RT-Thread RTOS
An open source embedded real-time operating system
PIC platform examples

Rockchip & Raspberry Pi DM patterns

Concrete BSP references (paths under **rt-thread/bsp/**).

Raspberry Pi 4 — GIC root (<tt>dm/dts/bcm2711-rpi-4-b.dts</tt>)

gicv2: interrupt-controller@40041000 {
compatible = "arm,gic-400";
interrupt-controller;
#interrupt-cells = <3>;
reg = <0x40041000 0x1000>, <0x40042000 0x2000>;
};
  • Probed by in-tree **pic-gicv2.c** during **rt_pic_init**
  • All devices: **interrupt-parent = <&gicv2>** + **GIC_SPI n type**
  • Drivers: **rt_dm_dev_get_irq** → virtual IRQ → **rt_pic_attach_irq**

PCIe **interrupt-map** on host points at **&gicv2 GIC_SPI 143…**.

Raspberry Pi — BCM2835 mailbox (<tt>dm/mailbox/mailbox-bcm2835.c</tt>)

bcm_mbox->irq = rt_dm_dev_get_irq(dev, 0);
rt_hw_interrupt_install(bcm_mbox->irq, bcm2835_mbox_isr, …);
rt_hw_interrupt_umask(bcm_mbox->irq);
rt_hw_interrupt_install
void rt_hw_interrupt_install(int vector, rt_isr_handler_t new_handler, rt_isr_handler_t *old_handler)
rt_hw_interrupt_umask
void rt_hw_interrupt_umask(int vector)

Single interrupt line from GIC — no cascade. Shows standard DM consumer pattern.

Rockchip — RK8xx PMIC IRQ (<tt>dm/mfd/rk8xx.c</tt>)

Piece Detail
Root PMIC **rk8xx->irq** from SoC GPIO
Child PIC **rk8xx_irqchip**, **rt_pic_linear_irq**
Cascade **rt_pic_cascade(pirq, rk8xx->irq)** in **rk8xx_irq_map**
Demux Thread reads **status_base** regs → **rt_pic_handle_isr**
DT **interrupts = <&rk8xx_intc 0>** on sub-devices

Template for GPIO/PMIC expander IRQ chips.

Rockchip — PCIe DW INTx (<tt>dm/pci/pcie-dw-rockchip.c</tt>)

Piece Detail
Child node **legacy-interrupt-controller** (OFW child)
Child PIC **rockchip_intx_ops**, 4 lines (**RT_PCI_INTX_PIN_MAX**)
**rt_ofw_data(intx_np) = &intx_pic** PCI **interrupt-map** targets this
Parent ISR **rockchip_pcie_legacy_isr** on **legacy** GIC IRQ
No RT_PIC_F_IRQ_ROUTING Software poll of legacy status register

PCI function drivers use **rt_pci_ofw_irq_parse_and_map** → maps through **intx_pic** → GIC.

Rockchip DM consumers (simple)

Many drivers only use allocated virtual IRQ:

i2c->irq = rt_dm_dev_get_irq(dev, 0);
rt_pic_attach_irq(i2c->irq, handler, i2c, name, flags);
rt_pic_irq_unmask(i2c->irq);

Examples: **i2c-rk3x.c**, **spi-rockchip.c**, **mailbox-rockchip.c**.

Choosing a pattern

Hardware Pattern Example
Single GIC line per device **get_irq + attach** UART, I2C
Aggregated status register Child PIC + parent ISR poll RK PCIe INTx
Many lines behind one pin Child PIC + cascade RK8xx PMIC
Message-signalled MSI PIC + PCI See PIC and PCI MSI

See also