[PATCH 1/2] misc: at24: parse OF-data, too
Grant Likely
grant.likely at secretlab.ca
Tue Nov 16 08:41:06 EST 2010
On Mon, Nov 15, 2010 at 10:25 AM, Wolfram Sang <w.sang at pengutronix.de> wrote:
> Information about the pagesize and read-only-status may also come from
> the devicetree. Parse this data, too, and act accordingly. While we are
> here, change the initialization printout a bit. write_max is useful to
> know to detect performance bottlenecks, the rest is superfluous.
>
> Signed-off-by: Wolfram Sang <w.sang at pengutronix.de>
> ---
>
> Grant: As mentioned at ELCE10, I could pretty much respin this old approach I
> tried roughly a year ago (just with archdata then). If the approach and docs
> are good, I am fine with the patches entering via one of your trees.
>
> Documentation/powerpc/dts-bindings/eeprom.txt | 28 ++++++++++++++++++++++
> drivers/misc/eeprom/at24.c | 33 ++++++++++++++++++++-----
> 2 files changed, 53 insertions(+), 6 deletions(-)
> create mode 100644 Documentation/powerpc/dts-bindings/eeprom.txt
>
> diff --git a/Documentation/powerpc/dts-bindings/eeprom.txt b/Documentation/powerpc/dts-bindings/eeprom.txt
> new file mode 100644
> index 0000000..4342c10
> --- /dev/null
> +++ b/Documentation/powerpc/dts-bindings/eeprom.txt
> @@ -0,0 +1,28 @@
> +EEPROMs (I2C)
> +
> +Required properties:
> +
> + - compatible : should be "<manufacturer>,<type>"
> + If there is no specific driver for <manufacturer>, a generic
> + driver based on <type> is selected. Possible types are:
> + 24c00, 24c01, 24c02, 24c04, 24c08, 24c16, 24c32, 24c64,
> + 24c128, 24c256, 24c512, 24c1024, spd
> +
> + - reg : the I2C address of the EEPROM
> +
> +Optional properties:
> +
> + - pagesize : the length of the pagesize for writing. Please consult the
> + manual of your device, that value varies a lot. A wrong value
> + may result in data loss! If not specified, a safety value of
> + '1' is used which will be very slow.
As Anton mentions, the compatible value should be specific enough that
a pagesize property isn't needed (assuming there aren't at24 devices
with differing page sizes), but that leaves the question of where to
put the page size data in the driver. I think the obvious answer is
to put it in the at24_ids table. This would also be a good thing for
the non-OF use-cases too. Unfortunately the driver_data field is
already in use and requires refactoring to turn driver_data into a
pointer to a structure, and so requires more work (sorry).
A refactored at24_ids table might look something like (there may be a
cleaner way to go about it though, I used the macro to solve the
problem of constructing an at24_platform_data structure for each entry
and storing a pointer to it in the unsigned long driver_data field):
#define AT24_DEVDATA(_len, _page_size, _flags) \
((unsigned long)((struct at24_platform_data[]) \
{{.byte_len = len, .page_size = _page_size, .flags =
_flags}}))
static const struct i2c_device_id at24_ids[] = {
/* needs 8 addresses as A0-A2 are ignored */
{ "24c00", AT24_DEVDATA(128 / 8, 16, AT24_FLAG_TAKE8ADDR) },
/* old variants can't be handled with this generic entry! */
{ "24c01", AT24_DEVDATA(1024 / 8, 16, 0) },
{ "24c02", AT24_DEVDATA(2048 / 8, 16, 0) },
...
};
This will also make the probe code simpler.
However, if I am wrong and similarly named at24 devices have different
page sizes, then encoding it in a property is the right thing to do.
Also, the read-only property is fine.
g.
> +
> + - read-only: this parameterless property disables writes to the eeprom
> +
> +Example:
> +
> +eeprom at 52 {
> + compatible = "atmel,24c32";
> + reg = <0x52>;
> + pagesize = <32>;
> +};
> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> index 559b0b3..aaf16cb 100644
> --- a/drivers/misc/eeprom/at24.c
> +++ b/drivers/misc/eeprom/at24.c
> @@ -20,6 +20,7 @@
> #include <linux/log2.h>
> #include <linux/bitops.h>
> #include <linux/jiffies.h>
> +#include <linux/of.h>
> #include <linux/i2c.h>
> #include <linux/i2c/at24.h>
>
> @@ -457,6 +458,27 @@ static ssize_t at24_macc_write(struct memory_accessor *macc, const char *buf,
>
> /*-------------------------------------------------------------------------*/
>
> +#ifdef CONFIG_OF
> +static void at24_get_ofdata(struct i2c_client *client,
> + struct at24_platform_data *chip)
> +{
> + const u32 *val;
> + struct device_node *node = client->dev.of_node;
> +
> + if (node) {
> + if (of_get_property(node, "read-only", NULL))
> + chip->flags |= AT24_FLAG_READONLY;
> + val = of_get_property(node, "pagesize", NULL);
> + if (val)
> + chip->page_size = *val;
> + }
> +}
> +#else
> +static void at24_get_ofdata(struct i2c_client *client,
> + struct at24_platform_data *chip)
> +{ }
> +#endif /* CONFIG_OF */
> +
> static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
> {
> struct at24_platform_data chip;
> @@ -485,6 +507,9 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
> */
> chip.page_size = 1;
>
> + /* update chipdata if OF is present */
> + at24_get_ofdata(client, &chip);
> +
> chip.setup = NULL;
> chip.context = NULL;
> }
> @@ -597,19 +622,15 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
>
> i2c_set_clientdata(client, at24);
>
> - dev_info(&client->dev, "%zu byte %s EEPROM %s\n",
> + dev_info(&client->dev, "%zu byte %s EEPROM, %s, %u bytes/write\n",
> at24->bin.size, client->name,
> - writable ? "(writable)" : "(read-only)");
> + writable ? "writable" : "read-only", at24->write_max);
> if (use_smbus == I2C_SMBUS_WORD_DATA ||
> use_smbus == I2C_SMBUS_BYTE_DATA) {
> dev_notice(&client->dev, "Falling back to %s reads, "
> "performance will suffer\n", use_smbus ==
> I2C_SMBUS_WORD_DATA ? "word" : "byte");
> }
> - dev_dbg(&client->dev,
> - "page_size %d, num_addresses %d, write_max %d, use_smbus %d\n",
> - chip.page_size, num_addresses,
> - at24->write_max, use_smbus);
>
> /* export data to kernel code */
> if (chip.setup)
> --
> 1.7.2.3
>
>
--
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
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