rtc: update and use the MAX6900 century byte
Dale Farnsworth [Sat, 21 Jul 2007 11:37:57 +0000 (04:37 -0700)]
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@farnsworth.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/rtc-max6900.c

index eee4ee5..a1cd448 100644 (file)
 #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)