We see some monitors and docks report incorrect hdcp version
and capability in first few reads so we read rx_caps three times
before we conclude the monitor's or docks HDCP capability
--v2
-Add comment to justify the 3 time read loop for hdcp capability[Ankit]
Signed-off-by: Suraj Kandpal <suraj.kandpal@xxxxxxxxx>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@xxxxxxxxx>
---
drivers/gpu/drm/i915/display/intel_dp_hdcp.c | 29 ++++++++++++++------
1 file changed, 20 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/i915/display/intel_dp_hdcp.c b/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
index ed7afde417bc..bddc2e5f329e 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
@@ -640,18 +640,29 @@ int _intel_dp_hdcp2_get_capability(struct drm_dp_aux *aux,
bool *capable)
{
u8 rx_caps[3];
- int ret;
+ int ret, i;
*capable = false;
- ret = drm_dp_dpcd_read(aux,
- DP_HDCP_2_2_REG_RX_CAPS_OFFSET,
- rx_caps, HDCP_2_2_RXCAPS_LEN);
- if (ret != HDCP_2_2_RXCAPS_LEN)
- return ret >= 0 ? -EIO : ret;
- if (rx_caps[0] == HDCP_2_2_RX_CAPS_VERSION_VAL &&
- HDCP_2_2_DP_HDCP_CAPABLE(rx_caps[2]))
- *capable = true;
+ /*
+ * Some HDCP monitors act really shady by not giving the correct hdcp
+ * capability on the first rx_caps read and usually take an extra read
+ * to give the capability. We read rx_caps three times before we
+ * declare a monitor not capable of HDCP 2.2.
+ */
+ for (i = 0; i < 3; i++) {
+ ret = drm_dp_dpcd_read(aux,
+ DP_HDCP_2_2_REG_RX_CAPS_OFFSET,
+ rx_caps, HDCP_2_2_RXCAPS_LEN);
+ if (ret != HDCP_2_2_RXCAPS_LEN)
+ return ret >= 0 ? -EIO : ret;
+
+ if (rx_caps[0] == HDCP_2_2_RX_CAPS_VERSION_VAL &&
+ HDCP_2_2_DP_HDCP_CAPABLE(rx_caps[2])) {
+ *capable = true;
+ break;
+ }
+ }
return 0;
}
--
2.25.1
