[PATCH v5 0/5] DSC MST support in DRM

[PATCH v5 0/5] DSC MST support in DRM

[David Francis]

Add necessary support for MST DSC.
(Display Stream Compression over Multi-Stream Transport)

v4: Split patchset and rebase onto drm-tip
v5: Clean up formatting, make new quirk

David Francis (5):
  drm/dp_mst: Add PBN calculation for DSC modes
  drm/dp_mst: Parse FEC capability on MST ports
  drm/dp_mst: Add MST support to DP DPCD R/W functions
  drm/dp_mst: Fill branch->num_ports
  drm/dp_mst: Add helper for finding right aux to enable/query DSC

 .../amd/display/amdgpu_dm/amdgpu_dm_helpers.c |   2 +-
 drivers/gpu/drm/drm_dp_aux_dev.c              |  12 +-
 drivers/gpu/drm/drm_dp_helper.c               |  32 ++--
 drivers/gpu/drm/drm_dp_mst_topology.c         | 167 +++++++++++++++++-
 drivers/gpu/drm/i915/display/intel_dp_mst.c   |   2 +-
 drivers/gpu/drm/nouveau/dispnv50/disp.c       |   2 +-
 drivers/gpu/drm/radeon/radeon_dp_mst.c        |   2 +-
 include/drm/drm_dp_helper.h                   |   7 +
 include/drm/drm_dp_mst_helper.h               |   8 +-
 9 files changed, 204 insertions(+), 30 deletions(-)

-- 
2.17.1

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[PATCH v5 1/5] drm/dp_mst: Add PBN calculation for DSC modes

[David Francis]

With DSC, bpp can be fractional in multiples of 1/16.

Change drm_dp_calc_pbn_mode to reflect this, adding a new
parameter bool dsc. When this parameter is true, treat the
bpp parameter as having units not of bits per pixel, but
1/16 of a bit per pixel

v2: Don't add separate function for this

Cc: Lyude Paul <lyude@redhat.com>
Signed-off-by: David Francis <David.Francis@amd.com>
---
 .../amd/display/amdgpu_dm/amdgpu_dm_helpers.c    |  2 +-
 drivers/gpu/drm/drm_dp_mst_topology.c            | 16 ++++++++++++----
 drivers/gpu/drm/i915/display/intel_dp_mst.c      |  2 +-
 drivers/gpu/drm/nouveau/dispnv50/disp.c          |  2 +-
 drivers/gpu/drm/radeon/radeon_dp_mst.c           |  2 +-
 include/drm/drm_dp_mst_helper.h                  |  3 +--
 6 files changed, 17 insertions(+), 10 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 a0ed0154a9f0..abafb5221b44 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
@@ -235,7 +235,7 @@ bool dm_helpers_dp_mst_write_payload_allocation_table(
 
 		/* TODO need to know link rate */
 
-		pbn = drm_dp_calc_pbn_mode(clock, bpp);
+		pbn = drm_dp_calc_pbn_mode(clock, bpp, false);
 
 		slots = drm_dp_find_vcpi_slots(mst_mgr, pbn);
 		ret = drm_dp_mst_allocate_vcpi(mst_mgr, mst_port, pbn, slots);
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 82add736e17d..157ffa30d984 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -3534,10 +3534,11 @@ EXPORT_SYMBOL(drm_dp_check_act_status);
  * drm_dp_calc_pbn_mode() - Calculate the PBN for a mode.
  * @clock: dot clock for the mode
  * @bpp: bpp for the mode.
+ * @dsc: DSC mode. If true, bpp has units of 1/16 of a bit per pixel
  *
  * This uses the formula in the spec to calculate the PBN value for a mode.
  */
-int drm_dp_calc_pbn_mode(int clock, int bpp)
+int drm_dp_calc_pbn_mode(int clock, int bpp, bool dsc)
 {
 	u64 kbps;
 	s64 peak_kbps;
@@ -3555,11 +3556,18 @@ int drm_dp_calc_pbn_mode(int clock, int bpp)
 	 * peak_kbps *= (1006/1000)
 	 * peak_kbps *= (64/54)
 	 * peak_kbps *= 8    convert to bytes
+	 *
+	 * If the bpp is in units of 1/16, further divide by 16. Put this
+	 * factor in the numberator rather than the denominator to avoid
+	 * integer overflow
 	 */
 
 	numerator = 64 * 1006;
 	denominator = 54 * 8 * 1000 * 1000;
 
+	if (dsc)
+		numerator /= 16;
+
 	kbps *= numerator;
 	peak_kbps = drm_fixp_from_fraction(kbps, denominator);
 
@@ -3570,19 +3578,19 @@ EXPORT_SYMBOL(drm_dp_calc_pbn_mode);
 static int test_calc_pbn_mode(void)
 {
 	int ret;
-	ret = drm_dp_calc_pbn_mode(154000, 30);
+	ret = drm_dp_calc_pbn_mode(154000, 30, false);
 	if (ret != 689) {
 		DRM_ERROR("PBN calculation test failed - clock %d, bpp %d, expected PBN %d, actual PBN %d.\n",
 				154000, 30, 689, ret);
 		return -EINVAL;
 	}
-	ret = drm_dp_calc_pbn_mode(234000, 30);
+	ret = drm_dp_calc_pbn_mode(234000, 30, false);
 	if (ret != 1047) {
 		DRM_ERROR("PBN calculation test failed - clock %d, bpp %d, expected PBN %d, actual PBN %d.\n",
 				234000, 30, 1047, ret);
 		return -EINVAL;
 	}
-	ret = drm_dp_calc_pbn_mode(297000, 24);
+	ret = drm_dp_calc_pbn_mode(297000, 24, false);
 	if (ret != 1063) {
 		DRM_ERROR("PBN calculation test failed - clock %d, bpp %d, expected PBN %d, actual PBN %d.\n",
 				297000, 24, 1063, ret);
diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index 2c5ac3dd647f..4f17f61f4453 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -61,7 +61,7 @@ static int intel_dp_mst_compute_link_config(struct intel_encoder *encoder,
 		crtc_state->pipe_bpp = bpp;
 
 		crtc_state->pbn = drm_dp_calc_pbn_mode(adjusted_mode->crtc_clock,
-						       crtc_state->pipe_bpp);
+						       crtc_state->pipe_bpp, false);
 
 		slots = drm_dp_atomic_find_vcpi_slots(state, &intel_dp->mst_mgr,
 						      port, crtc_state->pbn);
diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
index 5c36c75232e6..c68783c1f3fa 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
@@ -782,7 +782,7 @@ nv50_msto_atomic_check(struct drm_encoder *encoder,
 			const int bpp = connector->display_info.bpc * 3;
 			const int clock = crtc_state->adjusted_mode.clock;
 
-			asyh->dp.pbn = drm_dp_calc_pbn_mode(clock, bpp);
+			asyh->dp.pbn = drm_dp_calc_pbn_mode(clock, bpp, false);
 		}
 
 		slots = drm_dp_atomic_find_vcpi_slots(state, &mstm->mgr,
diff --git a/drivers/gpu/drm/radeon/radeon_dp_mst.c b/drivers/gpu/drm/radeon/radeon_dp_mst.c
index 2994f07fbad9..c997f88218f2 100644
--- a/drivers/gpu/drm/radeon/radeon_dp_mst.c
+++ b/drivers/gpu/drm/radeon/radeon_dp_mst.c
@@ -514,7 +514,7 @@ static bool radeon_mst_mode_fixup(struct drm_encoder *encoder,
 
 	mst_enc = radeon_encoder->enc_priv;
 
-	mst_enc->pbn = drm_dp_calc_pbn_mode(adjusted_mode->clock, bpp);
+	mst_enc->pbn = drm_dp_calc_pbn_mode(adjusted_mode->clock, bpp, false);
 
 	mst_enc->primary->active_device = mst_enc->primary->devices & mst_enc->connector->devices;
 	DRM_DEBUG_KMS("setting active device to %08x from %08x %08x for encoder %d\n",
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 2ba6253ea6d3..9116b2c95239 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -610,8 +610,7 @@ bool drm_dp_mst_port_has_audio(struct drm_dp_mst_topology_mgr *mgr,
 struct edid *drm_dp_mst_get_edid(struct drm_connector *connector, struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port);
 
 
-int drm_dp_calc_pbn_mode(int clock, int bpp);
-
+int drm_dp_calc_pbn_mode(int clock, int bpp, bool dsc);
 
 bool drm_dp_mst_allocate_vcpi(struct drm_dp_mst_topology_mgr *mgr,
 			      struct drm_dp_mst_port *port, int pbn, int slots);
-- 
2.17.1

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[PATCH v5 2/5] drm/dp_mst: Parse FEC capability on MST ports

[David Francis]

As of DP1.4, ENUM_PATH_RESOURCES returns a bit indicating
if FEC can be supported up to that point in the MST network.

The bit is the first byte of the ENUM_PATH_RESOURCES ack reply,
bottom-most bit (refer to section 2.11.9.4 of DP standard,
v1.4)

That value is needed for FEC and DSC support

Store it on drm_dp_mst_port

Signed-off-by: David Francis <David.Francis@amd.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 2 ++
 include/drm/drm_dp_mst_helper.h       | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 157ffa30d984..11b02f6b9e8a 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -553,6 +553,7 @@ static bool drm_dp_sideband_parse_enum_path_resources_ack(struct drm_dp_sideband
 {
 	int idx = 1;
 	repmsg->u.path_resources.port_number = (raw->msg[idx] >> 4) & 0xf;
+	repmsg->u.path_resources.fec_capable = raw->msg[idx] & 0x1;
 	idx++;
 	if (idx > raw->curlen)
 		goto fail_len;
@@ -2183,6 +2184,7 @@ static int drm_dp_send_enum_path_resources(struct drm_dp_mst_topology_mgr *mgr,
 			DRM_DEBUG_KMS("enum path resources %d: %d %d\n", txmsg->reply.u.path_resources.port_number, txmsg->reply.u.path_resources.full_payload_bw_number,
 			       txmsg->reply.u.path_resources.avail_payload_bw_number);
 			port->available_pbn = txmsg->reply.u.path_resources.avail_payload_bw_number;
+			port->fec_capable = txmsg->reply.u.path_resources.fec_capable;
 		}
 	}
 
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 9116b2c95239..f113ae04fa88 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -108,6 +108,8 @@ struct drm_dp_mst_port {
 	 * audio-capable.
 	 */
 	bool has_audio;
+
+	bool fec_capable;
 };
 
 /**
@@ -312,6 +314,7 @@ struct drm_dp_port_number_req {
 
 struct drm_dp_enum_path_resources_ack_reply {
 	u8 port_number;
+	bool fec_capable;
 	u16 full_payload_bw_number;
 	u16 avail_payload_bw_number;
 };
-- 
2.17.1

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[PATCH v5 3/5] drm/dp_mst: Add MST support to DP DPCD R/W functions

[David Francis]

Instead of having drm_dp_dpcd_read/write and
drm_dp_mst_dpcd_read/write as entry points into the
aux code, have drm_dp_dpcd_read/write handle both.

This means that DRM drivers can make MST DPCD read/writes.

v2: Fix spacing
v3: Dump dpcd access on MST read/writes

Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: David Francis <David.Francis@amd.com>
---
 drivers/gpu/drm/drm_dp_aux_dev.c | 12 ++----------
 drivers/gpu/drm/drm_dp_helper.c  | 30 ++++++++++++++++++++----------
 2 files changed, 22 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_aux_dev.c b/drivers/gpu/drm/drm_dp_aux_dev.c
index 0cfb386754c3..418cad4f649a 100644
--- a/drivers/gpu/drm/drm_dp_aux_dev.c
+++ b/drivers/gpu/drm/drm_dp_aux_dev.c
@@ -163,11 +163,7 @@ static ssize_t auxdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
 			break;
 		}
 
-		if (aux_dev->aux->is_remote)
-			res = drm_dp_mst_dpcd_read(aux_dev->aux, pos, buf,
-						   todo);
-		else
-			res = drm_dp_dpcd_read(aux_dev->aux, pos, buf, todo);
+		res = drm_dp_dpcd_read(aux_dev->aux, pos, buf, todo);
 
 		if (res <= 0)
 			break;
@@ -215,11 +211,7 @@ static ssize_t auxdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
 			break;
 		}
 
-		if (aux_dev->aux->is_remote)
-			res = drm_dp_mst_dpcd_write(aux_dev->aux, pos, buf,
-						    todo);
-		else
-			res = drm_dp_dpcd_write(aux_dev->aux, pos, buf, todo);
+		res = drm_dp_mst_dpcd_write(aux_dev->aux, pos, buf, todo);
 
 		if (res <= 0)
 			break;
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index ffc68d305afe..2cc21eff4cf3 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -30,6 +30,7 @@
 #include <linux/seq_file.h>
 
 #include <drm/drm_dp_helper.h>
+#include <drm/drm_dp_mst_helper.h>
 #include <drm/drm_print.h>
 #include <drm/drm_vblank.h>
 
@@ -251,7 +252,7 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
 
 /**
  * drm_dp_dpcd_read() - read a series of bytes from the DPCD
- * @aux: DisplayPort AUX channel
+ * @aux: DisplayPort AUX channel (SST or MST)
  * @offset: address of the (first) register to read
  * @buffer: buffer to store the register values
  * @size: number of bytes in @buffer
@@ -280,13 +281,18 @@ ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
 	 * We just have to do it before any DPCD access and hope that the
 	 * monitor doesn't power down exactly after the throw away read.
 	 */
-	ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV, buffer,
-				 1);
-	if (ret != 1)
-		goto out;
+	if (!aux->is_remote) {
+		ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV,
+					 buffer, 1);
+		if (ret != 1)
+			goto out;
+	}
 
-	ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer,
-				 size);
+	if (aux->is_remote)
+		ret = drm_dp_mst_dpcd_read(aux, offset, buffer, size);
+	else
+		ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset,
+					 buffer, size);
 
 out:
 	drm_dp_dump_access(aux, DP_AUX_NATIVE_READ, offset, buffer, ret);
@@ -296,7 +302,7 @@ EXPORT_SYMBOL(drm_dp_dpcd_read);
 
 /**
  * drm_dp_dpcd_write() - write a series of bytes to the DPCD
- * @aux: DisplayPort AUX channel
+ * @aux: DisplayPort AUX channel (SST or MST)
  * @offset: address of the (first) register to write
  * @buffer: buffer containing the values to write
  * @size: number of bytes in @buffer
@@ -313,8 +319,12 @@ ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,
 {
 	int ret;
 
-	ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_WRITE, offset, buffer,
-				 size);
+	if (aux->is_remote)
+		ret = drm_dp_mst_dpcd_write(aux, offset, buffer, size);
+	else
+		ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_WRITE, offset,
+					 buffer, size);
+
 	drm_dp_dump_access(aux, DP_AUX_NATIVE_WRITE, offset, buffer, ret);
 	return ret;
 }
-- 
2.17.1

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[PATCH v5 4/5] drm/dp_mst: Fill branch->num_ports

[David Francis]

This field on drm_dp_mst_branch was never filled

It is initialized to zero when the port is kzallocced.
When a port is added to the list, increment num_ports,
and when a port is removed from the list, decrement num_ports.

v2: remember to decrement on port removal
v3: don't explicitly init to 0

Signed-off-by: David Francis <David.Francis@amd.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 11b02f6b9e8a..a39e42c7d868 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -1669,6 +1669,7 @@ static void drm_dp_add_port(struct drm_dp_mst_branch *mstb,
 		mutex_lock(&mstb->mgr->lock);
 		drm_dp_mst_topology_get_port(port);
 		list_add(&port->next, &mstb->ports);
+		mstb->num_ports++;
 		mutex_unlock(&mstb->mgr->lock);
 	}
 
@@ -1703,6 +1704,7 @@ static void drm_dp_add_port(struct drm_dp_mst_branch *mstb,
 			/* remove it from the port list */
 			mutex_lock(&mstb->mgr->lock);
 			list_del(&port->next);
+			mstb->num_ports--;
 			mutex_unlock(&mstb->mgr->lock);
 			/* drop port list reference */
 			drm_dp_mst_topology_put_port(port);
-- 
2.17.1

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[PATCH v5 5/5] drm/dp_mst: Add helper for finding right aux to enable/query DSC

[David Francis]

Add drm_dp_mst_dsc_aux_for_port. To enable DSC, the DSC_ENABLED
register might have to be written on the leaf port's DPCD,
its parent's DPCD, or the MST manager's DPCD. This function
finds the correct aux for the job.

As part of this, add drm_dp_mst_is_virtual_dpcd. Virtual DPCD
is a DP feature new in DP v1.4, which exposes certain DPCD
registers on virtual ports.

ALso add a new quirk for Synatics MST hubs that support DSC
despite not supporting virtual DPCD.

Cc: Lyude Paul <lyude@redhat.com>
Cc: Wenjing Liu <Wenjing.Liu@amd.com>
Cc: Nikola Cornij <Nikola.Cornij@amd.com>
Signed-off-by: David Francis <David.Francis@amd.com>
---
 drivers/gpu/drm/drm_dp_helper.c       |   2 +
 drivers/gpu/drm/drm_dp_mst_topology.c | 147 ++++++++++++++++++++++++++
 include/drm/drm_dp_helper.h           |   7 ++
 include/drm/drm_dp_mst_helper.h       |   2 +
 4 files changed, 158 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 2cc21eff4cf3..fc39323e7d52 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -1270,6 +1270,8 @@ static const struct dpcd_quirk dpcd_quirk_list[] = {
 	{ OUI(0x00, 0x10, 0xfa), DEVICE_ID_ANY, false, BIT(DP_DPCD_QUIRK_NO_PSR) },
 	/* CH7511 seems to leave SINK_COUNT zeroed */
 	{ OUI(0x00, 0x00, 0x00), DEVICE_ID('C', 'H', '7', '5', '1', '1'), false, BIT(DP_DPCD_QUIRK_NO_SINK_COUNT) },
+	/* Synaptics DP1.4 MST hubs can support DSC without virtual DPCD */
+	{ OUI(0x90, 0xCC, 0x24), DEVICE_ID_ANY, true, BIT(DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD) },
 };
 
 #undef OUI
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index a39e42c7d868..559bc09b6b94 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -4150,3 +4150,150 @@ static void drm_dp_mst_unregister_i2c_bus(struct drm_dp_aux *aux)
 {
 	i2c_del_adapter(&aux->ddc);
 }
+
+/**
+ * drm_dp_mst_is_virtual_dpcd() - Is the given port a virtual DP Peer Device
+ * @port: The port to check
+ *
+ * A single physical MST hub object can be represented in the topology
+ * by multiple branches, with virtual ports between those branches.
+ *
+ * As of DP1.4, An MST hub with internal (virtual) ports must expose
+ * certain DPCD registers over those ports. See sections 2.6.1.1.1
+ * and 2.6.1.1.2 of Display Port specification v1.4 for details.
+ *
+ * May acquire mgr->lock
+ *
+ * Returns:
+ * true if the port is a virtual DP peer device, false otherwise
+ */
+static bool drm_dp_mst_is_virtual_dpcd(struct drm_dp_mst_port *port)
+{
+	struct drm_dp_mst_port *downstream_port;
+
+	if (!port)
+		return false;
+
+	/* Virtual DP Sink (Internal Display Panel) */
+	if (port->port_num >= 8 && port->dpcd_rev >= DP_DPCD_REV_14)
+		return true;
+
+	/* DP-to-HDMI Protocol Converter */
+	if (port->pdt == DP_PEER_DEVICE_DP_LEGACY_CONV &&
+			!port->mcs &&
+			port->ldps &&
+			port->dpcd_rev >= DP_DPCD_REV_14)
+		return true;
+
+	/* DP-to-DP */
+	mutex_lock(&port->mgr->lock);
+	if (port->pdt == DP_PEER_DEVICE_MST_BRANCHING &&
+			port->mstb &&
+			port->dpcd_rev >= DP_DPCD_REV_14 &&
+			port->mstb->num_ports == 2) {
+		list_for_each_entry(downstream_port, &port->mstb->ports, next) {
+			if (!downstream_port->input &&
+				downstream_port->pdt == DP_PEER_DEVICE_SST_SINK)
+				return true;
+		}
+	}
+	mutex_unlock(&port->mgr->lock);
+
+	return false;
+}
+
+/**
+ * drm_dp_mst_dsc_aux_for_port() - Find the correct aux for DSC
+ * @port: The port to check. A leaf of the MST tree with an attached display.
+ *
+ * Depending on the situation, DSC may be enabled via the endpoint aux,
+ * the immediately upstream aux, or the connector's physical aux.
+ *
+ * This is both the correct aux to read DSC_CAPABILITY and the
+ * correct aux to write DSC_ENABLED.
+ *
+ * This operation can be expensive (up to four aux reads), so
+ * the caller should cache the return.
+ *
+ * Returns:
+ * NULL if DSC cannot be enabled on this port, otherwise the aux device
+ */
+struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port)
+{
+	struct drm_dp_mst_port *immediate_upstream_port;
+	struct drm_dp_mst_port *fec_port;
+	struct drm_dp_desc *desc;
+
+	if (port && port->parent)
+		immediate_upstream_port = port->parent->port_parent;
+	else
+		immediate_upstream_port = NULL;
+
+	fec_port = immediate_upstream_port;
+	while (fec_port) {
+		/*
+		 * Each physical link (i.e. not a virtual port) between the
+		 * output and the primary device must support FEC
+		 */
+		if (!drm_dp_mst_is_virtual_dpcd(fec_port) &&
+				!fec_port->fec_capable)
+			return NULL;
+
+		fec_port = fec_port->parent->port_parent;
+	}
+
+	/* Enpoint decompression with DP-to-DP peer device */
+	if (drm_dp_mst_is_virtual_dpcd(immediate_upstream_port)) {
+		u8 upstream_dsc;
+		u8 endpoint_dsc;
+		u8 endpoint_fec;
+
+		if (drm_dp_dpcd_read(&port->aux,
+				     DP_DSC_SUPPORT, &endpoint_dsc, 1) < 0)
+			return NULL;
+		if (drm_dp_dpcd_read(&port->aux,
+				     DP_FEC_CAPABILITY, &endpoint_fec, 1) < 0)
+			return NULL;
+		if (drm_dp_dpcd_read(&immediate_upstream_port->aux,
+				     DP_DSC_SUPPORT, &upstream_dsc, 1) < 0)
+			return NULL;
+
+		if ((endpoint_dsc & DP_DSC_DECOMPRESSION_IS_SUPPORTED)
+				&& (endpoint_fec & DP_FEC_CAPABLE)
+				&& (upstream_dsc & 0x2) /* DSC passthrough */)
+			return &port->aux;
+
+		/* Virtual DPCD decompression with DP-to-DP peer device */
+		return &immediate_upstream_port->aux;
+	}
+
+	/* Virtual DPCD decompression with DP-to-HDMI or Virtual DP Sink */
+	if (drm_dp_mst_is_virtual_dpcd(port))
+		return &port->aux;
+
+	/*
+	 * Synaptics quirk
+	 * Applies to ports for which:
+	 * - Physical aux has Synaptics OUI
+	 * - DPv1.4 or higher
+	 * - Port is on primary branch device
+	 * - Not a VGA adapter (DP_DWN_STRM_PORT_TYPE_ANALOG)
+	 */
+	drm_dp_read_desc(port->mgr->aux, desc, true);
+	if (drm_dp_has_quirk(desc, DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD &&
+			port->mgr->dpcd[DP_DPCD_REV] >= DP_DPCD_REV_14) &&
+			port->parent == port->mgr->mst_primary) {
+		u8 downstreamport;
+
+		drm_dp_dpcd_read(&port->aux, DP_DOWNSTREAMPORT_PRESENT,
+				 &downstreamport, 1);
+
+		if ((downstreamport & DP_DWN_STRM_PORT_PRESENT) &&
+				(downstreamport & DP_DWN_STRM_PORT_TYPE_MASK
+				!= DP_DWN_STRM_PORT_TYPE_ANALOG))
+			return port->mgr->aux;
+	}
+
+	return NULL;
+}
+EXPORT_SYMBOL(drm_dp_mst_dsc_aux_for_port);
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 8364502f92cf..a1331b08705f 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -1434,6 +1434,13 @@ enum drm_dp_quirk {
 	 * The driver should ignore SINK_COUNT during detection.
 	 */
 	DP_DPCD_QUIRK_NO_SINK_COUNT,
+	/**
+	 * @DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD:
+	 *
+	 * The device supports MST DSC despite not supporting Virtual DPCD.
+	 * The DSC caps can be read from the physical aux instead.
+	 */
+	DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD,
 };
 
 /**
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index f113ae04fa88..4cf738545dfb 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -673,6 +673,8 @@ int __must_check drm_dp_mst_atomic_check(struct drm_atomic_state *state);
 void drm_dp_mst_get_port_malloc(struct drm_dp_mst_port *port);
 void drm_dp_mst_put_port_malloc(struct drm_dp_mst_port *port);
 
+struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port);
+
 extern const struct drm_private_state_funcs drm_dp_mst_topology_state_funcs;
 
 /**
-- 
2.17.1

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Re: [PATCH v5 1/5] drm/dp_mst: Add PBN calculation for DSC modes

[Lyude Paul]

On Fri, 2019-08-23 at 16:28 -0400, David Francis wrote:
> With DSC, bpp can be fractional in multiples of 1/16.
> 
> Change drm_dp_calc_pbn_mode to reflect this, adding a new
> parameter bool dsc. When this parameter is true, treat the
> bpp parameter as having units not of bits per pixel, but
> 1/16 of a bit per pixel
> 
> v2: Don't add separate function for this
> 
> Cc: Lyude Paul <lyude@redhat.com>
> Signed-off-by: David Francis <David.Francis@amd.com>
> ---
>  .../amd/display/amdgpu_dm/amdgpu_dm_helpers.c    |  2 +-
>  drivers/gpu/drm/drm_dp_mst_topology.c            | 16 ++++++++++++----
>  drivers/gpu/drm/i915/display/intel_dp_mst.c      |  2 +-
>  drivers/gpu/drm/nouveau/dispnv50/disp.c          |  2 +-
>  drivers/gpu/drm/radeon/radeon_dp_mst.c           |  2 +-
>  include/drm/drm_dp_mst_helper.h                  |  3 +--
>  6 files changed, 17 insertions(+), 10 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 a0ed0154a9f0..abafb5221b44 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
> @@ -235,7 +235,7 @@ bool dm_helpers_dp_mst_write_payload_allocation_table(
>  
>  		/* TODO need to know link rate */
>  
> -		pbn = drm_dp_calc_pbn_mode(clock, bpp);
> +		pbn = drm_dp_calc_pbn_mode(clock, bpp, false);
>  
>  		slots = drm_dp_find_vcpi_slots(mst_mgr, pbn);
>  		ret = drm_dp_mst_allocate_vcpi(mst_mgr, mst_port, pbn, slots);
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 82add736e17d..157ffa30d984 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -3534,10 +3534,11 @@ EXPORT_SYMBOL(drm_dp_check_act_status);
>   * drm_dp_calc_pbn_mode() - Calculate the PBN for a mode.
>   * @clock: dot clock for the mode
>   * @bpp: bpp for the mode.
> + * @dsc: DSC mode. If true, bpp has units of 1/16 of a bit per pixel
>   *
>   * This uses the formula in the spec to calculate the PBN value for a mode.
>   */
> -int drm_dp_calc_pbn_mode(int clock, int bpp)
> +int drm_dp_calc_pbn_mode(int clock, int bpp, bool dsc)
>  {
>  	u64 kbps;
>  	s64 peak_kbps;
> @@ -3555,11 +3556,18 @@ int drm_dp_calc_pbn_mode(int clock, int bpp)
>  	 * peak_kbps *= (1006/1000)
>  	 * peak_kbps *= (64/54)
>  	 * peak_kbps *= 8    convert to bytes
> +	 *
> +	 * If the bpp is in units of 1/16, further divide by 16. Put this
> +	 * factor in the numberator rather than the denominator to avoid
> +	 * integer overflow
s/numberator/numerator/

With that, this patch is:

Reviewed-by: Lyude Paul <lyude@redhat.com>

>  	 */
>  
>  	numerator = 64 * 1006;
>  	denominator = 54 * 8 * 1000 * 1000;
>  
> +	if (dsc)
> +		numerator /= 16;
> +
>  	kbps *= numerator;
>  	peak_kbps = drm_fixp_from_fraction(kbps, denominator);
>  
> @@ -3570,19 +3578,19 @@ EXPORT_SYMBOL(drm_dp_calc_pbn_mode);
>  static int test_calc_pbn_mode(void)
>  {
>  	int ret;
> -	ret = drm_dp_calc_pbn_mode(154000, 30);
> +	ret = drm_dp_calc_pbn_mode(154000, 30, false);
>  	if (ret != 689) {
>  		DRM_ERROR("PBN calculation test failed - clock %d, bpp %d,
> expected PBN %d, actual PBN %d.\n",
>  				154000, 30, 689, ret);
>  		return -EINVAL;
>  	}
> -	ret = drm_dp_calc_pbn_mode(234000, 30);
> +	ret = drm_dp_calc_pbn_mode(234000, 30, false);
>  	if (ret != 1047) {
>  		DRM_ERROR("PBN calculation test failed - clock %d, bpp %d,
> expected PBN %d, actual PBN %d.\n",
>  				234000, 30, 1047, ret);
>  		return -EINVAL;
>  	}
> -	ret = drm_dp_calc_pbn_mode(297000, 24);
> +	ret = drm_dp_calc_pbn_mode(297000, 24, false);
>  	if (ret != 1063) {
>  		DRM_ERROR("PBN calculation test failed - clock %d, bpp %d,
> expected PBN %d, actual PBN %d.\n",
>  				297000, 24, 1063, ret);
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index 2c5ac3dd647f..4f17f61f4453 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -61,7 +61,7 @@ static int intel_dp_mst_compute_link_config(struct
> intel_encoder *encoder,
>  		crtc_state->pipe_bpp = bpp;
>  
>  		crtc_state->pbn = drm_dp_calc_pbn_mode(adjusted_mode-
> >crtc_clock,
> -						       crtc_state->pipe_bpp);
> +						       crtc_state->pipe_bpp,
> false);
>  
>  		slots = drm_dp_atomic_find_vcpi_slots(state, &intel_dp-
> >mst_mgr,
>  						      port, crtc_state->pbn);
> diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c
> b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> index 5c36c75232e6..c68783c1f3fa 100644
> --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
> +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> @@ -782,7 +782,7 @@ nv50_msto_atomic_check(struct drm_encoder *encoder,
>  			const int bpp = connector->display_info.bpc * 3;
>  			const int clock = crtc_state->adjusted_mode.clock;
>  
> -			asyh->dp.pbn = drm_dp_calc_pbn_mode(clock, bpp);
> +			asyh->dp.pbn = drm_dp_calc_pbn_mode(clock, bpp,
> false);
>  		}
>  
>  		slots = drm_dp_atomic_find_vcpi_slots(state, &mstm->mgr,
> diff --git a/drivers/gpu/drm/radeon/radeon_dp_mst.c
> b/drivers/gpu/drm/radeon/radeon_dp_mst.c
> index 2994f07fbad9..c997f88218f2 100644
> --- a/drivers/gpu/drm/radeon/radeon_dp_mst.c
> +++ b/drivers/gpu/drm/radeon/radeon_dp_mst.c
> @@ -514,7 +514,7 @@ static bool radeon_mst_mode_fixup(struct drm_encoder
> *encoder,
>  
>  	mst_enc = radeon_encoder->enc_priv;
>  
> -	mst_enc->pbn = drm_dp_calc_pbn_mode(adjusted_mode->clock, bpp);
> +	mst_enc->pbn = drm_dp_calc_pbn_mode(adjusted_mode->clock, bpp, false);
>  
>  	mst_enc->primary->active_device = mst_enc->primary->devices & mst_enc-
> >connector->devices;
>  	DRM_DEBUG_KMS("setting active device to %08x from %08x %08x for
> encoder %d\n",
> diff --git a/include/drm/drm_dp_mst_helper.h
> b/include/drm/drm_dp_mst_helper.h
> index 2ba6253ea6d3..9116b2c95239 100644
> --- a/include/drm/drm_dp_mst_helper.h
> +++ b/include/drm/drm_dp_mst_helper.h
> @@ -610,8 +610,7 @@ bool drm_dp_mst_port_has_audio(struct
> drm_dp_mst_topology_mgr *mgr,
>  struct edid *drm_dp_mst_get_edid(struct drm_connector *connector, struct
> drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port);
>  
>  
> -int drm_dp_calc_pbn_mode(int clock, int bpp);
> -
> +int drm_dp_calc_pbn_mode(int clock, int bpp, bool dsc);
>  
>  bool drm_dp_mst_allocate_vcpi(struct drm_dp_mst_topology_mgr *mgr,
>  			      struct drm_dp_mst_port *port, int pbn, int
> slots);
-- 
Cheers,
	Lyude Paul

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Re: [PATCH v5 1/5] drm/dp_mst: Add PBN calculation for DSC modes

[Manasi Navare]

On Fri, Aug 23, 2019 at 04:28:05PM -0400, David Francis wrote:
> With DSC, bpp can be fractional in multiples of 1/16.
> 
> Change drm_dp_calc_pbn_mode to reflect this, adding a new
> parameter bool dsc. When this parameter is true, treat the
> bpp parameter as having units not of bits per pixel, but
> 1/16 of a bit per pixel
> 
> v2: Don't add separate function for this
> 
> Cc: Lyude Paul <lyude@redhat.com>
> Signed-off-by: David Francis <David.Francis@amd.com>

Looks good to me except for the typo that Lyude pointed.
Also would be good if you send the patches that modify the intel_ functions to intel-gfx mailing list as well

Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>

Manasi

> ---
>  .../amd/display/amdgpu_dm/amdgpu_dm_helpers.c    |  2 +-
>  drivers/gpu/drm/drm_dp_mst_topology.c            | 16 ++++++++++++----
>  drivers/gpu/drm/i915/display/intel_dp_mst.c      |  2 +-
>  drivers/gpu/drm/nouveau/dispnv50/disp.c          |  2 +-
>  drivers/gpu/drm/radeon/radeon_dp_mst.c           |  2 +-
>  include/drm/drm_dp_mst_helper.h                  |  3 +--
>  6 files changed, 17 insertions(+), 10 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 a0ed0154a9f0..abafb5221b44 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
> @@ -235,7 +235,7 @@ bool dm_helpers_dp_mst_write_payload_allocation_table(
>  
>  		/* TODO need to know link rate */
>  
> -		pbn = drm_dp_calc_pbn_mode(clock, bpp);
> +		pbn = drm_dp_calc_pbn_mode(clock, bpp, false);
>  
>  		slots = drm_dp_find_vcpi_slots(mst_mgr, pbn);
>  		ret = drm_dp_mst_allocate_vcpi(mst_mgr, mst_port, pbn, slots);
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 82add736e17d..157ffa30d984 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -3534,10 +3534,11 @@ EXPORT_SYMBOL(drm_dp_check_act_status);
>   * drm_dp_calc_pbn_mode() - Calculate the PBN for a mode.
>   * @clock: dot clock for the mode
>   * @bpp: bpp for the mode.
> + * @dsc: DSC mode. If true, bpp has units of 1/16 of a bit per pixel
>   *
>   * This uses the formula in the spec to calculate the PBN value for a mode.
>   */
> -int drm_dp_calc_pbn_mode(int clock, int bpp)
> +int drm_dp_calc_pbn_mode(int clock, int bpp, bool dsc)
>  {
>  	u64 kbps;
>  	s64 peak_kbps;
> @@ -3555,11 +3556,18 @@ int drm_dp_calc_pbn_mode(int clock, int bpp)
>  	 * peak_kbps *= (1006/1000)
>  	 * peak_kbps *= (64/54)
>  	 * peak_kbps *= 8    convert to bytes
> +	 *
> +	 * If the bpp is in units of 1/16, further divide by 16. Put this
> +	 * factor in the numberator rather than the denominator to avoid
> +	 * integer overflow
>  	 */
>  
>  	numerator = 64 * 1006;
>  	denominator = 54 * 8 * 1000 * 1000;
>  
> +	if (dsc)
> +		numerator /= 16;
> +
>  	kbps *= numerator;
>  	peak_kbps = drm_fixp_from_fraction(kbps, denominator);
>  
> @@ -3570,19 +3578,19 @@ EXPORT_SYMBOL(drm_dp_calc_pbn_mod
>  {
>  	int ret;
> -	ret = drm_dp_calc_pbn_mode(154000, 30);
> +	ret = drm_dp_calc_pbn_mode(154000, 30, false);
>  	if (ret != 689) {
>  		DRM_ERROR("PBN calculation test failed - clock %d, bpp %d, expected PBN %d, actual PBN %d.\n",
>  				154000, 30, 689, ret);
>  		return -EINVAL;
>  	}
> -	ret = drm_dp_calc_pbn_mode(234000, 30);
> +	ret = drm_dp_calc_pbn_mode(234000, 30, false);
>  	if (ret != 1047) {
>  		DRM_ERROR("PBN calculation test failed - clock %d, bpp %d, expected PBN %d, actual PBN %d.\n",
>  				234000, 30, 1047, ret);
>  		return -EINVAL;
>  	}
> -	ret = drm_dp_calc_pbn_mode(297000, 24);
> +	ret = drm_dp_calc_pbn_mode(297000, 24, false);
>  	if (ret != 1063) {
>  		DRM_ERROR("PBN calculation test failed - clock %d, bpp %d, expected PBN %d, actual PBN %d.\n",
>  				297000, 24, 1063, ret);
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index 2c5ac3dd647f..4f17f61f4453 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -61,7 +61,7 @@ static int intel_dp_mst_compute_link_config(struct intel_encoder *encoder,
>  		crtc_state->pipe_bpp = bpp;
>  
>  		crtc_state->pbn = drm_dp_calc_pbn_mode(adjusted_mode->crtc_clock,
> -						       crtc_state->pipe_bpp);
> +						       crtc_state->pipe_bpp, false);
>  
>  		slots = drm_dp_atomic_find_vcpi_slots(state, &intel_dp->mst_mgr,
>  						      port, crtc_state->pbn);
> diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> index 5c36c75232e6..c68783c1f3fa 100644
> --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
> +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> @@ -782,7 +782,7 @@ nv50_msto_atomic_check(struct drm_encoder *encoder,
>  			const int bpp = connector->display_info.bpc * 3;
>  			const int clock = crtc_state->adjusted_mode.clock;
>  
> -			asyh->dp.pbn = drm_dp_calc_pbn_mode(clock, bpp);
> +			asyh->dp.pbn = drm_dp_calc_pbn_mode(clock, bpp, false);
>  		}
>  
>  		slots = drm_dp_atomic_find_vcpi_slots(state, &mstm->mgr,
> diff --git a/drivers/gpu/drm/radeon/radeon_dp_mst.c b/drivers/gpu/drm/radeon/radeon_dp_mst.c
> index 2994f07fbad9..c997f88218f2 100644
> --- a/drivers/gpu/drm/radeon/radeon_dp_mst.c
> +++ b/drivers/gpu/drm/radeon/radeon_dp_mst.c
> @@ -514,7 +514,7 @@ static bool radeon_mst_mode_fixup(struct drm_encoder *encoder,
>  
>  	mst_enc = radeon_encoder->enc_priv;
>  
> -	mst_enc->pbn = drm_dp_calc_pbn_mode(adjusted_mode->clock, bpp);
> +	mst_enc->pbn = drm_dp_calc_pbn_mode(adjusted_mode->clock, bpp, false);
>  
>  	mst_enc->primary->active_device = mst_enc->primary->devices & mst_enc->connector->devices;
>  	DRM_DEBUG_KMS("setting active device to %08x from %08x %08x for encoder %d\n",
> diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
> index 2ba6253ea6d3..9116b2c95239 100644
> --- a/include/drm/drm_dp_mst_helper.h
> +++ b/include/drm/drm_dp_mst_helper.h
> @@ -610,8 +610,7 @@ bool drm_dp_mst_port_has_audio(struct drm_dp_mst_topology_mgr *mgr,
>  struct edid *drm_dp_mst_get_edid(struct drm_connector *connector, struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port);
>  
>  
> -int drm_dp_calc_pbn_mode(int clock, int bpp);
> -
> +int drm_dp_calc_pbn_mode(int clock, int bpp, bool dsc);
>  
>  bool drm_dp_mst_allocate_vcpi(struct drm_dp_mst_topology_mgr *mgr,
>  			      struct drm_dp_mst_port *port, int pbn, int slots);
> -- 
> 2.17.1
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
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Re: [PATCH v5 3/5] drm/dp_mst: Add MST support to DP DPCD R/W functions

[Jani Nikula]

On Fri, 23 Aug 2019, David Francis <David.Francis@amd.com> wrote:
> Instead of having drm_dp_dpcd_read/write and
> drm_dp_mst_dpcd_read/write as entry points into the
> aux code, have drm_dp_dpcd_read/write handle both.
>
> This means that DRM drivers can make MST DPCD read/writes.
>
> v2: Fix spacing
> v3: Dump dpcd access on MST read/writes
>
> Reviewed-by: Lyude Paul <lyude@redhat.com>
> Signed-off-by: David Francis <David.Francis@amd.com>

Cc: Ville who added drm_dp_mst_dpcd_read and _write.

BR,
Jani.


> ---
>  drivers/gpu/drm/drm_dp_aux_dev.c | 12 ++----------
>  drivers/gpu/drm/drm_dp_helper.c  | 30 ++++++++++++++++++++----------
>  2 files changed, 22 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_aux_dev.c b/drivers/gpu/drm/drm_dp_aux_dev.c
> index 0cfb386754c3..418cad4f649a 100644
> --- a/drivers/gpu/drm/drm_dp_aux_dev.c
> +++ b/drivers/gpu/drm/drm_dp_aux_dev.c
> @@ -163,11 +163,7 @@ static ssize_t auxdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
>  			break;
>  		}
>  
> -		if (aux_dev->aux->is_remote)
> -			res = drm_dp_mst_dpcd_read(aux_dev->aux, pos, buf,
> -						   todo);
> -		else
> -			res = drm_dp_dpcd_read(aux_dev->aux, pos, buf, todo);
> +		res = drm_dp_dpcd_read(aux_dev->aux, pos, buf, todo);
>  
>  		if (res <= 0)
>  			break;
> @@ -215,11 +211,7 @@ static ssize_t auxdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
>  			break;
>  		}
>  
> -		if (aux_dev->aux->is_remote)
> -			res = drm_dp_mst_dpcd_write(aux_dev->aux, pos, buf,
> -						    todo);
> -		else
> -			res = drm_dp_dpcd_write(aux_dev->aux, pos, buf, todo);
> +		res = drm_dp_mst_dpcd_write(aux_dev->aux, pos, buf, todo);
>  
>  		if (res <= 0)
>  			break;
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index ffc68d305afe..2cc21eff4cf3 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -30,6 +30,7 @@
>  #include <linux/seq_file.h>
>  
>  #include <drm/drm_dp_helper.h>
> +#include <drm/drm_dp_mst_helper.h>
>  #include <drm/drm_print.h>
>  #include <drm/drm_vblank.h>
>  
> @@ -251,7 +252,7 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
>  
>  /**
>   * drm_dp_dpcd_read() - read a series of bytes from the DPCD
> - * @aux: DisplayPort AUX channel
> + * @aux: DisplayPort AUX channel (SST or MST)
>   * @offset: address of the (first) register to read
>   * @buffer: buffer to store the register values
>   * @size: number of bytes in @buffer
> @@ -280,13 +281,18 @@ ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
>  	 * We just have to do it before any DPCD access and hope that the
>  	 * monitor doesn't power down exactly after the throw away read.
>  	 */
> -	ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV, buffer,
> -				 1);
> -	if (ret != 1)
> -		goto out;
> +	if (!aux->is_remote) {
> +		ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV,
> +					 buffer, 1);
> +		if (ret != 1)
> +			goto out;
> +	}
>  
> -	ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer,
> -				 size);
> +	if (aux->is_remote)
> +		ret = drm_dp_mst_dpcd_read(aux, offset, buffer, size);
> +	else
> +		ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset,
> +					 buffer, size);
>  
>  out:
>  	drm_dp_dump_access(aux, DP_AUX_NATIVE_READ, offset, buffer, ret);
> @@ -296,7 +302,7 @@ EXPORT_SYMBOL(drm_dp_dpcd_read);
>  
>  /**
>   * drm_dp_dpcd_write() - write a series of bytes to the DPCD
> - * @aux: DisplayPort AUX channel
> + * @aux: DisplayPort AUX channel (SST or MST)
>   * @offset: address of the (first) register to write
>   * @buffer: buffer containing the values to write
>   * @size: number of bytes in @buffer
> @@ -313,8 +319,12 @@ ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,
>  {
>  	int ret;
>  
> -	ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_WRITE, offset, buffer,
> -				 size);
> +	if (aux->is_remote)
> +		ret = drm_dp_mst_dpcd_write(aux, offset, buffer, size);
> +	else
> +		ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_WRITE, offset,
> +					 buffer, size);
> +
>  	drm_dp_dump_access(aux, DP_AUX_NATIVE_WRITE, offset, buffer, ret);
>  	return ret;
>  }

-- 
Jani Nikula, Intel Open Source Graphics Center
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Re: [PATCH v5 5/5] drm/dp_mst: Add helper for finding right aux to enable/query DSC

[Jani Nikula]

On Fri, 23 Aug 2019, David Francis <David.Francis@amd.com> wrote:
> Add drm_dp_mst_dsc_aux_for_port. To enable DSC, the DSC_ENABLED
> register might have to be written on the leaf port's DPCD,
> its parent's DPCD, or the MST manager's DPCD. This function
> finds the correct aux for the job.
>
> As part of this, add drm_dp_mst_is_virtual_dpcd. Virtual DPCD
> is a DP feature new in DP v1.4, which exposes certain DPCD
> registers on virtual ports.
>
> ALso add a new quirk for Synatics MST hubs that support DSC
> despite not supporting virtual DPCD.

"Also" in the commit message often means, "should be a separate
patch". I think this is true here.

BR,
Jani.


>
> Cc: Lyude Paul <lyude@redhat.com>
> Cc: Wenjing Liu <Wenjing.Liu@amd.com>
> Cc: Nikola Cornij <Nikola.Cornij@amd.com>
> Signed-off-by: David Francis <David.Francis@amd.com>
> ---
>  drivers/gpu/drm/drm_dp_helper.c       |   2 +
>  drivers/gpu/drm/drm_dp_mst_topology.c | 147 ++++++++++++++++++++++++++
>  include/drm/drm_dp_helper.h           |   7 ++
>  include/drm/drm_dp_mst_helper.h       |   2 +
>  4 files changed, 158 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 2cc21eff4cf3..fc39323e7d52 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -1270,6 +1270,8 @@ static const struct dpcd_quirk dpcd_quirk_list[] = {
>  	{ OUI(0x00, 0x10, 0xfa), DEVICE_ID_ANY, false, BIT(DP_DPCD_QUIRK_NO_PSR) },
>  	/* CH7511 seems to leave SINK_COUNT zeroed */
>  	{ OUI(0x00, 0x00, 0x00), DEVICE_ID('C', 'H', '7', '5', '1', '1'), false, BIT(DP_DPCD_QUIRK_NO_SINK_COUNT) },
> +	/* Synaptics DP1.4 MST hubs can support DSC without virtual DPCD */
> +	{ OUI(0x90, 0xCC, 0x24), DEVICE_ID_ANY, true, BIT(DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD) },
>  };
>  
>  #undef OUI
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index a39e42c7d868..559bc09b6b94 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -4150,3 +4150,150 @@ static void drm_dp_mst_unregister_i2c_bus(struct drm_dp_aux *aux)
>  {
>  	i2c_del_adapter(&aux->ddc);
>  }
> +
> +/**
> + * drm_dp_mst_is_virtual_dpcd() - Is the given port a virtual DP Peer Device
> + * @port: The port to check
> + *
> + * A single physical MST hub object can be represented in the topology
> + * by multiple branches, with virtual ports between those branches.
> + *
> + * As of DP1.4, An MST hub with internal (virtual) ports must expose
> + * certain DPCD registers over those ports. See sections 2.6.1.1.1
> + * and 2.6.1.1.2 of Display Port specification v1.4 for details.
> + *
> + * May acquire mgr->lock
> + *
> + * Returns:
> + * true if the port is a virtual DP peer device, false otherwise
> + */
> +static bool drm_dp_mst_is_virtual_dpcd(struct drm_dp_mst_port *port)
> +{
> +	struct drm_dp_mst_port *downstream_port;
> +
> +	if (!port)
> +		return false;
> +
> +	/* Virtual DP Sink (Internal Display Panel) */
> +	if (port->port_num >= 8 && port->dpcd_rev >= DP_DPCD_REV_14)
> +		return true;
> +
> +	/* DP-to-HDMI Protocol Converter */
> +	if (port->pdt == DP_PEER_DEVICE_DP_LEGACY_CONV &&
> +			!port->mcs &&
> +			port->ldps &&
> +			port->dpcd_rev >= DP_DPCD_REV_14)
> +		return true;
> +
> +	/* DP-to-DP */
> +	mutex_lock(&port->mgr->lock);
> +	if (port->pdt == DP_PEER_DEVICE_MST_BRANCHING &&
> +			port->mstb &&
> +			port->dpcd_rev >= DP_DPCD_REV_14 &&
> +			port->mstb->num_ports == 2) {
> +		list_for_each_entry(downstream_port, &port->mstb->ports, next) {
> +			if (!downstream_port->input &&
> +				downstream_port->pdt == DP_PEER_DEVICE_SST_SINK)
> +				return true;
> +		}
> +	}
> +	mutex_unlock(&port->mgr->lock);
> +
> +	return false;
> +}
> +
> +/**
> + * drm_dp_mst_dsc_aux_for_port() - Find the correct aux for DSC
> + * @port: The port to check. A leaf of the MST tree with an attached display.
> + *
> + * Depending on the situation, DSC may be enabled via the endpoint aux,
> + * the immediately upstream aux, or the connector's physical aux.
> + *
> + * This is both the correct aux to read DSC_CAPABILITY and the
> + * correct aux to write DSC_ENABLED.
> + *
> + * This operation can be expensive (up to four aux reads), so
> + * the caller should cache the return.
> + *
> + * Returns:
> + * NULL if DSC cannot be enabled on this port, otherwise the aux device
> + */
> +struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port)
> +{
> +	struct drm_dp_mst_port *immediate_upstream_port;
> +	struct drm_dp_mst_port *fec_port;
> +	struct drm_dp_desc *desc;
> +
> +	if (port && port->parent)
> +		immediate_upstream_port = port->parent->port_parent;
> +	else
> +		immediate_upstream_port = NULL;
> +
> +	fec_port = immediate_upstream_port;
> +	while (fec_port) {
> +		/*
> +		 * Each physical link (i.e. not a virtual port) between the
> +		 * output and the primary device must support FEC
> +		 */
> +		if (!drm_dp_mst_is_virtual_dpcd(fec_port) &&
> +				!fec_port->fec_capable)
> +			return NULL;
> +
> +		fec_port = fec_port->parent->port_parent;
> +	}
> +
> +	/* Enpoint decompression with DP-to-DP peer device */
> +	if (drm_dp_mst_is_virtual_dpcd(immediate_upstream_port)) {
> +		u8 upstream_dsc;
> +		u8 endpoint_dsc;
> +		u8 endpoint_fec;
> +
> +		if (drm_dp_dpcd_read(&port->aux,
> +				     DP_DSC_SUPPORT, &endpoint_dsc, 1) < 0)
> +			return NULL;
> +		if (drm_dp_dpcd_read(&port->aux,
> +				     DP_FEC_CAPABILITY, &endpoint_fec, 1) < 0)
> +			return NULL;
> +		if (drm_dp_dpcd_read(&immediate_upstream_port->aux,
> +				     DP_DSC_SUPPORT, &upstream_dsc, 1) < 0)
> +			return NULL;
> +
> +		if ((endpoint_dsc & DP_DSC_DECOMPRESSION_IS_SUPPORTED)
> +				&& (endpoint_fec & DP_FEC_CAPABLE)
> +				&& (upstream_dsc & 0x2) /* DSC passthrough */)
> +			return &port->aux;
> +
> +		/* Virtual DPCD decompression with DP-to-DP peer device */
> +		return &immediate_upstream_port->aux;
> +	}
> +
> +	/* Virtual DPCD decompression with DP-to-HDMI or Virtual DP Sink */
> +	if (drm_dp_mst_is_virtual_dpcd(port))
> +		return &port->aux;
> +
> +	/*
> +	 * Synaptics quirk
> +	 * Applies to ports for which:
> +	 * - Physical aux has Synaptics OUI
> +	 * - DPv1.4 or higher
> +	 * - Port is on primary branch device
> +	 * - Not a VGA adapter (DP_DWN_STRM_PORT_TYPE_ANALOG)
> +	 */
> +	drm_dp_read_desc(port->mgr->aux, desc, true);
> +	if (drm_dp_has_quirk(desc, DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD &&
> +			port->mgr->dpcd[DP_DPCD_REV] >= DP_DPCD_REV_14) &&
> +			port->parent == port->mgr->mst_primary) {
> +		u8 downstreamport;
> +
> +		drm_dp_dpcd_read(&port->aux, DP_DOWNSTREAMPORT_PRESENT,
> +				 &downstreamport, 1);
> +
> +		if ((downstreamport & DP_DWN_STRM_PORT_PRESENT) &&
> +				(downstreamport & DP_DWN_STRM_PORT_TYPE_MASK
> +				!= DP_DWN_STRM_PORT_TYPE_ANALOG))
> +			return port->mgr->aux;
> +	}
> +
> +	return NULL;
> +}
> +EXPORT_SYMBOL(drm_dp_mst_dsc_aux_for_port);
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index 8364502f92cf..a1331b08705f 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -1434,6 +1434,13 @@ enum drm_dp_quirk {
>  	 * The driver should ignore SINK_COUNT during detection.
>  	 */
>  	DP_DPCD_QUIRK_NO_SINK_COUNT,
> +	/**
> +	 * @DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD:
> +	 *
> +	 * The device supports MST DSC despite not supporting Virtual DPCD.
> +	 * The DSC caps can be read from the physical aux instead.
> +	 */
> +	DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD,
>  };
>  
>  /**
> diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
> index f113ae04fa88..4cf738545dfb 100644
> --- a/include/drm/drm_dp_mst_helper.h
> +++ b/include/drm/drm_dp_mst_helper.h
> @@ -673,6 +673,8 @@ int __must_check drm_dp_mst_atomic_check(struct drm_atomic_state *state);
>  void drm_dp_mst_get_port_malloc(struct drm_dp_mst_port *port);
>  void drm_dp_mst_put_port_malloc(struct drm_dp_mst_port *port);
>  
> +struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port);
> +
>  extern const struct drm_private_state_funcs drm_dp_mst_topology_state_funcs;
>  
>  /**

-- 
Jani Nikula, Intel Open Source Graphics Center
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