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Message-ID: <dfe328fc-349b-3357-a8ac-6fc363f403fc@kernel.org>
Date:   Thu, 5 Jan 2023 22:53:58 +0100
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Subject: Re: [RFC PATCH 3/7] dt-bindings: bus: add STM32MP15 ETZPC firewall
 bus bindings
To:     Gatien CHEVALLIER <gatien.chevallier@foss.st.com>,
        alexandre.torgue@foss.st.com, robh+dt@kernel.org,
        Oleksii_Moisieiev@epam.com, linus.walleij@linaro.org,
        gregkh@linuxfoundation.org
Cc:     linux-stm32@st-md-mailman.stormreply.com,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        loic.pallardy@st.com, devicetree@vger.kernel.org,
        mark.rutland@arm.com, arnd@arndb.de
References: <20221221173055.11719-1-gatien.chevallier@foss.st.com>
 <20221221173055.11719-4-gatien.chevallier@foss.st.com>
 <879325d2-4b2d-bc1d-310c-ece4c449ad8f@kernel.org>
 <8357d887-c8ab-39bc-4ef0-62e9225fb2a6@foss.st.com>
 <118e7f0c-bf5d-4bda-ee70-92eb2b71649c@kernel.org>
 <8f022dc8-d728-ba91-35ed-8a4006855f0d@foss.st.com>
Content-Language: en-US
From:   Krzysztof Kozlowski <krzk@kernel.org>
In-Reply-To: <8f022dc8-d728-ba91-35ed-8a4006855f0d@foss.st.com>
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On 04/01/2023 14:43, Gatien CHEVALLIER wrote:
> Hello Krzysztof,
> 
> On 12/22/22 14:57, Krzysztof Kozlowski wrote:
>> On 22/12/2022 14:51, Gatien CHEVALLIER wrote:
>>> Hello,
>>>
>>> On 12/22/22 11:26, Krzysztof Kozlowski wrote:
>>>> On 21/12/2022 18:30, Gatien Chevallier wrote:
>>>>> Adds the list of peripherals IDs under firewall bus on STM32MP15.
>>>>>
>>>>> Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
>>>>> ---
>>>>>    include/dt-bindings/bus/stm32mp15_sys_bus.h | 98 +++++++++++++++++++++
>>>>>    1 file changed, 98 insertions(+)
>>>>>    create mode 100644 include/dt-bindings/bus/stm32mp15_sys_bus.h
>>>>>
>>>>> diff --git a/include/dt-bindings/bus/stm32mp15_sys_bus.h b/include/dt-bindings/bus/stm32mp15_sys_bus.h
>>>>> new file mode 100644
>>>>> index 000000000000..97eacc7b5f16
>>>>> --- /dev/null
>>>>> +++ b/include/dt-bindings/bus/stm32mp15_sys_bus.h
>>>>
>>>> That's wrong in multiple ways:
>>>> 1. No underscores
>>>> 2. Missing vendor prefix
>>>> 3. Name not matching compatible.
>>>
>>> Sure, will comply in V3.
>>>
>>>>
>>>>> @@ -0,0 +1,98 @@
>>>>> +/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) */
>>>>> +/*
>>>>> + * Copyright (C) STMicroelectronics 2022 - All Rights Reserved
>>>>> + */
>>>>> +#ifndef _DT_BINDINGS_BUS_STM32MP15_SYS_BUS_H
>>>>> +#define _DT_BINDINGS_BUS_STM32MP15_SYS_BUS_H
>>>>> +
>>>>> +/* ETZPC IDs */
>>>>> +#define STM32MP1_ETZPC_STGENC_ID	0
>>>>> +#define STM32MP1_ETZPC_BKPSRAM_ID	1
>>>>> +#define STM32MP1_ETZPC_IWDG1_ID		2
>>>>> +#define STM32MP1_ETZPC_USART1_ID	3
>>>>> +#define STM32MP1_ETZPC_SPI6_ID		4
>>>>> +#define STM32MP1_ETZPC_I2C4_ID		5
>>>>> +/* ID 6 reserved */
>>>>
>>>> Reserved why? These are IDs so they start from 0 and go by 0. Don't
>>>> hard-code some register offsets.
>>>
>>> Here, I do define IDs. Some appear as reserved based on what I've seen
>>> in the SoC datasheet that states these as "indexes"
>>>
>>> Please see the table 94 in chapter 15.6 (ETZPC) of the STM32MP157
>>> Reference manual:
>>> [1] https://www.st.com/resource/en/reference_manual/DM00327659-.pdf
>>
>> Then why do you define them in bindings? Use raw numbers. Do you see
>> anywhere in arm/arm64 bindings for GIC_SPI interrupt numbers?
>>
> 
> What would you think of simply removing the comments that state that IDs 
> are reserved, mimicking the way it is for qcom bindings? Fundamentally, 
> they are indeed only IDs and could be raw numbers.

If these are IDs then there are no reserved numbers and they are
continuous from 0 to X. Without gaps.

> IMO, this makes reading the device tree harder. Because you'd have to 
> look what the raw number corresponds to.

Sure, but that's not the reason to put numbers to the bindings... You
mix defines with bindings.

> To take an example, it has already been done for SCMI clocks and I find 
> it eases comprehension.

You need to be a bit more specific...

Anyway, IDs should be placed in bindings. Some mapping of
internal/hardware ports, registers, offsets, values - usually not.

I don't know where exactly your case fits, but when some IDs are
reserved it is a clear sign that these are not IDs (again - IDs start
from 0 and go incrementally by one, without gaps).


Best regards,
Krzysztof