mn10300-serial-low.S
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###############################################################################
#
# Virtual DMA driver for MN10300 serial ports
#
# Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
# Written by David Howells (dhowells@redhat.com)
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public Licence
# as published by the Free Software Foundation; either version
# 2 of the Licence, or (at your option) any later version.
#
###############################################################################
#include <linux/sys.h>
#include <linux/linkage.h>
#include <asm/page.h>
#include <asm/smp.h>
#include <asm/cpu-regs.h>
#include <asm/frame.inc>
#include <asm/timer-regs.h>
#include <proc/cache.h>
#include <unit/timex.h>
#include "mn10300-serial.h"
#define SCxCTR 0x00
#define SCxICR 0x04
#define SCxTXB 0x08
#define SCxRXB 0x09
#define SCxSTR 0x0c
#define SCxTIM 0x0d
.text
###############################################################################
#
# serial port interrupt virtual DMA entry point
# - intended to run at interrupt priority 1 (not affected by local_irq_disable)
#
###############################################################################
.balign L1_CACHE_BYTES
ENTRY(mn10300_serial_vdma_interrupt)
# or EPSW_IE,psw # permit overriding by
# debugging interrupts
movm [d2,d3,a2,a3,exreg0],(sp)
movhu (IAGR),a2 # see if which interrupt is
# pending
and IAGR_GN,a2
add a2,a2
add mn10300_serial_int_tbl,a2
mov (a2+),a3
mov (__iobase,a3),e2
mov (a2),a2
jmp (a2)
###############################################################################
#
# serial port receive interrupt virtual DMA entry point
# - intended to run at interrupt priority 1 (not affected by local_irq_disable)
# - stores data/status byte pairs in the ring buffer
# - induces a scheduler tick timer interrupt when done, which we then subvert
# on entry:
# A3 struct mn10300_serial_port *
# E2 I/O port base
#
###############################################################################
ENTRY(mn10300_serial_vdma_rx_handler)
mov (__rx_icr,a3),e3
mov GxICR_DETECT,d2
movbu d2,(e3) # ACK the interrupt
movhu (e3),d2 # flush
mov (__rx_inp,a3),d3
mov d3,a2
add 2,d3
and MNSC_BUFFER_SIZE-1,d3
mov (__rx_outp,a3),d2
cmp d3,d2
beq mnsc_vdma_rx_overflow
mov (__rx_buffer,a3),d2
add d2,a2
movhu (SCxSTR,e2),d2
movbu d2,(1,a2)
movbu (SCxRXB,e2),d2
movbu d2,(a2)
mov d3,(__rx_inp,a3)
bset MNSCx_RX_AVAIL,(__intr_flags,a3)
mnsc_vdma_rx_done:
mov (__tm_icr,a3),a2
mov GxICR_LEVEL_6|GxICR_ENABLE|GxICR_REQUEST|GxICR_DETECT,d2
movhu d2,(a2) # request a slow interrupt
movhu (a2),d2 # flush
movm (sp),[d2,d3,a2,a3,exreg0]
rti
mnsc_vdma_rx_overflow:
bset MNSCx_RX_OVERF,(__intr_flags,a3)
bra mnsc_vdma_rx_done
###############################################################################
#
# serial port transmit interrupt virtual DMA entry point
# - intended to run at interrupt priority 1 (not affected by local_irq_disable)
# - retrieves data bytes from the ring buffer and passes them to the serial port
# - induces a scheduler tick timer interrupt when done, which we then subvert
# A3 struct mn10300_serial_port *
# E2 I/O port base
#
###############################################################################
.balign L1_CACHE_BYTES
ENTRY(mn10300_serial_vdma_tx_handler)
mov (__tx_icr,a3),e3
mov GxICR_DETECT,d2
movbu d2,(e3) # ACK the interrupt
movhu (e3),d2 # flush
btst 0x01,(__tx_break,a3) # handle transmit break request
bne mnsc_vdma_tx_break
movbu (SCxSTR,e2),d2 # don't try and transmit a char if the
# buffer is not empty
btst SC01STR_TBF,d2 # (may have tried to jumpstart)
bne mnsc_vdma_tx_noint
movbu (__tx_xchar,a3),d2 # handle hi-pri XON/XOFF
or d2,d2
bne mnsc_vdma_tx_xchar
mov (__uart_state,a3),a2 # see if the TTY Tx queue has anything in it
mov (__xmit_tail,a2),d3
mov (__xmit_head,a2),d2
cmp d3,d2
beq mnsc_vdma_tx_empty
mov (__xmit_buffer,a2),d2 # get a char from the buffer and
# transmit it
movbu (d3,d2),d2
movbu d2,(SCxTXB,e2) # Tx
inc d3 # advance the buffer pointer
and __UART_XMIT_SIZE-1,d3
mov (__xmit_head,a2),d2
mov d3,(__xmit_tail,a2)
sub d3,d2 # see if we've written everything
beq mnsc_vdma_tx_empty
and __UART_XMIT_SIZE-1,d2 # see if we just made a hole
cmp __UART_XMIT_SIZE-2,d2
beq mnsc_vdma_tx_made_hole
mnsc_vdma_tx_done:
mov (__tm_icr,a3),a2
mov GxICR_LEVEL_6|GxICR_ENABLE|GxICR_REQUEST|GxICR_DETECT,d2
movhu d2,(a2) # request a slow interrupt
movhu (a2),d2 # flush
mnsc_vdma_tx_noint:
movm (sp),[d2,d3,a2,a3,exreg0]
rti
mnsc_vdma_tx_empty:
mov +(NUM2GxICR_LEVEL(CONFIG_MN10300_SERIAL_IRQ_LEVEL)|GxICR_DETECT),d2
movhu d2,(e3) # disable the interrupt
movhu (e3),d2 # flush
bset MNSCx_TX_EMPTY,(__intr_flags,a3)
bra mnsc_vdma_tx_done
mnsc_vdma_tx_break:
movhu (SCxCTR,e2),d2 # turn on break mode
or SC01CTR_BKE,d2
movhu d2,(SCxCTR,e2)
mov +(NUM2GxICR_LEVEL(CONFIG_MN10300_SERIAL_IRQ_LEVEL)|GxICR_DETECT),d2
movhu d2,(e3) # disable transmit interrupts on this
# channel
movhu (e3),d2 # flush
bra mnsc_vdma_tx_noint
mnsc_vdma_tx_xchar:
bclr 0xff,(__tx_xchar,a3)
movbu d2,(SCxTXB,e2)
bra mnsc_vdma_tx_done
mnsc_vdma_tx_made_hole:
bset MNSCx_TX_SPACE,(__intr_flags,a3)
bra mnsc_vdma_tx_done