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diff --git a/arch/mn10300/kernel/mn10300-serial-low.S b/arch/mn10300/kernel/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 <asm/proc/cache.h>
+#include <asm/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 (__tx_info_buffer,a3),a2 # get the uart_info struct for Tx
+ 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 +(GxICR_LEVEL_1|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 +(GxICR_LEVEL_1|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