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

From: Jerome Brunet <[email-masked]>
Date: Thu, 19 Sep 2019 18:26:15 +0200

On Wed 18 Sep 2019 at 14:36, Qianggui Song <[email-masked]> wrote:

> On 2019/9/17 22:07, Jerome Brunet wrote:
>> 
>> On Tue 17 Sep 2019 at 13:51, Qianggui Song <[email-masked]> 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.
>> 
> For #1. It would be like
> generic_parse_dt()
> {
> 	1. parse all register regions (mux gpio pull pull_en ds)
> 	
> 	2. call  specific function through function pointer in
>  	   meson_pinctrl_data.(each platform should have AO and EE two
>            specific functions for they are not the same)
> 	{
> 		do work you mentioned above
> 	}
> }
> right ?
> If that so, maybe there are a lot of duplicated codes

Only if you make it so. Providing a callback and duplicating code are
not the same thing

> for most Socs share the same reg layout.

That's not really accurate:

So far they all have the "mux" and "gpio" region but

gxbb, gxl, axg, meson8 EE:
 has: pull, pull-en
 remap: non
 unsupported: ds

gxbb, gxl, axg, meson8 AO:
 has: pull
 remap: pull-en -> pull
 unsupported: ds

g12 and sm1 EE:
 has: pull, pull-en, ds
 remap: none

g12 and sm1 AO:
 has: ds
 remap: pull->gpio, pull_en->gpio

And now a1 chip remaps "ds" to "pull_en" ...

As said previouly all this is getting pretty difficult to follow and
maintain. Adding a proper callback for each meson pinctrl would make the
above explicit in the code ... which helps maintain thing, at least for
a while ...

Judging by the offsets between those regions, I still think one single
region would make things a whole lot simpler. If it is not possible to
map it with one single region, could you tell us why ? What non-pinctrl
related device do we have there ?

> So I guess five specific functions are
> enough: AXG and before(ao,ee), G12A(ao,ee) and A1(will place them in
> pinctrl_meson.c). Since m8 to AXG are the same register layout for both
> ee and ao, G12A with new feature ds and new ao register layout.
>
> Or I misunderstood the #1 ?
>>>>> +		} 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 {
>>>>
>>>> .
>>>>
>> 
>> .
>> 

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