diff options
| author | Lothar Waßmann <LW@KARO-electronics.de> | 2013-08-13 16:00:56 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-08-13 17:57:48 -0700 |
| commit | 28a0c88312973792f439493d801ceac61baae9b3 (patch) | |
| tree | 64cf598f048c5db0c9cfc9d6c453946fee19cd0b | |
| parent | b610ded71918654748b6b49f1e2636dc6bbfc96e (diff) | |
drivers/rtc/rtc-stmp3xxx.c: provide timeout for potentially endless loop polling a HW bit
It's always a bad idea to poll on HW bits without a timeout.
The i.MX28 RTC can be easily brought into a state in which the RTC is
not running (until after a power-on-reset) and thus the status bits
which are polled in the driver won't ever change.
This patch prevents the kernel from getting stuck in this case.
Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
Acked-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | drivers/rtc/rtc-stmp3xxx.c | 35 |
1 files changed, 25 insertions, 10 deletions
diff --git a/drivers/rtc/rtc-stmp3xxx.c b/drivers/rtc/rtc-stmp3xxx.c index 767fee2ab340..26019531db15 100644 --- a/drivers/rtc/rtc-stmp3xxx.c +++ b/drivers/rtc/rtc-stmp3xxx.c @@ -23,6 +23,7 @@ #include <linux/init.h> #include <linux/platform_device.h> #include <linux/interrupt.h> +#include <linux/delay.h> #include <linux/rtc.h> #include <linux/slab.h> #include <linux/of_device.h> @@ -119,24 +120,39 @@ static void stmp3xxx_wdt_register(struct platform_device *rtc_pdev) } #endif /* CONFIG_STMP3XXX_RTC_WATCHDOG */ -static void stmp3xxx_wait_time(struct stmp3xxx_rtc_data *rtc_data) +static int stmp3xxx_wait_time(struct stmp3xxx_rtc_data *rtc_data) { + int timeout = 5000; /* 3ms according to i.MX28 Ref Manual */ /* - * The datasheet doesn't say which way round the - * NEW_REGS/STALE_REGS bitfields go. In fact it's 0x1=P0, - * 0x2=P1, .., 0x20=P5, 0x40=ALARM, 0x80=SECONDS + * The i.MX28 Applications Processor Reference Manual, Rev. 1, 2010 + * states: + * | The order in which registers are updated is + * | Persistent 0, 1, 2, 3, 4, 5, Alarm, Seconds. + * | (This list is in bitfield order, from LSB to MSB, as they would + * | appear in the STALE_REGS and NEW_REGS bitfields of the HW_RTC_STAT + * | register. For example, the Seconds register corresponds to + * | STALE_REGS or NEW_REGS containing 0x80.) */ - while (readl(rtc_data->io + STMP3XXX_RTC_STAT) & - (0x80 << STMP3XXX_RTC_STAT_STALE_SHIFT)) - cpu_relax(); + do { + if (!(readl(rtc_data->io + STMP3XXX_RTC_STAT) & + (0x80 << STMP3XXX_RTC_STAT_STALE_SHIFT))) + return 0; + udelay(1); + } while (--timeout > 0); + return (readl(rtc_data->io + STMP3XXX_RTC_STAT) & + (0x80 << STMP3XXX_RTC_STAT_STALE_SHIFT)) ? -ETIME : 0; } /* Time read/write */ static int stmp3xxx_rtc_gettime(struct device *dev, struct rtc_time *rtc_tm) { + int ret; struct stmp3xxx_rtc_data *rtc_data = dev_get_drvdata(dev); - stmp3xxx_wait_time(rtc_data); + ret = stmp3xxx_wait_time(rtc_data); + if (ret) + return ret; + rtc_time_to_tm(readl(rtc_data->io + STMP3XXX_RTC_SECONDS), rtc_tm); return 0; } @@ -146,8 +162,7 @@ static int stmp3xxx_rtc_set_mmss(struct device *dev, unsigned long t) struct stmp3xxx_rtc_data *rtc_data = dev_get_drvdata(dev); writel(t, rtc_data->io + STMP3XXX_RTC_SECONDS); - stmp3xxx_wait_time(rtc_data); - return 0; + return stmp3xxx_wait_time(rtc_data); } /* interrupt(s) handler */ |