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 <[email protected]>

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 <[email protected]>

---
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;
  }

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