linux-kernel - Re: [PATCH 2/3] pinctrl: meson-a1: add pinctrl driver for Meson A1 Soc

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Message-ID: <1j8sqn3tjt.fsf@starbuckisacylon.baylibre.com>
Date:   Tue, 17 Sep 2019 16:07:34 +0200
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Qianggui Song <qianggui.song@...ogic.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        linux-gpio@...r.kernel.org, Xingyu Chen <xingyu.chen@...ogic.com>,
        Jianxin Pan <jianxin.pan@...ogic.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Carlo Caione <carlo@...one.org>,
        "Rob Herring" <robh+dt@...nel.org>,
        Hanjie Lin <hanjie.lin@...ogic.com>,
        "Mark Rutland" <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] pinctrl: meson-a1: add pinctrl driver for Meson A1 Soc


On Tue 17 Sep 2019 at 13:51, Qianggui Song <qianggui.song@...ogic.com> wrote:
>>> diff --git a/drivers/pinctrl/meson/pinctrl-meson.c b/drivers/pinctrl/meson/pinctrl-meson.c
>>> index 8bba9d0..885b89d 100644
>>> --- a/drivers/pinctrl/meson/pinctrl-meson.c
>>> +++ b/drivers/pinctrl/meson/pinctrl-meson.c
>>> @@ -688,8 +688,12 @@ static int meson_pinctrl_parse_dt(struct meson_pinctrl *pc,
>>>  
>>>  	pc->reg_ds = meson_map_resource(pc, gpio_np, "ds");
>>>  	if (IS_ERR(pc->reg_ds)) {
>>> -		dev_dbg(pc->dev, "ds registers not found - skipping\n");
>>> -		pc->reg_ds = NULL;
>>> +		if (pc->data->reg_layout == A1_LAYOUT) {
>>> +			pc->reg_ds = pc->reg_pullen;
>> 
>> IMO, this kind of ID based init fixup is not going to scale and will
>> lead to something difficult to maintain in the end.
>> 
>> The way the different register sets interract with each other is already
>> pretty complex to follow.
>> 
>> You could rework this in 2 different ways:
>> #1 - Have the generic function parse all the register sets and have all
>> drivers provide a specific (as in gxbb, gxl, axg, etc ...)  function to :
>>  - Verify the expected sets have been provided
>>  - Make assignement fixup as above if necessary
>> 
>> #2 - Rework the driver to have only one single register region
>>  I think one of your colleague previously mentionned this was not
>>  possible. It is still unclear to me why ...
>> 
> Appreciate your advice.  I have an idea based on #1, how about providing
> only two dt parse function, one is for chips before A1(the old one),
> another is for A1 and later chips that share the same layout. Assign
> these two functions to their own driver.

That's roughly the same thing as your initial proposition with function
pointer instead of IDs ... IMO, this would still be a quick fix to
address your immediate topic instead of dealing with the driver as
whole, which is my concern here.

>>> +		} else {
>>> +			dev_dbg(pc->dev, "ds registers not found - skipping\n");
>>> +			pc->reg_ds = NULL;
>>> +		}
>>>  	}
>>>  
>>>  	return 0;
>>> diff --git a/drivers/pinctrl/meson/pinctrl-meson.h b/drivers/pinctrl/meson/pinctrl-meson.h
>>> index c696f32..3d0c58d 100644
>>> --- a/drivers/pinctrl/meson/pinctrl-meson.h
>>> +++ b/drivers/pinctrl/meson/pinctrl-meson.h
>>> @@ -80,6 +80,14 @@ enum meson_pinconf_drv {
>>>  };
>>>  
>>>  /**
>>> + * enum meson_reg_layout - identify two types of reg layout
>>> + */
>>> +enum meson_reg_layout {
>>> +	LEGACY_LAYOUT,
>>> +	A1_LAYOUT,
>>> +};
>>> +
>>> +/**
>>>   * struct meson bank
>>>   *
>>>   * @name:	bank name
>>> @@ -114,6 +122,7 @@ struct meson_pinctrl_data {
>>>  	unsigned int num_banks;
>>>  	const struct pinmux_ops *pmx_ops;
>>>  	void *pmx_data;
>>> +	unsigned int reg_layout;
>>>  };
>>>  
>>>  struct meson_pinctrl {
>> 
>> .
>>