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drm/i915/hdcp: Read Rxcaps for robustibility

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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@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240226063051.1685326-7-suraj.kandpal@intel.com
This commit is contained in:
Suraj Kandpal 2024-02-26 12:00:52 +05:30 committed by Ankit Nautiyal
parent 66bd692404
commit 610d7bc2e2
1 changed files with 20 additions and 9 deletions
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29
drivers/gpu/drm/i915/display/intel_dp_hdcp.c
View file

@ -644,18 +644,29 @@ 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;
}