path: root/drivers/net/ipa/gsi_trans.c

// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2012-2018, The Linux Foundation. All rights reserved.
 * Copyright (C) 2019-2020 Linaro Ltd.
 */

#include <linux/types.h>
#include <linux/bits.h>
#include <linux/bitfield.h>
#include <linux/refcount.h>
#include <linux/scatterlist.h>
#include <linux/dma-direction.h>

#include "gsi.h"
#include "gsi_private.h"
#include "gsi_trans.h"
#include "ipa_gsi.h"
#include "ipa_data.h"
#include "ipa_cmd.h"

/**
 * DOC: GSI Transactions
 *
 * A GSI transaction abstracts the behavior of a GSI channel by representing
 * everything about a related group of IPA commands in a single structure.
 * (A "command" in this sense is either a data transfer or an IPA immediate
 * command.)  Most details of interaction with the GSI hardware are managed
 * by the GSI transaction core, allowing users to simply describe commands
 * to be performed.  When a transaction has completed a callback function
 * (dependent on the type of endpoint associated with the channel) allows
 * cleanup of resources associated with the transaction.
 *
 * To perform a command (or set of them), a user of the GSI transaction
 * interface allocates a transaction, indicating the number of TREs required
 * (one per command).  If sufficient TREs are available, they are reserved
 * for use in the transaction and the allocation succeeds.  This way
 * exhaustion of the available TREs in a channel ring is detected
 * as early as possible.  All resources required to complete a transaction
 * are allocated at transaction allocation time.
 *
 * Commands performed as part of a transaction are represented in an array
 * of Linux scatterlist structures.  This array is allocated with the
 * transaction, and its entries are initialized using standard scatterlist
 * functions (such as sg_set_buf() or skb_to_sgvec()).
 *
 * Once a transaction's scatterlist structures have been initialized, the
 * transaction is committed.  The caller is responsible for mapping buffers
 * for DMA if necessary, and this should be done *before* allocating
 * the transaction.  Between a successful allocation and commit of a
 * transaction no errors should occur.
 *
 * Committing transfers ownership of the entire transaction to the GSI
 * transaction core.  The GSI transaction code formats the content of
 * the scatterlist array into the channel ring buffer and informs the
 * hardware that new TREs are available to process.
 *
 * The last TRE in each transaction is marked to interrupt the AP when the
 * GSI hardware has completed it.  Because transfers described by TREs are
 * performed strictly in order, signaling the completion of just the last
 * TRE in the transaction is sufficient to indicate the full transaction
 * is complete.
 *
 * When a transaction is complete, ipa_gsi_trans_complete() is called by the
 * GSI code into the IPA layer, allowing it to perform any final cleanup
 * required before the transaction is freed.
 */

/* Hardware values representing a transfer element type */
enum gsi_tre_type {
	GSI_RE_XFER	= 0x2,
	GSI_RE_IMMD_CMD	= 0x3,
};

/* An entry in a channel ring */
struct gsi_tre {
	__le64 addr;		/* DMA address */
	__le16 len_opcode;	/* length in bytes or enum IPA_CMD_* */
	__le16 reserved;
	__le32 flags;		/* TRE_FLAGS_* */
};

/* gsi_tre->flags mask values (in CPU byte order) */
#define TRE_FLAGS_CHAIN_FMASK	GENMASK(0, 0)
#define TRE_FLAGS_IEOT_FMASK	GENMASK(9, 9)
#define TRE_FLAGS_BEI_FMASK	GENMASK(10, 10)
#define TRE_FLAGS_TYPE_FMASK	GENMASK(23, 16)

int gsi_trans_pool_init(struct gsi_trans_pool *pool, size_t size, u32 count,
			u32 max_alloc)
{
	void *virt;

#ifdef IPA_VALIDATE
	if (!size || size % 8)
		return -EINVAL;
	if (count < max_alloc)
		return -EINVAL;
	if (!max_alloc)
		return -EINVAL;
#endif /* IPA_VALIDATE */

	/* By allocating a few extra entries in our pool (one less
	 * than the maximum number that will be requested in a
	 * single allocation), we can always satisfy requests without
	 * ever worrying about straddling the end of the pool array.
	 * If there aren't enough entries starting at the free index,
	 * we just allocate free entries from the beginning of the pool.
	 */
	virt = kcalloc(count + max_alloc - 1, size, GFP_KERNEL);
	if (!virt)
		return -ENOMEM;

	pool->base = virt;
	/* If the allocator gave us any extra memory, use it */
	pool->count = ksize(pool->base) / size;
	pool->free = 0;
	pool->max_alloc = max_alloc;
	pool->size = size;
	pool->addr = 0;		/* Only used for DMA pools */

	return 0;
}

void gsi_trans_pool_exit(struct gsi_trans_pool *pool)
{
	kfree(pool->base);
	memset(pool, 0, sizeof(*pool));
}

/* Allocate the requested number of (zeroed) entries from the pool */
/* Home-grown DMA pool.  This way we can preallocate and use the tre_count
 * to guarantee allocations will succeed.  Even though we specify max_alloc
 * (and it can be more than one), we only allow allocation of a single
 * element from a DMA pool.
 */
int gsi_trans_pool_init_dma(struct device *dev, struct gsi_trans_pool *pool,
			    size_t size, u32 count, u32 max_alloc)
{
	size_t total_size;
	dma_addr_t addr;
	void *virt;

#ifdef IPA_VALIDATE
	if (!size || size % 8)
		return -EINVAL;
	if (count < max_alloc)
		return -EINVAL;
	if (!max_alloc)
		return -EINVAL;
#endif /* IPA_VALIDATE */

	/* Don't let allocations cross a power-of-two boundary */
	size = __roundup_pow_of_two(size);
	total_size = (count + max_alloc - 1) * size;

	/* The allocator will give us a power-of-2 number of pages.  But we
	 * can't guarantee that, so request it.  That way we won't waste any
	 * memory that would be available beyond the required space.
	 *
	 * Note that gsi_trans_pool_exit_dma() assumes the total allocated
	 * size is exactly (count * size).
	 */
	total_size = get_order(total_size) << PAGE_SHIFT;

	virt = dma_alloc_coherent(dev, total_size, &addr, GFP_KERNEL);
	if (!virt)
		return -ENOMEM;

	pool->base = virt;
	pool->count = total_size / size;
	pool->free = 0;
	pool->size = size;
	pool->max_alloc = max_alloc;
	pool->addr = addr;

	return 0;
}

void gsi_trans_pool_exit_dma(struct device *dev, struct gsi_trans_pool *pool)
{
	size_t total_size = pool->count * pool->size;

	dma_free_coherent(dev, total_size, pool->base, pool->addr);
	memset(pool, 0, sizeof(*pool));
}

/* Return the byte offset of the next free entry in the pool */
static u32 gsi_trans_pool_alloc_common(struct gsi_trans_pool *pool, u32 count)
{
	u32 offset;

	/* assert(count > 0); */
	/* assert(count <= pool->max_alloc); */

	/* Allocate from beginning if wrap would occur */
	if (count > pool->count - pool->free)
		pool->free = 0;

	offset = pool->free * pool->size;
	pool->free += count;
	memset(pool->base + offset, 0, count * pool->size);

	return offset;
}

/* Allocate a contiguous block of zeroed entries from a pool */
void *gsi_trans_pool_alloc(struct gsi_trans_pool *pool, u32 count)
{
	return pool->base + gsi_trans_pool_alloc_common(pool, count);
}

/* Allocate a single zeroed entry from a DMA pool */
void *gsi_trans_pool_alloc_dma(struct gsi_trans_pool *pool, dma_addr_t *addr)
{
	u32 offset = gsi_trans_pool_alloc_common(pool, 1);

	*addr = pool->addr + offset;

	return pool->base + offset;
}

/* Return the pool element that immediately follows the one given.
 * This only works done if elements are allocated one at a time.
 */
void *gsi_trans_pool_next(struct gsi_trans_pool *pool, void *element)