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-rw-r--r--drivers/gpu/drm/display/drm_dp_helper.c35
1 files changed, 35 insertions, 0 deletions
diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
index 26c188ce5f..fb80843e7f 100644
--- a/drivers/gpu/drm/display/drm_dp_helper.c
+++ b/drivers/gpu/drm/display/drm_dp_helper.c
@@ -533,6 +533,15 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
mutex_lock(&aux->hw_mutex);
/*
+ * If the device attached to the aux bus is powered down then there's
+ * no reason to attempt a transfer. Error out immediately.
+ */
+ if (aux->powered_down) {
+ ret = -EBUSY;
+ goto unlock;
+ }
+
+ /*
* The specification doesn't give any recommendation on how often to
* retry native transactions. We used to retry 7 times like for
* aux i2c transactions but real world devices this wasn't
@@ -600,6 +609,29 @@ int drm_dp_dpcd_probe(struct drm_dp_aux *aux, unsigned int offset)
EXPORT_SYMBOL(drm_dp_dpcd_probe);
/**
+ * drm_dp_dpcd_set_powered() - Set whether the DP device is powered
+ * @aux: DisplayPort AUX channel; for convenience it's OK to pass NULL here
+ * and the function will be a no-op.
+ * @powered: true if powered; false if not
+ *
+ * If the endpoint device on the DP AUX bus is known to be powered down
+ * then this function can be called to make future transfers fail immediately
+ * instead of needing to time out.
+ *
+ * If this function is never called then a device defaults to being powered.
+ */
+void drm_dp_dpcd_set_powered(struct drm_dp_aux *aux, bool powered)
+{
+ if (!aux)
+ return;
+
+ mutex_lock(&aux->hw_mutex);
+ aux->powered_down = !powered;
+ mutex_unlock(&aux->hw_mutex);
+}
+EXPORT_SYMBOL(drm_dp_dpcd_set_powered);
+
+/**
* drm_dp_dpcd_read() - read a series of bytes from the DPCD
* @aux: DisplayPort AUX channel (SST or MST)
* @offset: address of the (first) register to read
@@ -1858,6 +1890,9 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
struct drm_dp_aux_msg msg;
int err = 0;
+ if (aux->powered_down)
+ return -EBUSY;
+
dp_aux_i2c_transfer_size = clamp(dp_aux_i2c_transfer_size, 1, DP_AUX_MAX_PAYLOAD_BYTES);
memset(&msg, 0, sizeof(msg));