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From ffc137a8949cd7859bdf139fa7a56b9dbdb4b2ce Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.com>
Date: Fri, 15 May 2020 16:28:32 +0100
Subject: [PATCH] rtc: rv3028: Write BSM and TCE/TCR to EEPROM
Periodically the RV3028 refreshes registers from the EEPROM. When this
happens, some settings that have only been committed to registers are
lost. Change the handling of backup-switchover-mode and
trickle-resistor-ohms to write the EEPROM instead (if something has
changed), on the understanding that registers will be refreshed
afterwards.
See: https://github.com/raspberrypi/linux/issues/2912
Signed-off-by: Phil Elwell <phil@raspberrypi.com>
---
drivers/rtc/rtc-rv3028.c | 60 ++++++++++++++++++++++++++++------------
1 file changed, 43 insertions(+), 17 deletions(-)
--- a/drivers/rtc/rtc-rv3028.c
+++ b/drivers/rtc/rtc-rv3028.c
@@ -18,6 +18,7 @@
#include <linux/of_device.h>
#include <linux/regmap.h>
#include <linux/rtc.h>
+//#include "rtc-core.h"
#define RV3028_SEC 0x00
#define RV3028_MIN 0x01
@@ -73,7 +74,7 @@
#define RV3028_BACKUP_TCE BIT(5)
#define RV3028_BACKUP_TCR_MASK GENMASK(1,0)
-#define RV3028_BACKUP_BSM_MASK 0x0C
+#define RV3028_BACKUP_BSM_MASK GENMASK(3,2)
#define OFFSET_STEP_PPT 953674
@@ -601,7 +602,8 @@ static int rv3028_probe(struct i2c_clien
struct rv3028_data *rv3028;
int ret, status;
u32 ohms;
- u8 bsm;
+ u32 bsm;
+ u8 backup, backup_bits, backup_mask;
struct nvmem_config nvmem_cfg = {
.name = "rv3028_nvram",
.word_size = 1,
@@ -673,16 +675,17 @@ static int rv3028_probe(struct i2c_clien
if (ret)
return ret;
+ backup_bits = 0;
+ backup_mask = 0;
+
/* setup backup switchover mode */
- if (!device_property_read_u8(&client->dev, "backup-switchover-mode",
- &bsm)) {
+ dev_dbg(&client->dev, "Checking RTC backup switchover-mode\n");
+ if (!device_property_read_u32(&client->dev,
+ "backup-switchover-mode",
+ &bsm)) {
if (bsm <= 3) {
- ret = regmap_update_bits(rv3028->regmap, RV3028_BACKUP,
- RV3028_BACKUP_BSM_MASK,
- (bsm & 0x03) << 2);
-
- if (ret)
- return ret;
+ backup_bits |= (u8)(bsm << 2);
+ backup_mask |= RV3028_BACKUP_BSM_MASK;
} else {
dev_warn(&client->dev, "invalid backup switchover mode value\n");
}
@@ -698,15 +701,38 @@ static int rv3028_probe(struct i2c_clien
break;
if (i < ARRAY_SIZE(rv3028_trickle_resistors)) {
- ret = regmap_update_bits(rv3028->regmap, RV3028_BACKUP,
- RV3028_BACKUP_TCE |
- RV3028_BACKUP_TCR_MASK,
- RV3028_BACKUP_TCE | i);
- if (ret)
- return ret;
+ backup_bits |= RV3028_BACKUP_TCE | i;
+ backup_mask |= RV3028_BACKUP_TCE |
+ RV3028_BACKUP_TCR_MASK;
} else {
- dev_warn(&client->dev, "invalid trickle resistor value\n");
+ dev_warn(&client->dev,
+ "invalid trickle resistor value\n");
+ }
+ }
+
+ if (backup_mask) {
+ ret = rv3028_eeprom_read((void *)(rv3028->regmap),
+ RV3028_BACKUP,
+ (void *)&backup, 1);
+ if (!ret) {
+ /* Write EEPROM only if needed */
+ if ((backup & backup_mask) != backup_bits) {
+ backup = (backup & ~backup_mask) | backup_bits;
+ dev_dbg(&client->dev,
+ "Backup register doesn't match: EEPROM write required\n");
+ ret = rv3028_eeprom_write(
+ (void *)(rv3028->regmap),
+ RV3028_BACKUP, (void *)&backup, 1);
+ }
}
+
+ /* In the event of an EEPROM failure, update the register
+ instead. */
+ if (ret)
+ ret = regmap_update_bits(rv3028->regmap, RV3028_BACKUP,
+ backup_mask, backup_bits);
+ if (ret)
+ return ret;
}
ret = rtc_add_group(rv3028->rtc, &rv3028_attr_group);
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