arch/arm/core/cortex_m/mpu/nxp_mpu.c

/*
 * Copyright (c) 2017 Linaro Limited.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <device.h>
#include <init.h>
#include <kernel.h>
#include <soc.h>
#include <arch/arm/cortex_m/cmsis.h>
#include <arch/arm/cortex_m/mpu/nxp_mpu.h>
#include <logging/sys_log.h>
#include <misc/__assert.h>

#define STACK_GUARD_REGION_SIZE 32

/* NXP MPU Enabled state */
static u8_t nxp_mpu_enabled;

/**
 * This internal function is utilized by the MPU driver to parse the intent
 * type (i.e. THREAD_STACK_REGION) and return the correct parameter set.
 */
static inline u32_t _get_region_attr_by_type(u32_t type)
{
	switch (type) {
	case THREAD_STACK_REGION:
		return 0;
	case THREAD_STACK_GUARD_REGION:
		/* The stack guard region has to be not accessible */
		return REGION_RO_ATTR;
	default:
		/* Size 0 region */
		return 0;
	}
}

static inline u8_t _get_num_regions(void)
{
	return FSL_FEATURE_SYSMPU_DESCRIPTOR_COUNT;
}

static void _region_init(u32_t index, u32_t region_base,
			 u32_t region_end, u32_t region_attr)
{
	if (index == 0) {
		/* The MPU does not allow writes from the core to affect the
		 * RGD0 start or end addresses nor the permissions associated
		 * with the debugger; it can only write the permission fields
		 * associated with the other masters. These protections
		 * guarantee that the debugger always has access to the entire
		 * address space.
		 */
		__ASSERT(region_base == SYSMPU->WORD[index][0],
			 "Region %d base address got 0x%08x expected 0x%08x",
			 index, region_base, SYSMPU->WORD[index][0]);

		__ASSERT(region_end == SYSMPU->WORD[index][1],
			 "Region %d end address got 0x%08x expected 0x%08x",
			 index, region_end, SYSMPU->WORD[index][1]);

		/* Changes to the RGD0_WORD2 alterable fields should be done
		 * via a write to RGDAAC0.
		 */
		SYSMPU->RGDAAC[index] = region_attr;

	} else {
		SYSMPU->WORD[index][0] = region_base;
		SYSMPU->WORD[index][1] = region_end;
		SYSMPU->WORD[index][2] = region_attr;
		SYSMPU->WORD[index][3] = SYSMPU_WORD_VLD_MASK;
	}

	SYS_LOG_DBG("[%d] 0x%08x 0x%08x 0x%08x 0x%08x", index,
		    SYSMPU->WORD[index][0],
		    SYSMPU->WORD[index][1],
		    SYSMPU->WORD[index][2],
		    SYSMPU->WORD[index][3]);
}

/* ARM Core MPU Driver API Implementation for NXP MPU */

/**
 * @brief enable the MPU
 */
void arm_core_mpu_enable(void)
{
	if (nxp_mpu_enabled == 0) {
		/* Enable MPU */
		SYSMPU->CESR |= SYSMPU_CESR_VLD_MASK;

		nxp_mpu_enabled = 1;
	}
}

/**
 * @brief disable the MPU
 */
void arm_core_mpu_disable(void)
{
	if (nxp_mpu_enabled == 1) {
		/* Disable MPU */
		SYSMPU->CESR &= ~SYSMPU_CESR_VLD_MASK;
		/* Clear Interrupts */
		SYSMPU->CESR |=  SYSMPU_CESR_SPERR_MASK;

		nxp_mpu_enabled = 0;
	}
}

/**
 * @brief configure the base address and size for an MPU region
 *
 * @param   type    MPU region type
 * @param   base    base address in RAM
 * @param   size    size of the region
 */
void arm_core_mpu_configure(u8_t type, u32_t base, u32_t size)
{
	SYS_LOG_DBG("Region info: 0x%x 0x%x", base, size);
	/*
	 * The new MPU regions are allocated per type after the statically
	 * configured regions. The type is one-indexed rather than
	 * zero-indexed, therefore we need to subtract by one to get the region
	 * index.
	 */
	u32_t region_index = mpu_config.num_regions + type - 1;
	u32_t region_attr = _get_region_attr_by_type(type);
	u32_t last_region = _get_num_regions() - 1;

	/*
	 * The NXP MPU manages the permissions of the overlapping regions
	 * doing the logic OR in between them, hence they can't be used
	 * for stack/stack guard protection. For this reason the last region of
	 * the MPU will be reserved.
	 *
	 * A consequence of this is that the SRAM is splitted in different
	 * regions. In example if THREAD_STACK_GUARD_REGION is selected:
	 * - SRAM before THREAD_STACK_GUARD_REGION: RW
	 * - SRAM THREAD_STACK_GUARD_REGION: RO
	 * - SRAM after THREAD_STACK_GUARD_REGION: RW
	 */
	/* NXP MPU supports up to 16 Regions */
	if (region_index > _get_num_regions() - 2) {
		return;
	}

	/* Configure SRAM_0 region */
	/*
	 * The mpu_config.sram_region contains the index of the region in
	 * the mpu_config.mpu_regions array but the region 0 on the NXP MPU
	 * is the background region, so on this MPU the regions are mapped
	 * starting from 1, hence the mpu_config.sram_region on the data
	 * structure is mapped on the mpu_config.sram_region + 1 region of
	 * the MPU.
	 */
	_region_init(mpu_config.sram_region,
		     mpu_config.mpu_regions[mpu_config.sram_region].base,
		     ENDADDR_ROUND(base),
		     mpu_config.mpu_regions[mpu_config.sram_region].attr);

	switch (type) {
	case THREAD_STACK_REGION:
		break;
	case THREAD_STACK_GUARD_REGION:
		_region_init(region_index, base,
			     ENDADDR_ROUND(base + STACK_GUARD_REGION_SIZE),
			     region_attr);
		break;
	default:
		break;
	}

	/* Configure SRAM_1 region */
	_region_init(last_region,
		     base + STACK_GUARD_REGION_SIZE,
		     ENDADDR_ROUND(
			    mpu_config.mpu_regions[mpu_config.sram_region].end),
		     mpu_config.mpu_regions[mpu_config.sram_region].attr);

}

/* NXP MPU Driver Initial Setup */

/*
 * @brief MPU default configuration
 *
 * This function provides the default configuration mechanism for the Memory
 * Protection Unit (MPU).
 */
static void _nxp_mpu_config(void)
{
	u32_t r_index;

	SYS_LOG_DBG("region number: %d", _get_num_regions());

	/* NXP MPU supports up to 16 Regions */
	if (mpu_config.num_regions > _get_num_regions()) {
		return;
	}

	/* Disable MPU */
	SYSMPU->CESR &= ~SYSMPU_CESR_VLD_MASK;
	/* Clear Interrupts */
	SYSMPU->CESR |=  SYSMPU_CESR_SPERR_MASK;

	/* MPU Configuration */

	/* Configure regions */
	for (r_index = 0; r_index < mpu_config.num_regions; r_index++) {
		_region_init(r_index,
			     mpu_config.mpu_regions[r_index].base,
			     mpu_config.mpu_regions[r_index].end,
			     mpu_config.mpu_regions[r_index].attr);
	}

	/* Enable MPU */
	SYSMPU->CESR |= SYSMPU_CESR_VLD_MASK;

	nxp_mpu_enabled = 1;

	/* Make sure that all the registers are set before proceeding */
	__DSB();
	__ISB();
}

/*
 * @brief MPU clock configuration
 *
 * This function provides the clock configuration for the Memory Protection
 * Unit (MPU).
 */
static void _nxp_mpu_clock_cfg(void)
{
	/* Enable Clock */
	CLOCK_EnableClock(kCLOCK_Sysmpu0);
}

static int nxp_mpu_init(struct device *arg)
{
	ARG_UNUSED(arg);

	_nxp_mpu_clock_cfg();

	_nxp_mpu_config();

	return 0;
}

#if defined(CONFIG_SYS_LOG)
/* To have logging the driver needs to be initialized later */
SYS_INIT(nxp_mpu_init, POST_KERNEL,
	 CONFIG_KERNEL_INIT_PRIORITY_DEFAULT);
#else
SYS_INIT(nxp_mpu_init, PRE_KERNEL_1,
	 CONFIG_KERNEL_INIT_PRIORITY_DEFAULT);
#endif