Changes between Version 7 and Version 8 of hba_driver


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Timestamp:
Apr 2, 2015, 12:26:42 PM (9 years ago)
Author:
alain
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  • hba_driver

    v7 v8  
    77The ''vci_multi_ahci'' component is a multi-channels, block oriented, external mass storage controller respecting the AHCI standard. Each channel define an independant physical disk, but this driver supports only one channel, because the GIET-VM uses only one physical disk.
    88
    9 The '''Command List''' is a software FIFO that can contain up to 32 independant commands, posted by different user tasks. These independant transfers are handled by the HBA device in the same order as they have been written in the command list. There is no global lock protecting the the HBA device, but the command list being a shared structure, the driver uses an ''_atomicc_increment()'' to get a slot in the Command List, and increment the write pointer.
     9The '''Command List''' is a software FIFO that can contain up to 32 independant commands, posted by different user tasks. These independant transfers are handled by the HBA device in the same order as they have been written in the command list. There is no global lock protecting the the HBA device, but the command list being a shared structure, the driver uses a ''ptw'' pointer on the next free slot in the command list, and uses an ''_atomic_increment()'' to increment this  ''ptw'' pointer.
    1010
    1111This driver implements two operating mode:
    … …  
    1313 * In '''descheduling mode''', the calling task is descheduled, and the calling task global index is saved in the ''_hba_gtid[32]'' array, indexed by the command index. The task must be reactivated  when the command is completed. This mode is used, to handle the user system calls.
    1414
    15 As several user tasks can concurrently register commands in the command list, and there is only one HBA interrupt per channel, this interrupt is not linked to a specific calling task: in descheduling mode, the HBA IRQ is a "global" IRQ that is statically routed to processor P[x_io,y_io,0] in cluster_io.  The associated global HBA_ISR send a WAKUP WTI to all tasks that have a completed command. This HBA_ISR uses a read pointer on the Command List to identify the expected command completion. The incrementation of this read pointer does not require ''_atomic_increment()'' as there is no concurrent access on this pointer.
     15As several user tasks can concurrently register commands in the command list, and there is only one HBA interrupt per channel, this interrupt is not linked to a specific command. In descheduling mode, the HBA IRQ is a "global" IRQ that is statically routed to processor P[0,0,0].  The associated global HBA_ISR send a WAKUP WTI to all tasks that have a completed command. This HBA_ISR uses a ''ptr'' pointer on the first active command in the Command List to identify the completed commands. The incrementation of this ''ptr'' pointer does not require ''_atomic_increment()'' as there is no concurrent access on this pointer.
    1616
    1717The SEG_IOC_BASE address must be defined in the hard_config.h file.
    … …  
    1919The addressable registers map is defined [source:soft/giet_vm/giet_drivers/hba_driver.h here].
    2020
     21 == __Software data structures__
     22
     23The HBA component support split memory buffers (several physical buffers for one single command), but this driver supports only one single buffer commands, because a contiguous buffer in virtual space is also contiguous in physical space. This is a nice property of the the static memory allocation policy implemented by the GIET_VM.
     24
     25There exist 32 command tables associated to the 32 commands in the command list, and each command table occupies only 32 bytes.
     26
     27 === Command List ===
     28
     29The command List is an array of 32 Command Descriptors. Each Command Descriptor occupies 16 bytes, and is aligned on a 16 bytes boundary.
     30{{{
     31typedef struct hba_cmd_desc_s  // size = 16 bytes
     32{
     33    unsigned char       flag[2];    // W in bit 6 of flag[0]
     34    unsigned char       prdtl[2];       // Number of buffers
     35    unsigned int        prdbc;          // Number of bytes actually transfered
     36    unsigned int        ctba;           // Command Table base address 32 LSB bits
     37    unsigned int        ctbau;          // Command Table base address 32 MSB bits
     38} hba_cmd_desc_t;
     39}}}
     40
     41 === Command Table ===
     42
     43The GIET_VM define an array of 32 Command Tables. A Command Table contains one header, and one Buffer Descriptor. Each Command Table occupies 32 bytes, and is aligned on a 32 bytes boundary.
     44{{{
     45typedef struct hba_cmd_header_s // size = 16 bytes
     46{
     47    unsigned int        res0;       // reserved
     48    unsigned char           lba0;           // LBA 7:0
     49    unsigned char           lba1;           // LBA 15:8
     50    unsigned char           lba2;           // LBA 23:16
     51    unsigned char           res1;           // reserved
     52    unsigned char           lba3;           // LBA 31:24
     53    unsigned char           lba4;           // LBA 39:32
     54    unsigned char           lba5;           // LBA 47:40
     55    unsigned char           res2;           // reserved
     56    unsigned int        res3;       // reserved
     57} hba_cmd_header_t;
     58
     59typedef struct hba_cmd_buffer_s  // size = 16 bytes
     60{
     61    unsigned int        dba;        // Buffer base address 32 LSB bits
     62    unsigned int        dbau;       // Buffer base address 32 MSB bits
     63    unsigned int        res0;       // reserved
     64    unsigned int        dbc;        // Buffer byte count
     65} hba_cmd_buffer_t;
     66
     67typedef struct hba_cmd_table_s  // size = 32 bytes
     68{
     69    hba_cmd_header_t   header;      // contains LBA
     70    hba_cmd_buffer_t   buffer;      // only one physical buffer
     71} hba_cmd_table_t;
     72}}}
     73
     74 == __Access Functions__ ==
     75
     76 === unsigned int '''_hba_init'' ( ) ===
     77This function checks the block size and desactivates interrupts. It initializes
     78the HBA hardware registers, and the Command List.that is statically routed to processor P[x_io,y_io,0] in cluster_io.
     79//    The associated global HBA_ISR send a WAKUP WTI to all tasks that have
     80//    a completed command. This HBA_ISR uses a read pointer on the command
     81//    to identify the first expected command completion. The incrementation
     82//    of this read pointer does
    2183 == __Access Functions__ ==
    2284
    … …  
    40102 * '''irq-id'''     : index returned by XCU
    41103 * '''channel'''  : unused (only one HBA channel is supported).
    42