[PATCH] rtc: update and use the MAX6900 century byte
From: Dale Farnsworth
Date: Wed Jul 18 2007 - 11:26:21 EST
We now read and write the century byte in the max6900 chip.
We probably don't need to do so on Linux-only system, but it's
necessary when the chip is shared by another OS that uses the
century byte.
Signed-off-by: Dale Farnsworth <dale@xxxxxxxxxxxxxx>
---
drivers/rtc/rtc-max6900.c | 96 +++++++++++++++++++++++++++---------
1 file changed, 72 insertions(+), 24 deletions(-)
diff --git a/drivers/rtc/rtc-max6900.c b/drivers/rtc/rtc-max6900.c
index eee4ee5..a1cd448 100644
--- a/drivers/rtc/rtc-max6900.c
+++ b/drivers/rtc/rtc-max6900.c
@@ -31,17 +31,24 @@
#define MAX6900_REG_DW 5 /* day of week 1-7 */
#define MAX6900_REG_YR 6 /* year 00-99 */
#define MAX6900_REG_CT 7 /* control */
-#define MAX6900_REG_LEN 8
+ /* register 8 is undocumented */
+#define MAX6900_REG_CENTURY 9 /* century */
+#define MAX6900_REG_LEN 10
+
+#define MAX6900_BURST_LEN 8 /* can burst r/w first 8 regs */
#define MAX6900_REG_CT_WP (1 << 7) /* Write Protect */
+
/*
* register read/write commands
*/
#define MAX6900_REG_CONTROL_WRITE 0x8e
-#define MAX6900_REG_BURST_READ 0xbf
-#define MAX6900_REG_BURST_WRITE 0xbe
+#define MAX6900_REG_CENTURY_WRITE 0x92
+#define MAX6900_REG_CENTURY_READ 0x93
#define MAX6900_REG_RESERVED_READ 0x96
+#define MAX6900_REG_BURST_WRITE 0xbe
+#define MAX6900_REG_BURST_READ 0xbf
#define MAX6900_IDLE_TIME_AFTER_WRITE 3 /* specification says 2.5 mS */
@@ -58,19 +65,32 @@ static int max6900_probe(struct i2c_adapter *adapter, int addr, int kind);
static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)
{
- u8 reg_addr[1] = { MAX6900_REG_BURST_READ };
- struct i2c_msg msgs[2] = {
+ u8 reg_burst_read[1] = { MAX6900_REG_BURST_READ };
+ u8 reg_century_read[1] = { MAX6900_REG_CENTURY_READ };
+ struct i2c_msg msgs[4] = {
{
.addr = client->addr,
.flags = 0, /* write */
- .len = sizeof(reg_addr),
- .buf = reg_addr
+ .len = sizeof(reg_burst_read),
+ .buf = reg_burst_read
},
{
.addr = client->addr,
.flags = I2C_M_RD,
- .len = MAX6900_REG_LEN,
+ .len = MAX6900_BURST_LEN,
.buf = buf
+ },
+ {
+ .addr = client->addr,
+ .flags = 0, /* write */
+ .len = sizeof(reg_century_read),
+ .buf = reg_century_read
+ },
+ {
+ .addr = client->addr,
+ .flags = I2C_M_RD,
+ .len = sizeof(buf[MAX6900_REG_CENTURY]),
+ .buf = &buf[MAX6900_REG_CENTURY]
}
};
int rc;
@@ -86,33 +106,58 @@ static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)
static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf)
{
- u8 i2c_buf[MAX6900_REG_LEN + 1] = { MAX6900_REG_BURST_WRITE };
- struct i2c_msg msgs[1] = {
+ u8 i2c_century_buf[1 + 1] = { MAX6900_REG_CENTURY_WRITE };
+ struct i2c_msg century_msgs[1] = {
{
.addr = client->addr,
.flags = 0, /* write */
- .len = MAX6900_REG_LEN + 1,
- .buf = i2c_buf
+ .len = sizeof(i2c_century_buf),
+ .buf = i2c_century_buf
+ }
+ };
+ u8 i2c_burst_buf[MAX6900_BURST_LEN + 1] = { MAX6900_REG_BURST_WRITE };
+ struct i2c_msg burst_msgs[1] = {
+ {
+ .addr = client->addr,
+ .flags = 0, /* write */
+ .len = sizeof(i2c_burst_buf),
+ .buf = i2c_burst_buf
}
};
int rc;
- memcpy(&i2c_buf[1], buf, MAX6900_REG_LEN);
+ /*
+ * We have to make separate calls to i2c_transfer because of
+ * the need to delay after each write to the chip. Also,
+ * we write the century byte first, since we set the write-protect
+ * bit as part of the burst write.
+ */
+ i2c_century_buf[1] = buf[MAX6900_REG_CENTURY];
+ rc = i2c_transfer(client->adapter, century_msgs,
+ ARRAY_SIZE(century_msgs));
+ if (rc != ARRAY_SIZE(century_msgs))
+ goto write_failed;
+ msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
- rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
- if (rc != ARRAY_SIZE(msgs)) {
- dev_err(&client->dev, "%s: register write failed\n",
- __FUNCTION__);
- return -EIO;
- }
+ memcpy(&i2c_burst_buf[1], buf, MAX6900_BURST_LEN);
+
+ rc = i2c_transfer(client->adapter, burst_msgs, ARRAY_SIZE(burst_msgs));
+ if (rc != ARRAY_SIZE(burst_msgs))
+ goto write_failed;
msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
+
return 0;
+
+write_failed:
+ dev_err(&client->dev, "%s: register write failed\n",
+ __FUNCTION__);
+ return -EIO;
}
static int max6900_i2c_validate_client(struct i2c_client *client)
{
u8 regs[MAX6900_REG_LEN];
- u8 zero_mask[MAX6900_REG_LEN] = {
+ u8 zero_mask[] = {
0x80, /* seconds */
0x80, /* minutes */
0x40, /* hours */
@@ -134,7 +179,7 @@ static int max6900_i2c_validate_client(struct i2c_client *client)
if (rc < 0)
return rc;
- for (i = 0; i < MAX6900_REG_LEN; ++i) {
+ for (i = 0; i < ARRAY_SIZE(zero_mask); ++i) {
if (regs[i] & zero_mask[i])
return -ENODEV;
}
@@ -156,7 +201,8 @@ static int max6900_i2c_read_time(struct i2c_client *client, struct rtc_time *tm)
tm->tm_hour = BCD2BIN(regs[MAX6900_REG_HR] & 0x3f);
tm->tm_mday = BCD2BIN(regs[MAX6900_REG_DT]);
tm->tm_mon = BCD2BIN(regs[MAX6900_REG_MO]) - 1;
- tm->tm_year = BCD2BIN(regs[MAX6900_REG_YR]) + 100;
+ tm->tm_year = BCD2BIN(regs[MAX6900_REG_YR]) +
+ BCD2BIN(regs[MAX6900_REG_CENTURY]) * 100 - 1900;
tm->tm_wday = BCD2BIN(regs[MAX6900_REG_DW]);
return 0;
@@ -189,9 +235,11 @@ static int max6900_i2c_set_time(struct i2c_client *client,
regs[MAX6900_REG_HR] = BIN2BCD(tm->tm_hour);
regs[MAX6900_REG_DT] = BIN2BCD(tm->tm_mday);
regs[MAX6900_REG_MO] = BIN2BCD(tm->tm_mon + 1);
- regs[MAX6900_REG_YR] = BIN2BCD(tm->tm_year - 100);
regs[MAX6900_REG_DW] = BIN2BCD(tm->tm_wday);
- regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP; /* set write protect */
+ regs[MAX6900_REG_YR] = BIN2BCD(tm->tm_year % 100);
+ regs[MAX6900_REG_CENTURY] = BIN2BCD((tm->tm_year + 1900) / 100);
+ /* set write protect */
+ regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP;
rc = max6900_i2c_write_regs(client, regs);
if (rc < 0)
-
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