[PATCH v8 2/5] nvmem: eeprom: at25: add support for FRAM

From: Jiri Prchal
Date: Mon Jun 07 2021 - 12:12:16 EST

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Added support for Cypress FRAMs.
These frams have ID and some of them have serial number too.
Size of them is recognized by ID. They don't have pages, it could
be read or written at once, but it's limited in this driver to
io limit 4096.

Signed-off-by: Jiri Prchal <jiri.prchal@xxxxxxxxxxx>
---
v2: fixed warning at %zd at int
Reported-by: kernel test robot <lkp@xxxxxxxxx>
v3: resend and added more recipients
v4: resend
v5: used in-kernel function int_pow
v6: no change here
v7: moved definition of sernum size to patch 4
v8: changed buffer type to u8
---
drivers/misc/eeprom/Kconfig | 5 +-
drivers/misc/eeprom/at25.c | 140 ++++++++++++++++++++++++++++--------
2 files changed, 113 insertions(+), 32 deletions(-)

diff --git a/drivers/misc/eeprom/Kconfig b/drivers/misc/eeprom/Kconfig
index 0f791bfdc1f5..f0a7531f354c 100644
--- a/drivers/misc/eeprom/Kconfig
+++ b/drivers/misc/eeprom/Kconfig
@@ -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.

diff --git a/drivers/misc/eeprom/at25.c b/drivers/misc/eeprom/at25.c
index b76e4901b4a4..e25cec7c474b 100644
--- a/drivers/misc/eeprom/at25.c
+++ b/drivers/misc/eeprom/at25.c
@@ -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
*/
@@ -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
@@ -34,6 +38,7 @@ struct at25_data {
unsigned addrlen;
struct nvmem_config nvmem_config;
struct nvmem_device *nvmem;
+ int has_sernum;
};

#define AT25_WREN 0x06 /* latch the write enable */
@@ -42,6 +47,9 @@ 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) */
@@ -51,6 +59,8 @@ 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;
@@ -58,6 +68,9 @@ struct at25_data {
*/
#define EE_TIMEOUT 25

+#define IS_EEPROM 0
+#define IS_FRAM 1
+
/*-------------------------------------------------------------------------*/

#define io_limit PAGE_SIZE /* bytes */
@@ -129,6 +142,36 @@ 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 int at25_ee_write(void *priv, unsigned int off, void *val, size_t count)
{
struct at25_data *at25 = priv;
@@ -303,34 +346,37 @@ 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];
+ 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)(uintptr_t)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!
@@ -349,9 +395,49 @@ 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])
+ at25->has_sernum = 1;
+ else
+ at25->has_sernum = 0;
+
+ 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;
@@ -370,23 +456,17 @@ 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",
--
2.25.1

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