Changes between Initial Version and Version 1 of mnc_driver

Timestamp:

Dec 3, 2016, 2:50:07 PM (9 years ago)

Author:

alain

Comment:

--

mnc_driver

@@ +1 @@
+= GIET-VM / NIC_MNC Driver = 
+
+[[PageOutline]]
+
+The [source:soft/giet_vm/giet_drivers/mnc_driver.c mnc_driver.c] and [source:soft/giet_vm/giet_drivers/mnc_driver.h mnc_driver.h] files define the NIC_MNC driver. 
+
+This driver supports the vci_master_nic component, that is a Gigabit Ethernet network controller.
+
+This component has a DMA capability, to access the memory mapped RX and TX ethernet packets queues.
+These queues are implemented by a chained buffers structure, called NIC_CHBUF, and implemented by the ''nic_chbuf_t'' structure.
+
+It can exist only one ethernet network controller in the architecture, but to improve the throughput, it supports up to 4 channels (i.e. 4 TX and 4 RX queues), indexed by a key depending on the source IP address for the RX packets, and depending on the destination IP address for the TX packets. All channels use the same source MAC address.
+
+The Ethernet packet length can have any value, between 64 to 1538 bytes.
+The data transfer unit between software and the NIC is a 4 Kbytes "container", containing an integer number of variable size packets. The max number of packets in a container is 66 packets.
+The first 34 words of a container are the container header :
+|     word0     |       NB_WORDS        |       NB_PACKETS      |
+|     word1     |       PLEN[0]         |       PLEN[1]         |
+|      ...             |     .......            |       ........        |
+|     word33    |       PLEN[64]        |       PLEN[65]        |
+NB_PACKETS is the actual number of packets in the container, NB_WORDS is the number of useful words in the container, PLEN[i]  is the number of bytes for packet[i]. Packets are stored in the (1024 - 34) following words, and are word-aligned.
+
+Each 4 Kbytes container is protected by a SET/RESET synchronisation variable. To access both the container status, and the container itself, the NIC uses two physical addresses, that are packed in a 64 bits "container descriptor". 
+ * desc[25:0]  contain bits[31:6] of the status physical address.
+ * desc[51:26] contain bits[31:6] of the buffer physical address.
+ * desc[63:52] contain the common 12 physical address extension bits.
+
+To each TX or RX queue is associated a kernel thread that is in charge of moving the infinite stream of containers between the NIC and the RX/TX queue.
+
+The RX/TX queues (and the associated kernel threads) are physically distributed on various clusters, using a round robin policy (modulo the number of clusters).
+
+The actual number of channels is defined by the NB_NIC_CHANNELS parameter in the ''hard_config.h'' file, and
+the SEG_NIC_BASE address must be defined in the hard_config.h file.
+
+The addressable registers map is defined [source:soft/giet_vm/giet_drivers/mnc_driver.h here].
+
+== Access Functions ==
+
+ === 1) void '''_mnc_init'''( ) ===
+This function allocates memory for the RX_CHBUF and TX_CHBUF, using a round-robin policy to have one CHBUF
+per cluster if the number of clusters is larger than 2 * NB_NIC_CHANNELS. It initialises both the CHBUF descriptors,
+and the hardware NIC registers. returns the value contained in a channel register.
+
+ === 2) unsigned int '''_mnc_writable'''( unsigned int channel,  unsigned int length ) ===
+This function returns a Boolean indicating if an Ethernet packet of a given length can be stored in the TX queue defined by the channel argument.
+The internal state of the queue (write pointer) can be modified if required.
+ * '''channel''' : channel index
+ * '''length''' : register index
+ * return a non-zero value if packet can be written / return zero if queue is full.
+
+ === 3) unsigned int '''_mnc_readable'''( unsigned int channel , unsigned int * src_ip , unsigned int * src_port , unsigned int * dst_ip , unsigned int * dst_port , unsigned int * length ) ===
+This function returns a Boolean indicating if an Ethernet packet is available in the RX queue defined by the channel argument. It also returns various informations contained in the IP and TCP/UDP headers. The internal state of the queue (read pointer) can be modified if required.
+ * '''channel''' : channel index
+ * '''src_ip''' : source IP address (from IP header)
+ * '''src_port''' : source port index (from TCP/UDP header)
+ * '''src_ip''' : source IP address (from IP header)
+ * '''src_port''' : source port index (from TCP/UDP header)
+ * '''length''' : Ethernet packet length (bytes)
+ * return a non-zero value if packet can be read / return zero if queue is empty.
+                         
+ === 4) void '''_mnc_write'''( unsigned int channel ,  void * buffer , unsigned int length ) ===
+This function writes an Ethernet packet in the TX queue defined by the channel argument. It should be called after the _mnc_writable() function.
+ * '''channel''' : channel index
+ * '''buffer''' : pointer on buffer containing packet
+ * '''length''' : Ethernet packet length (bytes)
+
+ === 5) int '''_mnc_read'''( unsigned int channel , void * buffer ) ===
+This function read an Ethernet packet from the RX queue defined by the channel argument. It should be called after the _mnc_readable() function.
+ * '''channel''' : channel index
+ * '''buffer''' : pointer on buffer containing packet
+
+ === 6) void '''_mnc_set_global_register( unsigned int index , unsigned int value ) ===
+This function set a given value in a given NIC global register.
+ * '''index''' : register index
+ * '''value''' : value to be written
+
+ === 7) unsigned int '''_mnc_get_global_register( unsigned int index ) ===
+This function returns the value contained in a given NIC global register.
+ * '''index''' : register index
+ * return value
+
+== __ Interrupt Service Routines__ ==
+
+ === 8) void '''_nic_rx_isr'''( unsigned int irq_type,  unsigned int irq_id,  unsigned int channel ) ===
+This interrupt Service Routine  handles IRQs from a NIC_RX channel.
+WARNING : Not fully implemented yet : no IRQ acknowledge...
+
+ === 9) void '''_nic_tx_isr'''( unsigned int irq_type,  unsigned int irq_id,  unsigned int channel ) ===
+This interrupt Service Routine  handles IRQs from a NIC_TX channel.
+WARNING : Not fully implemented yet : no IRQ acknowledge...