io_reg.h File Reference

RP2040 atomic register access macros. More...

Detailed Description

RP2040 atomic register access macros.

This allows individual fields of a control register to be modified without performing a read-modify-write sequence. See section "2.1.2. Atomic Register Access" in https://datasheets.raspberrypi.org/rpx0xx/rpx0xx-datasheet.pdf

Warning

The Single-cycle IO block (SIO), which contains the GPIO, does not support atomic access using these aliases.

Author

Marian Buschsieweke maria.nosp@m.n.bu.nosp@m.schsi.nosp@m.ewek.nosp@m.e@ovg.nosp@m.u.de

Fabian Hüßler fabia.nosp@m.n.hu.nosp@m.essle.nosp@m.r@ov.nosp@m.gu.de

Definition in file io_reg.h.

#include <stdint.h>

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#define	REG_ATOMIC_XOR_BIT   (0x1000U)
	Bit to be set if an atomic XOR operation shall be done.
#define	REG_ATOMIC_SET_BIT   (0x2000U)
	Bit to be set if an atomic set operation shall be done.
#define	REG_ATOMIC_CLEAR_BIT   (0x3000U)
	Bits to be set if an atomic clear operation shall be done.
#define	REG_ATOMIC_XOR(reg)   ((volatile uint32_t *)(((uintptr_t)(reg)) | REG_ATOMIC_XOR_BIT))
	The operation to be performed to the register at address reg will be an atomic XOR of the bits of the right-hand-side operand.
#define	REG_ATOMIC_SET(reg)   ((volatile uint32_t *)(((uintptr_t)(reg)) | REG_ATOMIC_SET_BIT))
	The operation to be performed to the register at address reg will be an atomic set of the bits of the right-hand-side operand.
#define	REG_ATOMIC_CLEAR(reg)   ((volatile uint32_t *)(((uintptr_t)(reg)) | REG_ATOMIC_CLEAR_BIT))
	The operation to be performed to the register at address reg will be an atomic clear of the bits of the right-hand-side operand.
static void	io_reg_atomic_xor (volatile uint32_t *reg, uint32_t mask)
	Performed an atomic XOR of the set bits in op with the bits in the register at address reg. More...
static void	io_reg_atomic_set (volatile uint32_t *reg, uint32_t mask)
	Set the bits in the register at address reg as given by the set bits in operand op. More...
static void	io_reg_atomic_clear (volatile uint32_t *reg, uint32_t mask)
	Clear the bits in the register at address reg as given by the set bits in operand op. More...
static void	io_reg_write_dont_corrupt (volatile uint32_t *reg, uint32_t value, uint32_t mask)
	Updates part of an I/O register without corrupting its contents. More...

Function Documentation

io_reg_atomic_clear()

static void io_reg_atomic_clear ( volatile uint32_t *  reg, uint32_t  mask  )

inlinestatic

Clear the bits in the register at address reg as given by the set bits in operand op.

Parameters

reg	Register address
mask	Mask of bits to be cleared

Definition at line 96 of file io_reg.h.

io_reg_atomic_set()

static void io_reg_atomic_set ( volatile uint32_t *  reg, uint32_t  mask  )

inlinestatic

Set the bits in the register at address reg as given by the set bits in operand op.

Parameters

reg	Register address
mask	Mask of bits to be set

Definition at line 84 of file io_reg.h.

io_reg_atomic_xor()

static void io_reg_atomic_xor ( volatile uint32_t *  reg, uint32_t  mask  )

inlinestatic

Performed an atomic XOR of the set bits in op with the bits in the register at address reg.

Parameters

reg	Register address
mask	Mask of bits to be XORed

Definition at line 72 of file io_reg.h.

io_reg_write_dont_corrupt()

static void io_reg_write_dont_corrupt ( volatile uint32_t *  reg, uint32_t  value, uint32_t  mask  )

inlinestatic

Updates part of an I/O register without corrupting its contents.

Parameters

reg	Register address
value	bits to set in the register (e.g. the new value shifted to the right position)
mask	bits to clear in the register (e.g. bitmask indicating the part to update with one bits, and everything else with zero bits)

The RP2040 only correctly implements 32 bit writes to I/O register. When updating parts of an I/O register using the structs in the CMSIS header, the C compiler might implement those updates e.g. using 8-bit writes, especially when the part to update is 8-bit in size and byte-aligned. The RP2040 will then sneakily corrupt the I/O register, rather than triggering a hard fault. This hard to debug silent corruption issue is NOT a bug, but an intentional feature, obviously.

Precondition

value & (~mask) == 0

Example use:

io_reg_write_dont_corrupt(&CLOCKS->CLK_SYS_CTRL, source << CLOCKS_CLK_SYS_CTRL_SRC_Pos,
                          CLOCKS_CLK_SYS_CTRL_SRC_Msk);

Definition at line 124 of file io_reg.h.