linux-kernel - Re: [PATCH 5/5] pinctrl: mediatek: Add initial pinctrl driver for MT6797 SoC

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Date:   Tue, 16 Oct 2018 15:58:41 +0200
From:   Matthias Brugger <matthias.bgg@...il.com>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     sean.wang@...iatek.com, linus.walleij@...aro.org,
        robh+dt@...nel.org, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, amit.kucheria@...aro.org,
        Mars Cheng <mars.cheng@...iatek.com>
Subject: Re: [PATCH 5/5] pinctrl: mediatek: Add initial pinctrl driver for
 MT6797 SoC



On 11/10/2018 18:44, Manivannan Sadhasivam wrote:
> On Thu, Oct 11, 2018 at 05:50:19PM +0200, Matthias Brugger wrote:
>>
>>
>> On 08/10/2018 21:14, Manivannan Sadhasivam wrote:
>>> Add initial pinctrl driver for Mediatek MT6797 SoC supporting only
>>> GPIO and pinmux configurations.
>>>
>>> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
>>> ---
>>>  drivers/pinctrl/mediatek/Kconfig              |    7 +
>>>  drivers/pinctrl/mediatek/Makefile             |    1 +
>>>  drivers/pinctrl/mediatek/pinctrl-mt6797.c     |   82 +
>>>  drivers/pinctrl/mediatek/pinctrl-mtk-mt6797.h | 2430 +++++++++++++++++
>>>  4 files changed, 2520 insertions(+)
>>>  create mode 100644 drivers/pinctrl/mediatek/pinctrl-mt6797.c
>>>  create mode 100644 drivers/pinctrl/mediatek/pinctrl-mtk-mt6797.h
>>>
>> [...]
>>> diff --git a/drivers/pinctrl/mediatek/pinctrl-mtk-mt6797.h b/drivers/pinctrl/mediatek/pinctrl-mtk-mt6797.h
>>> new file mode 100644
>>> index 000000000000..8949d2a15c39
>>> --- /dev/null
>>> +++ b/drivers/pinctrl/mediatek/pinctrl-mtk-mt6797.h
>>> @@ -0,0 +1,2430 @@
>>> +/* SPDX-License-Identifier: GPL-2.0 */
>>> +/*
>>> + * Based on pinctrl-mtk-mt6765.h
>>> + *
>>> + * Copyright (C) 2018 MediaTek Inc.
>>> + *
>>> + * Author: ZH Chen <zh.chen@...iatek.com>
>>> + *
>>> + * Copyright (c) 2018 Manivannan Sadhasivam
>>> + */
>>> +
>>> +#ifndef __PINCTRL_MTK_MT6797_H
>>> +#define __PINCTRL_MTK_MT6797_H
>>> +
>>> +#include "pinctrl-paris.h"
>>> +
>>> +static const struct mtk_pin_desc mtk_pins_mt6797[] = {
>>> +	MTK_PIN(
>>> +		0, "GPIO0",
>>> +		MTK_EINT_FUNCTION(NO_EINT_SUPPORT, NO_EINT_SUPPORT),
>>> +		DRV_GRP3,
>>
>> As far as I have seen, you put all pins in driving group 3, but from the public
>> available "Functional Specification" (page 51-81) I can see that there exist
>> several driving groups:
>> 2/4/6/8 mA (DRV_GRP3)
>> 4/8/12/16 mA (not sure which group this is)
>> 2/4/6/8/10/12/14/16 mA (DRV_GRP4).
>>
> 
> Not sure about that. But I derived the configuration from DRV_CFGx
> registers available in "Application Software Register Table - Part 1"
> from page no: 906.
> 
> This register supports 2/4/6/8mA and this belongs to DRV_GRP2/DRV_GRP3
> [1].

I can see other driving groups as defined in the "Functional Specification" [1]
which gets also reflected in the "Application Software Register Table - Part 1"
[2], see for example page 852.

CCing Mars, maybe he can help to clarify.

Regards,
Matthias

[1]
https://www.96boards.org/documentation/consumer/mediatekx20/additional-docs/docs/MT6797_Functional_Specification_V1_0.pdf
[2]
https://www.96boards.org/documentation/consumer/mediatekx20/additional-docs/docs/MT6797_Register_Table_Part_1.pdf

> 
> Still I'm not fully confident of my choice here. Maybe Sean can throw
> some inputs!
> 
> Thanks,
> Mani
> 
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.c#n40
> 
>> Regards,
>> Matthias
>>