[PATCH 7/7] drivers/eeprom: at24: add I2C eeprom driver for 24c01/02
Uwe Kleine-König
u.kleine-koenig at pengutronix.de
Mon Jul 30 04:25:05 EDT 2012
Hello Marc,
On Sun, Jul 29, 2012 at 05:41:54PM +1000, Marc Reilly wrote:
> This series adds a driver for at24 eeproms. Much of the guts of the code
> was taken from the at24 driver in the linux kernel.
>
> The device is polled for write completion. All the datasheets I looked
> at had a max of 10ms for eeprom write time.
> The driver automatically wraps the writes to page boundaries, so we don't
> write more than is remaining in the page.
>
> The driver can not yet handle addressing offsets > 256 in devices with
> larger capacities.
>
> The platform data fields are all optional, if they are zero they are
> assigned default values. As the device capabilities can not be probed,
> the default assumption is that the device is 256 bytes.
>
> Signed-off-by: Marc Reilly <marc at cpdesign.com.au>
> ---
> drivers/eeprom/Kconfig | 7 ++
> drivers/eeprom/Makefile | 1 +
> drivers/eeprom/at24.c | 233 +++++++++++++++++++++++++++++++++++++++++++++++
> include/i2c/at24.h | 13 +++
> 4 files changed, 254 insertions(+), 0 deletions(-)
> create mode 100644 drivers/eeprom/at24.c
> create mode 100644 include/i2c/at24.h
>
> diff --git a/drivers/eeprom/Kconfig b/drivers/eeprom/Kconfig
> index a0b5489..a2bcaaa 100644
> --- a/drivers/eeprom/Kconfig
> +++ b/drivers/eeprom/Kconfig
> @@ -8,4 +8,11 @@ config EEPROM_AT25
> after you configure the board init code to know about each eeprom
> on your target board.
>
> +config EEPROM_AT24
> + bool "at24 based eeprom"
> + depends on I2C
> + help
> + Provides read/write for the at24 family of I2C EEPROMS.
> + Currently only the 2K bit versions are supported.
> +
> endmenu
> diff --git a/drivers/eeprom/Makefile b/drivers/eeprom/Makefile
> index e323bd0..e287eb0 100644
> --- a/drivers/eeprom/Makefile
> +++ b/drivers/eeprom/Makefile
> @@ -1 +1,2 @@
> obj-$(CONFIG_EEPROM_AT25) += at25.o
> +obj-$(CONFIG_EEPROM_AT24) += at24.o
nitpick: sort at24 before at25?
> diff --git a/drivers/eeprom/at24.c b/drivers/eeprom/at24.c
> new file mode 100644
> index 0000000..fa16d88
> --- /dev/null
> +++ b/drivers/eeprom/at24.c
> @@ -0,0 +1,233 @@
> +/*
> + * Copyright (C) 2007 Sascha Hauer, Pengutronix
> + * 2009 Marc Kleine-Budde <mkl at pengutronix.de>
> + * 2010 Marc Reilly, Creative Product Design
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License as
> + * published by the Free Software Foundation; either version 2 of
> + * the License, or (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
> + * MA 02111-1307 USA
> + *
> + */
> +
> +#include <common.h>
> +#include <init.h>
> +#include <clock.h>
> +#include <driver.h>
> +#include <xfuncs.h>
> +#include <errno.h>
> +
> +#include <i2c/i2c.h>
> +#include <i2c/at24.h>
> +
> +#define DRIVERNAME "at24"
> +#define DEVICENAME "eeprom"
why not DEVICENAME == DRIVERNAME?
> +
> +struct at24 {
> + struct cdev cdev;
> + struct i2c_client *client;
> + /* size in bytes */
> + unsigned int size;
> + unsigned int page_size;
> +};
> +
> +#define to_at24(a) container_of(a, struct at24, cdev)
> +
> +static ssize_t at24_read(struct cdev *cdev, void *_buf, size_t count,
> + ulong offset, ulong flags)
> +{
> + struct at24 *priv = to_at24(cdev);
> + u8 *buf = _buf;
> + size_t i = count;
> + ssize_t numwritten = 0;
s/written/read/
> + int retries = 5;
> + int ret;
> +
> + while (i && retries) {
> + ret = i2c_read_reg(priv->client, offset, buf, i);
> + if (ret < 0)
> + return (ssize_t)ret;
This cast is also done implicitly.
> + else if (ret == 0)
> + --retries;
> +
> + numwritten += ret;
> + i -= ret;
> + offset += ret;
> + buf += ret;
> + }
IMHO this loop should be in a more generic place once instead of
repeating it for each driver. Also I wonder if you saw the eeprom
yielding some but not all requested bytes on a read request.
> +
> + return numwritten;
> +}
> +
> +static int at24_poll_device(struct i2c_client *client)
> +{
> + uint64_t start;
> + u8 dummy;
> + int ret;
> +
> + /*
> + * eeprom can take 5-10ms to write, during which time it
> + * will not respond. Poll it by attempting reads.
> + */
> + start = get_time_ns();
> + while (1) {
> + ret = i2c_master_recv(client, &dummy, 1);
I implemented a write of length 0 here. IMHO this is better.
> + if (ret > 0)
> + return ret;
> +
> + if (is_timeout(start, 20 * MSECOND))
> + return -EIO;
> + }
> +
> + return 0;
> +}
> +
> +static ssize_t at24_write(struct cdev *cdev, const void *_buf, size_t count,
> + ulong offset, ulong flags)
> +{
> + struct at24 *priv = to_at24(cdev);
> + const u8 *buf = _buf;
> + const int pagesize = priv->page_size;
> + ssize_t numwritten = 0;
> +
> + while (count) {
> + int ret, numtowrite;
> + int page_remain = pagesize - (offset % pagesize);
> +
> + numtowrite = count;
> + if (numtowrite > pagesize)
> + numtowrite = pagesize;
I think you can skip this if in the presence of the the if below.
> + /* don't write past page */
> + if (numtowrite > page_remain)
> + numtowrite = page_remain;
> +
> + ret = i2c_write_reg(priv->client, offset, buf, numtowrite);
> + if (ret < 0)
> + return (ssize_t)ret;
> +
> + numwritten += ret;
> + buf += ret;
> + count -= ret;
> + offset += ret;
> +
> + ret = at24_poll_device(priv->client);
> + if (ret < 0)
> + return (ssize_t)ret;
Don't you need to poll before writing instead of after a write?
> + }
> +
> + return numwritten;
> +}
> +
> +/* max page size of any of the at24 family devices is 16 bytes */
> +#define AT24_MAX_PAGE_SIZE 16
That is wrong. My eeprom has a page size of 64 bytes.
> +
> +static ssize_t at24_erase(struct cdev *cdev, size_t count, unsigned long offset)
> +{
> + struct at24 *priv = to_at24(cdev);
> + char erase[AT24_MAX_PAGE_SIZE];
> + const int pagesize = priv->page_size;
> + ssize_t numwritten = 0;
> +
> + memset(erase, 0xff, sizeof(erase));
> +
> + while (count) {
> + int ret, numtowrite;
> + int page_remain = pagesize - (offset % pagesize);
> +
> + numtowrite = count;
> + if (numtowrite > pagesize)
> + numtowrite = pagesize;
> + /* don't write past page */
> + if (numtowrite > page_remain)
> + numtowrite = page_remain;
> +
> + ret = i2c_write_reg(priv->client, offset, erase, numtowrite);
> + if (ret < 0)
> + return (ssize_t)ret;
> +
> + numwritten += ret;
> + count -= ret;
> + offset += ret;
> +
> + ret = at24_poll_device(priv->client);
> + if (ret < 0)
> + return (ssize_t)ret;
> + }
> +
> + return 0;
> +}
I think conceptually you don't need the erase callback for this eeprom.
> +
> +static struct file_operations at24_fops = {
> + .lseek = dev_lseek_default,
> + .read = at24_read,
> + .write = at24_write,
> + .erase = at24_erase,
> +};
> +
> +static int at24_probe(struct device_d *dev)
> +{
> + const struct at24_platform_data *pdata;
> + struct at24 *at24;
> + at24 = xzalloc(sizeof(*at24));
> +
> + dev->priv = at24;
> + at24->client = to_i2c_client(dev);
> + at24->cdev.dev = dev;
> + at24->cdev.ops = &at24_fops;
> +
> + pdata = dev->platform_data;
> + if (pdata) {
> + at24->cdev.size = pdata->size_bytes;
> + at24->cdev.name = strdup(pdata->name);
> + at24->page_size = pdata->page_size;
> + }
> +
> + if (at24->cdev.size == 0)
> + at24->cdev.size = 256;
> + if (!at24->cdev.name || at24->cdev.name[0] == '\0') {
> + char buf[20];
> + sprintf(buf, DEVICENAME"%d", dev->id);
> + at24->cdev.name = strdup(buf);
> + }
> + if (at24->page_size == 0) {
> + switch (at24->cdev.size) {
> + case 512:
> + case 1024:
> + case 2048:
> + at24->page_size = 16;
> + break;
> + case 128:
> + case 256:
> + default:
> + at24->page_size = 8;
> + break;
> + }
> + }
> +
> + devfs_create(&at24->cdev);
> +
> + return 0;
> +}
> +
> +static struct driver_d at24_driver = {
> + .name = DRIVERNAME,
> + .probe = at24_probe,
> +};
> +
> +static int at24_init(void)
> +{
> + register_driver(&at24_driver);
> + return 0;
return register_driver(&at24_driver) ?
> +}
> +
> +device_initcall(at24_init);
> diff --git a/include/i2c/at24.h b/include/i2c/at24.h
> new file mode 100644
> index 0000000..00e4624
> --- /dev/null
> +++ b/include/i2c/at24.h
> @@ -0,0 +1,13 @@
> +#ifndef _EEPROM_AT24_H
> +#define _EEPROM_AT24_H
> +
> +struct at24_platform_data {
> + /* preferred device name */
> + const char name[10];
> + /* page write size in bytes */
> + u8 page_size;
> + /* device size in bytes */
> + u16 size_bytes;
> +};
> +
> +#endif /* _EEPROM_AT24_H */
> --
> 1.7.7
>
>
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--
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Industrial Linux Solutions | http://www.pengutronix.de/ |
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