Re: [PATCH v2 2/2] mfd: ene-kb3930: Add driver for ENE KB3930 Embedded Controller

[Lee Jones <lee.jones@linaro.org>]

On Sat, 25 Apr 2020, Lubomir Rintel wrote:

> This driver provides access to the EC RAM of said embedded controller
> attached to the I2C bus as well as optionally supporting its slightly weird
> power-off/restart protocol.
> 
> A particular implementation of the EC firmware can be identified by a
> model byte. If this driver identifies the Dell Ariel platform, it
> registers the appropriate cells.
> 
> Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
> ---
>  drivers/mfd/Kconfig      |  10 ++
>  drivers/mfd/Makefile     |   1 +
>  drivers/mfd/ene-kb3930.c | 209 +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 220 insertions(+)
>  create mode 100644 drivers/mfd/ene-kb3930.c
> 
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 0a59249198d3..dae18a2beab5 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -398,6 +398,16 @@ config MFD_DLN2
>  	  etc. must be enabled in order to use the functionality of
>  	  the device.
>  
> +config MFD_ENE_KB3930
> +	tristate "ENE KB3930 Embedded Controller support"
> +	depends on I2C
> +	depends on MACH_MMP3_DT || COMPILE_TEST
> +	select MFD_CORE
> +	help
> +	  This adds support for accessing the registers on ENE KB3930, Embedded
> +	  Controller. Additional drivers such as LEDS_ARIEL must be enabled in
> +	  order to use the functionality of the device.
> +
>  config MFD_EXYNOS_LPASS
>  	tristate "Samsung Exynos SoC Low Power Audio Subsystem"
>  	depends on ARCH_EXYNOS || COMPILE_TEST
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index f935d10cbf0f..2d2f5bc12841 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -14,6 +14,7 @@ obj-$(CONFIG_ARCH_BCM2835)	+= bcm2835-pm.o
>  obj-$(CONFIG_MFD_BCM590XX)	+= bcm590xx.o
>  obj-$(CONFIG_MFD_BD9571MWV)	+= bd9571mwv.o
>  obj-$(CONFIG_MFD_CROS_EC_DEV)	+= cros_ec_dev.o
> +obj-$(CONFIG_MFD_ENE_KB3930)	+= ene-kb3930.o
>  obj-$(CONFIG_MFD_EXYNOS_LPASS)	+= exynos-lpass.o
>  
>  obj-$(CONFIG_HTC_PASIC3)	+= htc-pasic3.o
> diff --git a/drivers/mfd/ene-kb3930.c b/drivers/mfd/ene-kb3930.c
> new file mode 100644
> index 000000000000..1123f3a1c816
> --- /dev/null
> +++ b/drivers/mfd/ene-kb3930.c
> @@ -0,0 +1,209 @@
> +// SPDX-License-Identifier: BSD-2-Clause OR GPL-2.0-or-later
> +/*
> + * ENE KB3930 Embedded Controller Driver
> + *
> + * Copyright (C) 2020 Lubomir Rintel
> + */
> +
> +#include <linux/module.h>
> +#include <linux/i2c.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/delay.h>
> +#include <linux/reboot.h>
> +#include <linux/regmap.h>
> +#include <linux/mfd/core.h>

Alphabetical.

> +enum {
> +	EC_DATA_IN	= 0x00,
> +	EC_RAM_OUT	= 0x80,
> +	EC_RAM_IN	= 0x81,
> +};

Are these registers?

> +enum {
> +	EC_MODEL_ID	= 0x30,
> +	EC_VERSION_MAJ	= 0x31,
> +	EC_VERSION_MIN	= 0x32,
> +};

As above?

> +struct kb3930 {
> +	struct i2c_client *client;
> +	struct regmap *ec_ram;

This is usually called 'regmap'.

> +	struct gpio_descs *off_gpios; 
> +};
> +
> +struct kb3930 *global_kb3930;

Globals are massively frowned upon.  Please move it.

> +static void kb3930_off(struct kb3930 *priv, int poweroff)
> +{
> +	gpiod_direction_output(priv->off_gpios->desc[1], poweroff);
> +
> +	while (1) {
> +		mdelay(50);

Why 50?

> +		gpiod_direction_output(priv->off_gpios->desc[0], 0);
> +		mdelay(50);
> +		gpiod_direction_output(priv->off_gpios->desc[0], 1);
> +	}
> +}

Please define all of the magic numbers in this function.

> +static int kb3930_restart(struct notifier_block *this,
> +			  unsigned long mode, void *cmd)
> +{

Put 'struct kb3930_restart_nb' into 'struct kb3930' then use
container_of to obtain a pointer to 'struct kb3930_restart_nb'.

See drivers/power/reset/gpio-restart.c for an example.

> +	kb3930_off(global_kb3930, 0);

Define the 0 please.

> +	return NOTIFY_DONE;
> +}
> +
> +static void kb3930_power_off(void)
> +{
> +	kb3930_off(global_kb3930, 1);

Define the 1 please.

> +}
> +
> +static struct notifier_block kb3930_restart_nb = {
> +	.notifier_call = kb3930_restart,
> +	.priority = 128,

Why 128?

> +};
> +
> +static const struct mfd_cell ariel_ec_cells[] = {
> +	{ .name = "dell-wyse-ariel-led", },
> +	{ .name = "dell-wyse-ariel-power", },
> +};
> +
> +static int kb3930_ec_ram_reg_write(void *context, unsigned int reg,
> +				   unsigned int val)
> +{
> +	struct kb3930 *priv = context;
> +
> +	return i2c_smbus_write_word_data(priv->client, EC_RAM_OUT,
> +					 (val << 8) | reg);
> +}
> +
> +static int kb3930_ec_ram_reg_read(void *context, unsigned int reg,
> +				  unsigned int *val)
> +{
> +	struct kb3930 *priv = context;
> +	int ret;
> +
> +	ret = i2c_smbus_write_word_data(priv->client, EC_RAM_IN, reg);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = i2c_smbus_read_word_data(priv->client, EC_DATA_IN);
> +	if (ret < 0)
> +		return ret;
> +
> +	*val = ret >> 8;
> +	return 0;
> +}
> +
> +static const struct regmap_config kb3930_ec_ram_regmap_config = {
> +	.name = "ec_ram",
> +	.reg_bits = 8,
> +	.val_bits = 8,
> +	.reg_stride = 1,
> +	.max_register = 0xff,

Where are the list of register defines/enums?

> +	.reg_write = kb3930_ec_ram_reg_write,
> +	.reg_read = kb3930_ec_ram_reg_read,
> +	.fast_io = false,
> +};
> +
> +static int kb3930_probe(struct i2c_client *client,
> +			const struct i2c_device_id *id)
> +{
> +	struct device *dev = &client->dev;
> +	struct device_node *np = dev->of_node;
> +	struct kb3930 *priv;

Not keen on 'info' or 'priv' for these.

Prefer it if you call this ddata (device/driver data).

> +	unsigned int model_id;

Just 'model' is fine.

> +	int ret;
> +
> +	if (global_kb3930)
> +		return -EEXIST;

Please no!

> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	global_kb3930 = priv;
> +	priv->client = client;
> +	i2c_set_clientdata(client, priv);
> +
> +	priv->ec_ram = devm_regmap_init(dev, NULL, priv,
> +					&kb3930_ec_ram_regmap_config);
> +	if (IS_ERR(priv->ec_ram))
> +		return PTR_ERR(priv->ec_ram);
> +
> +	ret = regmap_read(priv->ec_ram, EC_MODEL_ID, &model_id);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (model_id == 'J') {
> +		ret = devm_mfd_add_devices(dev, PLATFORM_DEVID_NONE,

Why NONE over AUTO?

> +					   ariel_ec_cells,
> +					   ARRAY_SIZE(ariel_ec_cells),
> +					   NULL, 0, NULL);
> +		if (ret < 0)
> +			return ret;
> +	} else {
> +		dev_err(dev, "unknown board model: %02x\n", model_id);
> +		return -ENODEV;

If you reverse the logic here, you can put this in the if() and omit
the else.

> +	}
> +
> +	if (of_property_read_bool (np, "system-power-controller")) {

Remove the space before the '('.

> +		priv->off_gpios = devm_gpiod_get_array_optional(dev, "off",
> +								GPIOD_IN);

Please try to split the line just after the '='.

> +	}
> +	if (IS_ERR(priv->off_gpios))
> +		return PTR_ERR(priv->off_gpios);

Shouldn't this be in the if() above?

> +	if (priv->off_gpios->ndescs < 2) {
> +		dev_err(dev, "invalid off-gpios property\n");
> +		return -EINVAL;
> +	}

This doesn't seem right.  I thought they were optional?

> +	if (priv->off_gpios) {
> +		register_restart_handler(&kb3930_restart_nb);
> +		if (pm_power_off == NULL)
> +			pm_power_off = kb3930_power_off;
> +	}
> +
> +	dev_info(dev, "ENE KB3930 Embedded Controller\n");

Remove this line please.

> +	return 0;
> +}
> +
> +static int kb3930_remove(struct i2c_client *client)
> +{
> +	struct kb3930 *priv = i2c_get_clientdata(client);
> +
> +	if (priv->off_gpios) {
> +		if (pm_power_off == kb3930_power_off)
> +			pm_power_off = NULL;
> +		unregister_restart_handler(&kb3930_restart_nb);
> +	}
> +	global_kb3930 = NULL;
> +
> +	return 0;
> +}
> +
> +static const struct i2c_device_id kb3930_ids[] = {
> +	{ "kb3930", 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, kb3930_ids);

You can use .probe_new and omit this table.

> +static const struct of_device_id kb3930_dt_ids[] = {
> +	{ .compatible = "ene,kb3930" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, kb3930_dt_ids);
> +
> +static struct i2c_driver kb3930_driver = {
> +	.probe = kb3930_probe,
> +	.remove = kb3930_remove,
> +	.driver = {
> +		.name = "ene-kb3930",
> +		.of_match_table = of_match_ptr(kb3930_dt_ids),
> +	},
> +	.id_table = kb3930_ids,
> +};
> +
> +module_i2c_driver(kb3930_driver);
> +
> +MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
> +MODULE_DESCRIPTION("ENE KB3930 Embedded Controller Driver");
> +MODULE_LICENSE("Dual BSD/GPL");

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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