Date:   Mon, 22 Jun 2020 07:51:48 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Lubomir Rintel <lkundrak@...sk>
Cc:     Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/2] mfd: ene-kb3930: Add driver for ENE KB3930
 Embedded Controller

On Wed, 17 Jun 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@...sk>
> 
> ---
> Changes since v3:
> - Clarify that the power-off function is provided by this driver while
>   LEDS_ARIEL is necessary to drive the leds in Kconfig help text
> - s/kb3930_power_off/kb3930_pm_power_off/, s/global_kb3930/kb3930_power_off/
> - Don't fail with -EEXIST with more than one instance
> - s/ret < 0/ret/ for devm_mfd_add_devices() return value
> - Drop a \n between struct i2c_driver and module_i2c_driver()
> 
> Changes since v2:
> - Sort the includes
> - s/EC_MODEL_ID/EC_MODEL/
> - Add a couple of clarifying comments
> - Use #defines for values used in poweroff routine
> - Remove priority from a restart notifier block
> - s/priv/ddata/
> - s/ec_ram/ram_regmap/ for the regmap name
> - Fix the error handling when getting off gpios was not successful
> - Remove a useless dev_info at the end of probe()
> - Use i2c probe_new() callback, drop i2c_device_id
> - Modify the logic in checking the model ID

Much better.  Just a couple of nits to fix.

>  drivers/mfd/Kconfig      |  11 ++
>  drivers/mfd/Makefile     |   1 +
>  drivers/mfd/ene-kb3930.c | 211 +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 223 insertions(+)
>  create mode 100644 drivers/mfd/ene-kb3930.c
> 
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index a37d7d1713820..7569f1d1703e3 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -398,6 +398,17 @@ 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"

What is "ENE"?

> +	depends on I2C
> +	depends on MACH_MMP3_DT || COMPILE_TEST
> +	select MFD_CORE
> +	help
> +	  This adds support for the power-off functionality and access to
> +	  the registers that control LEDS and USB port power on ENE KB3930
> +	  Embedded Controller. To use the LED functionality LEDS_ARIEL must
> +	  be enabled.
> +
>  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 9367a92f795a6..11085a6968398 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_MFD_GATEWORKS_GSC)	+= gateworks-gsc.o
>  
> diff --git a/drivers/mfd/ene-kb3930.c b/drivers/mfd/ene-kb3930.c
> new file mode 100644
> index 0000000000000..75eced148ce53
> --- /dev/null
> +++ b/drivers/mfd/ene-kb3930.c
> @@ -0,0 +1,211 @@
> +// SPDX-License-Identifier: BSD-2-Clause OR GPL-2.0-or-later
> +/*
> + * ENE KB3930 Embedded Controller Driver
> + *
> + * Copyright (C) 2020 Lubomir Rintel
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/i2c.h>
> +#include <linux/mfd/core.h>
> +#include <linux/module.h>
> +#include <linux/reboot.h>
> +#include <linux/regmap.h>
> +
> +/* I2C registers that are multiplexing access to the EC RAM. */
> +enum {
> +	EC_DATA_IN	= 0x00,
> +	EC_RAM_OUT	= 0x80,
> +	EC_RAM_IN	= 0x81,
> +};
> +
> +/* EC RAM registers. */
> +enum {
> +	EC_MODEL	= 0x30,
> +	EC_VERSION_MAJ	= 0x31,
> +	EC_VERSION_MIN	= 0x32,
> +};
> +
> +struct kb3930 {
> +	struct i2c_client *client;
> +	struct regmap *ram_regmap;
> +	struct gpio_descs *off_gpios;
> +};
> +
> +struct kb3930 *kb3930_power_off;
> +
> +#define EC_GPIO_WAVE		0
> +#define EC_GPIO_OFF_MODE	1
> +
> +#define EC_OFF_MODE_REBOOT	0
> +#define EC_OFF_MODE_POWER	1
> +
> +static void kb3930_off(struct kb3930 *ddata, int off_mode)
> +{
> +	gpiod_direction_output(ddata->off_gpios->desc[EC_GPIO_OFF_MODE],
> +			       off_mode);
> +
> +	/*
> +	 * The EC initiates a shutdown when it detects a 10 MHz wave, inspecting the
> +	 * other GPIO pin to decide whether it's supposed to turn the power off or
> +	 * reset the board.
> +	 */
> +	while (1) {
> +		mdelay(50);
> +		gpiod_direction_output(ddata->off_gpios->desc[EC_GPIO_WAVE], 0);
> +		mdelay(50);
> +		gpiod_direction_output(ddata->off_gpios->desc[EC_GPIO_WAVE], 1);
> +	}

The comment describes what the EC is expecting, but says nothing about
what these lines of code do, or why they're required.

> +}
> +
> +static int kb3930_restart(struct notifier_block *this,
> +			  unsigned long mode, void *cmd)
> +{
> +	kb3930_off(kb3930_power_off, EC_OFF_MODE_REBOOT);
> +	return NOTIFY_DONE;
> +}
> +
> +static void kb3930_pm_power_off(void)
> +{
> +	kb3930_off(kb3930_power_off, EC_OFF_MODE_POWER);
> +}
> +
> +static struct notifier_block kb3930_restart_nb = {
> +	.notifier_call = kb3930_restart,
> +};
> +
> +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 *ddata = context;
> +
> +	return i2c_smbus_write_word_data(ddata->client, EC_RAM_OUT,
> +					 (val << 8) | reg);
> +}
> +
> +static int kb3930_ec_ram_reg_read(void *context, unsigned int reg,
> +				  unsigned int *val)
> +{
> +	struct kb3930 *ddata = context;
> +	int ret;
> +
> +	ret = i2c_smbus_write_word_data(ddata->client, EC_RAM_IN, reg);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = i2c_smbus_read_word_data(ddata->client, EC_DATA_IN);
> +	if (ret < 0)
> +		return ret;
> +
> +	*val = ret >> 8;
> +	return 0;
> +}
> +
> +static const struct regmap_config kb3930_ram_regmap_config = {
> +	.name = "ec_ram",
> +	.reg_bits = 8,
> +	.val_bits = 8,
> +	.reg_stride = 1,
> +	.max_register = 0xff,
> +	.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)
> +{
> +	struct device *dev = &client->dev;
> +	struct device_node *np = dev->of_node;
> +	struct kb3930 *ddata;
> +	unsigned int model;
> +	int ret;
> +
> +	ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
> +	if (!ddata)
> +		return -ENOMEM;
> +
> +	kb3930_power_off = ddata;
> +	ddata->client = client;
> +	i2c_set_clientdata(client, ddata);
> +
> +	ddata->ram_regmap = devm_regmap_init(dev, NULL, ddata,
> +					     &kb3930_ram_regmap_config);
> +	if (IS_ERR(ddata->ram_regmap))
> +		return PTR_ERR(ddata->ram_regmap);
> +
> +	ret = regmap_read(ddata->ram_regmap, EC_MODEL, &model);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Currently we only support the cells present on Dell Ariel model. */
> +	if (model != 'J') {
> +		dev_err(dev, "unknown board model: %02x\n", model);
> +		return -ENODEV;
> +	}
> +
> +	/* These are the cells valid for model == 'J' only. */

The previous comment makes this superfluous.

> +	ret = devm_mfd_add_devices(dev, PLATFORM_DEVID_AUTO,
> +				   ariel_ec_cells,
> +				   ARRAY_SIZE(ariel_ec_cells),
> +				   NULL, 0, NULL);
> +	if (ret)
> +		return ret;
> +
> +	if (of_property_read_bool(np, "system-power-controller")) {
> +		ddata->off_gpios =
> +			devm_gpiod_get_array_optional(dev, "off", GPIOD_IN);
> +		if (IS_ERR(ddata->off_gpios))
> +			return PTR_ERR(ddata->off_gpios);
> +		if (ddata->off_gpios->ndescs < 2) {
> +			dev_err(dev, "invalid off-gpios property\n");
> +			return -EINVAL;
> +		}
> +	}

'\n' here.

> +	if (ddata->off_gpios) {
> +		register_restart_handler(&kb3930_restart_nb);
> +		if (pm_power_off == NULL)

if (!pm_power_off)

> +			pm_power_off = kb3930_pm_power_off;
> +	}
> +
> +	return 0;
> +}
> +
> +static int kb3930_remove(struct i2c_client *client)
> +{
> +	struct kb3930 *ddata = i2c_get_clientdata(client);
> +
> +	if (ddata->off_gpios) {
> +		if (pm_power_off == kb3930_pm_power_off)
> +			pm_power_off = NULL;
> +		unregister_restart_handler(&kb3930_restart_nb);
> +	}
> +	kb3930_power_off = NULL;
> +
> +	return 0;
> +}
> +
> +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_new = kb3930_probe,
> +	.remove = kb3930_remove,
> +	.driver = {
> +		.name = "ene-kb3930",
> +		.of_match_table = of_match_ptr(kb3930_dt_ids),
> +	},
> +};
> +module_i2c_driver(kb3930_driver);
> +
> +MODULE_AUTHOR("Lubomir Rintel <lkundrak@...sk>");
> +MODULE_DESCRIPTION("ENE KB3930 Embedded Controller Driver");
> +MODULE_LICENSE("Dual BSD/GPL");

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