dma.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * OpenRISC Linux
 *
 * Linux architectural port borrowing liberally from similar works of
 * others.  All original copyrights apply as per the original source
 * declaration.
 *
 * Modifications for the OpenRISC architecture:
 * Copyright (C) 2003 Matjaz Breskvar <[email protected]>
 * Copyright (C) 2010-2011 Jonas Bonn <[email protected]>
 *
 * DMA mapping callbacks...
 */

#include <linux/dma-map-ops.h>
#include <linux/pagewalk.h>

#include <asm/cpuinfo.h>
#include <asm/cacheflush.h>
#include <asm/spr_defs.h>
#include <asm/tlbflush.h>

static int
page_set_nocache(pte_t *pte, unsigned long addr,
		 unsigned long next, struct mm_walk *walk)
{
	pte_val(*pte) |= _PAGE_CI;

	/*
	 * Flush the page out of the TLB so that the new page flags get
	 * picked up next time there's an access
	 */
	flush_tlb_kernel_range(addr, addr + PAGE_SIZE);

	/* Flush page out of dcache */
	local_dcache_range_flush(__pa(addr), __pa(next));

	return 0;
}

static const struct mm_walk_ops set_nocache_walk_ops = {
	.pte_entry		= page_set_nocache,
};

static int
page_clear_nocache(pte_t *pte, unsigned long addr,
		   unsigned long next, struct mm_walk *walk)
{
	pte_val(*pte) &= ~_PAGE_CI;

	/*
	 * Flush the page out of the TLB so that the new page flags get
	 * picked up next time there's an access
	 */
	flush_tlb_kernel_range(addr, addr + PAGE_SIZE);

	return 0;
}

static const struct mm_walk_ops clear_nocache_walk_ops = {
	.pte_entry		= page_clear_nocache,
};

void *arch_dma_set_uncached(void *cpu_addr, size_t size)
{
	unsigned long va = (unsigned long)cpu_addr;
	int error;

	/*
	 * We need to iterate through the pages, clearing the dcache for
	 * them and setting the cache-inhibit bit.
	 */
	mmap_write_lock(&init_mm);
	error = walk_kernel_page_table_range(va, va + size,
			&set_nocache_walk_ops, NULL, NULL);
	mmap_write_unlock(&init_mm);

	if (error)
		return ERR_PTR(error);
	return cpu_addr;
}

void arch_dma_clear_uncached(void *cpu_addr, size_t size)
{
	unsigned long va = (unsigned long)cpu_addr;

	mmap_write_lock(&init_mm);
	/* walk_page_range shouldn't be able to fail here */
	WARN_ON(walk_kernel_page_table_range(va, va + size,
			&clear_nocache_walk_ops, NULL, NULL));
	mmap_write_unlock(&init_mm);
}

void arch_sync_dma_for_device(phys_addr_t addr, size_t size,
		enum dma_data_direction dir)
{
	switch (dir) {
	case DMA_TO_DEVICE:
		/* Flush the dcache for the requested range */
		local_dcache_range_flush(addr, addr + size);
		break;
	case DMA_FROM_DEVICE:
		/* Invalidate the dcache for the requested range */
		local_dcache_range_inv(addr, addr + size);
		break;
	default:
		/*
		 * NOTE: If dir == DMA_BIDIRECTIONAL then there's no need to
		 * flush nor invalidate the cache here as the area will need
		 * to be manually synced anyway.
		 */
		break;
	}
}