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Subject[PATCH v2 3/3] drm/amd/display: implement DSC pass-through support
Date
Currently, we only attempt to setup DSC at the virtual DPCD port,
however many modern displays come with DSC support and MST hubs can now
support DSC pass-through. So, to more optimally make use of the
available bandwidth, use DSC pass-through when possible by adding DSC
pass-through enablement support into the DSC enable sequence.

Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
---
v2: print the correct type of port that we are writing to using dsc_aux
in dm_helpers_dp_write_dsc_enable().
---
.../amd/display/amdgpu_dm/amdgpu_dm_helpers.c | 45 +++++++++++++++++--
1 file changed, 41 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
index a0154a5f7183..bd364d2cc4f7 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
@@ -729,8 +729,14 @@ bool dm_helpers_dp_write_dsc_enable(
const struct dc_stream_state *stream,
bool enable)
{
- uint8_t enable_dsc = enable ? 1 : 0;
+ static const uint8_t DSC_DISABLE;
+ static const uint8_t DSC_DECODING = 0x01;
+ static const uint8_t DSC_PASSTHROUGH = 0x02;
+
struct amdgpu_dm_connector *aconnector;
+ struct drm_dp_mst_port *port;
+ uint8_t enable_dsc = enable ? DSC_DECODING : DSC_DISABLE;
+ uint8_t enable_passthrough = enable ? DSC_PASSTHROUGH : DSC_DISABLE;
uint8_t ret = 0;

if (!stream)
@@ -750,8 +756,39 @@ bool dm_helpers_dp_write_dsc_enable(
aconnector->dsc_aux, stream, enable_dsc);
#endif

- ret = drm_dp_dpcd_write(aconnector->dsc_aux, DP_DSC_ENABLE, &enable_dsc, 1);
- DC_LOG_DC("Send DSC %s to MST RX\n", enable_dsc ? "enable" : "disable");
+ port = aconnector->port;
+
+ if (enable) {
+ if (port->passthrough_aux) {
+ ret = drm_dp_dpcd_write(port->passthrough_aux,
+ DP_DSC_ENABLE,
+ &enable_passthrough, 1);
+ DC_LOG_DC("Sent DSC pass-through enable to virtual dpcd port, ret = %u\n",
+ ret);
+ }
+
+ ret = drm_dp_dpcd_write(aconnector->dsc_aux,
+ DP_DSC_ENABLE, &enable_dsc, 1);
+ DC_LOG_DC("Sent DSC decoding enable to %s port, ret = %u\n",
+ (port->passthrough_aux) ? "remote RX" :
+ "virtual dpcd",
+ ret);
+ } else {
+ ret = drm_dp_dpcd_write(aconnector->dsc_aux,
+ DP_DSC_ENABLE, &enable_dsc, 1);
+ DC_LOG_DC("Sent DSC decoding disable to %s port, ret = %u\n",
+ (port->passthrough_aux) ? "remote RX" :
+ "virtual dpcd",
+ ret);
+
+ if (port->passthrough_aux) {
+ ret = drm_dp_dpcd_write(port->passthrough_aux,
+ DP_DSC_ENABLE,
+ &enable_passthrough, 1);
+ DC_LOG_DC("Sent DSC pass-through disable to virtual dpcd port, ret = %u\n",
+ ret);
+ }
+ }
}

if (stream->signal == SIGNAL_TYPE_DISPLAY_PORT || stream->signal == SIGNAL_TYPE_EDP) {
@@ -768,7 +805,7 @@ bool dm_helpers_dp_write_dsc_enable(
#endif
}

- return (ret > 0);
+ return ret;
}

bool dm_helpers_is_dp_sink_present(struct dc_link *link)
--
2.37.1
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