linux-kernel - Re: [PATCH v3 1/3] dt-bindings: pinctrl: Add support for Amlogic A4 SoCs

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Message-ID: <fdb4d0eb-a5e5-4061-b3cc-14958473baf3@linaro.org>
Date: Mon, 21 Oct 2024 09:38:44 +0200
From: neil.armstrong@...aro.org
To: Krzysztof Kozlowski <krzk@...nel.org>,
 Jerome Brunet <jbrunet@...libre.com>, Xianwei Zhao <xianwei.zhao@...ogic.com>
Cc: Linus Walleij <linus.walleij@...aro.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Kevin Hilman <khilman@...libre.com>,
 Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
 Bartosz Golaszewski <brgl@...ev.pl>, linux-gpio@...r.kernel.org,
 devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/3] dt-bindings: pinctrl: Add support for Amlogic A4
 SoCs

On 18/10/2024 17:31, Krzysztof Kozlowski wrote:
> On 18/10/2024 14:31, Neil Armstrong wrote:
>> On 18/10/2024 12:13, Krzysztof Kozlowski wrote:
>>> On 18/10/2024 11:20, Jerome Brunet wrote:
>>>> On Fri 18 Oct 2024 at 17:01, Xianwei Zhao <xianwei.zhao@...ogic.com> wrote:
>>>>
>>>>> Hi Jerome,
>>>>>      Thanks for your reply.
>>>>>
>>>>> On 2024/10/18 16:39, Jerome Brunet wrote:
>>>>>> [ EXTERNAL EMAIL ]
>>>>>> On Fri 18 Oct 2024 at 10:28, Krzysztof Kozlowski <krzk@...nel.org> wrote:
>>>>>>
>>>>>>> On 18/10/2024 10:10, Xianwei Zhao via B4 Relay wrote:
>>>>>>>> From: Xianwei Zhao <xianwei.zhao@...ogic.com>
>>>>>>>>
>>>>>>>> Add the new compatible name for Amlogic A4 pin controller, and add
>>>>>>>> a new dt-binding header file which document the detail pin names.
>>>>>> the change does not do what is described here. At least the description
>>>>>> needs updating.
>>>>>>
>>>>>
>>>>> Will do.
>>>>>
>>>>>> So if the pin definition is now in the driver, does it mean that pins have
>>>>>> to be referenced in DT directly using the made up numbers that are
>>>>>> created in pinctrl-amlogic-a4.c at the beginning of patch #2 ?
>>>>>>
>>>>>
>>>>> Yes.
>>>>>
>>>>>> If that's case, it does not look very easy a read.
>>>>>>
>>>>>
>>>>> It does happen. The pin definition does not fall under the category of
>>>>> binding.
>>>>>
>>>>> https://lore.kernel.org/all/106f4321-59e8-49b9-bad3-eeb57627c921@amlogic.com/
>>>>
>>>> So the expectation is that people will write something like:
>>>>
>>>>    reset-gpios = <&gpio 42 GPIO_ACTIVE_LOW>;
>>>>
>>>> And others will go in the driver to see that is maps to GPIOX_10 ? the number
>>>> being completly made up, with no link to anything HW/Datasheet
>>>> whatsoever ?
>>>>
>>>> This is how things should be done now ?
>>>
>>> Why would you need to do this? Why it cannot be <&gpio 10
>>> GPIO_ACTIVE_LOW>, assuming it is GPIO 10?
>>>
>>> Bindings have absolutely nothing to do with it. You have GPIO 10, not
>>> 42, right?
>>
>> There's no 1:1 mapping between the number and the pin on Amlogic platforms,
>> so either a supplementary gpio phandle cell is needed to encode the gpio pin
>> group or some bindings header is needed to map those to well known identifiers.
> 
> So I assume this is not linear mapping (simple offset)? If so, this fits
> the binding header with identifiers, but I have impression these were
> not really used in earlier versions of this patchset. Instead some offsets:
> https://lore.kernel.org/all/20241014-a4_pinctrl-v2-1-3e74a65c285e@amlogic.com/
> 
> and pre-proccessor.
> 
> These looked almost good:
> https://lore.kernel.org/all/20240613170816.GA2020944-robh@kernel.org/
> 
> but then 0 -> 0
> 1 -> 1
> so where is this need for IDs?

???

Of courses the first pins maps to linear values...

> 
> See also last comment from Rob in above email.

OK so I looked and v2 was in fact correct:
https://lore.kernel.org/all/20241014-a4_pinctrl-v2-1-3e74a65c285e@amlogic.com/

====><=================
+/* Standard port */
+#define GPIOB_START	0
+#define GPIOB_NUM	14
+
+#define GPIOD_START	(GPIOB_START + GPIOB_NUM)
+#define GPIOD_NUM	16
+
+#define GPIOE_START	(GPIOD_START + GPIOD_NUM)
+#define GPIOE_NUM	2
+
+#define GPIOT_START	(GPIOE_START + GPIOE_NUM)
+#define GPIOT_NUM	23
+
+#define GPIOX_START	(GPIOT_START + GPIOT_NUM)
+#define GPIOX_NUM	18
+
+#define PERIPHS_PIN_NUM	(GPIOX_START + GPIOX_NUM)
+
+/* Aobus port */
+#define GPIOAO_START	0
+#define GPIOAO_NUM	7
+
+/* It's a special definition, put at the end, just 1 num */
+#define	GPIO_TEST_N	(GPIOAO_START +  GPIOAO_NUM)
+#define	AOBUS_PIN_NUM	(GPIO_TEST_N + 1)
+
+#define AMLOGIC_GPIO(port, offset)	(port##_START + (offset))
====><=================

is exactly what rob asked for, and you nacked it.

Neil


> 
> Best regards,
> Krzysztof
>