diff options
author | Ahmad Fatoum <a.fatoum@pengutronix.de> | 2022-04-26 10:10:54 +0300 |
---|---|---|
committer | Alexandre Belloni <alexandre.belloni@bootlin.com> | 2022-06-24 22:24:02 +0300 |
commit | c27fee16fab17bc5d62b643285e7cd76a6c49d95 (patch) | |
tree | 191894837cf0414ce53bb267fb759f0f012f46f1 /drivers/rtc/rtc-rv8803.c | |
parent | f8176e0bb83ff8dcc6d9fa8595a0966e631d2ba7 (diff) | |
download | linux-c27fee16fab17bc5d62b643285e7cd76a6c49d95.tar.xz |
rtc: rv8803: re-initialize all Epson RX8803 registers on voltage loss
The reference manuals of both the RX8803 and RV8803 dictate that
"[On V2F/VLF = ] all registers must be initialized".
The RV-8803 application manual (rev. 1.6) further specifies that crossing
V_LOW2 threshold enables flag V2F and triggers a Power-On reset.
According to table 3.11 in the document, all control registers are
defined to sensible values.
However, The Epson RX-8803 doesn't offer the same guarantees.
It explicitly states:
During the initial power-up, the TEST bit is reset to "0" and the VLF
bit is set to "1".
∗ At this point, all other register values are _undefined_, so be sure to
perform a reset before using the module.
Commit d3700b6b6479 ("rtc: rv8803: Stop the clock while setting the time")
also had this rationale:
Indeed, all the registers must be initialized if the voltage has been
lower than VLOW2 (triggering V2F), but not low enough to trigger a POR.
We should follow the advice and initialize all applicable registers.
We can group the registers into 3 groups:
A) Already correctly handled registers:
* 0B-0Ch | Timer Counter | unused and disabled by clearing TE in 0Dh
* 0Dh | Extension Reg | already initialized in rv8803_regs_configure
* 0Eh | Flag Reg | handled in IRQ handler, except for VLF, VDET
* 0Eh | VLF, VDET | cleared in ->set_time
* 10h | 100th Seconds | Already reset via RESET bit
* 20-21h | Capture Buffer | holds timestamp unused by driver
* 2Fh | Event Control | resets automatically
B) Registers that are hardware initialized on POR, but not on VLF:
* 0Fh | Control Reg
* 2Ch | OSC Offset
C) RAM that is undefined on voltage loss:
* 00-06h | Date/Time
* 07h | RAM
* 08-0Ah | Alarm
This means we should initialize after VLF the registers in group B
(RV8803_CTRL and RV8803_OSC_OFFSET).
Group C is all-zero after voltage loss on the RV-8803, but undefined on
the RX-8803. This is ok for Date/Time because ->get_time returns an
error code for as long as the voltage loss flag is active. It's cleared
on ->set_time however. Zeroing both RAM and alarm ensures a fixed value
is read afterwards.
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20220426071056.1187235-4-s.hauer@pengutronix.de
Diffstat (limited to 'drivers/rtc/rtc-rv8803.c')
-rw-r--r-- | drivers/rtc/rtc-rv8803.c | 40 |
1 files changed, 38 insertions, 2 deletions
diff --git a/drivers/rtc/rtc-rv8803.c b/drivers/rtc/rtc-rv8803.c index 21a6f1eddb09..fe1247e771b9 100644 --- a/drivers/rtc/rtc-rv8803.c +++ b/drivers/rtc/rtc-rv8803.c @@ -9,6 +9,7 @@ #include <linux/bcd.h> #include <linux/bitops.h> +#include <linux/bitfield.h> #include <linux/log2.h> #include <linux/i2c.h> #include <linux/interrupt.h> @@ -33,6 +34,7 @@ #define RV8803_EXT 0x0D #define RV8803_FLAG 0x0E #define RV8803_CTRL 0x0F +#define RV8803_OSC_OFFSET 0x2C #define RV8803_EXT_WADA BIT(6) @@ -49,12 +51,15 @@ #define RV8803_CTRL_TIE BIT(4) #define RV8803_CTRL_UIE BIT(5) +#define RX8803_CTRL_CSEL GENMASK(7, 6) + #define RX8900_BACKUP_CTRL 0x18 #define RX8900_FLAG_SWOFF BIT(2) #define RX8900_FLAG_VDETOFF BIT(3) enum rv8803_type { rv_8803, + rx_8803, rx_8804, rx_8900 }; @@ -137,10 +142,41 @@ static int rv8803_write_regs(const struct i2c_client *client, return ret; } +static int rv8803_regs_init(struct rv8803_data *rv8803) +{ + int ret; + + ret = rv8803_write_reg(rv8803->client, RV8803_OSC_OFFSET, 0x00); + if (ret) + return ret; + + ret = rv8803_write_reg(rv8803->client, RV8803_CTRL, + FIELD_PREP(RX8803_CTRL_CSEL, 1)); /* 2s */ + if (ret) + return ret; + + ret = rv8803_write_regs(rv8803->client, RV8803_ALARM_MIN, 3, + (u8[]){ 0, 0, 0 }); + if (ret) + return ret; + + return rv8803_write_reg(rv8803->client, RV8803_RAM, 0x00); +} + static int rv8803_regs_configure(struct rv8803_data *rv8803); static int rv8803_regs_reset(struct rv8803_data *rv8803) { + /* + * The RV-8803 resets all registers to POR defaults after voltage-loss, + * the Epson RTCs don't, so we manually reset the remainder here. + */ + if (rv8803->type == rx_8803 || rv8803->type == rx_8900) { + int ret = rv8803_regs_init(rv8803); + if (ret) + return ret; + } + return rv8803_regs_configure(rv8803); } @@ -631,7 +667,7 @@ static int rv8803_probe(struct i2c_client *client, static const struct i2c_device_id rv8803_id[] = { { "rv8803", rv_8803 }, { "rv8804", rx_8804 }, - { "rx8803", rv_8803 }, + { "rx8803", rx_8803 }, { "rx8900", rx_8900 }, { } }; @@ -644,7 +680,7 @@ static const __maybe_unused struct of_device_id rv8803_of_match[] = { }, { .compatible = "epson,rx8803", - .data = (void *)rv_8803 + .data = (void *)rx_8803 }, { .compatible = "epson,rx8804", |