redonkable/alistair23-linux
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sh: lockless gpio_set_value()

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This patch optimizes the gpio data register handling for gpio_set_value().

Instead of using the good old spinlock-plus-read-modify-write strategy
we now use a shadow register and atomic operations.

This improves the bitbanging mmc performance on Migo-R from 26 Kbytes/s
to 40 Kbytes/s.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
This commit is contained in:
Magnus Damm 2008-12-25 18:17:26 +09:00 committed by Paul Mundt
parent 0fc64cc0a2
commit 3292094e88
2 changed files with 82 additions and 26 deletions
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2
arch/sh/include/asm/gpio.h
View file

@ -59,7 +59,7 @@ struct pinmux_cfg_reg {
.enum_ids = (pinmux_enum_t [(r_width / f_width) * (1 << f_width)]) \
struct pinmux_data_reg {
unsigned long reg, reg_width;
unsigned long reg, reg_width, reg_shadow;
pinmux_enum_t *enum_ids;
};

106
arch/sh/kernel/gpio.c
View file

@ -46,6 +46,62 @@ static int enum_in_range(pinmux_enum_t enum_id, struct pinmux_range *r)
return 1;
}
static unsigned long gpio_read_raw_reg(unsigned long reg,
unsigned long reg_width)
{
switch (reg_width) {
case 8:
return ctrl_inb(reg);
case 16:
return ctrl_inw(reg);
case 32:
return ctrl_inl(reg);
}
BUG();
return 0;
}
static void gpio_write_raw_reg(unsigned long reg,
unsigned long reg_width,
unsigned long data)
{
switch (reg_width) {
case 8:
ctrl_outb(data, reg);
return;
case 16:
ctrl_outw(data, reg);
return;
case 32:
ctrl_outl(data, reg);
return;
}
BUG();
}
static void gpio_write_bit(struct pinmux_data_reg *dr,
unsigned long in_pos, unsigned long value)
{
unsigned long pos;
pos = dr->reg_width - (in_pos + 1);
#ifdef DEBUG
pr_info("write_bit addr = %lx, value = %ld, pos = %ld, "
"r_width = %ld\n",
dr->reg, !!value, pos, dr->reg_width);
#endif
if (value)
set_bit(pos, &dr->reg_shadow);
else
clear_bit(pos, &dr->reg_shadow);
gpio_write_raw_reg(dr->reg, dr->reg_width, dr->reg_shadow);
}
static int gpio_read_reg(unsigned long reg, unsigned long reg_width,
unsigned long field_width, unsigned long in_pos)
{
@ -61,18 +117,7 @@ static int gpio_read_reg(unsigned long reg, unsigned long reg_width,
reg, pos, reg_width, field_width);
#endif
switch (reg_width) {
case 8:
data = ctrl_inb(reg);
break;
case 16:
data = ctrl_inw(reg);
break;
case 32:
data = ctrl_inl(reg);
break;
}
data = gpio_read_raw_reg(reg, reg_width);
return (data >> pos) & mask;
}
@ -140,6 +185,26 @@ static int setup_data_reg(struct pinmux_info *gpioc, unsigned gpio)
return -1;
}
static void setup_data_regs(struct pinmux_info *gpioc)
{
struct pinmux_data_reg *drp;
int k;
for (k = gpioc->first_gpio; k <= gpioc->last_gpio; k++)
setup_data_reg(gpioc, k);
k = 0;
while (1) {
drp = gpioc->data_regs + k;
if (!drp->reg_width)
break;
drp->reg_shadow = gpio_read_raw_reg(drp->reg, drp->reg_width);
k++;
}
}
static int get_data_reg(struct pinmux_info *gpioc, unsigned gpio,
struct pinmux_data_reg **drp, int *bitp)
{
@ -465,7 +530,7 @@ static void __gpio_set_value(struct pinmux_info *gpioc,
if (!gpioc || get_data_reg(gpioc, gpio, &dr, &bit) != 0)
BUG();
else
gpio_write_reg(dr->reg, dr->reg_width, 1, bit, !!value);
gpio_write_bit(dr, bit, value);
}
int gpio_direction_output(unsigned gpio, int value)
@ -474,8 +539,8 @@ int gpio_direction_output(unsigned gpio, int value)
unsigned long flags;
int ret;
spin_lock_irqsave(&gpio_lock, flags);
__gpio_set_value(gpioc, gpio, value);
spin_lock_irqsave(&gpio_lock, flags);
ret = pinmux_direction(gpioc, gpio, PINMUX_TYPE_OUTPUT);
spin_unlock_irqrestore(&gpio_lock, flags);
@ -504,25 +569,16 @@ EXPORT_SYMBOL(gpio_get_value);
void gpio_set_value(unsigned gpio, int value)
{
struct pinmux_info *gpioc = gpio_controller(gpio);
unsigned long flags;
spin_lock_irqsave(&gpio_lock, flags);
__gpio_set_value(gpioc, gpio, value);
spin_unlock_irqrestore(&gpio_lock, flags);
__gpio_set_value(gpio_controller(gpio), gpio, value);
}
EXPORT_SYMBOL(gpio_set_value);
int register_pinmux(struct pinmux_info *pip)
{
int k;
registered_gpio = pip;
setup_data_regs(pip);
pr_info("pinmux: %s handling gpio %d -> %d\n",
pip->name, pip->first_gpio, pip->last_gpio);
for (k = pip->first_gpio; k <= pip->last_gpio; k++)
setup_data_reg(pip, k);
return 0;
}