From: "Mateusz Jończyk" <mat.jonczyk@o2.pl>
To: linux-kernel@vger.kernel.org, linux-rtc@vger.kernel.org
Cc: "Mateusz Jończyk" <mat.jonczyk@o2.pl>,
"Alessandro Zummo" <a.zummo@towertech.it>,
"Alexandre Belloni" <alexandre.belloni@bootlin.com>
Subject: [DEBUG PATCH v3] rtc-cmos: cmos_read_alarm bug demonstration
Date: Fri, 19 Nov 2021 21:46:14 +0100 [thread overview]
Message-ID: <20211119204614.78957-1-mat.jonczyk@o2.pl> (raw)
In-Reply-To: <20211119204221.66918-7-mat.jonczyk@o2.pl>
Before my commit "rtc-cmos: avoid UIP when reading alarm time",
applying this patch and reading the CMOS time like so:
while true; do cat /sys/class/rtc/rtc0/time ; sleep 0.5; done
produces errors in dmesg on my Intel Kaby Lake laptop.
Signed-off-by: Mateusz Jończyk <mat.jonczyk@o2.pl>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
---
drivers/rtc/rtc-cmos.c | 61 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 61 insertions(+)
diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index b6d7dd3cf066..3de049930745 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -43,6 +43,9 @@
#include <linux/dmi.h>
#endif
+#include <linux/ktime.h>
+#include <linux/timekeeping.h>
+
/* this is for "generic access to PC-style RTC" using CMOS_READ/CMOS_WRITE */
#include <linux/mc146818rtc.h>
@@ -220,6 +223,8 @@ static inline void cmos_write_bank2(unsigned char val, unsigned char addr)
/*----------------------------------------------------------------*/
+static void cmos_read_alarm_uip_debugging(struct device *dev);
+
static int cmos_read_time(struct device *dev, struct rtc_time *t)
{
/*
@@ -230,6 +235,8 @@ static int cmos_read_time(struct device *dev, struct rtc_time *t)
return -EIO;
mc146818_get_time(t);
+
+ cmos_read_alarm_uip_debugging(dev);
return 0;
}
@@ -338,6 +345,60 @@ static int cmos_read_alarm(struct device *dev, struct rtc_wkalrm *t)
return 0;
}
+static void cmos_read_alarm_uip_debugging(struct device *dev)
+{
+ unsigned long flags;
+ unsigned char rtc_uip_baseline, rtc_uip;
+ struct rtc_wkalrm t_baseline, t;
+ ktime_t time_start, time_end;
+ int i;
+
+ spin_lock_irqsave(&rtc_lock, flags);
+ rtc_uip_baseline = CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP;
+ spin_unlock_irqrestore(&rtc_lock, flags);
+
+ cmos_read_alarm(dev, &t_baseline);
+
+ time_start = ktime_get();
+
+ for (i = 0; i < 2000; i++) {
+ spin_lock_irqsave(&rtc_lock, flags);
+ rtc_uip = CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP;
+ spin_unlock_irqrestore(&rtc_lock, flags);
+
+ cmos_read_alarm(dev, &t);
+
+ if (t_baseline.time.tm_sec != t.time.tm_sec) {
+ dev_err(dev,
+ "Inconsistent alarm tm_sec value: %d != %d (RTC_UIP = %d; %d)\n",
+ t_baseline.time.tm_sec,
+ t.time.tm_sec,
+ rtc_uip_baseline, rtc_uip);
+ }
+ if (t_baseline.time.tm_min != t.time.tm_min) {
+ dev_err(dev,
+ "Inconsistent alarm tm_min value: %d != %d (RTC_UIP = %d; %d)\n",
+ t_baseline.time.tm_min,
+ t.time.tm_min,
+ rtc_uip_baseline, rtc_uip);
+ }
+ if (t_baseline.time.tm_hour != t.time.tm_hour) {
+ dev_err(dev,
+ "Inconsistent alarm tm_hour value: %d != %d (RTC_UIP = %d; %d)\n",
+ t_baseline.time.tm_hour,
+ t.time.tm_hour,
+ rtc_uip_baseline, rtc_uip);
+ }
+
+ }
+
+ time_end = ktime_get();
+
+ pr_info_ratelimited("%s: loop executed in %lld ns\n",
+ __func__, ktime_to_ns(ktime_sub(time_end, time_start)));
+}
+
+
static void cmos_checkintr(struct cmos_rtc *cmos, unsigned char rtc_control)
{
unsigned char rtc_intr;
--
2.25.1
next prev parent reply other threads:[~2021-11-19 20:46 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-19 20:42 [PATCH RESEND v3 0/7] rtc-cmos,rtc-mc146818-lib: fixes Mateusz Jończyk
2021-11-19 20:42 ` [PATCH RESEND v3 1/7] rtc-cmos: take rtc_lock while reading from CMOS Mateusz Jończyk
2021-11-19 20:42 ` [PATCH RESEND v3 2/7] rtc-mc146818-lib: fix RTC presence check Mateusz Jończyk
2021-11-24 22:31 ` Alexandre Belloni
2021-11-25 22:12 ` Mateusz Jończyk
2021-12-10 15:26 ` Alexandre Belloni
2021-12-10 19:05 ` Mateusz Jończyk
2021-11-19 20:42 ` [PATCH RESEND v3 3/7] rtc-mc146818-lib: extract mc146818_do_avoiding_UIP Mateusz Jończyk
2021-11-24 22:39 ` Alexandre Belloni
2021-11-25 5:28 ` Mateusz Jończyk
2021-11-25 8:04 ` Alexandre Belloni
2021-11-19 20:42 ` [PATCH RESEND v3 4/7] rtc-mc146818-lib: refactor mc146818_get_time Mateusz Jończyk
2021-11-24 22:41 ` Alexandre Belloni
2021-11-25 5:48 ` Mateusz Jończyk
2021-11-25 8:05 ` Alexandre Belloni
2021-11-19 20:42 ` [PATCH RESEND v3 5/7] rtc-mc146818-lib: refactor mc146818_does_rtc_work Mateusz Jończyk
2021-11-19 20:42 ` [PATCH RESEND v3 6/7] rtc-cmos: avoid UIP when reading alarm time Mateusz Jończyk
2021-11-19 20:46 ` Mateusz Jończyk [this message]
2021-11-24 22:44 ` Alexandre Belloni
2021-11-19 20:42 ` [PATCH RESEND v3 7/7] rtc-cmos: avoid UIP when writing " Mateusz Jończyk
2021-11-19 21:20 ` [PATCH RESEND v3 0/7] rtc-cmos,rtc-mc146818-lib: fixes Alexandre Belloni
-- strict thread matches above, loose matches on Subject: below --
2021-10-30 21:46 [PATCH " Mateusz Jończyk
2021-10-30 21:46 ` [DEBUG PATCH v3] rtc-cmos: cmos_read_alarm bug demonstration Mateusz Jończyk
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20211119204614.78957-1-mat.jonczyk@o2.pl \
--to=mat.jonczyk@o2.pl \
--cc=a.zummo@towertech.it \
--cc=alexandre.belloni@bootlin.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-rtc@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).