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SubjectRe: [PATCH v4 1/1] mfd: Add I2C based System Configuaration (SYSCON) access
Hi Lee,

Am 2020-06-30 11:16, schrieb Michael Walle:
> I'm just trying to use this for my sl28 driver. Some remarks, see
> below.
>
> Am 2020-06-22 09:51, schrieb Lee Jones:
>> The existing SYSCON implementation only supports MMIO (memory mapped)
>> accesses, facilitated by Regmap. This extends support for registers
>> held behind I2C busses.
>>
>> Signed-off-by: Lee Jones <lee.jones@linaro.org>
>> ---
>> Changelog:
>>
>> v3 => v4
>> - Add ability to provide a non-default Regmap configuration
>>
>> v2 => v3
>> - Change 'is CONFIG' present check to include loadable modules
>> - s/#ifdef CONFIG_MFD_SYSCON_I2C/#if
>> IS_ENABLED(CONFIG_MFD_SYSCON_I2C)/
>>
>> v1 => v2
>> - Remove legacy references to OF
>> - Allow building as a module (fixes h8300 0-day issue)
>>
>> drivers/mfd/Kconfig | 7 +++
>> drivers/mfd/Makefile | 1 +
>> drivers/mfd/syscon-i2c.c | 104
>> +++++++++++++++++++++++++++++++++
>> include/linux/mfd/syscon-i2c.h | 36 ++++++++++++
>> 4 files changed, 148 insertions(+)
>> create mode 100644 drivers/mfd/syscon-i2c.c
>> create mode 100644 include/linux/mfd/syscon-i2c.h
>>
>
> [..]
>
>> +static struct regmap *syscon_i2c_get_regmap(struct i2c_client
>> *client,
>> + struct regmap_config *regmap_config)
>> +{
>> + struct device *dev = &client->dev;
>> + struct syscon *entry, *syscon = NULL;
>> +
>> + spin_lock(&syscon_i2c_list_slock);
>> +
>> + list_for_each_entry(entry, &syscon_i2c_list, list)
>> + if (entry->dev == dev) {
>> + syscon = entry;
>> + break;
>> + }
>> +
>> + spin_unlock(&syscon_i2c_list_slock);
>> +
>> + if (!syscon)
>> + syscon = syscon_i2c_register(client, regmap_config);
>> +
>> + if (IS_ERR(syscon))
>> + return ERR_CAST(syscon);
>> +
>> + return syscon->regmap;
>> +}
>> +
>> +struct regmap *syscon_i2c_to_regmap_config(struct i2c_client *client,
>> + struct regmap_config *regmap_config)
>> +{
>> + return syscon_i2c_get_regmap(client, regmap_config);
>> +}
>> +EXPORT_SYMBOL_GPL(syscon_i2c_to_regmap_config);
>> +
>> +struct regmap *syscon_i2c_to_regmap(struct i2c_client *client)
>> +{
>> + return syscon_i2c_get_regmap(client, &syscon_i2c_regmap_config);
>> +}
>> +EXPORT_SYMBOL_GPL(syscon_i2c_to_regmap);
>
> What do you think about
>
> struct regmap *syscon_i2c_to_regmap(struct device *dev)
> {
> struct i2c_client *client = i2c_verify_client(dev);
>
> if (!client)
> return ERR_PTR(-EINVAL);
>
> return syscon_i2c_get_regmap(client, &syscon_i2c_regmap_config);
> }
>
> Or even move it to syscon_i2c_get_regmap().
>
> This way, (a) a driver doesn't have to use "#include <linux/i2c.h>"
> just
> to call to_i2c_client() (or i2c_verify_client()) and (b) you won't do
> it
> all over again in all sub drivers.
>
> So you could just do a
> regmap = syscon_i2c_to_regmap(pdev->dev.parent);
>
> I've also noticed that the mmio syscon uses device_node as parameter.
> What
> was the reason to divert from that? Just curious.

How is this supposed to be used?

I had something like the following in mind:

&i2c {
cpld@4a {
compatible = "simple-mfd";
reg = <0x4a>;

gpio@4 {
compatible = "vendor,gpio";
reg = <0x4>;
};
};
};

But I think the childen are not enumerated if its an I2C device. And
the actual i2c driver is also missing.

-michael

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