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Subject[PATCH v5 2/4] drm/dp: add helpers for capture of frame CRCs
Date
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.

v2: Reuse drm_crtc_wait_one_vblank
Update locking, as drm_crtc_add_crc_entry now takes the lock

v3: Don't call wake_up_interruptible directly, that's now done in
drm_crtc_add_crc_entry.

v4: Style fixes (Sean Paul)
Reworked retry of CRC reads (Sean Paul)
Flush worker after stopping CRC generationa (Sean Paul)

v5: Move back to make the retry explicitly once

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

drivers/gpu/drm/drm_dp_helper.c | 124 ++++++++++++++++++++++++++++++++++++++++
include/drm/drm_dp_helper.h | 7 +++
2 files changed, 131 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 3e6fe82c6d64..6dd550c7a8bd 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -981,6 +981,78 @@ static const struct i2c_lock_operations drm_dp_i2c_lock_ops = {
.unlock_bus = unlock_bus,
};

+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;
+ u8 crc_bytes[6];
+ uint32_t crcs[3];
+ int ret;
+
+ if (WARN_ON(!aux->connector))
+ return;
+
+ crtc = aux->connector->state->crtc;
+ while (crtc->crc.opened) {
+ drm_crtc_wait_one_vblank(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 == -EAGAIN) {
+ DRM_DEBUG_KMS("Get CRC failed after retrying: %d\n",
+ ret);
+ continue;
+ } else if (ret) {
+ DRM_DEBUG_KMS("Failed to get a CRC: %d\n", ret);
+ continue;
+ }
+
+ 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;
+ drm_crtc_add_crc_entry(crtc, false, 0, crcs);
+ }
+}
+
/**
* drm_dp_aux_init() - minimally initialise an aux channel
* @aux: DisplayPort AUX channel
@@ -993,6 +1065,7 @@ static const struct i2c_lock_operations drm_dp_i2c_lock_ops = {
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;
@@ -1081,3 +1154,54 @@ 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;
+
+ aux->crc_count = 0;
+ 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;
+
+ flush_work(&aux->crc_work);
+
+ 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 eb598078bf89..7af40fea2ff9 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -734,6 +734,8 @@ 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
@@ -771,6 +773,8 @@ 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);
/**
@@ -849,4 +853,7 @@ 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_ */
--
2.9.3
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