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 mode
Here 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 | 24
pinctrl-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 | 24
The 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(-)
diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
index b8e2ecc3eade..a471a152f318 100644
--- a/drivers/gpio/gpio-omap.c
+++ b/drivers/gpio/gpio-omap.c
@@ -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)
--
2.25.1
[RFC] gpio-omap: handle bias flags
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
- Subject: [RFC] gpio-omap: handle bias flags
- From: Drew Fustini <drew@xxxxxxxxxxxxxxx>
- Date: Thu, 9 Jul 2020 19:30:07 +0200
- Prev by Date: [gpio:gpiochip-no-driver-h 4/4] drivers/net/wireless/broadcom/brcm80211/brcmsmac/led.c:91:6: warning: variable 'err' is uninitialized when used here
- Next by Date: [PATCH] gpio: omap: handle pin config bias flags
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