[patch 07/21] rtc-pcf8563: detect polarity of century bit automatically

Greg KH
2007-02-21T01:47:12Z

[-- Attachment #1: rtc-pcf8563-detect-polarity-of-century-bit-automatically.patch --]
[-- Type: text/plain, Size: 4901 bytes --]

-stable review patch. If anyone has any objections, please let us know.

------------------

From: Atsushi Nemoto <anemo@mba.ocn.ne.jp>

The usage of the century bit was inverted on 2.6.19 following to PCF8563's
description, but it was not match to usage suggested by RTC8564's
datasheet. Anyway what MO_C=1 means can vary on each platform. This patch
is to detect its polarity in get_datetime routine. The default value of
c_polarity is 0 (MO_C=1 means 19xx) so that this patch does not change
current behavior even if get_datetime was not called before set_datetime.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Cc: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@teamlog.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/rtc/rtc-pcf8563.c | 40 ++++++++++++++++++++++++++++++++++------
1 file changed, 34 insertions(+), 6 deletions(-)

--- linux-2.6.19.4.orig/drivers/rtc/rtc-pcf8563.c
+++ linux-2.6.19.4/drivers/rtc/rtc-pcf8563.c
@@ -53,6 +53,25 @@ I2C_CLIENT_INSMOD;
#define PCF8563_SC_LV 0x80 /* low voltage */
#define PCF8563_MO_C 0x80 /* century */

+struct pcf8563 {
+ struct i2c_client client;
+ /*
+ * The meaning of MO_C bit varies by the chip type.
+ * From PCF8563 datasheet: this bit is toggled when the years
+ * register overflows from 99 to 00
+ * 0 indicates the century is 20xx
+ * 1 indicates the century is 19xx
+ * From RTC8564 datasheet: this bit indicates change of
+ * century. When the year digit data overflows from 99 to 00,
+ * this bit is set. By presetting it to 0 while still in the
+ * 20th century, it will be set in year 2000, ...
+ * There seems no reliable way to know how the system use this
+ * bit. So let's do it heuristically, assuming we are live in
+ * 1970...2069.
+ */
+ int c_polarity; /* 0: MO_C=1 means 19xx, otherwise MO_C=1 means 20xx */
+};
+
static int pcf8563_probe(struct i2c_adapter *adapter, int address, int kind);
static int pcf8563_detach(struct i2c_client *client);

@@ -62,6 +81,7 @@ static int pcf8563_detach(struct i2c_cli
*/
static int pcf8563_get_datetime(struct i2c_client *client, struct rtc_time *tm)
{
+ struct pcf8563 *pcf8563 = container_of(client, struct pcf8563, client);
unsigned char buf[13] = { PCF8563_REG_ST1 };

struct i2c_msg msgs[] = {
@@ -94,8 +114,12 @@ static int pcf8563_get_datetime(struct i
tm->tm_mday = BCD2BIN(buf[PCF8563_REG_DM] & 0x3F);
tm->tm_wday = buf[PCF8563_REG_DW] & 0x07;
tm->tm_mon = BCD2BIN(buf[PCF8563_REG_MO] & 0x1F) - 1; /* rtc mn 1-12 */
- tm->tm_year = BCD2BIN(buf[PCF8563_REG_YR])
- + (buf[PCF8563_REG_MO] & PCF8563_MO_C ? 0 : 100);
+ tm->tm_year = BCD2BIN(buf[PCF8563_REG_YR]);
+ if (tm->tm_year < 70)
+ tm->tm_year += 100; /* assume we are in 1970...2069 */
+ /* detect the polarity heuristically. see note above. */
+ pcf8563->c_polarity = (buf[PCF8563_REG_MO] & PCF8563_MO_C) ?
+ (tm->tm_year >= 100) : (tm->tm_year < 100);

dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d, "
"mday=%d, mon=%d, year=%d, wday=%d\n",
@@ -114,6 +138,7 @@ static int pcf8563_get_datetime(struct i

static int pcf8563_set_datetime(struct i2c_client *client, struct rtc_time *tm)
{
+ struct pcf8563 *pcf8563 = container_of(client, struct pcf8563, client);
int i, err;
unsigned char buf[9];

@@ -135,7 +160,7 @@ static int pcf8563_set_datetime(struct i

/* year and century */
buf[PCF8563_REG_YR] = BIN2BCD(tm->tm_year % 100);
- if (tm->tm_year < 100)
+ if (pcf8563->c_polarity ? (tm->tm_year >= 100) : (tm->tm_year < 100))
buf[PCF8563_REG_MO] |= PCF8563_MO_C;

buf[PCF8563_REG_DW] = tm->tm_wday & 0x07;
@@ -248,6 +273,7 @@ static struct i2c_driver pcf8563_driver

static int pcf8563_probe(struct i2c_adapter *adapter, int address, int kind)
{
+ struct pcf8563 *pcf8563;
struct i2c_client *client;
struct rtc_device *rtc;

@@ -260,11 +286,12 @@ static int pcf8563_probe(struct i2c_adap
goto exit;
}

- if (!(client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL))) {
+ if (!(pcf8563 = kzalloc(sizeof(struct pcf8563), GFP_KERNEL))) {
err = -ENOMEM;
goto exit;
}

+ client = &pcf8563->client;
client->addr = address;
client->driver = &pcf8563_driver;
client->adapter = adapter;
@@ -301,7 +328,7 @@ exit_detach:
i2c_detach_client(client);

exit_kfree:
- kfree(client);
+ kfree(pcf8563);

exit:
return err;
@@ -309,6 +336,7 @@ exit:

static int pcf8563_detach(struct i2c_client *client)
{
+ struct pcf8563 *pcf8563 = container_of(client, struct pcf8563, client);
int err;
struct rtc_device *rtc = i2c_get_clientdata(client);

@@ -318,7 +346,7 @@ static int pcf8563_detach(struct i2c_cli
if ((err = i2c_detach_client(client)))
return err;

- kfree(client);
+ kfree(pcf8563);

return 0;
}

--