linux-kernel - Re: [PATCH v6 1/2] clk: uniphier: add core support code for UniPhier clock driver

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Message-ID: <CAK7LNAQ9byodJTu-itbnhFrUGDQS5bxYUydyJ3zyZ+aLroQ6FA@mail.gmail.com>
Date:   Mon, 5 Sep 2016 13:02:26 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Stephen Boyd <sboyd@...eaurora.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Michael Turquette <mturquette@...libre.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "David S. Miller" <davem@...emloft.net>,
        Guenter Roeck <linux@...ck-us.net>
Subject: Re: [PATCH v6 1/2] clk: uniphier: add core support code for UniPhier
 clock driver

Hi Stephen,


2016-08-30 3:22 GMT+09:00 Stephen Boyd <sboyd@...eaurora.org>:
> On 08/29, Masahiro Yamada wrote:
>> Hi Stephen,
>>
>>
>> 2016-08-20 4:16 GMT+09:00 Stephen Boyd <sboyd@...eaurora.org>:
>> >>
>> >> >> +
>> >> >> +     parent = of_get_parent(dev->of_node); /* parent should be syscon node */
>> >> >> +     regmap = syscon_node_to_regmap(parent);
>> >> >> +     of_node_put(parent);
>> >> >
>> >> > devm_get_regmap(dev->parent) should work then? Why do we need to
>> >> > use OF APIs?
>> >>
>> >> "git grep devm_get_regmap" did not hit anything.
>> >>
>> >> Where is it defined?
>> >>
>> >
>> > Sorry I meant dev_get_regmap().
>> >
>>
>> I tried this, but it did not work.
>>
>> To make dev_get_regmap() work,
>> the parent device needs to call dev_regmap_init_mmio() beforehand.
>>
>>
>> Since commit bdb0066df96e74a4002125467ebe459feff1ebef
>> (mfd: syscon: Decouple syscon interface from platform devices),
>> syscon_probe() is not called for platform devices,
>> so that never happens.
>>
>
> Ok. Is the syscon also a simple-mfd?
>
> It sounds like there's a device for the parent, but we've failed
> to attach a regmap to it. Maybe the core DT code should assign
> the regmap to the parent device when it creates it so that child
> devices don't need to know this detail? It could look for
> simple-mfd devices with compatible = "syscon" and then create the
> regmap? Here's a totally untested patch for that.
>
> ----8<----
> diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
> index 2f2225e845ef..5f7d3f015b82 100644
> --- a/drivers/mfd/syscon.c
> +++ b/drivers/mfd/syscon.c
> @@ -136,6 +136,17 @@ struct regmap *syscon_node_to_regmap(struct device_node *np)
>  }
>  EXPORT_SYMBOL_GPL(syscon_node_to_regmap);
>
> +int device_attach_syscon(struct device *dev)
> +{
> +       struct regmap *regmap;
> +
> +       regmap = syscon_node_to_regmap(dev->of_node);
> +       if (IS_ERR(regmap))
> +               return PTR_ERR(regmap);
> +
> +       return regmap_attach_dev(dev, regmap, &syscon_regmap_config);
> +}
> +
>  struct regmap *syscon_regmap_lookup_by_compatible(const char *s)
>  {
>         struct device_node *syscon_np;
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index 8aa197691074..58a018e15006 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -25,6 +25,7 @@
>  #include <linux/of_irq.h>
>  #include <linux/of_platform.h>
>  #include <linux/platform_device.h>
> +#include <linux/mfd/syscon.h>
>
>  const struct of_device_id of_default_bus_match_table[] = {
>         { .compatible = "simple-bus", },
> @@ -383,7 +384,12 @@ static int of_platform_bus_create(struct device_node *bus,
>                 return 0;
>         }
>
> +
>         dev = of_platform_device_create_pdata(bus, bus_id, platform_data, parent);
> +       if (of_device_is_compatible(bus, "simple-mfd") &&
> +           of_device_is_compatible(bus, "syscon"))
> +               device_attach_syscon(&dev->dev);
> +
>         if (!dev || !of_match_node(matches, bus))
>                 return 0;
>
> diff --git a/include/linux/mfd/syscon.h b/include/linux/mfd/syscon.h
> index 40a76b97b7ab..e19e5d15f4e6 100644
> --- a/include/linux/mfd/syscon.h
> +++ b/include/linux/mfd/syscon.h
> @@ -18,9 +18,11 @@
>  #include <linux/err.h>
>  #include <linux/errno.h>
>
> +struct device;
>  struct device_node;
>
>  #ifdef CONFIG_MFD_SYSCON
> +extern int device_attach_syscon(struct device *dev);
>  extern struct regmap *syscon_node_to_regmap(struct device_node *np);
>  extern struct regmap *syscon_regmap_lookup_by_compatible(const char *s);
>  extern struct regmap *syscon_regmap_lookup_by_pdevname(const char *s);
> @@ -28,6 +30,11 @@ extern struct regmap *syscon_regmap_lookup_by_phandle(
>                                         struct device_node *np,
>                                         const char *property);
>  #else
> +static inline int device_attach_syscon(struct device *dev)
> +{
> +       return 0;
> +}
> +
>  static inline struct regmap *syscon_node_to_regmap(struct device_node *np)
>  {
>         return ERR_PTR(-ENOTSUPP);


I was not quire sure about this,
but maybe worth submitting to DT subsystem?

Anyway, I will go with syscon_node_to_regmap() for v7.
Of course, I am happy to replace it with dev_get_regmap()
when the issue is solved in the mainline.



-- 
Best Regards
Masahiro Yamada