linux-kernel - Re: [PATCH v3 0/6] Add support to retrieve the bootstatus from watchdog for RZ/V2H(P) SoC

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Message-ID: <e74391e7-c7ab-422b-9dab-dbde9ce55204@roeck-us.net>
Date: Tue, 14 Jan 2025 12:17:08 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Rob Herring <robh@...nel.org>, Biju Das <biju.das.jz@...renesas.com>
Cc: Prabhakar <prabhakar.csengg@...il.com>,
 Geert Uytterhoeven <geert+renesas@...der.be>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Wim Van Sebroeck
 <wim@...ux-watchdog.org>, Magnus Damm <magnus.damm@...il.com>,
 Wolfram Sang <wsa+renesas@...g-engineering.com>,
 "linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
 "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
 Fabrizio Castro <fabrizio.castro.jz@...esas.com>,
 Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH v3 0/6] Add support to retrieve the bootstatus from
 watchdog for RZ/V2H(P) SoC

On 1/14/25 12:03, Rob Herring wrote:
> On Mon, Jan 13, 2025 at 11:38:08AM +0000, Biju Das wrote:
>> Hi Prabhakar,
>>
>>> -----Original Message-----
>>> From: Prabhakar <prabhakar.csengg@...il.com>
>>> Sent: 13 January 2025 11:24
>>> Subject: [PATCH v3 0/6] Add support to retrieve the bootstatus from watchdog for RZ/V2H(P) SoC
>>>
>>> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
>>>
>>> Hi All,
>>>
>>> This patch series adds SYSCON support to retrieve boot status information for RZ/V2H(P) SoC.
>>> Summary of Changes,
>>>
>>>      Clock:
>>>          Add syscon compatible support to the CPG block in bindings and
>>>          device trees.
>>>
>>>      Watchdog:
>>>          Document the renesas,r9a09g057-syscon-wdt-errorrst property.
>>>          Update the watchdog driver to fetch and report boot status via
>>>          Error Reset Registers (CPG_ERROR_RSTm).
>>>
>>>      Device Tree:
>>>          Add the syscon property to CPG and WDT nodes in R9A09G057 and
>>>          R9A09G047 SoC DTSI.
>>>
>>> These changes enable the watchdog driver to identify boot sources like Power-on Reset and Watchdog
>>> Reset, improving system diagnostics.
>>
>> This means that, we should assume U-boot/bootloader should not clear the WDT reset status bit.
>>
>> If they clear it, there should be a way to propagate it from u-boot/bootloader to linux,
>> otherwise, we get wrong bootstatus in linux.
>> But the clearing of watchdog status by one of the cases:
>>
>> 1) u-boot identify the boot source and clear the status bit
>> 2) u-boot identify the boot source and does not clear the status bit, but linux clear it.
>> 3) u-boot does not touch WDT status bits, but linux clear it.
> 
> Sounds like the same problem as this[1]. If that works for you, please
> comment there. Always better if there is more than 1 user for something
> "common".
> 
> Rob
> 
> [1]https://lore.kernel.org/devicetree-spec/48defa98-9718-4997-86cb-b171187708a6@cherry.de/T/#u

If this ends up being provided through /chosen, it should probably be supported
in the watchdog core.

Guenter