[PATCH v2] pinctrl: bcm283x: Add GPIO pull-up/down control for BCM2835 and BCM2711
Matthias Brugger
mbrugger at suse.com
Fri Nov 14 09:51:07 CET 2025
On 14/11/25 00:45, Cibil Pankiras wrote:
> This patch adds support for configuring GPIO pull-up and pull-down
> resistors in the BCM283x pinctrl driver. It implements the brcm,pull
> device tree property to control pin bias settings.
>
> The implementation follows the hardware-specific pull control
> mechanisms:
> - BCM2835: two-step GPPUD register sequence
> - BCM2711: direct per-pin control registers
>
> This enables device tree configurations to specify pull-up, pull-down,
> or no bias for individual GPIO pins.
>
> Tested on Raspberry Pi boards with both BCM2835 and BCM2711 SoCs.
>
> Signed-off-by: Cibil Pankiras <cibil.pankiras at egym.com>
We check the brcm,pull byte lenght to be on par with the DT binding.
That's not something I would expect normally to be done in a driver. But
as this is also done for brcm,pin in this driver and also done in the
kernel: let's not bike-shed.
Reviewed-by: Matthias Brugger <mbrugger at suse.com>
> ---
> Changes in v2:
> - If brcm,pull contains a single value, apply it to all pins listed in brcm,pins
> ---
> arch/arm/mach-bcm283x/include/mach/gpio.h | 10 ++
> drivers/pinctrl/broadcom/pinctrl-bcm283x.c | 105 ++++++++++++++++++++-
> 2 files changed, 112 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm/mach-bcm283x/include/mach/gpio.h b/arch/arm/mach-bcm283x/include/mach/gpio.h
> index 4aeb48eeb20..c54414a012c 100644
> --- a/arch/arm/mach-bcm283x/include/mach/gpio.h
> +++ b/arch/arm/mach-bcm283x/include/mach/gpio.h
> @@ -26,6 +26,16 @@
> #define BCM2835_GPIO_FSEL_BANK(gpio) (gpio / 10)
> #define BCM2835_GPIO_FSEL_SHIFT(gpio) ((gpio % 10) * 3)
>
> +/* BCM2835 GPIO Pull-up/down register offsets */
> +#define BCM2835_GPPUD 37
> +#define BCM2835_GPPUDCLK0 38
> +
> +/* BCM2711 GPIO Pull-up/down control */
> +#define BCM2711_GPPUD_CNTRL_REG0 57
> +#define BCM2711_PUD_REG_OFFSET(gpio) ((gpio) / 16)
> +#define BCM2711_PUD_REG_SHIFT(gpio) (((gpio) % 16) * 2)
> +#define BCM2711_PUD_2711_MASK 0x3
> +
> struct bcm2835_gpio_regs {
> u32 gpfsel[6];
> u32 reserved1;
> diff --git a/drivers/pinctrl/broadcom/pinctrl-bcm283x.c b/drivers/pinctrl/broadcom/pinctrl-bcm283x.c
> index cf9350c151e..4ecc8bac645 100644
> --- a/drivers/pinctrl/broadcom/pinctrl-bcm283x.c
> +++ b/drivers/pinctrl/broadcom/pinctrl-bcm283x.c
> @@ -21,6 +21,8 @@
> #include <asm/system.h>
> #include <asm/io.h>
> #include <asm/gpio.h>
> +#include <dt-bindings/pinctrl/bcm2835.h>
> +#include <linux/delay.h>
>
> struct bcm283x_pinctrl_priv {
> u32 *base_reg;
> @@ -54,7 +56,66 @@ static int bcm2835_gpio_get_func_id(struct udevice *dev, unsigned int gpio)
> }
>
> /*
> - * bcm283x_pinctrl_set_state: configure pin functions.
> + * bcm2835_gpio_set_pull: Set GPIO pull-up/down resistor for BCM2835
> + * @dev: the pinctrl device
> + * @gpio: the GPIO pin number
> + * @pull: pull setting (BCM2835_PUD_OFF, BCM2835_PUD_DOWN, BCM2835_PUD_UP)
> + */
> +static void bcm2835_gpio_set_pull(struct udevice *dev, unsigned int gpio, int pull)
> +{
> + struct bcm283x_pinctrl_priv *priv = dev_get_priv(dev);
> + u32 bank = BCM2835_GPPUDCLK0 + BCM2835_GPIO_COMMON_BANK(gpio);
> + u32 bit = BCM2835_GPIO_COMMON_SHIFT(gpio);
> +
> + /* Set required control signal */
> + writel(pull & 0x3, &priv->base_reg[BCM2835_GPPUD]);
> + udelay(1);
> +
> + /* Clock the control signal into the GPIO pads */
> + writel(1 << bit, &priv->base_reg[bank]);
> + udelay(1);
> +
> + /* Remove the control signal and clock */
> + writel(0, &priv->base_reg[BCM2835_GPPUD]);
> + writel(0, &priv->base_reg[bank]);
> +}
> +
> +/*
> + * bcm2711_gpio_set_pull: Set GPIO pull-up/down resistor for BCM2711
> + * @dev: the pinctrl device
> + * @gpio: the GPIO pin number
> + * @pull: pull setting (BCM2835_PUD_OFF, BCM2835_PUD_DOWN, BCM2835_PUD_UP)
> + */
> +static void bcm2711_gpio_set_pull(struct udevice *dev, unsigned int gpio, int pull)
> +{
> + struct bcm283x_pinctrl_priv *priv = dev_get_priv(dev);
> + u32 reg_offset;
> + u32 bit_shift;
> + u32 pull_bits;
> +
> + /* Findout which GPIO_PUP_PDN_CNTRL register to use */
> + reg_offset = BCM2711_GPPUD_CNTRL_REG0 + BCM2711_PUD_REG_OFFSET(gpio);
> +
> + /* Findout the bit position */
> + bit_shift = BCM2711_PUD_REG_SHIFT(gpio);
> +
> + /* Update the 2-bit field for this GPIO */
> + pull_bits = pull & BCM2711_PUD_2711_MASK;
> + clrsetbits_le32(&priv->base_reg[reg_offset],
> + BCM2711_PUD_2711_MASK << bit_shift,
> + pull_bits << bit_shift);
> +}
> +
> +static void bcm283x_gpio_set_pull(struct udevice *dev, unsigned int gpio, int pull)
> +{
> + if (device_is_compatible(dev, "brcm,bcm2835-gpio"))
> + bcm2835_gpio_set_pull(dev, gpio, pull);
> + else
> + bcm2711_gpio_set_pull(dev, gpio, pull);
> +}
> +
> +/*
> + * bcm283x_pinctrl_set_state: configure pin functions and pull states.
> * @dev: the pinctrl device to be configured.
> * @config: the state to be configured.
> * @return: 0 in success
> @@ -62,8 +123,10 @@ static int bcm2835_gpio_get_func_id(struct udevice *dev, unsigned int gpio)
> int bcm283x_pinctrl_set_state(struct udevice *dev, struct udevice *config)
> {
> u32 pin_arr[MAX_PINS_PER_BANK];
> + u32 pull_arr[MAX_PINS_PER_BANK];
> int function;
> - int i, len, pin_count = 0;
> + int i, len, pin_count = 0, pull_len = 0, pull_count = 0;
> + int pull_value;
>
> if (!dev_read_prop(config, "brcm,pins", &len) || !len ||
> len & 0x3 || dev_read_u32_array(config, "brcm,pins", pin_arr,
> @@ -82,8 +145,44 @@ int bcm283x_pinctrl_set_state(struct udevice *dev, struct udevice *config)
> return -EINVAL;
> }
>
> - for (i = 0; i < pin_count; i++)
> + /* Check if brcm,pull property exists */
> + if (dev_read_prop(config, "brcm,pull", &pull_len) && pull_len > 0) {
> + if (pull_len & 0x3) {
> + debug("Invalid pull array length for pinconfig %s (%d)\n",
> + config->name, pull_len);
> + return -EINVAL;
> + }
> +
> + pull_count = pull_len / sizeof(u32);
> +
> + if (pull_count != 1 && pull_count != pin_count) {
> + debug("Pull array count (%d) must be 1 or match pin count (%d) for pinconfig %s\n",
> + pull_count, pin_count, config->name);
> + return -EINVAL;
> + }
> +
> + if (dev_read_u32_array(config, "brcm,pull", pull_arr, pull_count)) {
> + debug("Failed reading pull array for pinconfig %s\n", config->name);
> + return -EINVAL;
> + }
> +
> + /* Validate pull values */
> + for (i = 0; i < pull_count; i++) {
> + if (pull_arr[i] > 2) {
> + debug("Invalid pull value %d for pin %d in pinconfig %s\n",
> + pull_arr[i], pin_arr[i], config->name);
> + return -EINVAL;
> + }
> + }
> + }
> +
> + for (i = 0; i < pin_count; i++) {
> bcm2835_gpio_set_func_id(dev, pin_arr[i], function);
> + if (pull_count > 0) {
> + pull_value = (pull_count == 1) ? pull_arr[0] : pull_arr[i];
> + bcm283x_gpio_set_pull(dev, pin_arr[i], pull_value);
> + }
> + }
>
> return 0;
> }
More information about the U-Boot
mailing list