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drm/mst: Support simultaneous down replies
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Currently we have one down reply message servicing the mst manager, so
we need to serialize all tx msgs to ensure we only have one message in
flight at a time. For obvious reasons this is suboptimal (but less
suboptimal than the free-for-all we had before serialization).

This patch removes the single down_rep_recv message from manager and
adds 2 replies in the branch structure. The 2 replies mirrors the tx_slots
which we use to rate-limit outgoing messages and correspond to seqno in
the packet headers.

Cc: Wayne Lin <[email protected]>
Reviewed-by: Lyude Paul <[email protected]>
Reviewed-by: Wayne Lin <[email protected]>
Signed-off-by: Sean Paul <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
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@atseanpaul
atseanpaul committed Mar 27, 2020
1 parent 21a729d commit fbc821c
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Showing 2 changed files with 78 additions and 61 deletions.
80 changes: 48 additions & 32 deletions drivers/gpu/drm/drm_dp_mst_topology.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3696,7 +3696,8 @@ int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr,
}
EXPORT_SYMBOL(drm_dp_mst_topology_mgr_resume);

static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up)
static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up,
struct drm_dp_mst_branch **mstb, int *seqno)
{
int len;
u8 replyblock[32];
Expand All @@ -3708,7 +3709,8 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up)
int basereg = up ? DP_SIDEBAND_MSG_UP_REQ_BASE :
DP_SIDEBAND_MSG_DOWN_REP_BASE;

msg = up ? &mgr->up_req_recv : &mgr->down_rep_recv;
*mstb = NULL;
*seqno = -1;

len = min(mgr->max_dpcd_transaction_bytes, 16);
ret = drm_dp_dpcd_read(mgr->aux, basereg, replyblock, len);
Expand All @@ -3725,6 +3727,21 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up)
return false;
}

*seqno = hdr.seqno;

if (up) {
msg = &mgr->up_req_recv;
} else {
/* Caller is responsible for giving back this reference */
*mstb = drm_dp_get_mst_branch_device(mgr, hdr.lct, hdr.rad);
if (!*mstb) {
DRM_DEBUG_KMS("Got MST reply from unknown device %d\n",
hdr.lct);
return false;
}
msg = &(*mstb)->down_rep_recv[hdr.seqno];
}

if (!drm_dp_sideband_msg_set_header(msg, &hdr, hdrlen)) {
DRM_DEBUG_KMS("sideband msg set header failed %d\n",
replyblock[0]);
Expand Down Expand Up @@ -3765,67 +3782,68 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up)
static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr)
{
struct drm_dp_sideband_msg_tx *txmsg;
struct drm_dp_mst_branch *mstb;
struct drm_dp_sideband_msg_hdr *hdr = &mgr->down_rep_recv.initial_hdr;
int slot = -1;
struct drm_dp_mst_branch *mstb = NULL;
struct drm_dp_sideband_msg_rx *msg = NULL;
int seqno = -1;

if (!drm_dp_get_one_sb_msg(mgr, false))
goto clear_down_rep_recv;
if (!drm_dp_get_one_sb_msg(mgr, false, &mstb, &seqno))
goto out_clear_reply;

if (!mgr->down_rep_recv.have_eomt)
return 0;
msg = &mstb->down_rep_recv[seqno];

mstb = drm_dp_get_mst_branch_device(mgr, hdr->lct, hdr->rad);
if (!mstb) {
DRM_DEBUG_KMS("Got MST reply from unknown device %d\n",
hdr->lct);
goto clear_down_rep_recv;
}
/* Multi-packet message transmission, don't clear the reply */
if (!msg->have_eomt)
goto out;

/* find the message */
slot = hdr->seqno;
mutex_lock(&mgr->qlock);
txmsg = mstb->tx_slots[slot];
txmsg = mstb->tx_slots[seqno];
/* remove from slots */
mutex_unlock(&mgr->qlock);

if (!txmsg) {
struct drm_dp_sideband_msg_hdr *hdr;
hdr = &msg->initial_hdr;
DRM_DEBUG_KMS("Got MST reply with no msg %p %d %d %02x %02x\n",
mstb, hdr->seqno, hdr->lct, hdr->rad[0],
mgr->down_rep_recv.msg[0]);
goto no_msg;
msg->msg[0]);
goto out_clear_reply;
}

drm_dp_sideband_parse_reply(&mgr->down_rep_recv, &txmsg->reply);
drm_dp_sideband_parse_reply(msg, &txmsg->reply);

if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK)
if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK) {
DRM_DEBUG_KMS("Got NAK reply: req 0x%02x (%s), reason 0x%02x (%s), nak data 0x%02x\n",
txmsg->reply.req_type,
drm_dp_mst_req_type_str(txmsg->reply.req_type),
txmsg->reply.u.nak.reason,
drm_dp_mst_nak_reason_str(txmsg->reply.u.nak.reason),
txmsg->reply.u.nak.nak_data);
goto out_clear_reply;
}

memset(&mgr->down_rep_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx));
drm_dp_mst_topology_put_mstb(mstb);

mutex_lock(&mgr->qlock);
txmsg->state = DRM_DP_SIDEBAND_TX_RX;
mstb->tx_slots[slot] = NULL;
mstb->tx_slots[seqno] = NULL;
mgr->is_waiting_for_dwn_reply = false;
mutex_unlock(&mgr->qlock);

wake_up_all(&mgr->tx_waitq);

return 0;

no_msg:
drm_dp_mst_topology_put_mstb(mstb);
clear_down_rep_recv:
out_clear_reply:
mutex_lock(&mgr->qlock);
mgr->is_waiting_for_dwn_reply = false;
mutex_unlock(&mgr->qlock);
memset(&mgr->down_rep_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
if (msg)
memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx));
out:
if (mstb)
drm_dp_mst_topology_put_mstb(mstb);

return 0;
}
Expand Down Expand Up @@ -3901,11 +3919,10 @@ static void drm_dp_mst_up_req_work(struct work_struct *work)

static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr)
{
struct drm_dp_sideband_msg_hdr *hdr = &mgr->up_req_recv.initial_hdr;
struct drm_dp_pending_up_req *up_req;
bool seqno;
int seqno;

if (!drm_dp_get_one_sb_msg(mgr, true))
if (!drm_dp_get_one_sb_msg(mgr, true, NULL, &seqno))
goto out;

if (!mgr->up_req_recv.have_eomt)
Expand All @@ -3918,7 +3935,6 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr)
}
INIT_LIST_HEAD(&up_req->next);

seqno = hdr->seqno;
drm_dp_sideband_parse_req(&mgr->up_req_recv, &up_req->msg);

if (up_req->msg.req_type != DP_CONNECTION_STATUS_NOTIFY &&
Expand Down Expand Up @@ -3952,7 +3968,7 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr)
res_stat->available_pbn);
}

up_req->hdr = *hdr;
up_req->hdr = mgr->up_req_recv.initial_hdr;
mutex_lock(&mgr->up_req_lock);
list_add_tail(&up_req->next, &mgr->up_req_list);
mutex_unlock(&mgr->up_req_lock);
Expand Down
59 changes: 30 additions & 29 deletions include/drm/drm_dp_mst_helper.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -160,6 +160,31 @@ struct drm_dp_mst_port {
bool fec_capable;
};

/* sideband msg header - not bit struct */
struct drm_dp_sideband_msg_hdr {
u8 lct;
u8 lcr;
u8 rad[8];
bool broadcast;
bool path_msg;
u8 msg_len;
bool somt;
bool eomt;
bool seqno;
};

struct drm_dp_sideband_msg_rx {
u8 chunk[48];
u8 msg[256];
u8 curchunk_len;
u8 curchunk_idx; /* chunk we are parsing now */
u8 curchunk_hdrlen;
u8 curlen; /* total length of the msg */
bool have_somt;
bool have_eomt;
struct drm_dp_sideband_msg_hdr initial_hdr;
};

/**
* struct drm_dp_mst_branch - MST branch device.
* @rad: Relative Address to talk to this branch device.
Expand Down Expand Up @@ -232,24 +257,16 @@ struct drm_dp_mst_branch {
int last_seqno;
bool link_address_sent;

/**
* @down_rep_recv: Message receiver state for down replies.
*/
struct drm_dp_sideband_msg_rx down_rep_recv[2];

/* global unique identifier to identify branch devices */
u8 guid[16];
};


/* sideband msg header - not bit struct */
struct drm_dp_sideband_msg_hdr {
u8 lct;
u8 lcr;
u8 rad[8];
bool broadcast;
bool path_msg;
u8 msg_len;
bool somt;
bool eomt;
bool seqno;
};

struct drm_dp_nak_reply {
u8 guid[16];
u8 reason;
Expand Down Expand Up @@ -306,18 +323,6 @@ struct drm_dp_remote_i2c_write_ack_reply {
};


struct drm_dp_sideband_msg_rx {
u8 chunk[48];
u8 msg[256];
u8 curchunk_len;
u8 curchunk_idx; /* chunk we are parsing now */
u8 curchunk_hdrlen;
u8 curlen; /* total length of the msg */
bool have_somt;
bool have_eomt;
struct drm_dp_sideband_msg_hdr initial_hdr;
};

#define DRM_DP_MAX_SDP_STREAMS 16
struct drm_dp_allocate_payload {
u8 port_number;
Expand Down Expand Up @@ -555,10 +560,6 @@ struct drm_dp_mst_topology_mgr {
*/
int conn_base_id;

/**
* @down_rep_recv: Message receiver state for down replies.
*/
struct drm_dp_sideband_msg_rx down_rep_recv;
/**
* @up_req_recv: Message receiver state for up requests.
*/
Expand Down

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