[PATCH v2 4/8] rtc: ds1307: apply DS13XX_TRICKLE_CHARGER_MAGIC only conditionally

Bastian Krause
2020-09-17T18:34:51Z

DS13XX_TRICKLE_CHARGER_MAGIC sets the trickle-charge select (TCS) bits
(7..4). The datasheet of Maxim Integrated's DS1339 [1] for instance
reads:

"To prevent accidental enabling, only a pattern on 1010 enables the
trickle charger. All other patterns disable the trickle charger."

Since not all RTCs connected to a backup battery or supercap use these
bits DS13XX_TRICKLE_CHARGER_MAGIC should not get applied for all charger
setups unconditionally.
Epson's RX8130 is such an example: Instead of TCS bits "SMPTSEL1",
"SMPTSEL0", "CHGEN" and "INIEN" are expected as bit 7..4.

DS1339 and DS1340 are currently the only RTCs in the ds1307 driver that
apply DS13XX_TRICKLE_CHARGER_MAGIC to their setup register value. So
apply DS13XX_TRICKLE_CHARGER_MAGIC in do_trickle_setup_ds1339() which
is used by both RTCs.

[1] https://datasheets.maximintegrated.com/en/ds/DS1339-DS1339U.pdf
[2] https://support.epson.biz/td/api/doc_check.php?dl=app_RX8130CE

Signed-off-by: Bastian Krause <bst@pengutronix.de>
---
No changes since v1.

v1 notes:
No previous version.
---
drivers/rtc/rtc-ds1307.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index 54c85cdd019d..ff5242d10b21 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -507,6 +507,8 @@ static u8 do_trickle_setup_ds1339(struct ds1307 *ds1307, u32 ohms, bool diode)
u8 setup = (diode) ? DS1307_TRICKLE_CHARGER_DIODE :
DS1307_TRICKLE_CHARGER_NO_DIODE;

+ setup |= DS13XX_TRICKLE_CHARGER_MAGIC;
+
switch (ohms) {
case 250:
setup |= DS1307_TRICKLE_CHARGER_250_OHM;
@@ -1758,7 +1760,6 @@ static int ds1307_probe(struct i2c_client *client,
trickle_charger_setup = pdata->trickle_charger_setup;

if (trickle_charger_setup && chip->trickle_charger_reg) {
- trickle_charger_setup |= DS13XX_TRICKLE_CHARGER_MAGIC;
dev_dbg(ds1307->dev,
"writing trickle charger info 0x%x to 0x%x\n",
trickle_charger_setup, chip->trickle_charger_reg);
--
2.28.0