npcx/timer: Unroll udelayfirmware-nami-10775.108.B

This patch flattens udelay by unrolling __hw_clock_source_read.
This increases the chance that we record LR of the instruction
near which an infinite loop happened.

> battery 1 1000000
...

WATCHDOG PC=1008a76c / LR=1008c81f / pSP=200c44f8 (task 10) ###
Time:     0x0000000000f22630 us,   15.869488 s
Deadline: 0x0000000000f43946 ->    0.135958 s from now
Active timers:
  Tsk 14  0x0000000000f43946 ->    0.135958
Task Ready Name         Events      Time (s)  StkUsed
   0 R << idle >>       00000001    4.840735   80/672
   1 R HOOKS            80000000    0.788073  648/800
   2   USB_CHG_P0       00000000    0.001591  312/672
   3   USB_CHG_P1       00000000    0.004209  320/672
   4 R CHARGER          40000000    0.103775  400/800
   5 R MOTIONSENSE      80000004    0.098946  560/928
   6   CHIPSET          00000000    0.000588  296/800
   7   KEYPROTO         00000000    0.000019  128/672
   8   PDCMD            00000000    0.001017  328/672
   9   HOSTCMD          00000000    0.043613  336/800
  10 R CONSOLE          00000000    2.342869  384/800

--- UART initialized after reboot ---
[Reset cause: watchdog]
[Image: RO, nami_v1.1.8956-b85666cd37 2021-11-10 15:07:11 some@host]
[0.003867 init buttons]
[0.004086 Inits done]
Restarting system with PMIC.

...

WATCHDOG PC=1008a76c / LR=1008c81f / task=10
r0 :         r1 :         r2 :         r3 :
r4 :dead6664 r5 :1008a76c r6 :00000000 r7 :00000000
r8 :00000000 r9 :00000000 r10:00000000 r11:00000000
r12:         sp :00000000 lr :         pc :

mmfs = 0, shcsr = 0, hfsr = 10000028, dfsr = 0, ipsr = 1008c81f

BUG=b:200593658, b:205841546
BRANCH=
TEST=Run hacked battery command to trigger WDT on Sona. Verify the LR
     points to command_battery instead of udelay. See above.

Change-Id: Ibd6cbcf18ab6d58c06ddfd19021058268289bf00
Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3235653
Reviewed-by: caveh jalali <caveh@chromium.org>

6 files changed, 25 insertions, 13 deletions

diff --git a/board/cr50/board.h b/board/cr50/board.h
index 9a2f79717b..e2640dfd29 100644
--- a/board/cr50/board.h
+++ b/board/cr50/board.h
@@ -139,9 +139,6 @@
 #define CONFIG_DCRYPTO
 #define CONFIG_UPTO_SHA512
 
-/* Implement custom udelay, due to usec hwtimer imprecision. */
-#define CONFIG_HW_SPECIFIC_UDELAY
-
 #define CONFIG_TPM_LOGGING
 
 #ifndef __ASSEMBLER__
diff --git a/chip/g/hwtimer.c b/chip/g/hwtimer.c
index 91dba78c40..267cf395cf 100644
--- a/chip/g/hwtimer.c
+++ b/chip/g/hwtimer.c
@@ -178,14 +178,13 @@ int __hw_clock_source_init(uint32_t start_t)
 	return GC_IRQNUM_TIMELS0_TIMINT1;
 }
 
-#ifdef CONFIG_HW_SPECIFIC_UDELAY
 /*
  * Custom chip/g udelay(), guaranteed to delay for at least us microseconds.
  *
  * Lost time during timer wrap is not taken into account since interrupt latency
  * and __hw_clock_source_irq() execution time likely exceeds the lost 3us.
  */
-void udelay(unsigned us)
+__override void udelay(unsigned us)
 {
 	unsigned t0 = __hw_clock_source_read();
 
@@ -210,4 +209,3 @@ void udelay(unsigned us)
 	while (__hw_clock_source_read() - t0 <= us)
 		;
 }
-#endif /* CONFIG_HW_SPECIFIC_UDELAY */
diff --git a/chip/npcx/hwtimer.c b/chip/npcx/hwtimer.c
index e46a56fb1e..d9a5728942 100644
--- a/chip/npcx/hwtimer.c
+++ b/chip/npcx/hwtimer.c
@@ -16,6 +16,7 @@
 #include "console.h"
 #include "task.h"
 #include "timer.h"
+#include "registers.h"
 #include "util.h"
 
 /* Depth of event timer */
@@ -332,3 +333,24 @@ int __hw_clock_source_init(uint32_t start_t)
 
 	return NPCX_IRQ_ITIM32;
 }
+
+/*
+ * Unrolled udelay. It preserves LR, which points to the root cause of WD crash.
+ */
+__override void udelay(unsigned us)
+{
+	uint32_t cnt, cnt2;
+	unsigned t0;
+
+	cnt = NPCX_ITCNT32;
+	while ((cnt2 = NPCX_ITCNT32) != cnt)
+		cnt = cnt2;
+
+	t0 = TICK_ITIM32_MAX_CNT - cnt;
+
+	do {
+		cnt = NPCX_ITCNT32;
+		while ((cnt2 = NPCX_ITCNT32) != cnt)
+			cnt = cnt2;
+	} while (TICK_ITIM32_MAX_CNT - cnt - t0 <= us);
+}
diff --git a/common/timer.c b/common/timer.c
index 117cea4b71..6f31d93b09 100644
--- a/common/timer.c
+++ b/common/timer.c
@@ -94,8 +94,7 @@ void process_timers(int overflow)
 	} while (next.val <= get_time().val);
 }
 
-#ifndef CONFIG_HW_SPECIFIC_UDELAY
-void udelay(unsigned us)
+__overridable void udelay(unsigned us)
 {
 	unsigned t0 = __hw_clock_source_read();
 
@@ -112,7 +111,6 @@ void udelay(unsigned us)
 	while (__hw_clock_source_read() - t0 <= us)
 		;
 }
-#endif
 
 int timer_arm(timestamp_t tstamp, task_id_t tskid)
 {
diff --git a/include/config.h b/include/config.h
index 443f93d738..86c1707512 100644
--- a/include/config.h
+++ b/include/config.h
@@ -1850,9 +1850,6 @@
  */
 #undef CONFIG_HIBERNATE_PSL
 
-/* Use a hardware specific udelay(). */
-#undef CONFIG_HW_SPECIFIC_UDELAY
-
 /*****************************************************************************/
 /* I2C configuration */
 
diff --git a/include/timer.h b/include/timer.h
index fb7800ce2e..4a008f6d06 100644
--- a/include/timer.h
+++ b/include/timer.h
@@ -71,7 +71,7 @@ int timestamp_expired(timestamp_t deadline, const timestamp_t *now);
  *
  * @param us		Number of microseconds to delay.
  */
-void udelay(unsigned us);
+__override_proto void udelay(unsigned us);
 
 /**
  * Sleep.