++++++++++++++++++++++++++++++++++
 include/drm/drm_dp_helper.h     |   7 +++
 2 files changed, 140 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index eae5ef963cb7..bf88ae7deb9a 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -790,6 +790,90 @@ static void unlock_bus(struct i2c_adapter *i2c, unsigned int flags)
 	mutex_unlock(&i2c_to_aux(i2c)->hw_mutex);
 }
 
+static int drm_dp_aux_get_crc(struct drm_dp_aux *aux, u8 *crc)
+{
+	u8 buf, count;
+	int ret;
+
+	ret = drm_dp_dpcd_readb(aux, DP_TEST_SINK, &buf);
+	if (ret < 0)
+		return ret;
+
+	WARN_ON(!(buf & DP_TEST_SINK_START));
+
+	ret = drm_dp_dpcd_readb(aux, DP_TEST_SINK_MISC, &buf);
+	if (ret < 0)
+		return ret;
+
+	count = buf & DP_TEST_COUNT_MASK;
+	if (count == aux->crc_count)
+		return -EAGAIN; /* No CRC yet */
+
+	aux->crc_count = count;
+
+	/* At DP_TEST_CRC_R_CR, there's 6 bytes containing CRC data, 2 bytes
+	 * per component (RGB or CrYCb).
+	 */
+	ret = drm_dp_dpcd_read(aux, DP_TEST_CRC_R_CR, crc, 6);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static void drm_dp_aux_crc_work(struct work_struct *work)
+{
+	struct drm_dp_aux *aux = container_of(work, struct drm_dp_aux,
+					      crc_work);
+	struct drm_crtc *crtc;
+	wait_queue_head_t *wq;
+	u8 crc_bytes[6];
+	uint32_t crcs[3];
+	u32 last;
+	int ret;
+
+	if (WARN_ON(!aux->connector))
+		return;
+
+	crtc = aux->connector->state->crtc;
+	wq = drm_crtc_vblank_waitqueue(crtc);
+	while (crtc->crc.opened) {
+		ret = drm_crtc_vblank_get(crtc);
+		if (WARN(ret, "vblank not available on crtc %i, ret=%i\n",
+			 crtc->index, ret))
+			return;
+
+		last = drm_crtc_vblank_count(crtc);
+		wait_event(*wq, last != drm_crtc_vblank_count(crtc));
+
+		drm_crtc_vblank_put(crtc);
+
+		if (!crtc->crc.opened)
+			break;
+
+		ret = drm_dp_aux_get_crc(aux, crc_bytes);
+		if (ret == -EAGAIN) {
+			usleep_range(1000, 2000);
+			ret = drm_dp_aux_get_crc(aux, crc_bytes);
+		}
+
+		if (ret) {
+			DRM_DEBUG_KMS("Failed to get a CRC even after retrying: %d\n",
+				      ret);
+			continue;
+		}
+
+		spin_lock_irq(&crtc->crc.lock);
+		crcs[0] = crc_bytes[0] | crc_bytes[1] << 8;
+		crcs[1] = crc_bytes[2] | crc_bytes[3] << 8;
+		crcs[2] = crc_bytes[4] | crc_bytes[5] << 8;
+		ret = drm_crtc_add_crc_entry(crtc, false, 0, crcs);
+		spin_unlock_irq(&crtc->crc.lock);
+		if (!ret)
+			wake_up_interruptible(&crtc->crc.wq);
+	}
+}
+
 /**
  * drm_dp_aux_init() - minimally initialise an aux channel
  * @aux: DisplayPort AUX channel
@@ -802,6 +886,7 @@ static void unlock_bus(struct i2c_adapter *i2c, unsigned int flags)
 void drm_dp_aux_init(struct drm_dp_aux *aux)
 {
 	mutex_init(&aux->hw_mutex);
+	INIT_WORK(&aux->crc_work, drm_dp_aux_crc_work);
 
 	aux->ddc.algo = &drm_dp_i2c_algo;
 	aux->ddc.algo_data = aux;
@@ -892,3 +977,51 @@ int drm_dp_psr_setup_time(const u8 psr_cap[EDP_PSR_RECEIVER_CAP_SIZE])
 EXPORT_SYMBOL(drm_dp_psr_setup_time);
 
 #undef PSR_SETUP_TIME
+
+/**
+ * drm_dp_start_crc() - start capture of frame CRCs
+ * @aux: DisplayPort AUX channel
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int drm_dp_start_crc(struct drm_dp_aux *aux)
+{
+	u8 buf;
+	int ret;
+
+	ret = drm_dp_dpcd_readb(aux, DP_TEST_SINK, &buf);
+	if (ret < 0)
+		return ret;
+
+	ret = drm_dp_dpcd_writeb(aux, DP_TEST_SINK, buf | DP_TEST_SINK_START);
+	if (ret < 0)
+		return ret;
+
+	schedule_work(&aux->crc_work);
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_dp_start_crc);
+
+/**
+ * drm_dp_stop_crc() - stop capture of frame CRCs
+ * @aux: DisplayPort AUX channel
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int drm_dp_stop_crc(struct drm_dp_aux *aux)
+{
+	u8 buf;
+	int ret;
+
+	ret = drm_dp_dpcd_readb(aux, DP_TEST_SINK, &buf);
+	if (ret < 0)
+		return ret;
+
+	ret = drm_dp_dpcd_writeb(aux, DP_TEST_SINK, buf & ~DP_TEST_SINK_START);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_dp_stop_crc);
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index f66cc8501d71..c6ddc4edda61 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -712,6 +712,8 @@ struct drm_dp_aux_msg {
  * @dev: pointer to struct device that is the parent for this AUX channel
  * @connector: backpointer to connector that uses this AUX channel
  * @hw_mutex: internal mutex used for locking transfers
+ * @crc_work: worker that captures CRCs for each frame
+ * @crc_count: counter of captured frame CRCs
  * @transfer: transfers a message representing a single AUX transaction
  *
  * The .dev field should be set to a pointer to the device that implements
@@ -749,6 +751,8 @@ struct drm_dp_aux {
 	struct device *dev;
 	struct drm_connector *connector;
 	struct mutex hw_mutex;
+	struct work_struct crc_work;
+	u8 crc_count;
 	ssize_t (*transfer)(struct drm_dp_aux *aux,
 			    struct drm_dp_aux_msg *msg);
 	/**
@@ -820,4 +824,7 @@ void drm_dp_aux_init(struct drm_dp_aux *aux);
 int drm_dp_aux_register(struct drm_dp_aux *aux);
 void drm_dp_aux_unregister(struct drm_dp_aux *aux);
 
+int drm_dp_start_crc(struct drm_dp_aux *aux);
+int drm_dp_stop_crc(struct drm_dp_aux *aux);
+
 #endif /* _DRM_DP_HELPER_H_ */
-- 
2.7.4