linux-kernel - Re: [PATCH 07/10] arm64: dts: st: add RIFSC as a domain controller for STM32MP25x boards

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Message-ID: <1faa5511-a341-9c17-5e2a-974f8139d1d6@foss.st.com>
Date:   Tue, 25 Jul 2023 16:07:49 +0200
From:   Gatien CHEVALLIER <gatien.chevallier@...s.st.com>
To:     Alexandre TORGUE <alexandre.torgue@...s.st.com>,
        <Oleksii_Moisieiev@...m.com>, <gregkh@...uxfoundation.org>,
        <herbert@...dor.apana.org.au>, <davem@...emloft.net>,
        <robh+dt@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
        <conor+dt@...nel.org>, <vkoul@...nel.org>, <jic23@...nel.org>,
        <olivier.moysan@...s.st.com>, <arnaud.pouliquen@...s.st.com>,
        <mchehab@...nel.org>, <fabrice.gasnier@...s.st.com>,
        <andi.shyti@...nel.org>, <ulf.hansson@...aro.org>,
        <edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
        <hugues.fruchet@...s.st.com>, <lee@...nel.org>, <will@...nel.org>,
        <catalin.marinas@....com>, <arnd@...nel.org>,
        <richardcochran@...il.com>
CC:     <linux-crypto@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <dmaengine@...r.kernel.org>,
        <linux-i2c@...r.kernel.org>, <linux-iio@...r.kernel.org>,
        <alsa-devel@...a-project.org>, <linux-media@...r.kernel.org>,
        <linux-mmc@...r.kernel.org>, <netdev@...r.kernel.org>,
        <linux-phy@...ts.infradead.org>, <linux-serial@...r.kernel.org>,
        <linux-spi@...r.kernel.org>, <linux-usb@...r.kernel.org>
Subject: Re: [PATCH 07/10] arm64: dts: st: add RIFSC as a domain controller
 for STM32MP25x boards

Hi Alex,

On 7/6/23 11:30, Gatien CHEVALLIER wrote:
> Hi Alex,
> 
> On 7/6/23 11:25, Alexandre TORGUE wrote:
>> Hi Gatien
>>
>> On 7/5/23 19:27, Gatien Chevallier wrote:
>>> RIFSC is a firewall controller. Change its compatible so that is matches
>>> the documentation and reference RIFSC as a feature-domain-controller.
>>>
>>> Signed-off-by: Gatien Chevallier <gatien.chevallier@...s.st.com>
>>> ---
>>>   arch/arm64/boot/dts/st/stm32mp251.dtsi | 5 ++++-
>>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/arm64/boot/dts/st/stm32mp251.dtsi 
>>> b/arch/arm64/boot/dts/st/stm32mp251.dtsi
>>> index 5268a4321841..62101084cab8 100644
>>> --- a/arch/arm64/boot/dts/st/stm32mp251.dtsi
>>> +++ b/arch/arm64/boot/dts/st/stm32mp251.dtsi
>>> @@ -106,17 +106,20 @@ soc@0 {
>>>           ranges = <0x0 0x0 0x0 0x80000000>;
>>>           rifsc: rifsc-bus@...80000 {
>>> -            compatible = "simple-bus";
>>> +            compatible = "st,stm32mp25-rifsc";
>>
>> You could keep "simple-bus" compatible (in second position). In case 
>> of the RIFSC is not probed, the platform will be able to boot. If you 
>> agree you can use the same for ETZPC.
>>
>> Cheers
>> Alex
> 
> Sure, good point.
> 
> I'll change that in V2
> 
> Best regards,
> Gatien

Actually, it would be a bad idea to keep "simple-bus" as a compatible.

Practical example:
1) Firewall controller forbids a device probe by marking the device's
node as populated (OF_POPULATED flag).
2) The simple-bus, which is simple, populates all the devices
from the device tree data, overriding what the firewall bus has done.
3)=>Forbidden device's driver will be probed.

I think it's best to keep one compatible. If someone wants these drivers
as external modules, then it'll be best to handle this differently.
I'll resubmit with a single compatible for V2, please do not
hesitate to comment on the V2 if you're not okay with this.

Best regards,
Gatien

>>
>>>               reg = <0x42080000 0x1000>;
>>>               #address-cells = <1>;
>>>               #size-cells = <1>;
>>>               ranges;
>>> +            feature-domain-controller;
>>> +            #feature-domain-cells = <1>;
>>>               usart2: serial@...e0000 {
>>>                   compatible = "st,stm32h7-uart";
>>>                   reg = <0x400e0000 0x400>;
>>>                   interrupts = <GIC_SPI 115 IRQ_TYPE_LEVEL_HIGH>;
>>>                   clocks = <&ck_flexgen_08>;
>>> +                feature-domains = <&rifsc 32>;
>>>                   status = "disabled";
>>>               };
>>>           };
>>