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Message-Id: <201204240451.q3O4pWCG003918@gatekeeper.vosshq.de>
Date: Mon, 23 Apr 2012 12:51:23 +0200
From: Nikolaus Voss <n.voss@...nmann.de>
To: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
rtc-linux@...glegroups.com
Cc: akpm@...ux-foundation.org, a.zummo@...ertech.it,
grant.likely@...retlab.ca
Subject: [PATCH v2] drivers/rtc/rtc-m41t93.c: don't let get_time() reset
M41T93_FLAG_OF
If the rtc reports the time might be invalid due to oscillator
failure, M41T93_FLAG_OF flag must not be reset by get_time() as
the read operation doesn't make the time valid.
Without this patch, only the first get_time() reported an invalid
time, the second get_time() reported a valid time althought the
reported time is probably wrong due to oscillator failure.
Instead of resetting in get_time(), with this patch M41T93_FLAG_OF
is reset in set_time() when a valid time is to be written.
Signed-off-by: Nikolaus Voss <n.voss@...nmann.de>
---
v2: better commit description
drivers/i2c/busses/i2c-at91.c | 5 +--
drivers/rtc/rtc-m41t93.c | 46 ++++++++++++++++++++++++-----------------
2 files changed, 29 insertions(+), 22 deletions(-)
diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
index ca142c5..a6f9e73 100644
--- a/drivers/i2c/busses/i2c-at91.c
+++ b/drivers/i2c/busses/i2c-at91.c
@@ -115,14 +115,13 @@ static void __devinit at91_calc_twi_clock(struct at91_twi_dev *dev, int twi_clk)
const int div = max(0, (int)DIV_ROUND_UP(clk_get_rate(dev->clk),
2 * twi_clk) - offset);
int ckdiv = fls(div >> 8);
- int cdiv = div >> ckdiv;;
+ int cdiv = div >> ckdiv;
if (dev->is_rm9200 && (ckdiv > 5)) {
dev_warn(dev->dev, "AT91RM9200 erratum 22: using ckdiv = 5.\n");
ckdiv = 5;
cdiv = 255;
- }
- else if (ckdiv > 7) {
+ } else if (ckdiv > 7) {
dev_warn(dev->dev, "%d exceeds 3 bits for ckdiv, limiting.\n",
ckdiv);
ckdiv = 7;
diff --git a/drivers/rtc/rtc-m41t93.c b/drivers/rtc/rtc-m41t93.c
index ef71132..f19f45c 100644
--- a/drivers/rtc/rtc-m41t93.c
+++ b/drivers/rtc/rtc-m41t93.c
@@ -48,6 +48,7 @@ static inline int m41t93_set_reg(struct spi_device *spi, u8 addr, u8 data)
static int m41t93_set_time(struct device *dev, struct rtc_time *tm)
{
struct spi_device *spi = to_spi_device(dev);
+ int tmp;
u8 buf[9] = {0x80}; /* write cmd + 8 data bytes */
u8 * const data = &buf[1]; /* ptr to first data byte */
@@ -62,6 +63,30 @@ static int m41t93_set_time(struct device *dev, struct rtc_time *tm)
return -EINVAL;
}
+ tmp = spi_w8r8(spi, M41T93_REG_FLAGS);
+ if (tmp < 0)
+ return tmp;
+
+ if (tmp & M41T93_FLAG_OF) {
+ dev_warn(&spi->dev, "OF bit is set, resetting.\n");
+ m41t93_set_reg(spi, M41T93_REG_FLAGS, tmp & ~M41T93_FLAG_OF);
+
+ tmp = spi_w8r8(spi, M41T93_REG_FLAGS);
+ if (tmp < 0) {
+ return tmp;
+ } else if (tmp & M41T93_FLAG_OF) {
+ /* OF cannot be immediately reset: oscillator has to be
+ * restarted. */
+ u8 reset_osc = buf[M41T93_REG_ST_SEC] | M41T93_FLAG_ST;
+
+ dev_warn(&spi->dev,
+ "OF bit is still set, kickstarting clock.\n");
+ m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc);
+ reset_osc &= ~M41T93_FLAG_ST;
+ m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc);
+ }
+ }
+
data[M41T93_REG_SSEC] = 0;
data[M41T93_REG_ST_SEC] = bin2bcd(tm->tm_sec);
data[M41T93_REG_MIN] = bin2bcd(tm->tm_min);
@@ -89,10 +114,7 @@ static int m41t93_get_time(struct device *dev, struct rtc_time *tm)
1. halt bit (HT) is set: the clock is running but update of readout
registers has been disabled due to power failure. This is normal
case after poweron. Time is valid after resetting HT bit.
- 2. oscillator fail bit (OF) is set. Oscillator has be stopped and
- time is invalid:
- a) OF can be immeditely reset.
- b) OF cannot be immediately reset: oscillator has to be restarted.
+ 2. oscillator fail bit (OF) is set: time is invalid.
*/
tmp = spi_w8r8(spi, M41T93_REG_ALM_HOUR_HT);
if (tmp < 0)
@@ -110,21 +132,7 @@ static int m41t93_get_time(struct device *dev, struct rtc_time *tm)
if (tmp & M41T93_FLAG_OF) {
ret = -EINVAL;
- dev_warn(&spi->dev, "OF bit is set, resetting.\n");
- m41t93_set_reg(spi, M41T93_REG_FLAGS, tmp & ~M41T93_FLAG_OF);
-
- tmp = spi_w8r8(spi, M41T93_REG_FLAGS);
- if (tmp < 0)
- return tmp;
- else if (tmp & M41T93_FLAG_OF) {
- u8 reset_osc = buf[M41T93_REG_ST_SEC] | M41T93_FLAG_ST;
-
- dev_warn(&spi->dev,
- "OF bit is still set, kickstarting clock.\n");
- m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc);
- reset_osc &= ~M41T93_FLAG_ST;
- m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc);
- }
+ dev_warn(&spi->dev, "OF bit is set, write time to restart.\n");
}
if (tmp & M41T93_FLAG_BL)
--
1.7.5.4
--
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