Tony and Linus -
I'm hoping you could give me some feedback on this approach. My goal is
to allow a userspace library (like libgpiod) to be able to set pull-up
and pull-downs on the AM3358.
I've changed gpio-omap.c so omap_gpio_set_config() will call
omap_gpio_bias() when the parameter is one of the PIN_CONFIG_BIAS_xxx
flags. That function will call gpiochip_generic_config() and the rest
proceeds normally without further changes.
However, this does require the following:
1) patch to fix return code in pcs_parse_pinconf() [0]
2) patch to add the gpio-ranges mappings [1]
2) change the compatible for the am33xx_pinmux node to "pinconf-single"
4) add "pinctrl-single,bias-pulldown" or "pinctrl-single,bias-pullup"
property to a pin node.
I found the binding documentation [2] for the bias properties to be very
confusing as to how those 4 values work:
> - pinctrl-single,bias-pullup : array of value that are used to configure the
> input bias pullup in the pinmux register.
>
> /* input, enabled pullup bits, disabled pullup bits, mask */
> pinctrl-single,bias-pullup = <0 1 0 1>;
>
> - pinctrl-single,bias-pulldown : array of value that are used to configure the
> input bias pulldown in the pinmux register.
> /* input, enabled pulldown bits, disabled pulldown bits, mask */
> pinctrl-single,bias-pulldown = <2 2 0 2>;
For AM3358, the pin conf register has the format [3]:
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
I figured out the values for bias-pull{up,down} properties based on:
16 8 4 2 1
2^4 2^3 2^2 2^1 2^0
mask 1 1 0 0 0 24
pull-up 1 1 0 0 0 24
pull-dn 0 1 0 0 0 8
none 0 0 0 0 0 0
Thus the properties are:
pinctrl-single,bias-pulldown = < 8 8 0 24>;
pinctrl-single,bias-pullup = <24 24 0 24>;
For an example, I added "pinctrl-single,bias-pulldown" to the node
pinmux-ehrpwm1-pins in am335x-pocketbeagle.dts:
ehrpwm1_pins: pinmux-ehrpwm1-pins {
pinctrl-single,pins = <
AM33XX_PADCONF(AM335X_PIN_GPMC_A2, PIN_OUTPUT_PULLDOWN, MUX_MODE6)
/* (U14) gpmc_a2.ehrpwm1A */
>;
pinctrl-single,bias-pulldown = <8 8 0 24>;
}
AM335X_PIN_GPMC_A2 is PIN18 based on the memory offset and corresponds
to gpiochip 1 line 18 (MUX_MODE1).
Here is function graph trace (note: I used -fno-inline) when gpiomon
runs with pull-down bias flag on gpiochip 1 line 18:
debian@beaglebone:~$ ./libgpiod/tools/gpiomon -B pull-down 1 18
0) | gpio_ioctl() {
0) 2.708 us | gpiochip_get_desc();
0) | gpiod_request() {
0) | gpiod_request_commit() {
0) 2.834 us | gpiochip_line_is_valid();
0) | omap_gpio_request() {
0) 2.708 us | omap_enable_gpio_module();
0) + 15.375 us | }
0) | gpiod_get_direction() {
0) 2.500 us | gpiod_to_chip();
0) 3.459 us | omap_gpio_get_direction();
0) + 16.125 us | }
0) + 52.875 us | }
0) + 60.750 us | }
0) | gpiod_direction_input() {
0) | omap_gpio_input() {
0) 2.500 us | omap_set_gpio_direction();
0) 8.125 us | }
0) | gpio_set_bias() {
0) | gpio_set_config() {
0) | gpio_do_set_config() {
0) | omap_gpio_set_config() {
0) | omap_gpio_bias() {
0) | gpiochip_generic_config() {
0) | pinctrl_gpio_set_config() {
0) | pinctrl_get_device_gpio_range() {
0) 3.292 us | pinctrl_match_gpio_range();
0) 8.667 us | }
0) | pinconf_set_config() {
0) | pcs_pinconf_set() {
0) 5.250 us | pcs_get_function();
0) 3.417 us | pcs_readl();
0) | pcs_pinconf_clear_bias() {
0) | pcs_pinconf_set() {
0) 3.125 us | pcs_get_function();
0) 2.833 us | pcs_readl();
0) 3.792 us | pcs_writel();
0) + 20.958 us | }
0) | pcs_pinconf_set() {
0) 2.750 us | pcs_get_function();
0) 8.083 us | }
0) + 37.333 us | }
0) 2.708 us | pcs_writel();
0) + 65.916 us | }
0) + 71.375 us | }
0) + 89.083 us | }
0) + 95.292 us | }
0) ! 100.750 us | }
0) ! 106.667 us | }
0) ! 111.791 us | }
0) ! 117.167 us | }
0) ! 122.917 us | }
0) 2.750 us | desc_to_gpio();
0) ! 146.459 us | }
Thus, all it seems I can do is set a bias flag on a gpio line if the
corresponding bias property is already set for that pin in dts. This
does not accomplish anything.
The ideal capability in my mind would be for pinctrl-single to
understand that a pin defined by a "pinctrl-single,pins" property has
both a configuration value and a mux mode value. The current pinconf
support is based on "pinctrl-single,bias-pull{up,down}" which does not
seem useful.
I would appreciate any feedback.
Thanks,
Drew
[0] https://lore.kernel.org/linux-omap/20200608125143.GA2789203@x1/
[1] https://lore.kernel.org/linux-omap/20200602131428.GA496390@x1/
[2] Documentation/devicetree/bindings/pinctrl/pinctrl-single.txt
[3] https://www.ti.com/lit/ug/spruh73q/spruh73q.pdf (see Figure 9-51)
---
arch/arm/boot/dts/am335x-pocketbeagle.dts | 2 ++
arch/arm/boot/dts/am33xx-l4.dtsi | 2 +-
drivers/gpio/Makefile | 2 +-
drivers/gpio/gpio-omap.c | 37 ++++++++++++++++++++---
drivers/pinctrl/Makefile | 2 +-
5 files changed, 38 insertions(+), 7 deletions(-)
diff --git a/arch/arm/boot/dts/am335x-pocketbeagle.dts b/arch/arm/boot/dts/am335x-pocketbeagle.dts
index 22d52516b7fc..f6de2028ba53 100644
--- a/arch/arm/boot/dts/am335x-pocketbeagle.dts
+++ b/arch/arm/boot/dts/am335x-pocketbeagle.dts
@@ -221,6 +221,8 @@ ehrpwm1_pins: pinmux-ehrpwm1-pins {
pinctrl-single,pins = <
AM33XX_PADCONF(AM335X_PIN_GPMC_A2, PIN_OUTPUT_PULLDOWN, MUX_MODE6) /* (U14) gpmc_a2.ehrpwm1A */
>;
+ pinctrl-single,bias-pulldown = <8 8 0 24>;
+ /*pinctrl-single,bias-pullup = <24 24 0 24>;*/
};
mmc0_pins: pinmux-mmc0-pins {
diff --git a/arch/arm/boot/dts/am33xx-l4.dtsi b/arch/arm/boot/dts/am33xx-l4.dtsi
index 903338015a68..cb8a57ed13c1 100644
--- a/arch/arm/boot/dts/am33xx-l4.dtsi
+++ b/arch/arm/boot/dts/am33xx-l4.dtsi
@@ -288,7 +288,7 @@ scm: scm@0 {
ranges = <0 0 0x2000>;
am33xx_pinmux: pinmux@800 {
- compatible = "pinctrl-single";
+ compatible = "pinconf-single";
reg = <0x800 0x238>;
#pinctrl-cells = <2>;
pinctrl-single,register-width = <32>;
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 1e4894e0bf0f..c55a5c167c43 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -1,7 +1,7 @@
# SPDX-License-Identifier: GPL-2.0
# generic gpio support: platform drivers, dedicated expander chips, etc
-ccflags-$(CONFIG_DEBUG_GPIO) += -DDEBUG
+ccflags-$(CONFIG_DEBUG_GPIO) += -DDEBUG -fno-inline
obj-$(CONFIG_GPIOLIB) += gpiolib.o
obj-$(CONFIG_GPIOLIB) += gpiolib-devres.o
diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
index b8e2ecc3eade..972629d69917 100644
--- a/drivers/gpio/gpio-omap.c
+++ b/drivers/gpio/gpio-omap.c
@@ -871,6 +871,21 @@ static int omap_gpio_get_multiple(struct gpio_chip *chip, unsigned long *mask,
return 0;
}
+/**
+ * omap_gpio_bias() - apply configuration for a pin
+ * @gc: the gpiochip owning the GPIO
+ * @offset: the offset of the GPIO to apply the configuration
+ * @config: the configuration to be applied
+ */
+static int omap_gpio_bias(struct gpio_chip *gc, unsigned offset, unsigned long config)
+{
+ int ret = 0;
+
+ ret = gpiochip_generic_config(gc, offset, config);
+ return ret;
+}
+
+
static int omap_gpio_debounce(struct gpio_chip *chip, unsigned offset,
unsigned debounce)
{
@@ -896,12 +911,26 @@ static int omap_gpio_set_config(struct gpio_chip *chip, unsigned offset,
unsigned long config)
{
u32 debounce;
+ u32 config_arg;
+ 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 = omap_gpio_bias(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)
diff --git a/drivers/pinctrl/Makefile b/drivers/pinctrl/Makefile
index 1731b2154df9..fc62c20702c6 100644
--- a/drivers/pinctrl/Makefile
+++ b/drivers/pinctrl/Makefile
@@ -1,7 +1,7 @@
# SPDX-License-Identifier: GPL-2.0
# generic pinmux support
-subdir-ccflags-$(CONFIG_DEBUG_PINCTRL) += -DDEBUG
+subdir-ccflags-$(CONFIG_DEBUG_PINCTRL) += -DDEBUG -fno-inline
obj-y += core.o pinctrl-utils.o
obj-$(CONFIG_PINMUX) += pinmux.o
--
2.25.1
gpio-omap: handle bias flag for gpio line
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- Subject: gpio-omap: handle bias flag for gpio line
- From: Drew Fustini <drew@xxxxxxxxxxxxxxx>
- Date: Thu, 25 Jun 2020 02:27:36 +0200
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