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nvmem: prepare basics for FRAM support
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Added enum and string for FRAM (ferroelectric RAM) to expose it as file
named "fram".
Added documentation of sysfs file.

Signed-off-by: Jiri Prchal <jiri.prchal@aksignal.cz>
Link: https://lore.kernel.org/r/20210611094601.95131-2-jiri.prchal@aksignal.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Jiri Prchal authored and Greg Kroah-Hartman committed Jun 11, 2021
1 parent 989f77e commit fd307a4
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19 changes: 19 additions & 0 deletions Documentation/ABI/testing/sysfs-class-spi-eeprom
Original file line number Diff line number Diff line change
@@ -0,0 +1,19 @@
What: /sys/class/spi_master/spi<bus>/spi<bus>.<dev>/fram
Date: June 2021
KernelVersion: 5.14
Contact: Jiri Prchal <jiri.prchal@aksignal.cz>
Description:
Contains the FRAM binary data. Same as EEPROM, just another file
name to indicate that it employs ferroelectric process.
It performs write operations at bus speed - no write delays.

What: /sys/class/spi_master/spi<bus>/spi<bus>.<dev>/sernum
Date: May 2021
KernelVersion: 5.14
Contact: Jiri Prchal <jiri.prchal@aksignal.cz>
Description:
Contains the serial number of the Cypress FRAM (FM25VN) if it is
present. It will be displayed as a 8 byte hex string, as read
from the device.

This is a read-only attribute.
31 changes: 25 additions & 6 deletions Documentation/devicetree/bindings/eeprom/at25.yaml
Original file line number Diff line number Diff line change
Expand Up @@ -4,14 +4,16 @@
$id: "http://devicetree.org/schemas/eeprom/at25.yaml#"
$schema: "http://devicetree.org/meta-schemas/core.yaml#"

title: SPI EEPROMs compatible with Atmel's AT25
title: SPI EEPROMs or FRAMs compatible with Atmel's AT25

maintainers:
- Christian Eggers <ceggers@arri.de>

properties:
$nodename:
pattern: "^eeprom@[0-9a-f]{1,2}$"
anyOf:
- pattern: "^eeprom@[0-9a-f]{1,2}$"
- pattern: "^fram@[0-9a-f]{1,2}$"

# There are multiple known vendors who manufacture EEPROM chips compatible
# with Atmel's AT25. The compatible string requires two items where the
Expand All @@ -31,6 +33,7 @@ properties:
- microchip,25lc040
- st,m95m02
- st,m95256
- cypress,fm25

- const: atmel,at25

Expand All @@ -47,7 +50,7 @@ properties:
$ref: /schemas/types.yaml#/definitions/uint32
enum: [1, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072]
description:
Size of the eeprom page.
Size of the eeprom page. FRAMs don't have pages.

size:
$ref: /schemas/types.yaml#/definitions/uint32
Expand Down Expand Up @@ -100,9 +103,19 @@ required:
- compatible
- reg
- spi-max-frequency
- pagesize
- size
- address-width

allOf:
- if:
properties:
compatible:
not:
contains:
const: cypress,fm25
then:
required:
- pagesize
- size
- address-width

additionalProperties: false

Expand All @@ -125,4 +138,10 @@ examples:
size = <32768>;
address-width = <16>;
};
fram@1 {
compatible = "cypress,fm25", "atmel,at25";
reg = <1>;
spi-max-frequency = <40000000>;
};
};
5 changes: 3 additions & 2 deletions drivers/misc/eeprom/Kconfig
Original file line number Diff line number Diff line change
Expand Up @@ -32,12 +32,13 @@ config EEPROM_AT24
will be called at24.

config EEPROM_AT25
tristate "SPI EEPROMs from most vendors"
tristate "SPI EEPROMs (FRAMs) from most vendors"
depends on SPI && SYSFS
select NVMEM
select NVMEM_SYSFS
help
Enable this driver to get read/write support to most SPI EEPROMs,
Enable this driver to get read/write support to most SPI EEPROMs
and Cypress FRAMs,
after you configure the board init code to know about each eeprom
on your target board.

Expand Down
161 changes: 131 additions & 30 deletions drivers/misc/eeprom/at25.c
Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* at25.c -- support most SPI EEPROMs, such as Atmel AT25 models
* and Cypress FRAMs FM25 models
*
* Copyright (C) 2006 David Brownell
*/
Expand All @@ -16,6 +17,9 @@
#include <linux/spi/spi.h>
#include <linux/spi/eeprom.h>
#include <linux/property.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/math.h>

/*
* NOTE: this is an *EEPROM* driver. The vagaries of product naming
Expand All @@ -27,13 +31,15 @@
* AT25M02, AT25128B
*/

#define FM25_SN_LEN 8 /* serial number length */
struct at25_data {
struct spi_device *spi;
struct mutex lock;
struct spi_eeprom chip;
unsigned addrlen;
struct nvmem_config nvmem_config;
struct nvmem_device *nvmem;
u8 sernum[FM25_SN_LEN];
};

#define AT25_WREN 0x06 /* latch the write enable */
Expand All @@ -42,6 +48,9 @@ struct at25_data {
#define AT25_WRSR 0x01 /* write status register */
#define AT25_READ 0x03 /* read byte(s) */
#define AT25_WRITE 0x02 /* write byte(s)/sector */
#define FM25_SLEEP 0xb9 /* enter sleep mode */
#define FM25_RDID 0x9f /* read device ID */
#define FM25_RDSN 0xc3 /* read S/N */

#define AT25_SR_nRDY 0x01 /* nRDY = write-in-progress */
#define AT25_SR_WEN 0x02 /* write enable (latched) */
Expand All @@ -51,13 +60,18 @@ struct at25_data {

#define AT25_INSTR_BIT3 0x08 /* Additional address bit in instr */

#define FM25_ID_LEN 9 /* ID length */

#define EE_MAXADDRLEN 3 /* 24 bit addresses, up to 2 MBytes */

/* Specs often allow 5 msec for a page write, sometimes 20 msec;
* it's important to recover from write timeouts.
*/
#define EE_TIMEOUT 25

#define IS_EEPROM 0
#define IS_FRAM 1

/*-------------------------------------------------------------------------*/

#define io_limit PAGE_SIZE /* bytes */
Expand Down Expand Up @@ -129,6 +143,51 @@ static int at25_ee_read(void *priv, unsigned int offset,
return status;
}

/*
* read extra registers as ID or serial number
*/
static int fm25_aux_read(struct at25_data *at25, u8 *buf, uint8_t command,
int len)
{
int status;
struct spi_transfer t[2];
struct spi_message m;

spi_message_init(&m);
memset(t, 0, sizeof(t));

t[0].tx_buf = &command;
t[0].len = 1;
spi_message_add_tail(&t[0], &m);

t[1].rx_buf = buf;
t[1].len = len;
spi_message_add_tail(&t[1], &m);

mutex_lock(&at25->lock);

status = spi_sync(at25->spi, &m);
dev_dbg(&at25->spi->dev, "read %d aux bytes --> %d\n", len, status);

mutex_unlock(&at25->lock);
return status;
}

static ssize_t sernum_show(struct device *dev, struct device_attribute *attr, char *buf)
{
struct at25_data *at25;

at25 = dev_get_drvdata(dev);
return sysfs_emit(buf, "%*ph\n", sizeof(at25->sernum), at25->sernum);
}
static DEVICE_ATTR_RO(sernum);

static struct attribute *sernum_attrs[] = {
&dev_attr_sernum.attr,
NULL,
};
ATTRIBUTE_GROUPS(sernum);

static int at25_ee_write(void *priv, unsigned int off, void *val, size_t count)
{
struct at25_data *at25 = priv;
Expand Down Expand Up @@ -303,34 +362,39 @@ static int at25_fw_to_chip(struct device *dev, struct spi_eeprom *chip)
return 0;
}

static const struct of_device_id at25_of_match[] = {
{ .compatible = "atmel,at25", .data = (const void *)IS_EEPROM },
{ .compatible = "cypress,fm25", .data = (const void *)IS_FRAM },
{ }
};
MODULE_DEVICE_TABLE(of, at25_of_match);

static int at25_probe(struct spi_device *spi)
{
struct at25_data *at25 = NULL;
struct spi_eeprom chip;
int err;
int sr;
int addrlen;
u8 id[FM25_ID_LEN];
u8 sernum[FM25_SN_LEN];
int i;
const struct of_device_id *match;
int is_fram = 0;

match = of_match_device(of_match_ptr(at25_of_match), &spi->dev);
if (match)
is_fram = (int)match->data;

/* Chip description */
if (!spi->dev.platform_data) {
err = at25_fw_to_chip(&spi->dev, &chip);
if (err)
return err;
if (!is_fram) {
err = at25_fw_to_chip(&spi->dev, &chip);
if (err)
return err;
}
} else
chip = *(struct spi_eeprom *)spi->dev.platform_data;

/* For now we only support 8/16/24 bit addressing */
if (chip.flags & EE_ADDR1)
addrlen = 1;
else if (chip.flags & EE_ADDR2)
addrlen = 2;
else if (chip.flags & EE_ADDR3)
addrlen = 3;
else {
dev_dbg(&spi->dev, "unsupported address type\n");
return -EINVAL;
}

/* Ping the chip ... the status register is pretty portable,
* unlike probing manufacturer IDs. We do expect that system
* firmware didn't write it in the past few milliseconds!
Expand All @@ -349,9 +413,51 @@ static int at25_probe(struct spi_device *spi)
at25->chip = chip;
at25->spi = spi;
spi_set_drvdata(spi, at25);
at25->addrlen = addrlen;

at25->nvmem_config.type = NVMEM_TYPE_EEPROM;
if (is_fram) {
/* Get ID of chip */
fm25_aux_read(at25, id, FM25_RDID, FM25_ID_LEN);
if (id[6] != 0xc2) {
dev_err(&spi->dev,
"Error: no Cypress FRAM (id %02x)\n", id[6]);
return -ENODEV;
}
/* set size found in ID */
if (id[7] < 0x21 || id[7] > 0x26) {
dev_err(&spi->dev, "Error: unsupported size (id %02x)\n", id[7]);
return -ENODEV;
}
chip.byte_len = int_pow(2, id[7] - 0x21 + 4) * 1024;

if (at25->chip.byte_len > 64 * 1024)
at25->chip.flags |= EE_ADDR3;
else
at25->chip.flags |= EE_ADDR2;

if (id[8]) {
fm25_aux_read(at25, sernum, FM25_RDSN, FM25_SN_LEN);
/* swap byte order */
for (i = 0; i < FM25_SN_LEN; i++)
at25->sernum[i] = sernum[FM25_SN_LEN - 1 - i];
}

at25->chip.page_size = PAGE_SIZE;
strncpy(at25->chip.name, "fm25", sizeof(at25->chip.name));
}

/* For now we only support 8/16/24 bit addressing */
if (at25->chip.flags & EE_ADDR1)
at25->addrlen = 1;
else if (at25->chip.flags & EE_ADDR2)
at25->addrlen = 2;
else if (at25->chip.flags & EE_ADDR3)
at25->addrlen = 3;
else {
dev_dbg(&spi->dev, "unsupported address type\n");
return -EINVAL;
}

at25->nvmem_config.type = is_fram ? NVMEM_TYPE_FRAM : NVMEM_TYPE_EEPROM;
at25->nvmem_config.name = dev_name(&spi->dev);
at25->nvmem_config.dev = &spi->dev;
at25->nvmem_config.read_only = chip.flags & EE_READONLY;
Expand All @@ -370,27 +476,22 @@ static int at25_probe(struct spi_device *spi)
if (IS_ERR(at25->nvmem))
return PTR_ERR(at25->nvmem);

dev_info(&spi->dev, "%d %s %s eeprom%s, pagesize %u\n",
(chip.byte_len < 1024) ? chip.byte_len : (chip.byte_len / 1024),
(chip.byte_len < 1024) ? "Byte" : "KByte",
at25->chip.name,
(chip.flags & EE_READONLY) ? " (readonly)" : "",
at25->chip.page_size);
dev_info(&spi->dev, "%d %s %s %s%s, pagesize %u\n",
(chip.byte_len < 1024) ? chip.byte_len : (chip.byte_len / 1024),
(chip.byte_len < 1024) ? "Byte" : "KByte",
at25->chip.name, is_fram ? "fram" : "eeprom",
(chip.flags & EE_READONLY) ? " (readonly)" : "",
at25->chip.page_size);
return 0;
}

/*-------------------------------------------------------------------------*/

static const struct of_device_id at25_of_match[] = {
{ .compatible = "atmel,at25", },
{ }
};
MODULE_DEVICE_TABLE(of, at25_of_match);

static struct spi_driver at25_driver = {
.driver = {
.name = "at25",
.of_match_table = at25_of_match,
.dev_groups = sernum_groups,
},
.probe = at25_probe,
};
Expand Down
4 changes: 4 additions & 0 deletions drivers/nvmem/core.c
Original file line number Diff line number Diff line change
Expand Up @@ -180,6 +180,7 @@ static const char * const nvmem_type_str[] = {
[NVMEM_TYPE_EEPROM] = "EEPROM",
[NVMEM_TYPE_OTP] = "OTP",
[NVMEM_TYPE_BATTERY_BACKED] = "Battery backed",
[NVMEM_TYPE_FRAM] = "FRAM",
};

#ifdef CONFIG_DEBUG_LOCK_ALLOC
Expand Down Expand Up @@ -359,6 +360,9 @@ static int nvmem_sysfs_setup_compat(struct nvmem_device *nvmem,
if (!config->base_dev)
return -EINVAL;

if (config->type == NVMEM_TYPE_FRAM)
bin_attr_nvmem_eeprom_compat.attr.name = "fram";

nvmem->eeprom = bin_attr_nvmem_eeprom_compat;
nvmem->eeprom.attr.mode = nvmem_bin_attr_get_umode(nvmem);
nvmem->eeprom.size = nvmem->size;
Expand Down
1 change: 1 addition & 0 deletions include/linux/nvmem-provider.h
Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,7 @@ enum nvmem_type {
NVMEM_TYPE_EEPROM,
NVMEM_TYPE_OTP,
NVMEM_TYPE_BATTERY_BACKED,
NVMEM_TYPE_FRAM,
};

#define NVMEM_DEVID_NONE (-1)
Expand Down

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