imx: mx7: psci: add system reset support

PATCH Superseded Anson Huang 4 participants 14 messages Jan 4, 2018 – May 10, 2018

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Arm (32-bit) Arm sub-architectures Arm i.MX and Layerscape

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Anson Huang

author

2018-01-04 09:03 UTC #0 lore raw

PATCH v2 1/1 imx: mx7: psci: add system reset support

Add i.MX7 PSCI system reset support, linux
kernel now can use "reboot" command to reset
system.

Signed-off-by Anson Huang <[email protected]>

---
changes since V1:
write WDOG register directly instead of calling reset_cpu which is NOT safe since it is NOT in secure section.

 arch/arm/mach-imx/mx7/psci-mx7.c | 5 +++++
 arch/arm/mach-imx/mx7/psci.S     | 7 +++++++
 2 files changed, 12 insertions(+)

arch/arm/mach-imx/mx7/psci-mx7.c +5 -0

index 7f429b0..66f6db6 100644
@@ -74,3 +74,8 @@ __secure int imx_cpu_off(int cpu)
 	writel(0, SRC_BASE_ADDR + cpu * 8 + SRC_GPR1_MX7D + 4);
 	return 0;
 }
+
+__secure void imx_system_reset(void)
+{
+	writew(1 << 2, WDOG1_BASE_ADDR);
+}

arch/arm/mach-imx/mx7/psci.S +7 -0

index fc5eb34..59f98cd 100644
@@ -43,4 +43,11 @@ psci_cpu_off:
 1: 	wfi
 	b 1b
 
+.globl psci_system_reset
+psci_system_reset:
+	b	imx_system_reset
+
+2: 	wfi
+	b 2b
+
 	.popsection

Signature · 1 line

1.9.1

Anson Huang

author

2018-01-04 10:46 UTC #2 lore raw

PATCH v2 1/1 imx: mx7: psci: add system reset support

Hi, Peng

Best Regards!
Anson Huang

Quoted 30 lines

-----Original Message-----
From: Peng Fan
Sent: 2018-01-04 5:48 PM
To: Anson Huang <[email protected]>; sbabic at denx.de; Fabio Estevam <[email protected]>; albert.u.boot at aribaud.net; christian.gmeiner at gmail.com; u-boot at lists.denx.de
Subject: RE: [PATCH V2] imx: mx7: psci: add system reset support
Hi Anson,
Quoted 20 lines
-----Original Message-----
From: Anson Huang [mailto:Anson.Huang at nxp.com]
Sent: Thursday, January 04, 2018 5:04 PM
To: sbabic at denx.de; Fabio Estevam <[email protected]>; albert.u.boot at aribaud.net; christian.gmeiner at gmail.com; Peng Fan <[email protected]>; u-boot at lists.denx.de
Subject: [PATCH V2] imx: mx7: psci: add system reset support
Add i.MX7 PSCI system reset support, linux kernel now can use "reboot" command to reset system.
Signed-off-by Anson Huang <[email protected]>
---
changes since V1:
write WDOG register directly instead of calling reset_cpu which is NOT safe since it is NOT in secure section.
 arch/arm/mach-imx/mx7/psci-mx7.c | 5 +++++
 arch/arm/mach-imx/mx7/psci.S     | 7 +++++++
 2 files changed, 12 insertions(+)

Quoted 15 lines

arch/arm/mach-imx/mx7/psci-mx7.c __secure int imx_cpu_off(int cpu) · line 80
Quoted 12 lines
arch/arm/mach- renamed from arch/arm/mach-imx/mx7/psci-mx7.c +0 -0
imx/mx7/psci-mx7.c index 7f429b0..66f6db6 100644
arch/arm/mach-imx/mx7/psci-mx7.c +4 -0
@@ -74,3 +74,8 @@ __secure int imx_cpu_off(int cpu)
 	writel(0, SRC_BASE_ADDR + cpu * 8 + SRC_GPR1_MX7D + 4);
 	return 0;
 }
+
+__secure void imx_system_reset(void)
+{
+	writew(1 << 2, WDOG1_BASE_ADDR);
I think this should be "writew((WCR_WDE | WCR_SRS), WDOG1_BASE_ADDR);"?

I use SRS reset which will assert reset signal immediately, no need to wait Wdog timeout.

Anson.

Quoted 23 lines

Regards,
Peng.
Quoted 19 lines
arch/arm/mach-imx/mx7/psci-mx7.c +1 -0
+}
(quoted diff) +0 -0
b/arch/arm/mach-imx/mx7/psci.S index fc5eb34..59f98cd 100644
arch/arm/mach-imx/mx7/psci.S +7 -1
@@ -43,4 +43,11 @@ psci_cpu_off:
 1: 	wfi
 	b 1b
 
+.globl psci_system_reset
+psci_system_reset:
+	b	imx_system_reset
+
+2: 	wfi
+	b 2b
+
 	.popsection
--
1.9.1

Fabio Estevam

reviewer

2018-01-04 12:57 UTC #3 lore raw

PATCH v2 1/1 imx: mx7: psci: add system reset support

In reply to Anson Huang

Hi Anson,

Quoted 3 lines · Anson Huang

Add i.MX7 PSCI system reset support, linux
kernel now can use "reboot" command to reset
system.

Reading this commit message gives me the impression that the 'reboot' command does not work currently.

However, the 'reboot' command works provided the boards connects the WDOG output pin to the PMIC due to the MX7 erratum.

What exactly are you fixing here? Please clarify.

Anson Huang

author

2018-01-05 06:25 UTC #4 lore raw

PATCH v2 1/1 imx: mx7: psci: add system reset support

Hi, Fabio

Best Regards!
Anson Huang

Quoted 16 lines

-----Original Message-----
From: Fabio Estevam [mailto:festevam at gmail.com]
Sent: 2018-01-04 8:57 PM
To: Anson Huang <[email protected]>
Cc: Stefano Babic <[email protected]>; Fabio Estevam <[email protected]>; Albert ARIBAUD <[email protected]>; Christian Gmeiner <[email protected]>; Peng Fan <[email protected]>; U-Boot-Denx <[email protected]>
Subject: Re: [U-Boot] [PATCH V2] imx: mx7: psci: add system reset support
Hi Anson,
Quoted 2 lines · Anson Huang
Add i.MX7 PSCI system reset support, linux kernel now can use "reboot" command to reset system.

Quoted 7 lines

Reading this commit message gives me the impression that the 'reboot' command does not work currently.
However, the 'reboot' command works provided the boards connects the WDOG output pin to the PMIC due to the MX7 erratum.
What exactly are you fixing here? Please clarify.

Thanks for the comments, the current reboot command works is just because wdog driver is enabled and when system reboot, the reboot notification callback in wdog driver will do reset. But if wdog is disabled in dtb, the reboot command will fail.

As now we use PSCI, the reboot operation will eventually call into u-boot's psci reset callback, we should support this feature, the reboot feature in Linux kernel should NOT depends on wdog's existence.

But I did notice that I miss a change to enable the psci reset feature, we should Use psci 1.0 instead of 0.1, psci 0.1 only supports very limited features which does NOT include system reset, power off etc..

So I re-send a patch series to do these changes, to support PSCI system reset, system power off, please help review, thanks.

Anson.

Fabio Estevam

reviewer

2018-01-06 22:47 UTC #5 lore raw

PATCH v2 1/1 imx: mx7: psci: add system reset support

Hi Anson,

Quoted 8 lines · Anson Huang

Thanks for the comments, the current reboot command works is just because wdog driver is enabled and when system reboot, the reboot notification callback in wdog driver will do reset. But if wdog is disabled in dtb, the reboot command will fail.
As now we use PSCI, the reboot operation will eventually call into u-boot's psci reset callback, we should support this feature, the reboot feature in Linux kernel should NOT depends on wdog's existence.

Ok, but what about erratum e10574 (Watchdog: A watchdog timeout or software trigger will not reset the SOC)?

According to this erratum WDOG_B pin needs to generate a system power on.

Anson Huang

author

2018-01-07 05:57 UTC #6 lore raw

PATCH v2 1/1 imx: mx7: psci: add system reset support

Best Regards!
Anson Huang

Quoted 19 lines

-----Original Message-----
From: Fabio Estevam [mailto:festevam at gmail.com]
Sent: 2018-01-07 6:48 AM
To: Anson Huang <[email protected]>
Cc: Stefano Babic <[email protected]>; Fabio Estevam <[email protected]>; Albert ARIBAUD <[email protected]>; Christian Gmeiner <[email protected]>; Peng Fan <[email protected]>; U-Boot-Denx <[email protected]>
Subject: Re: [U-Boot] [PATCH V2] imx: mx7: psci: add system reset support
Hi Anson,
Quoted 5 lines · Anson Huang
Thanks for the comments, the current reboot command works is just because wdog driver is enabled and when system reboot, the reboot notification callback in wdog driver will do reset. But if wdog is disabled in dtb, the reboot command will fail.

Quoted 8 lines

Quoted 3 lines
As now we use PSCI, the reboot operation will eventually call into u-boot's psci reset callback, we should support this feature, the reboot feature in Linux kernel should NOT depends on wdog's existence.
Ok, but what about erratum e10574 (Watchdog: A watchdog timeout or software trigger will not reset the SOC)?
According to this erratum WDOG_B pin needs to generate a system power on.

Correct, we need to enable WDA to toggle WDOG_B for reset, thanks. Will send a V3 patch set.

Anson.

Anson Huang

author

2018-01-07 06:27 UTC #7 lore raw

PATCH v2 1/1 imx: mx7: psci: add system reset support

In reply to Fabio Estevam

Best Regards!
Anson Huang

Quoted 19 lines

-----Original Message-----
From: Fabio Estevam [mailto:festevam at gmail.com]
Sent: 2018-01-07 6:48 AM
To: Anson Huang <[email protected]>
Cc: Stefano Babic <[email protected]>; Fabio Estevam <[email protected]>; Albert ARIBAUD <[email protected]>; Christian Gmeiner <[email protected]>; Peng Fan <[email protected]>; U-Boot-Denx <[email protected]>
Subject: Re: [U-Boot] [PATCH V2] imx: mx7: psci: add system reset support
Hi Anson,
Quoted 5 lines · Anson Huang
Thanks for the comments, the current reboot command works is just because wdog driver is enabled and when system reboot, the reboot notification callback in wdog driver will do reset. But if wdog is disabled in dtb, the reboot command will fail.

Quoted 8 lines

Quoted 3 lines
As now we use PSCI, the reboot operation will eventually call into u-boot's psci reset callback, we should support this feature, the reboot feature in Linux kernel should NOT depends on wdog's existence.
Ok, but what about erratum e10574 (Watchdog: A watchdog timeout or software trigger will not reset the SOC)?
According to this erratum WDOG_B pin needs to generate a system power on.

What should we do here? Writing 0x4 into WCR register will cause WDOG reset and WDOG_B will be asserted, if the board has WDOG_B connected to PMIC, then everything is right. Do you mean we need to handle the case of WDOG_B pin NOT connected to PMIC case? If the board has no such design, then the reset will be NOT safe using wdog.

Anson

Trent Piepho

2018-05-07 22:06 UTC #8 lore raw

PATCH v2 1/1 imx: mx7: psci: add system reset support

In reply to Anson Huang

arch/arm/mach-imx/mx7/psci-mx7.c __secure int imx_cpu_off(int cpu) · line 81

Quoted 9 lines · Anson Huang

Add i.MX7 PSCI system reset support, linux
kernel now can use "reboot" command to reset
system.
arch/arm/mach-imx/mx7/psci-mx7.c +4 -0
+__secure void imx_system_reset(void)
+{
+	writew(1 << 2, WDOG1_BASE_ADDR);
+}

This does not work properly on our board.

Due to an erratum in iMX7d it is necessary to wire the external WDOG_B signal to the pmic to cycle power in order to reset the board. The Linux IMX watchdog driver works when it does a reboot via the watchdog, but this code does not.

When the Linux drivers is configured for an external wdog signal, using a DT property, it sets WCR_SRS to prevent the internal system reset in response to watchdog triggering. When that is not done, as in this patch, the internal reset appears to reset the wdog module or iomux or something, which causes the imx7d to stop asserting the external wdog signal.

In my tests, this takes only about 2.4 Âµs. Such a short wdog_b pulse does not appear to be sufficient to trigger the pmic to cycle power.

When SRS is set, then the WDOG_B signal will remain asserted until the POR_B input signal to the imx7d is asserted. I.e., until pmic responds to the watchdog signal.

Peng Fan

2018-05-08 05:29 UTC #9 lore raw

PATCH v2 1/1 imx: mx7: psci: add system reset support

Quoted 16 lines

-----Original Message-----
From: Trent Piepho [mailto:tpiepho at impinj.com]
Sent: 2018年5月8日 6:07
To: christian.gmeiner at gmail.com; Peng Fan <[email protected]>; Anson Huang <[email protected]>; u-boot at lists.denx.de; albert.u.boot at aribaud.net; sbabic at denx.de
Cc: Fabio Estevam <[email protected]>
Subject: Re: [U-Boot,V2] imx: mx7: psci: add system reset support
Quoted 2 lines · Anson Huang
Add i.MX7 PSCI system reset support, linux kernel now can use "reboot" command to reset system.

Quoted 6 lines

arch/arm/mach-imx/mx7/psci-mx7.c __secure int imx_cpu_off(int cpu) · line 81
Quoted 4 lines
arch/arm/mach-imx/mx7/psci-mx7.c +4 -0
+__secure void imx_system_reset(void)
+{
+	writew(1 << 2, WDOG1_BASE_ADDR);
+}
This does not work properly on our board.

You could try write 0x14 to WDOG1_BASE_ADDR to see whether it works. Here using (1 << 2) triggers both SRS and WDOG_B which seems wrong.

-Peng.

Quoted 19 lines

Due to an erratum in iMX7d it is necessary to wire the external WDOG_B signal to the pmic to cycle power in order to reset the board. The Linux IMX watchdog driver works when it does a reboot via the watchdog, but this code does not.
When the Linux drivers is configured for an external wdog signal, using a DT property, it sets WCR_SRS to prevent the internal system reset in response to watchdog triggering. When that is not done, as in this patch, the internal reset appears to reset the wdog module or iomux or something, which causes the imx7d to stop asserting the external wdog signal.
In my tests, this takes only about 2.4 µs. Such a short wdog_b pulse does not appear to be sufficient to trigger the pmic to cycle power.
When SRS is set, then the WDOG_B signal will remain asserted until the POR_B input signal to the imx7d is asserted. I.e., until pmic responds to the watchdog signal.

Trent Piepho

2018-05-08 20:10 UTC #10 lore raw

PATCH v2 1/1 imx: mx7: psci: add system reset support

Quoted 21 lines · Peng Fan

Quoted 14 lines
-----Original Message-----
From: Trent Piepho [mailto:tpiepho at impinj.com]
Sent: 2018年5月8日 6:07
To: christian.gmeiner at gmail.com; Peng Fan <[email protected]>; Anson Huang <[email protected]>; u-boot at lists.denx.de; albert.u.boot at aribaud.net; sbabic at denx.de
Cc: Fabio Estevam <[email protected]>
Subject: Re: [U-Boot,V2] imx: mx7: psci: add system reset support
Quoted 2 lines · Anson Huang
Add i.MX7 PSCI system reset support, linux kernel now can use "reboot" command to reset system.
Quoted 6 lines
arch/arm/mach-imx/mx7/psci-mx7.c __secure int imx_cpu_off(int cpu) · line 81
Quoted 4 lines
arch/arm/mach-imx/mx7/psci-mx7.c +4 -0
+__secure void imx_system_reset(void)
+{
+	writew(1 << 2, WDOG1_BASE_ADDR);
+}
This does not work properly on our board.

Quoted 2 lines

You could try write 0x14 to WDOG1_BASE_ADDR to see whether it works. Here using (1 << 2) triggers both SRS and WDOG_B which seems wrong.

It works when the Linux driver does that and appears to work identically when uboot does it that way.

Triggering both SRS and WDOG_B does not work as it causes a very short wdog_b assertion.

There is a little difficulty here in just changing the code to use WCR_WDE|WCR_SRS, as that would be wrong if the board does not use an external signal. The Linux driver uses the device tree to determine what to do, but this will not work for PSCI.

Quoted 18 lines

Quoted 18 lines
Due to an erratum in iMX7d it is necessary to wire the external WDOG_B signal to the pmic to cycle power in order to reset the board. The Linux IMX watchdog driver works when it does a reboot via the watchdog, but this code does not.
When the Linux drivers is configured for an external wdog signal, using a DT property, it sets WCR_SRS to prevent the internal system reset in response to watchdog triggering. When that is not done, as in this patch, the internal reset appears to reset the wdog module or iomux or something, which causes the imx7d to stop asserting the external wdog signal.
In my tests, this takes only about 2.4 µs. Such a short wdog_b pulse does not appear to be sufficient to trigger the pmic to cycle power.
When SRS is set, then the WDOG_B signal will remain asserted until the POR_B input signal to the imx7d is asserted. I.e., until pmic responds to the watchdog signal.

Peng Fan

2018-05-09 01:13 UTC #11 lore raw

PATCH v2 1/1 imx: mx7: psci: add system reset support

Quoted 31 lines

-----Original Message-----
From: Trent Piepho [mailto:tpiepho at impinj.com]
Sent: 2018年5月9日 4:11
To: Peng Fan <[email protected]>; christian.gmeiner at gmail.com; Anson Huang <[email protected]>; u-boot at lists.denx.de; albert.u.boot at aribaud.net; sbabic at denx.de
Cc: Fabio Estevam <[email protected]>
Subject: Re: [U-Boot,V2] imx: mx7: psci: add system reset support
Quoted 19 lines · Peng Fan
Quoted 18 lines
-----Original Message-----
From: Trent Piepho [mailto:tpiepho at impinj.com]
Sent: 2018年5月8日 6:07
To: christian.gmeiner at gmail.com; Peng Fan <[email protected]>; Anson Huang <[email protected]>; u-boot at lists.denx.de; albert.u.boot at aribaud.net; sbabic at denx.de
Cc: Fabio Estevam <[email protected]>
Subject: Re: [U-Boot,V2] imx: mx7: psci: add system reset support
Review
Quoted 6 lines · Anson Huang
Add i.MX7 PSCI system reset support, linux kernel now can use "reboot" command to reset system.
(quoted diff) +2 -0
+__secure void imx_system_reset(void) {
+	writew(1 << 2, WDOG1_BASE_ADDR); }
This does not work properly on our board.

Quoted 8 lines

Quoted 2 lines
You could try write 0x14 to WDOG1_BASE_ADDR to see whether it works. Here using (1 << 2) triggers both SRS and WDOG_B which seems wrong.
It works when the Linux driver does that and appears to work identically when uboot does it that way.
Triggering both SRS and WDOG_B does not work as it causes a very short wdog_b assertion.

Yes.

Quoted 5 lines

There is a little difficulty here in just changing the code to use WCR_WDE|WCR_SRS, as that would be wrong if the board does not use an external signal. The Linux driver uses the device tree to determine what to do, but this will not work for PSCI.

U-Boot need parse the device tree and configure the WDOG accordingly.

-Peng

Quoted 19 lines

Quoted 19 lines
Quoted 19 lines
Due to an erratum in iMX7d it is necessary to wire the external WDOG_B signal to the pmic to cycle power in order to reset the board. The Linux IMX watchdog driver works when it does a reboot via the watchdog, but this code does not.
When the Linux drivers is configured for an external wdog signal, using a DT property, it sets WCR_SRS to prevent the internal system reset in response to watchdog triggering. When that is not done, as in this patch, the internal reset appears to reset the wdog module or iomux or something, which causes the imx7d to stop asserting the external wdog signal.
In my tests, this takes only about 2.4 µs. Such a short wdog_b pulse does not appear to be sufficient to trigger the pmic to cycle power.
When SRS is set, then the WDOG_B signal will remain asserted until the POR_B input signal to the imx7d is asserted. I.e., until pmic responds to the watchdog signal.

Trent Piepho

2018-05-09 19:22 UTC #12 lore raw

PATCH v2 1/1 imx: mx7: psci: add system reset support

Quoted 13 lines · Peng Fan

Quoted 13 lines
Quoted 11 lines · Anson Huang
Quoted 8 lines
Review
Quoted 6 lines
Add i.MX7 PSCI system reset support, linux kernel now can use "reboot" command to reset system.
(quoted diff) +2 -0
+__secure void imx_system_reset(void) {
+	writew(1 << 2, WDOG1_BASE_ADDR); }
This does not work properly on our board.
You could try write 0x14 to WDOG1_BASE_ADDR to see whether it works. Here using (1 << 2) triggers both SRS and WDOG_B which seems wrong.

Quoted 7 lines

Quoted 5 lines
It works when the Linux driver does that and appears to work identically when uboot does it that way.
Triggering both SRS and WDOG_B does not work as it causes a very short wdog_b assertion.
Yes.

In case it wasn't clear, this code is in the new 2018.05 u-boot release and I think will cause a problem for any imx7d board using the typical reset erratum option of connecting wdog_b to a pfuze3000 pmic's pwrwon pin.

An external watchdog monitor chip, I think as used on sabreD for instance, might still respond to the short pulse and allow it work.

Quoted 6 lines

Quoted 4 lines
There is a little difficulty here in just changing the code to use WCR_WDE|WCR_SRS, as that would be wrong if the board does not use an external signal. The Linux driver uses the device tree to determine what to do, but this will not work for PSCI.
U-Boot need parse the device tree and configure the WDOG accordingly.

Yes, but consider the difficulties:

There could be multiple Linux device trees, e.g. in a FIT image and chosen based on board revision. Should the PSCI code use the u-boot device tree? Which would then need to also have this board revision support. Or should it use the Linux DT, which it would need to get information from when the kernel DT is prepared before boot?

Of the five external watchdog signals from the iMX7d, which one should be used? I believe each imx watchdog configured in Linux will register a reset handler that are called in turn, so Linux should handle this ok. The uboot PSCI currently assumes wdog1 is the correct one to use.

The Linux driver interfaces with Linux pinctl to iomux the watchdog signal. The PSCI code is assuming the wdog signal is correctly muxed. Default iomux values doesn't have any wdog signal routed to a pin.

Not impossible, but it is not so simple as the original three lines of code might have made it seem at first glance.

If one has the Linux imx watchdog driver working, to use as watchdog, then one gets a wdog system reset for free with all the above taken care of. Which makes me wonder if disabling the PSCI reset might not be a better option in that situration.

Peng Fan

2018-05-10 01:53 UTC #13 lore raw

PATCH v2 1/1 imx: mx7: psci: add system reset support

Quoted 32 lines

-----Original Message-----
From: Trent Piepho [mailto:tpiepho at impinj.com]
Sent: 2018年5月10日 3:22
To: Peng Fan <[email protected]>; christian.gmeiner at gmail.com; Anson Huang <[email protected]>; u-boot at lists.denx.de; albert.u.boot at aribaud.net; sbabic at denx.de
Cc: Fabio Estevam <[email protected]>
Subject: Re: [U-Boot,V2] imx: mx7: psci: add system reset support
Quoted 2 lines · Peng Fan
Quoted 2 lines
Quoted 1 line · Anson Huang
Quoted 1 line
Quoted 1 line
Add i.MX7 PSCI system reset support, linux kernel now can use
"reboot"
Quoted 17 lines
Quoted 16 lines
Quoted 10 lines
Quoted 7 lines
Review
Quoted 5 lines
command to reset system.
(quoted diff) +2 -0
+__secure void imx_system_reset(void) {
+	writew(1 << 2, WDOG1_BASE_ADDR); }
This does not work properly on our board.
You could try write 0x14 to WDOG1_BASE_ADDR to see whether it works. Here using (1 << 2) triggers both SRS and WDOG_B which seems wrong.
It works when the Linux driver does that and appears to work identically when uboot does it that way.
Triggering both SRS and WDOG_B does not work as it causes a very short wdog_b assertion.

Quoted 8 lines

Quoted 1 line
Yes.
In case it wasn't clear, this code is in the new 2018.05 u-boot release and I think will cause a problem for any imx7d board using the typical reset erratum option of connecting wdog_b to a pfuze3000 pmic's pwrwon pin.
An external watchdog monitor chip, I think as used on sabreD for instance, might still respond to the short pulse and allow it work.

I understand this.

Quoted 21 lines

Quoted 7 lines
Quoted 5 lines
There is a little difficulty here in just changing the code to use WCR_WDE|WCR_SRS, as that would be wrong if the board does not use an external signal. The Linux driver uses the device tree to determine what to do, but this will not work for PSCI.
U-Boot need parse the device tree and configure the WDOG accordingly.
Yes, but consider the difficulties:
There could be multiple Linux device trees, e.g. in a FIT image and chosen based on board revision. Should the PSCI code use the u-boot device tree? Which would then need to also have this board revision support. Or should it use the Linux DT, which it would need to get information from when the kernel DT is prepared before boot?
Of the five external watchdog signals from the iMX7d, which one should be used? I believe each imx watchdog configured in Linux will register a reset handler that are called in turn, so Linux should handle this ok. The uboot PSCI currently assumes wdog1 is the correct one to use.

Quoted 6 lines

The Linux driver interfaces with Linux pinctl to iomux the watchdog signal. The PSCI code is assuming the wdog signal is correctly muxed.
Default iomux values doesn't have any wdog signal routed to a pin.
Not impossible, but it is not so simple as the original three lines of code might have made it seem at first glance.

The imx_system_reset might could be moved to per board specific. Then the board owner could have their own imeplementation.

Stefano, what do you think?

Quoted 5 lines

If one has the Linux imx watchdog driver working, to use as watchdog, then one gets a wdog system reset for free with all the above taken care of. Which makes me wonder if disabling the PSCI reset might not be a better option in that situration.

Just wonder, since you are using psci, you have the power related code ready?

-Peng.