///////////////////////////////////////////////////////////////////////////////////
// File     : irq_handler.c
// Date     : 01/04/2012
// Author   : alain greiner 
// Copyright (c) UPMC-LIP6
///////////////////////////////////////////////////////////////////////////////////
// The irq_handler.c and irq_handler.h files are part of the GIET-VM nano-kernel.
// They contain the code of the _irq_demux() function that access the XICU or
// ICU component (Interupt Controler Unit), and the various ISRs (Interrupt
// Service Routine) associated to the peripherals. 
///////////////////////////////////////////////////////////////////////////////////

#include <giet_config.h>
#include <irq_handler.h>
#include <sys_handler.h>
#include <drivers.h>
#include <common.h>
#include <ctx_handler.h>
#include <hwr_mapping.h>

///////////////////////////////////////////////////////////////////////////////////
// 	_irq_demux()
// This function uses the ICU or XICU component (Interrupt Controler Unit)
// to get the interrupt vector entry. There is one ICU or XICU component per
// cluster, and this component can support up to NB_PROCS_MAX output IRQs.
// It returns the highest priority active interrupt index (smaller
// indexes have the highest priority).
// Any value larger than 31 means "no active interrupt", and no ISR is executed.
//
// There is one interrupt vector per processor (stored in the scheduler associated
// to the processor. Each interrupt vector entry contains two 16 bits fields:
// - isr_id : defines the type of ISR to be executed.
// - channel_id : defines the specific channel for multi-channels peripherals.
//
// If the peripheral is replicated in clusters (TIMER or DMA), the channel_id is 
// a global index : channel_id = cluster_id * NB_CHANNELS_MAX + loc_id   
///////////////////////////////////////////////////////////////////////////////////
void _irq_demux()
{
    unsigned int    pid = _procid();
    unsigned int	irq_id;

    // get the highest priority active IRQ index 

#if GIET_USE_XICU

#else

    if ( _icu_read( pid / NB_PROCS_MAX,
                    pid % NB_PROCS_MAX,
                    ICU_IT_VECTOR,
                    &irq_id ) )
    {
        _puts("\n[GIET ERROR] wrong _icu_read in _irq_demux() function\n");
        _exit();
    }

#endif

    if ( irq_id < 32 )	// do nothing if no interrupt active 
    {
        unsigned int entry      = _get_interrupt_vector_entry(irq_id);
        unsigned int isr_id     = entry & 0x000000FF;
        unsigned int channel_id = (entry>>16) & 0x0000FFFF;
        if      ( isr_id == ISR_SWITCH  ) _isr_switch();
        else if ( isr_id == ISR_IOC     ) _isr_ioc();
        else if ( isr_id == ISR_DMA     ) _isr_dma( channel_id );
        else if ( isr_id == ISR_TTY     ) _isr_tty( channel_id );
        else if ( isr_id == ISR_TIMER   ) _isr_timer( channel_id );
        else                              _isr_default();
    }
}
///////////////////////////////////////////////////////////////////////////////////
// 	_isr_default()
// The default ISR is called when no specific ISR has been installed in the
// interrupt vector. It simply displays a message on kernel TTY[0].
///////////////////////////////////////////////////////////////////////////////////
void _isr_default()
{
    _puts("\n\n!!! Strange... Default ISR activated !!!\n");
}

///////////////////////////////////////////////////////////////////////////////////
// 	_isr_dma()
// This ISR handles all IRQs generated by the multi-channels DMA controlers.
// The multi_dma components can be distributed in the clusters.
// The channel_id argument is the global DMA channel index.
//     channel_id = cluster_id*NB_DMAS_MAX + loc_id
// - The ISR saves the transfert status in _dma_status[channel_id].
// - It acknowledges the interrupt to reinitialize the DMA controler.
// - it resets the synchronisation variable _dma_busy[channel_id].
///////////////////////////////////////////////////////////////////////////////////
void _isr_dma( unsigned int channel_id )
{
    // compute cluster_id and loc_id
    unsigned int cluster_id = channel_id / NB_DMAS_MAX;
    unsigned int loc_id     = channel_id % NB_DMAS_MAX;

    // compute DMA channel address
    unsigned int*	dma_address = (unsigned int*)&seg_dma_base + 
                                  (loc_id * DMA_SPAN) +
                                  (cluster_id * CLUSTER_SPAN);

    // save DMA channel status  
    _dma_status[channel_id] = dma_address[DMA_LEN];

    // reset DMA channel
    dma_address[DMA_RESET] = 0;			

    // release DMA channel 
    _dma_done[channel_id] = 1;  
}

///////////////////////////////////////////////////////////////////////////////////
// 	_isr_ioc()
// There is only one IOC controler shared by all tasks. 
// - The ISR save the status and acknowledge the IRQ.
// - It sets the _ioc_done variable to signal completion.
///////////////////////////////////////////////////////////////////////////////////
void _isr_ioc()
{
    unsigned int* ioc_address = (unsigned int*)&seg_ioc_base;

    _ioc_status = ioc_address[BLOCK_DEVICE_STATUS]; /* save status & reset IRQ */
    _ioc_done   = 1;                                /* signals completion */
}

///////////////////////////////////////////////////////////////////////////////////
// 	   _isr_timer()
// This ISR handles the IRQs generated by the "user" timers (the IRQs
// generated by the "system" timers should be handled by the _isr_switch().
// These timers are distributed in all clusters, and can be implemented
// in a vci_multi_timer component, or in a vci_xicu component.
// The channel_id argument is the global channel index:
//     channel_id = cluster_id*(NB_TIMERS_MAX+NB_PROCS_MAX) + loc_id 
// The user timer local index is (loc_id - NB_PROCS_MAX).
//
// The ISR acknowledges the IRQ and registers the event in the proper entry
// of the _timer_event[] array.
// A log message is displayed on the kernel terminal.
///////////////////////////////////////////////////////////////////////////////////
void _isr_timer(unsigned int channel_id)
{

    unsigned int cluster_id = channel_id / (NB_TIMERS_MAX + NB_PROCS_MAX);
    unsigned int loc_id     = channel_id % (NB_TIMERS_MAX + NB_PROCS_MAX); 

    if (loc_id < NB_PROCS_MAX )
    {
        _puts("[GIET ERROR] Receiving a user timer IRQ for a system timer\n");
        _puts("             cluster = ");
        _putw(cluster_id);
        _puts(" / local_id = ");
        _putw(loc_id);
    }

#if GIET_USE_XICU

// TODO

#else

    // compute Timer address
    unsigned int* timer_address = (unsigned int*)&seg_timer_base +
                                  (loc_id * TIMER_SPAN) +
                                  (cluster_id * CLUSTER_SPAN);

    // reset IRQ 
    timer_address[TIMER_RESETIRQ] = 0;

#endif

#if NB_TIMERS_MAX
    // register the event
    _timer_event[(cluster_id*NB_TIMERS_MAX) + (loc_id - NB_PROCS_MAX)] = 1;
#endif

    // display a message on TTY 0 
    _puts("[GIET] User Timer IRQ / cluster = ");
    _putw(cluster_id);
    _puts(" / timer = ");
    _putw(loc_id - NB_PROCS_MAX);
    _puts("\n");
}

///////////////////////////////////////////////////////////////////////////////////
//  _isr_tty()
// This ISR handles the IRQs generated by the multi_tty controler,
// signaling that a character is available.
// There is one single multi_tty component controling all TTYs, and the tty_id 
// argument is the global TTY index.
// There is one communication buffer _tty_buf[tty_id] per terminal.
// The sychronisation variable _tty_full[tty_id], is set by the ISR,
// and reset by the OS.
// A character is lost if the buffer is full when the ISR is executed.
///////////////////////////////////////////////////////////////////////////////////
void _isr_tty(unsigned int tty_id)
{
    // compute terminal base address 
    unsigned int *tty_address = (unsigned int*)&seg_tty_base + (tty_id * TTY_SPAN);

    // save character and reset IRQ 
    _tty_get_buf[tty_id] = (unsigned char)tty_address[TTY_READ];

    // signals character available 
    _tty_get_full[tty_id] = 1;
}

/////////////////////////////////////////////////////////////////////////////////////
// _isr_switch
// This ISR is in charge of context switch, and handle the IRQs generated by
// the "system" timers. 
// The IRQs can be generated by the MULTI_TIMER component or by the XICU component,
// that are distributed in all clusters.
// The ISR acknowledges the IRQ and calls the _ctx_switch() function.
/////////////////////////////////////////////////////////////////////////////////////
void _isr_switch()
{
    // get cluster index and proc local index
    unsigned int pid        = _procid();
    unsigned int loc_id     = pid % NB_PROCS_MAX;
    unsigned int cluster_id = pid / NB_PROCS_MAX;

#if GIET_USE_XICU

    unsigned int* timer_address = // TODO

#else

    // compute Timer address
    unsigned int* timer_address = (unsigned int*)&seg_timer_base +
                                  (loc_id * TIMER_SPAN) +
                                  (cluster_id * CLUSTER_SPAN);

    // reset IRQ
    timer_address[TIMER_RESETIRQ] = 0; 

#endif

    // performs the context switch
    _ctx_switch();

}