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authorDmitry Torokhov <dmitry.torokhov@gmail.com>2024-10-25 13:14:57 -0700
committerAlexandre Belloni <alexandre.belloni@bootlin.com>2024-11-01 00:19:22 +0100
commit0a6efab33eab4e973db26d9f90c3e97a7a82e399 (patch)
treec7dcd6cd8b721060499b1a71d4ad968eedf57bf8 /drivers/rtc
parentd4488377609e36cd9785533c29ccea4b86c292b9 (diff)
rtc: cmos: avoid taking rtc_lock for extended period of time
On my device reading entirety of /sys/devices/pnp0/00:03/cmos_nvram0/nvmem takes about 9 msec during which time interrupts are off on the CPU that does the read and the thread that performs the read can not be migrated or preempted by another higher priority thread (RT or not). Allow readers and writers be preempted by taking and releasing rtc_lock spinlock for each individual byte read or written rather than once per read/write request. Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> Reviewed-by: Mateusz Jończyk <mat.jonczyk@o2.pl> Link: https://lore.kernel.org/r/Zxv8QWR21AV4ztC5@google.com Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Diffstat (limited to 'drivers/rtc')
-rw-r--r--drivers/rtc/rtc-cmos.c31
1 files changed, 15 insertions, 16 deletions
diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index 35dca2accbb8..5849d2970bba 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -645,18 +645,17 @@ static int cmos_nvram_read(void *priv, unsigned int off, void *val,
unsigned char *buf = val;
off += NVRAM_OFFSET;
- spin_lock_irq(&rtc_lock);
- for (; count; count--, off++) {
+ for (; count; count--, off++, buf++) {
+ guard(spinlock_irq)(&rtc_lock);
if (off < 128)
- *buf++ = CMOS_READ(off);
+ *buf = CMOS_READ(off);
else if (can_bank2)
- *buf++ = cmos_read_bank2(off);
+ *buf = cmos_read_bank2(off);
else
- break;
+ return -EIO;
}
- spin_unlock_irq(&rtc_lock);
- return count ? -EIO : 0;
+ return 0;
}
static int cmos_nvram_write(void *priv, unsigned int off, void *val,
@@ -671,23 +670,23 @@ static int cmos_nvram_write(void *priv, unsigned int off, void *val,
* NVRAM to update, updating checksums is also part of its job.
*/
off += NVRAM_OFFSET;
- spin_lock_irq(&rtc_lock);
- for (; count; count--, off++) {
+ for (; count; count--, off++, buf++) {
/* don't trash RTC registers */
if (off == cmos->day_alrm
|| off == cmos->mon_alrm
|| off == cmos->century)
- buf++;
- else if (off < 128)
- CMOS_WRITE(*buf++, off);
+ continue;
+
+ guard(spinlock_irq)(&rtc_lock);
+ if (off < 128)
+ CMOS_WRITE(*buf, off);
else if (can_bank2)
- cmos_write_bank2(*buf++, off);
+ cmos_write_bank2(*buf, off);
else
- break;
+ return -EIO;
}
- spin_unlock_irq(&rtc_lock);
- return count ? -EIO : 0;
+ return 0;
}
/*----------------------------------------------------------------*/