This patch adds documentation for APM X-Gene SoC Queue Manager/Traffic Manager. Signed-off-by: Ravi Patel <rapatel@xxxxxxx> Signed-off-by: Keyur Chudgar <kchudgar@xxxxxxx> --- Documentation/mailbox/apm-xgene-qmtm.txt | 149 ++++++++++++++++++++++++++++++ 1 file changed, 149 insertions(+) create mode 100644 Documentation/mailbox/apm-xgene-qmtm.txt diff --git a/Documentation/mailbox/apm-xgene-qmtm.txt b/Documentation/mailbox/apm-xgene-qmtm.txt new file mode 100644 index 0000000..2b4ff09 --- /dev/null +++ b/Documentation/mailbox/apm-xgene-qmtm.txt @@ -0,0 +1,149 @@ +AppliedMicro X-Gene SOC Queue Manager/Traffic Manager Document + +Copyright (c) 2013 Applied Micro Circuits Corporation. +Author: Ravi Patel <rapatel@xxxxxxx> + +This program is free software; you can redistribute it and/or modify it +under the terms of the GNU General Public License version 2 as published by +the Free Software Foundation. + +This program is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +GNU General Public License for more details. + + +Overview: +QMTM is a device which interacts with CPU, Ethernet, PktDMA and Security +subsystems through AXI BUS. Its centralized resource manager/driver exports +APIs for CPU, Ethernet, PktDMA and Security subsystems to +1. Initialize & allocate queue & pbn. +2. Read queue state so that subsystems driver knows how much more work it can + offload to its subsystem. +3. Apply QoS for subsystems on their queues. + +Layout: +The layout represents run-time flow of messages between Ethernet subsystem, CPU +and QMTM in APM X-Gene SOC. PktDMA and Security subsystems interfaces with QMTM +in the same way as Ethernet. + + + CPU + o-------------------------o + | | + +----|[2] {5}|----+ + | | [1] {4} | | +Register | o------+-----------+------o | Register +Write | CPU WR | | CPU RD | Write +to start v MSG v ^ MSG v to notify +packet | | DDR | | packet +transmit | o--------+-----o-----+--------o | received + | | Q0 M . M M | M M . M Q1 | | + | | for S . S S | S S . S for | | + | | ETH G . G G | G G . G ETH | | + | | TX n . 2 1 | 1 2 . n RX | | + | o----------+---o---+----------o | + | | | | + v v ^ v + | | | | +o--------|-------------|-------|-------------|--------o +| | | | | | Coherent +| v v ^ v | I/O +| | | | | | BUS +o--------|-------------|-------|-------------|--------o + | [3] | | {3} | + v QMTM RD v ^ QMTM WR v + | MSG | | MSG | + o----+----o--------+---o---+--------o----+----o + | Queue 0 | | | Queue 1 | + | Command o ETH PBN 0 o CPU PBN 0 o Command | Queue Manager/ + | Register| | |Register | Traffic Manager + o---------o---+--------o--------+---o---------o + | | + v ^ +Ethernet RD MSG | [4] ETH {2} | Ethernet WR MSG +from its PBN o---+-----------------+---o to CPU PBN + | | + | Egress MAC Ingress MAC | + | [5] {1} | + o------|-----------|------o + v ^ + | | + TX Data RX Data + +Transmit Flow +[1] CPU (Ethernet driver) prepares 32 byte Ethernet egress work message and + enqueues the message to the queue in DDR. +[2] CPU (Ethernet driver) notifies QMTM that there is a message enqueued in + Ethernet transmit queue (e.g. Q0). +[3] QMTM prefetches the Ethernet egress work messages into Ethernet PBN + (e.g. ETH PBN 0). +[4] Ethernet reads work messages from its PBN. +[5] Ethernet DMAs payload from DDR to its egress FIFO and transmits data out. + +Receive Flow +{1} Ethernet receives data and DMAs payload from its ingress FIFO to DDR and + prepares a Ethernet ingress work message. +{2} Ethernet pushes work message to QMTM. +{3} QMTM prefetches the Ethernet ingress work messages into CPU PBN + (e.g. CPU PBN 0) and then interrupts CPU. +{4} CPU (Ethernet driver) dequeues the 32 bytes Ethernet ingress work message + from the queue in DDR. +{5} CPU (Ethernet driver) notifies QMTM that it dequeued a message from + Ethernet receive queue (e.g. Q1). + + +Definition: +1. QMTM (Queue/Traffic Manager) + QMTM manages queues and pbns for CPU, Ethernet, PktDMA and Security + Subsystems. It also performs flow control and QoS on queues. + +2. Slave/Client/Agent + Ethernet, PktDMA (XOR Engine) and Security Engine Subsystems & CPU whose + queues and pbn are managed by QMTM are called slave/client/agent. + +3. Queue + Queue is circular FIFO memory for QMTM hardware in which a 16 bytes, + 32 bytes or 64 bytes message is dequeued OR enqueued between CPU and + Ethernet, PktDMA and Security Engine Subsystems. + +4. PB + Each subsystem in the APM X-Gene SoC device has a prefetch buffer for + storing messages in order to pipeline the QMTM processing latency with the + subsystem processing latency. The number of buffers prefetched depends on + the QM/TM processing latency and the subsystem data rate. + + There are multiple PB for a subsystem, each PB is assigned a number which is + called PBN. Each subsystem and CPU can have max 32 pbns, however QMTM limits + how many pbns it supports for each subsystem. + +5. Message + The subsystems in the APM X-Gene SoC communicate with a central Queue Manager + (QM) that manages all the messages queued to the subsystems. The subsystems + communicate with the QM using messages that include information about the + work to be performed and the location of the buffers or data on which the + work is to be performed. + + A message consists of 16, 32 or 64 bytes which resides in a queue. A message + which is + a. 16 bytes contains information of data buffer, length, etc. allocated by + subsystem driver. + b. 32 or 64 bytes contains information about the work to be done for a + subsystem. Each subsystem defines its own format of work message. + + Each subsystem defines their own format of work message. A message (or queue + descriptor) has attribute fields (QMTM specific) which are common for all + subsystem work messages. The remaining fields of a message are specific to + subsystem. QMTM device doesn't have any knowledge of these subsystems + specific fields and the data operation which subsystem is going to perform + using these fields. + + e.g. + 1. Ethernet work message includes data address & length which is used by + Ethernet DMA engine for copying the data to/from its internal FIFO. + 2. PktDMA work message includes multiple data addresses & lengths for + doing scatter/gather, XOR operations and result data address/es to give + back result to the CPU (driver). + 3. Security work message includes data address & length for doing encryption + or decryption, the type of encryption or decryption and result data + address to give back result to the CPU (driver). -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html