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Merged
merged 1 commit into from
Aug 4, 2025
Merged

cpu/samd5: improve clock initialisation XOSC32 and FDPLL #21631

merged 1 commit into from
Aug 4, 2025

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kfessel
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@kfessel kfessel commented Jul 30, 2025 •
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Contribution description

current samd5 initialization is strange and might fail ( hardware dependant) while initializing this fixes that.
The failure is know a POR issue.

  • valid clock XOSC32 startup time
  • avoid gclk roundtrip for FDPLL when XOSC32 is used

Testing procedure

read and compare to documentation

Issues/PRs references

@kfessel kfessel requested review from benpicco and dylad as code owners July 30, 2025 13:50
@github-actions github-actions bot added Platform: ARM Platform: This PR/issue effects ARM-based platforms Area: cpu Area: CPU/MCU ports labels Jul 30, 2025
@crasbe crasbe added Type: bug The issue reports a bug / The PR fixes a bug (including spelling errors) CI: ready for build If set, CI server will compile all applications for all available boards for the labeled PR labels Jul 30, 2025
crasbe
crasbe reviewed Jul 30, 2025
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riot-ci commented Jul 30, 2025 •
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Murdock results

✔️ PASSED

991bf4a cpu/samd5: clock initialisation XOSC32 and FDPLL

Success Failures Total Runtime
10559 0 10560 11m:45s

Artifacts

@kfessel kfessel force-pushed the p-fix-samd5-init branch from da4df6a to 3b9ff6f Compare July 30, 2025 15:04
benpicco
benpicco reviewed Jul 30, 2025
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@kfessel kfessel force-pushed the p-fix-samd5-init branch 3 times, most recently from 9b2f3af to d7a8752 Compare July 31, 2025 12:32
@benpicco
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The spell checker has some comments 😉

@kfessel kfessel force-pushed the p-fix-samd5-init branch 2 times, most recently from 1f7f759 to b3ee32a Compare August 1, 2025 07:50
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kfessel commented Aug 1, 2025

i ran a test ULP vs XOSC32

boards/same54-xpro/include/periph_conf.h
@@ -39,7 +39,7 @@ extern "C" {
  * @name    external Oscillator (XOSC1) configuration
  * @{
  */
-#define XOSC1_FREQUENCY     MHZ(12)
+//#define XOSC1_FREQUENCY     MHZ(12)
 /** @} */
 
 /**
@@ -59,8 +59,8 @@ extern "C" {
  * @name    32kHz Oscillator configuration
  * @{
  */
-#define EXTERNAL_OSC32_SOURCE                    1
-#define ULTRA_LOW_POWER_INTERNAL_OSC_SOURCE      0
+#define EXTERNAL_OSC32_SOURCE                    0
+#define ULTRA_LOW_POWER_INTERNAL_OSC_SOURCE      1
 /** @} */
 
 /**

#define INTERVAL_SECS (60)
int main(void)
{
    uint32_t ole = (uint32_t)0 - ((uint32_t)INTERVAL_SECS * (uint32_t)2 * (uint32_t)US_PER_SEC);
    for (;;) {
        uint32_t now =  ztimer_now(ZTIMER_USEC);
        if ( now - ole >= INTERVAL_SECS * US_PER_SEC){
            printf("ZTIMER_USEC: %12"PRIu32"\n", now);
            ole = now;
        }
    }
    return 0;
}

results

2025-08-01 13:09:52,851 # main(): This is RIOT! (Version: 2025.10-devel-65-gb3ee32-p-fix-samd5-init)
2025-08-01 13:09:52,854 # ZTIMER_USEC:         6495
* 2025-08-01 13:10:53,000 # ZTIMER_USEC:     60006496
2025-08-01 13:11:53,137 # ZTIMER_USEC:    120006496
2025-08-01 13:12:53,278 # ZTIMER_USEC:    180006496
2025-08-01 13:13:53,426 # ZTIMER_USEC:    240006496
2025-08-01 13:14:53,564 # ZTIMER_USEC:    300006497
2025-08-01 13:15:53,698 # ZTIMER_USEC:    360006498
2025-08-01 13:16:53,833 # ZTIMER_USEC:    420006498
2025-08-01 13:17:53,979 # ZTIMER_USEC:    480006498
2025-08-01 13:18:54,134 # ZTIMER_USEC:    540006498
2025-08-01 13:19:54,293 # ZTIMER_USEC:    600006498
2025-08-01 13:20:54,441 # ZTIMER_USEC:    660006498
* 2025-08-01 13:21:54,582 # ZTIMER_USEC:    720006498

(13:21:54,582h-13:10:53,000h)/(720006498µs-60006496µs) = 1,002396966659403
1-(13:21:54,582h-13:10:53,000h)/(720006498µs-60006496µs) = −0,002396966659403131
(0.24% slow)

external XOSC32

2025-08-01 13:22:21,148 # main(): This is RIOT! (Version: 2025.10-devel-65-gb3ee32-p-fix-samd5-init)
2025-08-01 13:22:21,149 # ZTIMER_USEC:         6521
* 2025-08-01 13:23:20,984 # ZTIMER_USEC:     60006522
2025-08-01 13:24:20,979 # ZTIMER_USEC:    120006523
2025-08-01 13:25:20,974 # ZTIMER_USEC:    180006523
2025-08-01 13:26:20,970 # ZTIMER_USEC:    240006523
2025-08-01 13:27:20,965 # ZTIMER_USEC:    300006524
2025-08-01 13:28:20,960 # ZTIMER_USEC:    360006524
2025-08-01 13:29:20,956 # ZTIMER_USEC:    420006525
2025-08-01 13:30:20,951 # ZTIMER_USEC:    480006526
2025-08-01 13:31:20,947 # ZTIMER_USEC:    540006527
2025-08-01 13:32:20,943 # ZTIMER_USEC:    600006528
2025-08-01 13:33:20,939 # ZTIMER_USEC:    660006529
2025-08-01 13:34:20,935 # ZTIMER_USEC:    720006530
* 2025-08-01 13:35:20,931 # ZTIMER_USEC:    780006531

(13:35:20,931h-13:23:20,984h)/(780006531µs-60006522µs) = 0,9999263763898092
1 - (13:35:20,931h-13:23:20,984h)/(780006531µs-60006522µs) = 0,00007362361019081598
(0.0074% fast)

@cold (cooling icepack in envelop )
ext pre cooling ~1min
2025-08-01 13:39:01,327 # Try to reconnect to /dev/ttyACM3 again...
2025-08-01 13:39:01,328 # Reconnected to serial port /dev/ttyACM3
2025-08-01 13:39:59,982 # ZTIMER_USEC:     60006531
2025-08-01 13:40:59,977 # ZTIMER_USEC:    120006531
2025-08-01 13:41:59,973 # ZTIMER_USEC:    180006532
2025-08-01 13:42:59,969 # ZTIMER_USEC:    240006532
2025-08-01 13:43:59,964 # ZTIMER_USEC:    300006532
2025-08-01 13:44:59,960 # ZTIMER_USEC:    360006532
2025-08-01 13:45:59,956 # ZTIMER_USEC:    420006533
2025-08-01 13:46:59,952 # ZTIMER_USEC:    480006533
2025-08-01 13:47:59,947 # ZTIMER_USEC:    540006533

ext (cool)
2025-08-01 13:49:07,308 # main(): This is RIOT! (Version: 2025.10-devel-65-gb3ee32-p-fix-samd5-init)
2025-08-01 13:49:07,310 # ZTIMER_USEC:         6541
2025-08-01 13:50:07,306 # ZTIMER_USEC:     60006541
2025-08-01 13:51:07,301 # ZTIMER_USEC:    120006541
2025-08-01 13:52:07,297 # ZTIMER_USEC:    180006541
2025-08-01 13:53:07,293 # ZTIMER_USEC:    240006541
2025-08-01 13:54:07,288 # ZTIMER_USEC:    300006541
2025-08-01 13:55:07,284 # ZTIMER_USEC:    360006542
2025-08-01 13:56:07,279 # ZTIMER_USEC:    420006543
2025-08-01 13:57:07,275 # ZTIMER_USEC:    480006543
2025-08-01 13:58:07,271 # ZTIMER_USEC:    540006543
2025-08-01 13:59:07,266 # ZTIMER_USEC:    600006543
2025-08-01 14:00:07,262 # ZTIMER_USEC:    660006543
2025-08-01 14:01:07,257 # ZTIMER_USEC:    720006543
2025-08-01 14:02:07,253 # ZTIMER_USEC:    780006543

int ULP  (cool)
2025-08-01 14:03:05,602 # main(): This is RIOT! (Version: 2025.10-devel-65-gb3ee32-p-fix-samd5-init)
2025-08-01 14:03:05,604 # ZTIMER_USEC:         6368
* 2025-08-01 14:04:07,165 # ZTIMER_USEC:     60006368
2025-08-01 14:05:08,720 # ZTIMER_USEC:    120006369
2025-08-01 14:06:10,255 # ZTIMER_USEC:    180006369
2025-08-01 14:07:11,775 # ZTIMER_USEC:    240006369
2025-08-01 14:08:13,281 # ZTIMER_USEC:    300006369
2025-08-01 14:09:14,777 # ZTIMER_USEC:    360006369
2025-08-01 14:10:16,264 # ZTIMER_USEC:    420006370
2025-08-01 14:11:17,744 # ZTIMER_USEC:    480006370
2025-08-01 14:12:19,221 # ZTIMER_USEC:    540006370
2025-08-01 14:13:20,691 # ZTIMER_USEC:    600006371
2025-08-01 14:14:22,160 # ZTIMER_USEC:    660006372
2025-08-01 14:15:23,627 # ZTIMER_USEC:    720006372
* 2025-08-01 14:16:25,096 # ZTIMER_USEC:    780006373
=(14:16:25,096h-14:04:07,165h)/(780006373µs-60006368µs)= 1,024904159549277
1 - (14:16:25,096h-14:04:07,165h)/(780006373µs-60006368µs)= −0,02490415954927667
2.5% slow

ext (cool)
2025-08-01 14:17:44,723 # main(): This is RIOT! (Version: 2025.10-devel-65-gb3ee32-p-fix-samd5-init)
2025-08-01 14:17:44,725 # ZTIMER_USEC:         6537
* 2025-08-01 14:18:44,720 # ZTIMER_USEC:     60006537
2025-08-01 14:19:44,716 # ZTIMER_USEC:    120006538
2025-08-01 14:20:44,711 # ZTIMER_USEC:    180006538
2025-08-01 14:21:44,706 # ZTIMER_USEC:    240006538
2025-08-01 14:22:44,701 # ZTIMER_USEC:    300006538
2025-08-01 14:23:44,696 # ZTIMER_USEC:    360006539
2025-08-01 14:24:44,692 # ZTIMER_USEC:    420006539
2025-08-01 14:25:44,687 # ZTIMER_USEC:    480006540
2025-08-01 14:26:44,682 # ZTIMER_USEC:    540006540
2025-08-01 14:27:44,677 # ZTIMER_USEC:    600006541
2025-08-01 14:28:44,673 # ZTIMER_USEC:    660006541
2025-08-01 14:29:44,668 # ZTIMER_USEC:    720006541
* 2025-08-01 14:30:44,663 # ZTIMER_USEC:    780006542

=(14:30:44,663h-14:18:44,720h)/(780006542µs-60006537µs) = 0,9999208263894387
=1-(14:30:44,663h-14:18:44,720h)/(780006542µs-60006537µs) =0,00007917361056129437
0,0079% fast

@HendrikVE
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I tested this PR with hardware that reliably fails with the old initialization code. With this patch the MCU reliably boots and the RTC is still correct to the second.

@kfessel
cpu/samd5: clock initialisation XOSC32 and FDPLL
991bf4a 
- valid clock XOSC32 startup time
- avoid gclk roundtrip for FDPLL when XOSC32 is used
@kfessel kfessel changed the title cpu/samd5: valid XOSC32 statup time avoid gclk roundtrip for CPU FDPLL cpu/samd5: improve clock initialisation XOSC32 and FDPLL Aug 4, 2025
@kfessel kfessel added this pull request to the merge queue Aug 4, 2025
@benpicco benpicco mentioned this pull request Aug 4, 2025
Merged
@github-merge-queue github-merge-queue bot removed this pull request from the merge queue due to failed status checks Aug 4, 2025
@crasbe crasbe added this pull request to the merge queue Aug 4, 2025
Merged via the queue into RIOT-OS:master with commit 5e2665d Aug 4, 2025
26 checks passed
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