linux/arch/arm64/kernel/io.c
Mark Salyzyn 9ca255bf04 arm64: Avoid aligning normal memory pointers in __memcpy_{to,from}io
__memcpy_{to,from}io fall back to byte-at-a-time copying if both the
source and destination pointers are not 8-byte aligned. Since one of the
pointers always points at normal memory, this is unnecessary and
detrimental to performance, so only do byte copying until we hit an 8-byte
boundary for the device pointer.

This change was motivated by performance issues in the pstore driver.
On a test platform, measuring probe time for pstore, console buffer
size of 1/4MB and pmsg of 1/2MB, was in the 90-107ms region. Change
managed to reduce it to 10-25ms, an improvement in boot time.

Cc: Kees Cook <keescook@chromium.org>
Cc: Anton Vorontsov <anton@enomsg.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Anton Vorontsov <anton@enomsg.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
2017-10-24 16:23:07 +01:00

109 lines
2.1 KiB
C

/*
* Based on arch/arm/kernel/io.c
*
* Copyright (C) 2012 ARM Ltd.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <linux/export.h>
#include <linux/types.h>
#include <linux/io.h>
/*
* Copy data from IO memory space to "real" memory space.
*/
void __memcpy_fromio(void *to, const volatile void __iomem *from, size_t count)
{
while (count && !IS_ALIGNED((unsigned long)from, 8)) {
*(u8 *)to = __raw_readb(from);
from++;
to++;
count--;
}
while (count >= 8) {
*(u64 *)to = __raw_readq(from);
from += 8;
to += 8;
count -= 8;
}
while (count) {
*(u8 *)to = __raw_readb(from);
from++;
to++;
count--;
}
}
EXPORT_SYMBOL(__memcpy_fromio);
/*
* Copy data from "real" memory space to IO memory space.
*/
void __memcpy_toio(volatile void __iomem *to, const void *from, size_t count)
{
while (count && !IS_ALIGNED((unsigned long)to, 8)) {
__raw_writeb(*(u8 *)from, to);
from++;
to++;
count--;
}
while (count >= 8) {
__raw_writeq(*(u64 *)from, to);
from += 8;
to += 8;
count -= 8;
}
while (count) {
__raw_writeb(*(u8 *)from, to);
from++;
to++;
count--;
}
}
EXPORT_SYMBOL(__memcpy_toio);
/*
* "memset" on IO memory space.
*/
void __memset_io(volatile void __iomem *dst, int c, size_t count)
{
u64 qc = (u8)c;
qc |= qc << 8;
qc |= qc << 16;
qc |= qc << 32;
while (count && !IS_ALIGNED((unsigned long)dst, 8)) {
__raw_writeb(c, dst);
dst++;
count--;
}
while (count >= 8) {
__raw_writeq(qc, dst);
dst += 8;
count -= 8;
}
while (count) {
__raw_writeb(c, dst);
dst++;
count--;
}
}
EXPORT_SYMBOL(__memset_io);