rave-sp-eeprom.c

// SPDX-License-Identifier: GPL-2.0+

/*
 * EEPROM driver for RAVE SP
 *
 * Copyright (C) 2018 Zodiac Inflight Innovations
 *
 */
#include <linux/kernel.h>
#include <linux/mfd/rave-sp.h>
#include <linux/module.h>
#include <linux/nvmem-provider.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/sizes.h>

/**
 * enum rave_sp_eeprom_access_type - Supported types of EEPROM access
 *
 * @RAVE_SP_EEPROM_WRITE:	EEPROM write
 * @RAVE_SP_EEPROM_READ:	EEPROM read
 */
enum rave_sp_eeprom_access_type {
	RAVE_SP_EEPROM_WRITE = 0,
	RAVE_SP_EEPROM_READ  = 1,
};

/**
 * enum rave_sp_eeprom_header_size - EEPROM command header sizes
 *
 * @RAVE_SP_EEPROM_HEADER_SMALL: EEPROM header size for "small" devices (< 8K)
 * @RAVE_SP_EEPROM_HEADER_BIG:	 EEPROM header size for "big" devices (> 8K)
 */
enum rave_sp_eeprom_header_size {
	RAVE_SP_EEPROM_HEADER_SMALL = 4U,
	RAVE_SP_EEPROM_HEADER_BIG   = 5U,
};
#define RAVE_SP_EEPROM_HEADER_MAX	RAVE_SP_EEPROM_HEADER_BIG

#define	RAVE_SP_EEPROM_PAGE_SIZE	32U

/**
 * struct rave_sp_eeprom_page - RAVE SP EEPROM page
 *
 * @type:	Access type (see enum rave_sp_eeprom_access_type)
 * @success:	Success flag (Success = 1, Failure = 0)
 * @data:	Read data

 * Note this structure corresponds to RSP_*_EEPROM payload from RAVE
 * SP ICD
 */
struct rave_sp_eeprom_page {
	u8  type;
	u8  success;
	u8  data[RAVE_SP_EEPROM_PAGE_SIZE];
} __packed;

/**
 * struct rave_sp_eeprom - RAVE SP EEPROM device
 *
 * @sp:			Pointer to parent RAVE SP device
 * @mutex:		Lock protecting access to EEPROM
 * @address:		EEPROM device address
 * @header_size:	Size of EEPROM command header for this device
 * @dev:		Pointer to corresponding struct device used for logging
 */
struct rave_sp_eeprom {
	struct rave_sp *sp;
	struct mutex mutex;
	u8 address;
	unsigned int header_size;
	struct device *dev;
};

/**
 * rave_sp_eeprom_io - Low-level part of EEPROM page access
 *
 * @eeprom:	EEPROM device to write to
 * @type:	EEPROM access type (read or write)
 * @idx:	number of the EEPROM page
 * @page:	Data to write or buffer to store result (via page->data)
 *
 * This function does all of the low-level work required to perform a
 * EEPROM access. This includes formatting correct command payload,
 * sending it and checking received results.
 *
 * Returns zero in case of success or negative error code in
 * case of failure.
 */
static int rave_sp_eeprom_io(struct rave_sp_eeprom *eeprom,
			     enum rave_sp_eeprom_access_type type,
			     u16 idx,
			     struct rave_sp_eeprom_page *page)
{
	const bool is_write = type == RAVE_SP_EEPROM_WRITE;
	const unsigned int data_size = is_write ? sizeof(page->data) : 0;
	const unsigned int cmd_size = eeprom->header_size + data_size;
	const unsigned int rsp_size =
		is_write ? sizeof(*page) - sizeof(page->data) : sizeof(*page);
	unsigned int offset = 0;
	u8 cmd[RAVE_SP_EEPROM_HEADER_MAX + sizeof(page->data)];
	int ret;

	if (WARN_ON(cmd_size > sizeof(cmd)))
		return -EINVAL;

	cmd[offset++] = eeprom->address;
	cmd[offset++] = 0;
	cmd[offset++] = type;
	cmd[offset++] = idx;

	/*
	 * If there's still room in this command's header it means we
	 * are talkin to EEPROM that uses 16-bit page numbers and we
	 * have to specify index's MSB in payload as well.
	 */
	if (offset < eeprom->header_size)
		cmd[offset++] = idx >> 8;
	/*
	 * Copy our data to write to command buffer first. In case of
	 * a read data_size should be zero and memcpy would become a
	 * no-op
	 */
	memcpy(&cmd[offset], page->data, data_size);

	ret = rave_sp_exec(eeprom->sp, cmd, cmd_size, page, rsp_size);
	if (ret)
		return ret;

	if (page->type != type)
		return -EPROTO;

	if (!page->success)
		return -EIO;

	return 0;
}

/**
 * rave_sp_eeprom_page_access - Access single EEPROM page
 *
 * @eeprom:	EEPROM device to access
 * @type:	Access type to perform (read or write)
 * @offset:	Offset within EEPROM to access
 * @data:	Data buffer
 * @data_len:	Size of the data buffer
 *
 * This function performs a generic access to a single page or a
 * portion thereof. Requested access MUST NOT cross the EEPROM page
 * boundary.
 *
 * Returns zero in case of success or negative error code in
 * case of failure.
 */
static int
rave_sp_eeprom_page_access(struct rave_sp_eeprom *eeprom,
			   enum rave_sp_eeprom_access_type type,
			   unsigned int offset, u8 *data,
			   size_t data_len)
{
	const unsigned int page_offset = offset % RAVE_SP_EEPROM_PAGE_SIZE;
	const unsigned int page_nr     = offset / RAVE_SP_EEPROM_PAGE_SIZE;
	struct rave_sp_eeprom_page page;
	int ret;

	/*
	 * This function will not work if data access we've been asked
	 * to do is crossing EEPROM page boundary. Normally this
	 * should never happen and getting here would indicate a bug
	 * in the code.
	 */
	if (WARN_ON(data_len > sizeof(page.data) - page_offset))
		return -EINVAL;

	if (type == RAVE_SP_EEPROM_WRITE) {
		/*
		 * If doing a partial write we need to do a read first
		 * to fill the rest of the page with correct data.
		 */
		if (data_len < RAVE_SP_EEPROM_PAGE_SIZE) {
			ret = rave_sp_eeprom_io(eeprom, RAVE_SP_EEPROM_READ,
						page_nr, &page);
			if (ret)
				return ret;
		}

		memcpy(&page.data[page_offset], data, data_len);
	}

	ret = rave_sp_eeprom_io(eeprom, type, page_nr, &page);
	if (ret)
		return ret;

	/*
	 * Since we receive the result of the read via 'page.data'
	 * buffer we need to copy that to 'data'
	 */
	if (type == RAVE_SP_EEPROM_READ)
		memcpy(data, &page.data[page_offset], data_len);

	return 0;
}

/**
 * rave_sp_eeprom_access - Access EEPROM data
 *
 * @eeprom:	EEPROM device to access
 * @type:	Access type to perform (read or write)
 * @offset:	Offset within EEPROM to access
 * @data:	Data buffer
 * @data_len:	Size of the data buffer
 *
 * This function performs a generic access (either read or write) at
 * arbitrary offset (not necessary page aligned) of arbitrary length
 * (is not constrained by EEPROM page size).
 *
 * Returns zero in case of success or negative error code in case of
 * failure.
 */
static int rave_sp_eeprom_access(struct rave_sp_eeprom *eeprom,
				 enum rave_sp_eeprom_access_type type,
				 unsigned int offset, u8 *data,
				 unsigned int data_len)
{
	unsigned int residue;
	unsigned int chunk;
	unsigned int head;
	int ret;

	mutex_lock(&eeprom->mutex);

	head    = offset % RAVE_SP_EEPROM_PAGE_SIZE;
	residue = data_len;

	do {
		/*
		 * First iteration, if we are doing an access that is
		 * not 32-byte aligned, we need to access only data up
		 * to a page boundary to avoid corssing it in
		 * rave_sp_eeprom_page_access()
		 */
		if (unlikely(head)) {
			chunk = RAVE_SP_EEPROM_PAGE_SIZE - head;
			/*
			 * This can only happen once per
			 * rave_sp_eeprom_access() call, so we set
			 * head to zero to process all the other
			 * iterations normally.
			 */
			head  = 0;
		} else {
			chunk = RAVE_SP_EEPROM_PAGE_SIZE;
		}

		/*
		 * We should never read more that 'residue' bytes
		 */
		chunk = min(chunk, residue);
		ret = rave_sp_eeprom_page_access(eeprom, type, offset,
						 data, chunk);
		if (ret)
			goto out;

		residue -= chunk;
		offset  += chunk;
		data    += chunk;
	} while (residue);
out:
	mutex_unlock(&eeprom->mutex);
	return ret;
}

static int rave_sp_eeprom_reg_read(void *eeprom, unsigned int offset,
				   void *val, size_t bytes)
{
	return rave_sp_eeprom_access(eeprom, RAVE_SP_EEPROM_READ,
				     offset, val, bytes);
}

static int rave_sp_eeprom_reg_write(void *eeprom, unsigned int offset,
				    void *val, size_t bytes)
{
	return rave_sp_eeprom_access(eeprom, RAVE_SP_EEPROM_WRITE,
				     offset, val, bytes);
}

static int rave_sp_eeprom_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct rave_sp *sp = dev_get_drvdata(dev->parent);
	struct device_node *np = dev->of_node;
	struct nvmem_config config = { 0 };
	struct rave_sp_eeprom *eeprom;
	struct nvmem_device *nvmem;
	u32 reg[2], size;

	if (of_property_read_u32_array(np, "reg", reg, ARRAY_SIZE(reg))) {
		dev_err(dev, "Failed to parse \"reg\" property\n");
		return -EINVAL;
	}

	size = reg[1];
	/*
	 * Per ICD, we have no more than 2 bytes to specify EEPROM
	 * page.
	 */
	if (size > U16_MAX * RAVE_SP_EEPROM_PAGE_SIZE) {
		dev_err(dev, "Specified size is too big\n");
		return -EINVAL;
	}

	eeprom = devm_kzalloc(dev, sizeof(*eeprom), GFP_KERNEL);
	if (!eeprom)
		return -ENOMEM;

	eeprom->address = reg[0];
	eeprom->sp      = sp;
	eeprom->dev     = dev;

	if (size > SZ_8K)
		eeprom->header_size = RAVE_SP_EEPROM_HEADER_BIG;
	else
		eeprom->header_size = RAVE_SP_EEPROM_HEADER_SMALL;

	mutex_init(&eeprom->mutex);

	config.id		= -1;
	of_property_read_string(np, "zii,eeprom-name", &config.name);
	config.priv		= eeprom;
	config.dev		= dev;
	config.size		= size;
	config.reg_read		= rave_sp_eeprom_reg_read;
	config.reg_write	= rave_sp_eeprom_reg_write;
	config.word_size	= 1;
	config.stride		= 1;

	nvmem = devm_nvmem_register(dev, &config);

	return PTR_ERR_OR_ZERO(nvmem);
}

static const struct of_device_id rave_sp_eeprom_of_match[] = {
	{ .compatible = "zii,rave-sp-eeprom" },
	{}
};
MODULE_DEVICE_TABLE(of, rave_sp_eeprom_of_match);

static struct platform_driver rave_sp_eeprom_driver = {
	.probe = rave_sp_eeprom_probe,
	.driver	= {
		.name = KBUILD_MODNAME,
		.of_match_table = rave_sp_eeprom_of_match,
	},
};
module_platform_driver(rave_sp_eeprom_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Andrey Vostrikov <andrey.vostrikov@cogentembedded.com>");
MODULE_AUTHOR("Nikita Yushchenko <nikita.yoush@cogentembedded.com>");
MODULE_AUTHOR("Andrey Smirnov <andrew.smirnov@gmail.com>");
MODULE_DESCRIPTION("RAVE SP EEPROM driver");