From: Ahmad Fatoum <a.fatoum@pengutronix.de>
To: Alexandre Torgue <alexandre.torgue@st.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>,
Alexandre Torgue <alexandre.torgue@st.com>,
Christophe Roullier <christophe.roullier@st.com>,
Sascha Hauer <kernel@pengutronix.de>,
Arnaud Pouliquen <arnaud.pouliquen@st.com>,
devicetree@vger.kernel.org,
"moderated list:ARM/STM32 ARCHITECTURE"
<linux-stm32@st-md-mailman.stormreply.com>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Rob Herring <robh@kernel.org>
Subject: Re: [PATCH v2 1/2] dt-bindings: arm: stm32: add simple-mfd compatible for tamp node
Date: Tue, 10 Nov 2020 11:27:57 +0100 [thread overview]
Message-ID: <20d5ccf8-c98f-fe3c-767b-1ad99be9dd19@pengutronix.de> (raw)
In-Reply-To: <CAL_JsqL8sjw1o6PzCSRM9FtRx7XLDQg2bWXxo4Yw5t6fnroudw@mail.gmail.com>
Hello Alex,
On 10/27/20 1:15 PM, Rob Herring wrote:
> On Mon, Oct 26, 2020 at 4:30 PM Ahmad Fatoum <a.fatoum@pengutronix.de> wrote:
>>
>> Hello Rob,
>>
>> On 10/26/20 3:36 PM, Rob Herring wrote:
>>> On Wed, Oct 21, 2020 at 12:28:55PM +0200, Ahmad Fatoum wrote:
>>>> The stm32mp1 TAMP (Tamper and backup registers) does tamper detection
>>>> and features 32 backup registers that, being in the RTC domain, may
>>>> survive even with Vdd switched off.
>>>>
>>>> This makes it suitable for use to communicate a reboot mode from OS
>>>> to bootloader via the syscon-reboot-mode binding. Add a "simple-mfd"
>>>> to support probing such a child node. The actual reboot mode
>>>> node could then be defined in a board.dts or fixed up by the bootloader.
>>>
>>> 'simple-mfd' implies there is no dependency on the parent node for the
>>> child (such as the regmap perhaps). Is that the case here?
>>
>> No, there's a dependency and the Linux driver does syscon_node_to_regmap
>> on the device tree node's parent but that's how the syscon-reboot-mode binding
>> is documented:
>>
>> The SYSCON mapped register is retrieved from the
>> parental dt-node plus the offset. So the SYSCON reboot-mode node
>> should be represented as a sub-node of a "syscon", "simple-mfd" node.
>>
>> How would you prefer this being done instead?
>
> Well, probably the syscon driver could just probe any children, but
> I'm not sure if that would break anyone. So I guess fine as-is.
>
> Reviewed-by: Rob Herring <robh@kernel.org>
Gentle ping.
>
> Rob
>
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prev parent reply other threads:[~2020-11-10 10:28 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-21 10:28 [PATCH v2 1/2] dt-bindings: arm: stm32: add simple-mfd compatible for tamp node Ahmad Fatoum
2020-10-21 10:28 ` [PATCH v2 2/2] ARM: dts: stm32: support child mfd cells for the stm32mp1 TAMP syscon Ahmad Fatoum
2020-11-17 11:18 ` Alexandre Torgue
2020-10-26 14:36 ` [PATCH v2 1/2] dt-bindings: arm: stm32: add simple-mfd compatible for tamp node Rob Herring
2020-10-26 21:30 ` Ahmad Fatoum
2020-10-27 12:15 ` Rob Herring
2020-11-10 10:27 ` Ahmad Fatoum [this message]
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