From: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxx>
Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
---
drivers/rtc/rtc-rv8803.c | 40 ++++++++++++++++++++++++++++++++++++++--
1 file changed, 38 insertions(+), 2 deletions(-)
diff --git a/drivers/rtc/rtc-rv8803.c b/drivers/rtc/rtc-rv8803.c
index 21a6f1eddb092..fe1247e771b98 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",
--
2.30.2
