Re: [PATCH v2 03/10] mfd: Add base driver for Netronix embedded controller

Lee Jones
2020-09-08T19:37:36Z

On Sat, 05 Sep 2020, Jonathan Neuschäfer wrote:

> The Netronix embedded controller is a microcontroller found in some
> e-book readers designed by the ODM Netronix, Inc. It contains RTC,
> battery monitoring, system power management, and PWM functionality.
>
> This driver implements register access and version detection.
>
> Third-party hardware documentation is available at:
>
> https://github.com/neuschaefer/linux/wiki/Netronix-MSP430-embedded-controller
>
> The EC supports interrupts, but the driver doesn't make use of them so
> far.
>
> Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
> ---
>
> v2:
> - Add a description of the device to the patch text
> - Unify spelling as 'Netronix embedded controller'.
> 'Netronix' is the proper name of the manufacturer, but 'embedded controller'
> is just a label that I have assigned to the device.
> - Switch to regmap, avoid regmap use in poweroff and reboot handlers.
> Inspired by cf84dc0bb40f4 ("mfd: rn5t618: Make restart handler atomic safe")
> - Use a list of known-working firmware versions instead of checking for a
> known-incompatible version
> - Prefix registers with NTXEC_REG_
> - Define register values as constants
> - Various style cleanups as suggested by Lee Jones
> - Don't align = signs in struct initializers [Uwe Kleine-König]
> - Don't use dev_dbg for an error message
> - Explain sleep in poweroff handler
> - Remove (struct ntxec).client
> - Switch to .probe_new in i2c driver
> - Add .remove callback
> - Make CONFIG_MFD_NTXEC a tristate option
> ---
> drivers/mfd/Kconfig | 7 ++
> drivers/mfd/Makefile | 1 +
> drivers/mfd/ntxec.c | 217 ++++++++++++++++++++++++++++++++++++++
> include/linux/mfd/ntxec.h | 24 +++++
> 4 files changed, 249 insertions(+)
> create mode 100644 drivers/mfd/ntxec.c
> create mode 100644 include/linux/mfd/ntxec.h
>
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 33df0837ab415..bab999081f32d 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -978,6 +978,13 @@ config MFD_VIPERBOARD
> You need to select the mfd cell drivers separately.
> The drivers do not support all features the board exposes.
>
> +config MFD_NTXEC
> + tristate "Netronix embedded controller"

Nit: "Embedded Controller (EC)"

> + depends on I2C && OF

depends on (I2C && OF) || COMPILE_TEST

> + help
> + Say yes here if you want to support the embedded controller found in
> + certain e-book readers designed by the ODM Netronix.
> +
> config MFD_RETU
> tristate "Nokia Retu and Tahvo multi-function device"
> select MFD_CORE
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index a60e5f835283e..236a8acd917a0 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -217,6 +217,7 @@ obj-$(CONFIG_MFD_INTEL_MSIC) += intel_msic.o
> obj-$(CONFIG_MFD_INTEL_PMC_BXT) += intel_pmc_bxt.o
> obj-$(CONFIG_MFD_PALMAS) += palmas.o
> obj-$(CONFIG_MFD_VIPERBOARD) += viperboard.o
> +obj-$(CONFIG_MFD_NTXEC) += ntxec.o
> obj-$(CONFIG_MFD_RC5T583) += rc5t583.o rc5t583-irq.o
> obj-$(CONFIG_MFD_RK808) += rk808.o
> obj-$(CONFIG_MFD_RN5T618) += rn5t618.o
> diff --git a/drivers/mfd/ntxec.c b/drivers/mfd/ntxec.c
> new file mode 100644
> index 0000000000000..49cc4fa35b9fe
> --- /dev/null
> +++ b/drivers/mfd/ntxec.c
> @@ -0,0 +1,217 @@
> +// SPDX-License-Identifier: GPL-2.0-only

Why 2 only?

> +/*
> + * The Netronix embedded controller is a microcontroller found in some
> + * e-book readers designed by the ODM Netronix, Inc. It contains RTC,
> + * battery monitoring, system power management, and PWM functionality.
> + *
> + * This driver implements register access, version detection, and system
> + * power-off/reset.
> + *
> + * Copyright 2020 Jonathan Neuschäfer

Email?

> + */
> +
> +#include <asm/unaligned.h>
> +#include <linux/delay.h>
> +#include <linux/errno.h>
> +#include <linux/i2c.h>
> +#include <linux/mfd/ntxec.h>
> +#include <linux/module.h>
> +#include <linux/of_platform.h>
> +#include <linux/pm.h>
> +#include <linux/reboot.h>
> +#include <linux/regmap.h>
> +#include <linux/types.h>
> +
> +#define NTXEC_REG_VERSION 0x00
> +#define NTXEC_REG_POWEROFF 0x50
> +#define NTXEC_REG_POWERKEEP 0x70
> +#define NTXEC_REG_RESET 0x90
> +
> +#define NTXEC_POWEROFF_VALUE 0x0100
> +#define NTXEC_POWERKEEP_VALUE 0x0800
> +#define NTXEC_RESET_VALUE 0xff00
> +
> +static struct i2c_client *poweroff_restart_client;
> +
> +static void ntxec_poweroff(void)
> +{
> + int res;
> +

Remove this line please.

> + u8 buf[] = {
> + NTXEC_REG_POWEROFF,
> + (NTXEC_POWEROFF_VALUE >> 8) & 0xff,
> + NTXEC_POWEROFF_VALUE & 0xff,
> + };
> +

And this one.

> + struct i2c_msg msgs[] = {
> + {
> + .addr = poweroff_restart_client->addr,
> + .flags = 0,
> + .len = sizeof(buf),
> + .buf = buf
> + }
> + };
> +
> + res = i2c_transfer(poweroff_restart_client->adapter, msgs, ARRAY_SIZE(msgs));
> +

And this one.

> + if (res < 0)
> + dev_alert(&poweroff_restart_client->dev, "Failed to power off (err = %d)\n", res);

This looks way over 80 chars.

Did you run checkpatch.pl?

> + /*
> + * The time from the register write until the host CPU is powered off
> + * has been observed to be about 2.5 to 3 seconds. Sleep long enough to
> + * safely avoid returning from the poweroff handler.
> + */
> + msleep(5000);
> +}
> +
> +static int ntxec_restart(struct notifier_block *nb,
> + unsigned long action, void *data)
> +{
> + int res;
> +
> + /*
> + * NOTE: The lower half of the reset value is not sent, because sending
> + * it causes an error
> + */
> + u8 buf[] = {
> + NTXEC_REG_RESET,
> + (NTXEC_RESET_VALUE >> 8) & 0xff,
> + };
> +
> + struct i2c_msg msgs[] = {
> + {
> + .addr = poweroff_restart_client->addr,
> + .flags = 0,
> + .len = sizeof(buf),
> + .buf = buf
> + }
> + };
> +
> + res = i2c_transfer(poweroff_restart_client->adapter, msgs, ARRAY_SIZE(msgs));
> +
> + if (res < 0)
> + dev_alert(&poweroff_restart_client->dev, "Failed to restart (err = %d)\n", res);
> +
> + return NOTIFY_DONE;
> +}

All as above for this function.

> +static struct notifier_block ntxec_restart_handler = {
> + .notifier_call = ntxec_restart,
> + .priority = 128
> +};
> +
> +static const struct regmap_config regmap_config = {
> + .name = "ntxec",
> + .reg_bits = 8,
> + .val_bits = 16,
> + .cache_type = REGCACHE_NONE,
> + .val_format_endian = REGMAP_ENDIAN_BIG,
> +};
> +
> +static const struct ntxec_info ntxec_known_versions[] = {
> + { 0xd726 }, /* found in Kobo Aura */
> +};
> +
> +static const struct ntxec_info *ntxec_lookup_info(u16 version)
> +{
> + int i;
> +
> + for (i = 0; i < ARRAY_SIZE(ntxec_known_versions); i++) {
> + const struct ntxec_info *info = &ntxec_known_versions[i];
> +
> + if (info->version == version)
> + return info;
> + }
> +
> + return NULL;
> +}

Wait, what? This is over-engineered.

Just have a look-up table (switch) of supported devices.

> +static int ntxec_probe(struct i2c_client *client)
> +{
> + struct ntxec *ec;
> + unsigned int version;
> + int res;
> +
> + ec = devm_kmalloc(&client->dev, sizeof(*ec), GFP_KERNEL);
> + if (!ec)
> + return -ENOMEM;
> +
> + ec->dev = &client->dev;
> +
> + ec->regmap = devm_regmap_init_i2c(client, &regmap_config);
> + if (IS_ERR(ec->regmap)) {
> + dev_err(ec->dev, "Failed to set up regmap for device\n");
> + return res;
> + }
> +
> + /* Determine the firmware version */
> + res = regmap_read(ec->regmap, NTXEC_REG_VERSION, &version);
> + if (res < 0) {
> + dev_err(ec->dev, "Failed to read firmware version number\n");
> + return res;
> + }
> + dev_info(ec->dev,
> + "Netronix embedded controller version %04x detected.\n",
> + version);
> +
> + /* Bail out if we encounter an unknown firmware version */
> + ec->info = ntxec_lookup_info(version);
> + if (!ec->info)
> + return -EOPNOTSUPP;

#define EOPNOTSUPP 95 /* Operation not supported on transport endpoint */

I think you want:

#define ENODEV 19 /* No such device */

> + if (of_device_is_system_power_controller(ec->dev->of_node)) {
> + /*
> + * Set the 'powerkeep' bit. This is necessary on some boards
> + * in order to keep the system running.
> + */
> + res = regmap_write(ec->regmap, NTXEC_REG_POWERKEEP,
> + NTXEC_POWERKEEP_VALUE);
> + if (res < 0)
> + return res;
> +
> + /* Install poweroff handler */

Don't think this comment is required.

> + WARN_ON(poweroff_restart_client);
> + poweroff_restart_client = client;
> + if (pm_power_off)
> + dev_err(ec->dev, "pm_power_off already assigned\n");
> + else
> + pm_power_off = ntxec_poweroff;
> +
> + /* Install board reset handler */

Nor this.

> + res = register_restart_handler(&ntxec_restart_handler);
> + if (res)
> + dev_err(ec->dev,
> + "Failed to register restart handler: %d\n", res);
> + }
> +
> + i2c_set_clientdata(client, ec);
> +
> + return devm_of_platform_populate(ec->dev);
> +}
> +
> +static int ntxec_remove(struct i2c_client *i2c)

Why do you call it 'client' in .probe, but 'i2c' in .remove?

> +{
> + if (i2c == poweroff_restart_client) {
> + poweroff_restart_client = NULL;
> + pm_power_off = NULL;
> + unregister_restart_handler(&ntxec_restart_handler);
> + }
> +
> + return 0;
> +}
> +
> +static const struct of_device_id of_ntxec_match_table[] = {
> + { .compatible = "netronix,ntxec", },
> + {}
> +};
> +
> +static struct i2c_driver ntxec_driver = {
> + .driver = {
> + .name = "ntxec",
> + .of_match_table = of_ntxec_match_table,
> + },
> + .probe_new = ntxec_probe,
> + .remove = ntxec_remove,
> +};
> +module_i2c_driver(ntxec_driver);
> diff --git a/include/linux/mfd/ntxec.h b/include/linux/mfd/ntxec.h
> new file mode 100644
> index 0000000000000..65e389af79da6
> --- /dev/null
> +++ b/include/linux/mfd/ntxec.h
> @@ -0,0 +1,24 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright 2020 Jonathan Neuschäfer
> + *
> + * Register access and version information for the Netronix embedded
> + * controller.
> + */
> +
> +#ifndef NTXEC_H
> +#define NTXEC_H
> +
> +#include <linux/types.h>
> +
> +struct ntxec_info {
> + u16 version;
> +};
> +
> +struct ntxec {
> + struct device *dev;
> + struct regmap *regmap;

> + const struct ntxec_info *info;

What is this used for?

> +};
> +
> +#endif

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