///////////////////////////////////////////////////////////////////////////////////
// File     : tty_driver.c
// Date     : 23/05/2013
// Author   : alain greiner
// Copyright (c) UPMC-LIP6
///////////////////////////////////////////////////////////////////////////////////
// The tty_driver.c and tty_drivers.h files are part ot the GIET-VM kernel.
// This driver supports the SocLib vci_multi_tty component.
//
// The total number of TTY terminals must be defined by the configuration 
// parameter NB_TTY_CHANNELS in the hard_config.h file.
//
// The "system" terminal is TTY[0].
// The "user" TTYs are allocated to applications by the GIET in the boot phase,
// as defined in the mapping_info data structure. The corresponding tty_id must 
// be stored in the context of the task by the boot code.
//
// The seg_tty_base must be defined in giet_vsegs.ld file.
///////////////////////////////////////////////////////////////////////////////////
// Implementation note:
// 
// All physical accesses to device registers are done by the two
// _tty_get_register(), _tty_set_register() low-level functions,
// that are handling virtual / physical addressing.
///////////////////////////////////////////////////////////////////////////////////

#include <giet_config.h>
#include <tty_driver.h>
#include <xcu_driver.h>
#include <ctx_handler.h>
#include <utils.h>

#if !defined(NB_TTY_CHANNELS)
# error: You must define NB_TTY_CHANNELS in the hard_config.h file
#endif

#if (NB_TTY_CHANNELS < 1)
# error: NB_TTY_CHANNELS cannot be smaller than 1!
#endif

#define in_unckdata __attribute__((section (".unckdata")))
#define in_kdata    __attribute__((section (".kdata")))

//////////////////////////////////////////////////////////////////////////////
//   TTY global variables
//////////////////////////////////////////////////////////////////////////////

in_unckdata volatile unsigned int _tty_rx_buf[NB_TTY_CHANNELS];

in_unckdata volatile unsigned int _tty_rx_full[NB_TTY_CHANNELS] 
                                     = { [0 ... NB_TTY_CHANNELS - 1] = 0 };

in_kdata unsigned int _tty_lock[NB_TTY_CHANNELS] 
                        = { [0 ... NB_TTY_CHANNELS - 1] = 0 };

//////////////////////////////////////////////////////////////////////////////
// This low level function returns the value of register (channel / index)
//////////////////////////////////////////////////////////////////////////////
unsigned int _tty_get_register( unsigned int channel,
                                unsigned int index )
{
    unsigned int* vaddr = (unsigned int*)&seg_tty_base + channel*TTY_SPAN + index;
    return _io_extended_read( vaddr );
}

//////////////////////////////////////////////////////////////////////////////
// This low level function set a new value in register (channel / index)  
//////////////////////////////////////////////////////////////////////////////
void _tty_set_register( unsigned int channel,
                        unsigned int index,
                        unsigned int value )
{
    unsigned int* vaddr = (unsigned int*)&seg_tty_base + channel*TTY_SPAN + index;
    _io_extended_write( vaddr, value );
}

/////////////////////////////////////////////////////////////////////////////////
// This non-blocking function writes a character string from a fixed-length 
// buffer to a TTY terminal identified by the channel argument. 
// This function is intended to be used to handle a system call, and should
// not be used by the kernel for log messages on TTY 0.
// protecting exclusive access to the selected terminal.
// If channel argument is 0xFFFFFFFF, the TTY index is found in the task context. 
// This is a non blocking call: it tests the TTY_STATUS register, and stops
// the transfer as soon as the TTY_STATUS[WRITE] bit is set. 
/////////////////////////////////////////////////////////////////////////////////
// Returns  the number of characters that have been written.
/////////////////////////////////////////////////////////////////////////////////
unsigned int _tty_write( const char*  buffer,    
                         unsigned int length,    // number of characters
                         unsigned int channel)   // channel index 
{
    unsigned int  nwritten;

    // compute and check tty channel
    if( channel == 0xFFFFFFFF )  channel = _get_context_slot(CTX_TTY_ID);
    if( channel >= NB_TTY_CHANNELS ) return -1;

    // write string to TTY channel
    for (nwritten = 0; nwritten < length; nwritten++) 
    {
        // check tty's status 
        if ( _tty_get_register( channel, TTY_STATUS ) & 0x2 )  break;

        // write one byte
        if (buffer[nwritten] == '\n') {
            _tty_set_register( channel, TTY_WRITE, (unsigned int)'\r' );
        }
        _tty_set_register( channel, TTY_WRITE, (unsigned int)buffer[nwritten] );
    }
    
    return nwritten;
}

//////////////////////////////////////////////////////////////////////////////
// This non-blocking function fetches one character from the 
// terminal identified by the channel argument. If the channel argument 
// is 0xFFFFFFFF, the channel index is obtained from the current task context. 
// It uses the TTY_GET_IRQ[tty_id] interrupt and the buffer must have been
// filled by the TTY_ISR.
// It test the _tty_rx_full[tty_id] variable, read the _tty_rx_buf[tty_id] 
// buffer, writes this character to the target buffer, and resets the
// _tty_rx_full[tty_id] register.
// The length argument is not used.
//////////////////////////////////////////////////////////////////////////////
// Returns  the number of characters that have been read (0/1).
//////////////////////////////////////////////////////////////////////////////
unsigned int _tty_read( char*        buffer, 
                        unsigned int length,    // unused
                        unsigned int channel)   // channel index
{
    // compute and check tty channel
    if( channel == 0xFFFFFFFF )  channel = _get_context_slot(CTX_TTY_ID);
    if( channel >= NB_TTY_CHANNELS ) return -1;

    // read one character from TTY channel
    if (_tty_rx_full[channel] == 0) 
    {
        return 0;
    }
    else 
    {
        *buffer = _tty_rx_buf[channel];
        _tty_rx_full[channel] = 0;
        return 1;
    }
}

//////////////////////////////////////////////////////////////////////////////
// This function try to take the hardwired lock protecting 
// exclusive access to TTY terminal identified by the "channel" argument.
// It enters a critical section before taking the lock, and save the SR value
// at address defined by the "save_sr_ptr" argument.
// It returns only when the lock has been successfully taken.
//////////////////////////////////////////////////////////////////////////////
void _tty_get_lock( unsigned int   channel,
                    unsigned int * save_sr_ptr )
{
    if( channel >= NB_TTY_CHANNELS ) _exit();

    _it_disable( save_sr_ptr );

//    while ( _tty_get_register( channel, TTY_CONFIG ) ); // busy waiting

    _get_lock( &_tty_lock[channel] );
}

//////////////////////////////////////////////////////////////////////////////
// This function releases the hardwired lock protecting 
// exclusive access to TTY terminal identified by the channel argument.
// It exit the critical section after lock release, and restore SR value
// from address defined by the "save_sr_ptr" argument.
//////////////////////////////////////////////////////////////////////////////
void _tty_release_lock( unsigned int   channel,
                        unsigned int * save_sr_ptr )
{
    if( channel >= NB_TTY_CHANNELS ) _exit();

//    _tty_set_register( channel, TTY_CONFIG, 0 );

    _release_lock( &_tty_lock[channel] );
    
    _it_restore( save_sr_ptr );
}

///////////////////////////////////////////////////////////////////////////////////
// This ISR handles the IRQ signaling that the RX buffer is not empty.
// IT can be an HWI or an SWI.
// There is one communication buffer _tty_rx_buf[i] and one synchronisation
// variable _tty_rx_full[i] per channel.
// Does nothing if the TTY_RX buffer is empty, or if the kernel buffer is full
// when the ISR is called.
///////////////////////////////////////////////////////////////////////////////////
void _tty_rx_isr( unsigned int irq_type,   // HWI / WTI
                  unsigned int irq_id,     // index returned by XCU
                  unsigned int channel )   // TTY channel
{
    unsigned int cluster_xy = _get_procid() / NB_PROCS_MAX;

    // get TTY status
    unsigned int status = _tty_get_register( channel, TTY_STATUS );

    // check both TTY status and kernel buffer status:
    // does nothing if kernel buffer full or tty_buffer empty
    if ( ((status & 0x1) == 0) || 
         (_tty_rx_full[channel] != 0) )  return;
 
    // reset WTI in XCU if WTI type
    if ( irq_type == IRQ_TYPE_WTI ) 
    {
        unsigned int value;
        _xcu_get_wti_value( cluster_xy, irq_id, &value );
    }

    // transfer character to kernel buffer and acknowledge TTY IRQ 
    _tty_rx_buf[channel]  = _tty_get_register( channel, TTY_READ ); 

    // set kernel buffer status
    asm volatile( "sync" );
    _tty_rx_full[channel] = 1;

#if GIET_DEBUG_IRQS  // we don't take the TTY lock to avoid deadlock
unsigned int x              = cluster_xy >> Y_WIDTH;
unsigned int y              = cluster_xy & ((1<<Y_WIDTH)-1);
unsigned int lpid           = _get_procid() % NB_PROCS_MAX;
_puts("\n[IRQS DEBUG] Processor[");
_putd(x );
_puts(",");
_putd(y );
_puts(",");
_putd(lpid );
_puts("] enters _tty_rx_isr() at cycle ");
_putd(_get_proctime() );
_puts("\n  read byte = ");
_putx(_tty_rx_buf[channel] );
_puts("\n");
#endif

}

///////////////////////////////////////////////////////////////////////////////////
// This ISR handles the IRQ signaling that the TX buffer is empty.
// IT can be an HWI or an SWI.
// There is one single multi_tty component controling all channels.
// There is one communication buffer _tty_rx_buf[i] and one synchronisation
// variable _tty_rx_full[i] per channel.
// A character is lost if the buffer is full when the ISR is executed.
///////////////////////////////////////////////////////////////////////////////////
void _tty_tx_isr( unsigned int irq_type,   // HWI / WTI
                  unsigned int irq_id,     // index returned by XCU
                  unsigned int channel )   // TTY channel
{
    _puts("\n[GIET ERROR] the _tty_tx_isr() is not implemented\n");
    _exit();
}

// Local Variables:
// tab-width: 4
// c-basic-offset: 4
// c-file-offsets:((innamespace . 0)(inline-open . 0))
// indent-tabs-mode: nil
// End:
// vim: filetype=c:expandtab:shiftwidth=4:tabstop=4:softtabstop=4