rtc: ds1305/ds1306 driver

Support the Dallas/Maxim DS1305 and DS1306 RTC chips.  These use SPI, and
support alarms, NVRAM, and a trickle charger for use when their backup
power supply is a supercap or rechargeable cell.

This basic driver doesn't yet support suspend/resume or wakealarms.

Signed-off-by: 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: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 35 insertions, 0 deletions

diff --git a/include/linux/spi/ds1305.h b/include/linux/spi/ds1305.h
new file mode 100644
index 000000000000..287ec830eab7
--- /dev/null
+++ b/include/linux/spi/ds1305.h
@@ -0,0 +1,35 @@
+#ifndef __LINUX_SPI_DS1305_H
+#define __LINUX_SPI_DS1305_H
+
+/*
+ * One-time configuration for ds1305 and ds1306 RTC chips.
+ *
+ * Put a pointer to this in spi_board_info.platform_data if you want to
+ * be sure that Linux (re)initializes this as needed ... after losing
+ * backup power, and potentially on the first boot.
+ */
+struct ds1305_platform_data {
+
+        /* Trickle charge configuration:  it's OK to leave out the MAGIC
+         * bitmask; mask in either DS1 or DS2, and then one of 2K/4k/8K.
+         */
+#define DS1305_TRICKLE_MAGIC    0xa0
+#define DS1305_TRICKLE_DS2      0x08    /* two diodes */
+#define DS1305_TRICKLE_DS1      0x04    /* one diode */
+#define DS1305_TRICKLE_2K       0x01    /* 2 KOhm resistance */
+#define DS1305_TRICKLE_4K       0x02    /* 4 KOhm resistance */
+#define DS1305_TRICKLE_8K       0x03    /* 8 KOhm resistance */
+        u8      trickle;
+
+        /* set only on ds1306 parts */
+        bool    is_ds1306;
+
+        /* ds1306 only:  enable 1 Hz output */
+        bool    en_1hz;
+
+        /* REVISIT:  the driver currently expects nINT0 to be wired
+         * as the alarm IRQ.  ALM1 may also need to be set up ...
+         */
+};
+
+#endif /* __LINUX_SPI_DS1305_H */