m41txx chips can hold a calibration value to get correct clock bias.
Add offset handling (ranging between -63ppm and 126ppm) via sysfs.
Signed-off-by: Giulio Benetti <giulio.benetti@xxxxxxxxxxxxxxxx>
---
V6 => V7:
* changed PPM to PPB as rtc sysfs offset handles PPB
drivers/rtc/rtc-ds1307.c | 77 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 77 insertions(+)
diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index 0162a600ff1b..b2ef9defc349 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -114,6 +114,20 @@ enum ds_type {
# define RX8025_BIT_VDET 0x40
# define RX8025_BIT_XST 0x20
+#define M41TXX_REG_CONTROL 0x07
+# define M41TXX_BIT_OUT 0x80
+# define M41TXX_BIT_FT 0x40
+# define M41TXX_BIT_CALIB_SIGN 0x20
+# define M41TXX_M_CALIBRATION 0x1f