[v3,3/5] drm/dp: add helpers for capture of frame CRCs
diff mbox

Message ID 20170106143029.11553-4-tomeu.vizoso@collabora.com
State New
Headers show

Commit Message

Tomeu Vizoso Jan. 6, 2017, 2:30 p.m. UTC
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.

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

 drivers/gpu/drm/drm_dp_helper.c | 118 ++++++++++++++++++++++++++++++++++++++++
 include/drm/drm_dp_helper.h     |   7 +++
 2 files changed, 125 insertions(+)

Comments

Sean Paul Jan. 6, 2017, 3:56 p.m. UTC | #1
On Fri, Jan 6, 2017 at 9:30 AM, Tomeu Vizoso <tomeu.vizoso@collabora.com> wrote:
> 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.
>
> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
> ---
>
>  drivers/gpu/drm/drm_dp_helper.c | 118 ++++++++++++++++++++++++++++++++++++++++
>  include/drm/drm_dp_helper.h     |   7 +++
>  2 files changed, 125 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 3e6fe82c6d64..e531f1317268 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -981,6 +981,74 @@ 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).

nit: doesn't conform to CodingStyle

> +        */
> +       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) {
> +                       DRM_DEBUG_KMS("Failed to get a CRC even after retrying: %d\n",
> +                                     ret);
> +                       continue;
> +               }

I think it'd be better to restructure this to only call
drm_dp_aux_get_crc in one place (and differentiate between EAGAIN and
other failures):

bool retry = false;
while (...) {
        ...

        ret = drm_dp_aux_get_crc(aux, crc_bytes);
        if (ret == -EAGAIN) {
                if (retry)
                        DRM_DEBUG_KMS("Get CRC failed after retrying: %d\n",
                                      ret);
                retry = !retry;
                usleep_range(1000, 2000);
                continue;
        }

        retry = false;
        if (!ret) {
                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);
                if (ret)
                        DRM_DEBUG_KMS("Failed to add crc entry %d\n", ret);
        } else {
                DRM_DEBUG_KMS("Get CRC failed: %d\n", ret);
        }
}

> +
> +               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);
> +       }
> +}
> +
>  /**
>   * drm_dp_aux_init() - minimally initialise an aux channel
>   * @aux: DisplayPort AUX channel
> @@ -993,6 +1061,7 @@ 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 +1150,52 @@ 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;
> +

Can we flush the worker here to head off any races?


> +       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 4fa77b434594..276e1ecd947b 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -723,6 +723,8 @@ 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
> @@ -760,6 +762,8 @@ 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);
>         /**
> @@ -838,4 +842,7 @@ 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
>
Tomeu Vizoso Jan. 9, 2017, 1:24 p.m. UTC | #2
On 6 January 2017 at 16:56, Sean Paul <seanpaul@chromium.org> wrote:
> On Fri, Jan 6, 2017 at 9:30 AM, Tomeu Vizoso <tomeu.vizoso@collabora.com> wrote:
>> 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.
>>
>> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
>> ---
>>
>>  drivers/gpu/drm/drm_dp_helper.c | 118 ++++++++++++++++++++++++++++++++++++++++
>>  include/drm/drm_dp_helper.h     |   7 +++
>>  2 files changed, 125 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
>> index 3e6fe82c6d64..e531f1317268 100644
>> --- a/drivers/gpu/drm/drm_dp_helper.c
>> +++ b/drivers/gpu/drm/drm_dp_helper.c
>> @@ -981,6 +981,74 @@ 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).
>
> nit: doesn't conform to CodingStyle
>
>> +        */
>> +       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) {
>> +                       DRM_DEBUG_KMS("Failed to get a CRC even after retrying: %d\n",
>> +                                     ret);
>> +                       continue;
>> +               }
>
> I think it'd be better to restructure this to only call
> drm_dp_aux_get_crc in one place

I'm not completely sure, TBH, as I liked that it was very clear that
we only retry once. I'm about to send v4 with this change and you can
judge by yourself.

> (and differentiate between EAGAIN and
> other failures):

Good point.

> bool retry = false;
> while (...) {
>         ...
>
>         ret = drm_dp_aux_get_crc(aux, crc_bytes);
>         if (ret == -EAGAIN) {
>                 if (retry)
>                         DRM_DEBUG_KMS("Get CRC failed after retrying: %d\n",
>                                       ret);
>                 retry = !retry;
>                 usleep_range(1000, 2000);
>                 continue;
>         }
>
>         retry = false;
>         if (!ret) {
>                 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);
>                 if (ret)
>                         DRM_DEBUG_KMS("Failed to add crc entry %d\n", ret);
>         } else {
>                 DRM_DEBUG_KMS("Get CRC failed: %d\n", ret);
>         }
> }
>
>> +
>> +               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);
>> +       }
>> +}
>> +
>>  /**
>>   * drm_dp_aux_init() - minimally initialise an aux channel
>>   * @aux: DisplayPort AUX channel
>> @@ -993,6 +1061,7 @@ 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 +1150,52 @@ 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;
>> +
>
> Can we flush the worker here to head off any races?

Good point.

Thanks,

Tomeu

Patch
diff mbox

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 3e6fe82c6d64..e531f1317268 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -981,6 +981,74 @@  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) {
+			DRM_DEBUG_KMS("Failed to get a CRC even after retrying: %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;
+		ret = drm_crtc_add_crc_entry(crtc, false, 0, crcs);
+	}
+}
+
 /**
  * drm_dp_aux_init() - minimally initialise an aux channel
  * @aux: DisplayPort AUX channel
@@ -993,6 +1061,7 @@  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 +1150,52 @@  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;
+
+	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 4fa77b434594..276e1ecd947b 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -723,6 +723,8 @@  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
@@ -760,6 +762,8 @@  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);
 	/**
@@ -838,4 +842,7 @@  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_ */