gpio-omap: handle bias flags
Subsystems (2)
RFC 1/1 gpio-omap: handle bias flags
Tony - what do you think of this approach?
I have added this in arch/arm/boot/dts/am335x-pocketbeagle.dts to describe the pins which will be gpio lines accessed by userspace through gpiod ioctl() calls:
&am33xx_pinmux {
pinctrl-names = "default";
pinctrl-0 = < &gpio_pins >;
gpio_pins: pinmux-gpio-pins {
/* MUX_MODE7 is gpio mode */
pinctrl-single,pins = <
/* PIN 95 and PIN 94 */
AM33XX_PADCONF(AM335X_PIN_UART1_RTSN, PIN_INPUT, MUX_MODE7)
AM33XX_PADCONF(AM335X_PIN_UART1_CTSN, PIN_INPUT, MUX_MODE7)
/* PIN 100 */
AM33XX_PADCONF(AM335X_PIN_MCASP0_ACLKX, PIN_INPUT, MUX_MODE7)
/* PIN 18 */
AM33XX_PADCONF(AM335X_PIN_GPMC_A2, PIN_INPUT, MUX_MODE7)
>;
pinctrl-single,bias-pullup = < 8 16 8 24>;
pinctrl-single,bias-pulldown = < 8 0 8 24>;
};The "pinctrl-single,bias-pullup" and "pinctrl-single,bias-pulldown" pinconf properties are set for the gpio_pins pin group. The input value 0x8 causes both to be inactive but still added to the PIN_MAP_TYPE_CONFIGS_GROUP pinctrl map. This is necessary for pcs_pinconf_set() to be able to be able to set the bias config.
For AM335x, the pin conf register has the format [0]:
bit attribute value
6 slew { 0: fast, 1: slow }
5 rx_active { 0: rx disable, 1: rx enabled }
4 pu_typesel { 0: pulldown select, 1: pullup select }
3 puden { 0: pud enable, 1: disabled }
2 mode 3 bits to selec mode 0 to 7
1 mode
0 modeHere is how I derived the values:
pinctrl-single,bias-pullup = <[input] [enabled] [disable] [mask]>;
pinctrl-single,bias-pullup = < 8 16 8 24 >;
2^5 2^4 2^3 2^2 2^1 2^0 |
0x20 0x10 0x08 0x04 0x02 0x01 |
32 16 8 4 2 1 |
-------------------------------------------------------
input x 0 1 x x x | 8
enabled x 1 0 x x x | 16
disabled x 0 1 x x x | 8
mask x 1 1 x x x | 24pinctrl-single,bias-pulldown = <[input] [enabled] [disable] [mask]>;
pinctrl-single,bias-pulldown = < 8 0 8 24 >;
2^5 2^4 2^3 2^2 2^1 2^0 |
0x20 0x10 0x08 0x04 0x02 0x01 |
32 16 8 4 2 1 |
-------------------------------------------------------
input x 0 1 x x x | 8
enabled x 0 0 x x x | 0
disabled x 0 1 x x x | 8
mask x 1 1 x x x | 24The pinconf bias properties get applied to the pin group during boot when pcs_pinconf_group_set() calls pcs_pinconf_set() for each pin. Here is the output from function_graph tracer:
pinconf_apply_setting() {
pcs_pinconf_group_set() {
pinctrl_generic_get_group_pins();
pcs_pinconf_set() {
pcs_get_function() {
pinmux_generic_get_function();
}
pcs_readl();
pcs_writel();
pcs_readl();
pcs_writel();
}
pcs_pinconf_set() {
pcs_get_function() {
pinmux_generic_get_function();
}
pcs_readl();
pcs_writel();
pcs_readl();
pcs_writel();
}
pcs_pinconf_set() {
pcs_get_function() {
pinmux_generic_get_function();
}
pcs_readl();
pcs_writel();
pcs_readl();
pcs_writel();
}
pcs_pinconf_set() {
pcs_get_function() {
pinmux_generic_get_function();
}
pcs_readl();
pcs_writel();
pcs_readl();
pcs_writel();
}
}
}After boot, I then use gpiomon utility with bias flags:
gpiomon -B pull-up 3 14
gpiochip 3 line 14 maps to pin 100 which is AM335X_PIN_MCASP0_ACLKX at offset 0x990. For this to succeed, I modified omap_gpio_set_config() in gpio_omap.c to handle PIN_CONFIG_BIAS_PULL_{UP,DOWN} by calling gpiochip_generic_config(). Here is output of function_grapher tracer:
gpio_ioctl() {
gpiochip_get_desc();
gpiod_request() {
gpiod_request_commit() {
gpiochip_line_is_valid();
omap_gpio_request() {
omap_gpio_runtime_resume() {
omap_gpio_unidle() {
omap_gpio_restore_context();
}
}
omap_enable_gpio_module();
}
gpiod_get_direction() {
gpiod_to_chip();
omap_gpio_get_direction();
}
}
}
gpiod_direction_input() {
omap_gpio_input() {
omap_set_gpio_direction();
}
gpio_set_bias() {
gpio_set_config() {
gpio_do_set_config() {
omap_gpio_set_config() {
gpiochip_generic_config() {
pinctrl_gpio_set_config() {
pinctrl_get_device_gpio_range() {
pinctrl_match_gpio_range();
}
pinconf_set_config() {
pcs_pinconf_set() {
pcs_get_function() {
pinmux_generic_get_function();
}
pcs_readl();
pcs_pinconf_clear_bias.constprop.0();
pcs_writel();Thanks,
Drew
[0] http://www.ti.com/lit/ds/symlink/am3358.pdf
--- drivers/gpio/gpio-omap.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-)
drivers/gpio/gpio-omap.c +17 -4
@@ -896,12 +896,25 @@ static int omap_gpio_set_config(struct gpio_chip *chip, unsigned offset, unsigned long config) {u32 debounce; +int ret; -if (pinconf_to_config_param (config) !=PIN_CONFIG_INPUT_DEBOUNCE ) -return -ENOTSUPP ; +if ((pinconf_to_config_param (config) ==PIN_CONFIG_BIAS_DISABLE ) || + (pinconf_to_config_param (config) ==PIN_CONFIG_BIAS_PULL_UP ) || + (pinconf_to_config_param (config) ==PIN_CONFIG_BIAS_PULL_DOWN )) + { + ret =gpiochip_generic_config (chip, offset, config); + } +else if (pinconf_to_config_param (config) ==PIN_CONFIG_INPUT_DEBOUNCE ) + { + debounce =pinconf_to_config_argument (config); + ret =omap_gpio_debounce (chip, offset, debounce); + } +else + { + ret = -ENOTSUPP ; + } - debounce =pinconf_to_config_argument (config); -return omap_gpio_debounce (chip, offset, debounce); +return ret; }static void omap_gpio_set (struct gpio_chip *chip,unsigned offset,int value)
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2.25.1