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linux/drivers/scsi/atari_dma_emul.c
David Howells 7d12e780e0 IRQ: Maintain regs pointer globally rather than passing to IRQ handlers 
Maintain a per-CPU global "struct pt_regs *" variable which can be used instead
of passing regs around manually through all ~1800 interrupt handlers in the
Linux kernel.

The regs pointer is used in few places, but it potentially costs both stack
space and code to pass it around.  On the FRV arch, removing the regs parameter
from all the genirq function results in a 20% speed up of the IRQ exit path
(ie: from leaving timer_interrupt() to leaving do_IRQ()).

Where appropriate, an arch may override the generic storage facility and do
something different with the variable.  On FRV, for instance, the address is
maintained in GR28 at all times inside the kernel as part of general exception
handling.

Having looked over the code, it appears that the parameter may be handed down
through up to twenty or so layers of functions.  Consider a USB character
device attached to a USB hub, attached to a USB controller that posts its
interrupts through a cascaded auxiliary interrupt controller.  A character
device driver may want to pass regs to the sysrq handler through the input
layer which adds another few layers of parameter passing.

I've build this code with allyesconfig for x86_64 and i386.  I've runtested the
main part of the code on FRV and i386, though I can't test most of the drivers.
I've also done partial conversion for powerpc and MIPS - these at least compile
with minimal configurations.

This will affect all archs.  Mostly the changes should be relatively easy.
Take do_IRQ(), store the regs pointer at the beginning, saving the old one:

	struct pt_regs *old_regs = set_irq_regs(regs);

And put the old one back at the end:

	set_irq_regs(old_regs);

Don't pass regs through to generic_handle_irq() or __do_IRQ().

In timer_interrupt(), this sort of change will be necessary:

	-	update_process_times(user_mode(regs));
	-	profile_tick(CPU_PROFILING, regs);
	+	update_process_times(user_mode(get_irq_regs()));
	+	profile_tick(CPU_PROFILING);

I'd like to move update_process_times()'s use of get_irq_regs() into itself,
except that i386, alone of the archs, uses something other than user_mode().

Some notes on the interrupt handling in the drivers:

 (*) input_dev() is now gone entirely.  The regs pointer is no longer stored in
     the input_dev struct.

 (*) finish_unlinks() in drivers/usb/host/ohci-q.c needs checking.  It does
     something different depending on whether it's been supplied with a regs
     pointer or not.

 (*) Various IRQ handler function pointers have been moved to type
     irq_handler_t.

Signed-Off-By: David Howells <dhowells@redhat.com>
(cherry picked from 1b16e7ac850969f38b375e511e3fa2f474a33867 commit)
2006-10-05 15:10:12 +01:00

469 lines
11 KiB
C
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/*
* atari_dma_emul.c -- TT SCSI DMA emulator for the Hades.
*
* Copyright 1997 Wout Klaren <W.Klaren@inter.nl.net>
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file COPYING in the main directory of this archive
* for more details.
*
* This code was written using the Hades TOS source code as a
* reference. This source code can be found on the home page
* of Medusa Computer Systems.
*
* Version 0.1, 1997-09-24.
*
* This code should be considered experimental. It has only been
* tested on a Hades with a 68060. It might not work on a Hades
* with a 68040. Make backups of your hard drives before using
* this code.
*/
#include <linux/compiler.h>
#include <asm/thread_info.h>
#include <asm/uaccess.h>
#define hades_dma_ctrl (*(unsigned char *) 0xffff8717)
#define hades_psdm_reg (*(unsigned char *) 0xffff8741)
#define TRANSFER_SIZE 16
struct m68040_frame {
unsigned long effaddr; /* effective address */
unsigned short ssw; /* special status word */
unsigned short wb3s; /* write back 3 status */
unsigned short wb2s; /* write back 2 status */
unsigned short wb1s; /* write back 1 status */
unsigned long faddr; /* fault address */
unsigned long wb3a; /* write back 3 address */
unsigned long wb3d; /* write back 3 data */
unsigned long wb2a; /* write back 2 address */
unsigned long wb2d; /* write back 2 data */
unsigned long wb1a; /* write back 1 address */
unsigned long wb1dpd0; /* write back 1 data/push data 0*/
unsigned long pd1; /* push data 1*/
unsigned long pd2; /* push data 2*/
unsigned long pd3; /* push data 3*/
};
static void writeback (unsigned short wbs, unsigned long wba,
unsigned long wbd, void *old_buserr)
{
mm_segment_t fs = get_fs();
static void *save_buserr;
__asm__ __volatile__ ("movec.l %%vbr,%%a0\n\t"
"move.l %0,8(%%a0)\n\t"
:
: "r" (&&bus_error)
: "a0" );
save_buserr = old_buserr;
set_fs (MAKE_MM_SEG(wbs & WBTM_040));
switch (wbs & WBSIZ_040) {
case BA_SIZE_BYTE:
put_user (wbd & 0xff, (char *)wba);
break;
case BA_SIZE_WORD:
put_user (wbd & 0xffff, (short *)wba);
break;
case BA_SIZE_LONG:
put_user (wbd, (int *)wba);
break;
}
set_fs (fs);
return;
bus_error:
__asm__ __volatile__ ("cmp.l %0,2(%%sp)\n\t"
"bcs.s .jump_old\n\t"
"cmp.l %1,2(%%sp)\n\t"
"bls.s .restore_old\n"
".jump_old:\n\t"
"move.l %2,-(%%sp)\n\t"
"rts\n"
".restore_old:\n\t"
"move.l %%a0,-(%%sp)\n\t"
"movec.l %%vbr,%%a0\n\t"
"move.l %2,8(%%a0)\n\t"
"move.l (%%sp)+,%%a0\n\t"
"rte\n\t"
:
: "i" (writeback), "i" (&&bus_error),
"m" (save_buserr) );
}
/*
* static inline void set_restdata_reg(unsigned char *cur_addr)
*
* Set the rest data register if necessary.
*/
static inline void set_restdata_reg(unsigned char *cur_addr)
{
if (((long) cur_addr & ~3) != 0)
tt_scsi_dma.dma_restdata =
*((unsigned long *) ((long) cur_addr & ~3));
}
/*
* void hades_dma_emulator(int irq, void *dummy)
*
* This code emulates TT SCSI DMA on the Hades.
*
* Note the following:
*
* 1. When there is no byte available to read from the SCSI bus, or
* when a byte cannot yet bet written to the SCSI bus, a bus
* error occurs when reading or writing the pseudo DMA data
* register (hades_psdm_reg). We have to catch this bus error
* and try again to read or write the byte. If after several tries
* we still get a bus error, the interrupt handler is left. When
* the byte can be read or written, the interrupt handler is
* called again.
*
* 2. The SCSI interrupt must be disabled in this interrupt handler.
*
* 3. If we set the EOP signal, the SCSI controller still expects one
* byte to be read or written. Therefore the last byte is transferred
* separately, after setting the EOP signal.
*
* 4. When this function is left, the address pointer (start_addr) is
* converted to a physical address. Because it points one byte
* further than the last transferred byte, it can point outside the
* current page. If virt_to_phys() is called with this address we
* might get an access error. Therefore virt_to_phys() is called with
* start_addr - 1 if the count has reached zero. The result is
* increased with one.
*/
static irqreturn_t hades_dma_emulator(int irq, void *dummy)
{
unsigned long dma_base;
register unsigned long dma_cnt asm ("d3");
static long save_buserr;
register unsigned long save_sp asm ("d4");
register int tries asm ("d5");
register unsigned char *start_addr asm ("a3"), *end_addr asm ("a4");
register unsigned char *eff_addr;
register unsigned char *psdm_reg;
unsigned long rem;
atari_disable_irq(IRQ_TT_MFP_SCSI);
/*
* Read the dma address and count registers.
*/
dma_base = SCSI_DMA_READ_P(dma_addr);
dma_cnt = SCSI_DMA_READ_P(dma_cnt);
/*
* Check if DMA is still enabled.
*/
if ((tt_scsi_dma.dma_ctrl & 2) == 0)
{
atari_enable_irq(IRQ_TT_MFP_SCSI);
return IRQ_HANDLED;
}
if (dma_cnt == 0)
{
printk(KERN_NOTICE "DMA emulation: count is zero.\n");
tt_scsi_dma.dma_ctrl &= 0xfd; /* DMA ready. */
atari_enable_irq(IRQ_TT_MFP_SCSI);
return IRQ_HANDLED;
}
/*
* Install new bus error routine.
*/
__asm__ __volatile__ ("movec.l %%vbr,%%a0\n\t"
"move.l 8(%%a0),%0\n\t"
"move.l %1,8(%%a0)\n\t"
: "=&r" (save_buserr)
: "r" (&&scsi_bus_error)
: "a0" );
hades_dma_ctrl &= 0xfc; /* Bus error and EOP off. */
/*
* Save the stack pointer.
*/
__asm__ __volatile__ ("move.l %%sp,%0\n\t"
: "=&r" (save_sp) );
tries = 100; /* Maximum number of bus errors. */
start_addr = phys_to_virt(dma_base);
end_addr = start_addr + dma_cnt;
scsi_loop:
dma_cnt--;
rem = dma_cnt & (TRANSFER_SIZE - 1);
dma_cnt &= ~(TRANSFER_SIZE - 1);
psdm_reg = &hades_psdm_reg;
if (tt_scsi_dma.dma_ctrl & 1) /* Read or write? */
{
/*
* SCSI write. Abort when count is zero.
*/
switch (rem)
{
case 0:
while (dma_cnt > 0)
{
dma_cnt -= TRANSFER_SIZE;
*psdm_reg = *start_addr++;
case 15:
*psdm_reg = *start_addr++;
case 14:
*psdm_reg = *start_addr++;
case 13:
*psdm_reg = *start_addr++;
case 12:
*psdm_reg = *start_addr++;
case 11:
*psdm_reg = *start_addr++;
case 10:
*psdm_reg = *start_addr++;
case 9:
*psdm_reg = *start_addr++;
case 8:
*psdm_reg = *start_addr++;
case 7:
*psdm_reg = *start_addr++;
case 6:
*psdm_reg = *start_addr++;
case 5:
*psdm_reg = *start_addr++;
case 4:
*psdm_reg = *start_addr++;
case 3:
*psdm_reg = *start_addr++;
case 2:
*psdm_reg = *start_addr++;
case 1:
*psdm_reg = *start_addr++;
}
}
hades_dma_ctrl |= 1; /* Set EOP. */
udelay(10);
*psdm_reg = *start_addr++; /* Dummy byte. */
tt_scsi_dma.dma_ctrl &= 0xfd; /* DMA ready. */
}
else
{
/*
* SCSI read. Abort when count is zero.
*/
switch (rem)
{
case 0:
while (dma_cnt > 0)
{
dma_cnt -= TRANSFER_SIZE;
*start_addr++ = *psdm_reg;
case 15:
*start_addr++ = *psdm_reg;
case 14:
*start_addr++ = *psdm_reg;
case 13:
*start_addr++ = *psdm_reg;
case 12:
*start_addr++ = *psdm_reg;
case 11:
*start_addr++ = *psdm_reg;
case 10:
*start_addr++ = *psdm_reg;
case 9:
*start_addr++ = *psdm_reg;
case 8:
*start_addr++ = *psdm_reg;
case 7:
*start_addr++ = *psdm_reg;
case 6:
*start_addr++ = *psdm_reg;
case 5:
*start_addr++ = *psdm_reg;
case 4:
*start_addr++ = *psdm_reg;
case 3:
*start_addr++ = *psdm_reg;
case 2:
*start_addr++ = *psdm_reg;
case 1:
*start_addr++ = *psdm_reg;
}
}
hades_dma_ctrl |= 1; /* Set EOP. */
udelay(10);
*start_addr++ = *psdm_reg;
tt_scsi_dma.dma_ctrl &= 0xfd; /* DMA ready. */
set_restdata_reg(start_addr);
}
if (start_addr != end_addr)
printk(KERN_CRIT "DMA emulation: FATAL: Count is not zero at end of transfer.\n");
dma_cnt = end_addr - start_addr;
scsi_end:
dma_base = (dma_cnt == 0) ? virt_to_phys(start_addr - 1) + 1 :
virt_to_phys(start_addr);
SCSI_DMA_WRITE_P(dma_addr, dma_base);
SCSI_DMA_WRITE_P(dma_cnt, dma_cnt);
/*
* Restore old bus error routine.
*/
__asm__ __volatile__ ("movec.l %%vbr,%%a0\n\t"
"move.l %0,8(%%a0)\n\t"
:
: "r" (save_buserr)
: "a0" );
atari_enable_irq(IRQ_TT_MFP_SCSI);
return IRQ_HANDLED;
scsi_bus_error:
/*
* First check if the bus error is caused by our code.
* If not, call the original handler.
*/
__asm__ __volatile__ ("cmp.l %0,2(%%sp)\n\t"
"bcs.s .old_vector\n\t"
"cmp.l %1,2(%%sp)\n\t"
"bls.s .scsi_buserr\n"
".old_vector:\n\t"
"move.l %2,-(%%sp)\n\t"
"rts\n"
".scsi_buserr:\n\t"
:
: "i" (&&scsi_loop), "i" (&&scsi_end),
"m" (save_buserr) );
if (CPU_IS_060)
{
/*
* Get effective address and restore the stack.
*/
__asm__ __volatile__ ("move.l 8(%%sp),%0\n\t"
"move.l %1,%%sp\n\t"
: "=a&" (eff_addr)
: "r" (save_sp) );
}
else
{
register struct m68040_frame *frame;
__asm__ __volatile__ ("lea 8(%%sp),%0\n\t"
: "=a&" (frame) );
if (tt_scsi_dma.dma_ctrl & 1)
{
/*
* Bus error while writing.
*/
if (frame->wb3s & WBV_040)
{
if (frame->wb3a == (long) &hades_psdm_reg)
start_addr--;
else
writeback(frame->wb3s, frame->wb3a,
frame->wb3d, &&scsi_bus_error);
}
if (frame->wb2s & WBV_040)
{
if (frame->wb2a == (long) &hades_psdm_reg)
start_addr--;
else
writeback(frame->wb2s, frame->wb2a,
frame->wb2d, &&scsi_bus_error);
}
if (frame->wb1s & WBV_040)
{
if (frame->wb1a == (long) &hades_psdm_reg)
start_addr--;
}
}
else
{
/*
* Bus error while reading.
*/
if (frame->wb3s & WBV_040)
writeback(frame->wb3s, frame->wb3a,
frame->wb3d, &&scsi_bus_error);
}
eff_addr = (unsigned char *) frame->faddr;
__asm__ __volatile__ ("move.l %0,%%sp\n\t"
:
: "r" (save_sp) );
}
dma_cnt = end_addr - start_addr;
if (eff_addr == &hades_psdm_reg)
{
/*
* Bus error occurred while reading the pseudo
* DMA register. Time out.
*/
tries--;
if (tries <= 0)
{
if ((tt_scsi_dma.dma_ctrl & 1) == 0) /* Read or write? */
set_restdata_reg(start_addr);
if (dma_cnt <= 1)
printk(KERN_CRIT "DMA emulation: Fatal "
"error while %s the last byte.\n",
(tt_scsi_dma.dma_ctrl & 1)
? "writing" : "reading");
goto scsi_end;
}
else
goto scsi_loop;
}
else
{
/*
* Bus error during pseudo DMA transfer.
* Terminate the DMA transfer.
*/
hades_dma_ctrl |= 3; /* Set EOP and bus error. */
if ((tt_scsi_dma.dma_ctrl & 1) == 0) /* Read or write? */
set_restdata_reg(start_addr);
goto scsi_end;
}
}
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