[PATCH v4 3/7] mfd: Add base driver for Netronix embedded controller

[Lee Jones]

On Sun, 22 Nov 2020, Jonathan Neuschäfer wrote:

> The Netronix embedded controller is a microcontroller found in some
> e-book readers designed by the original design manufacturer 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 at gmx.net>
> ---
> 
> v4:
> - include asm/unaligned.h after linux/*
> - Use put_unaligned_be16 instead of open-coded big-endian packing
> - Clarify that 0x90=0xff00 causes an error in downstream kernel too
> - Add commas after non-sentinel positions
> - ntxec.h: declare structs device and regmap
> - Replace WARN_ON usage and add comments to explain errors
> - Replace dev_alert with dev_warn when the result isn't handled
> - Change subdevice registration error message to dev_err
> - Declare ntxec_reg8 as returning __be16
> - Restructure version detection code
> - Spell out ODM
> 
> v3:
> - https://lore.kernel.org/lkml/20200924192455.2484005-4-j.neuschaefer@gmx.net/
> - Add (EC) to CONFIG_MFD_NTXEC prompt
> - Relicense as GPLv2 or later
> - Add email address to copyright line
> - remove empty lines in ntxec_poweroff and ntxec_restart functions
> - Split long lines
> - Remove 'Install ... handler' comments
> - Make naming of struct i2c_client parameter consistent
> - Remove struct ntxec_info
> - Rework 'depends on' lines in Kconfig, hard-depend on I2C, select REGMAP_I2C and
>   MFD_CORE
> - Register subdevices via mfd_cells
> - Move 8-bit register conversion to ntxec.h
> 
> v2:
> - https://lore.kernel.org/lkml/20200905133230.1014581-4-j.neuschaefer@gmx.net/
> - 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       |  11 ++
>  drivers/mfd/Makefile      |   1 +
>  drivers/mfd/ntxec.c       | 216 ++++++++++++++++++++++++++++++++++++++
>  include/linux/mfd/ntxec.h |  34 ++++++
>  4 files changed, 262 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 8b99a13669bfc..d96751f884dc6 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -990,6 +990,17 @@ 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 (EC)"
> +	depends on OF || COMPILE_TEST
> +	depends on I2C
> +	select REGMAP_I2C
> +	select MFD_CORE
> +	help
> +	  Say yes here if you want to support the embedded controller found in
> +	  certain e-book readers designed by the original design manufacturer
> +	  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 1780019d24748..815c99b84019e 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -218,6 +218,7 @@ 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..c1510711d7363
> --- /dev/null
> +++ b/drivers/mfd/ntxec.c
> @@ -0,0 +1,216 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * The Netronix embedded controller is a microcontroller found in some
> + * e-book readers designed by the original design manufacturer 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 <j.neuschaefer at gmx.net>
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/errno.h>
> +#include <linux/i2c.h>
> +#include <linux/mfd/core.h>
> +#include <linux/mfd/ntxec.h>
> +#include <linux/module.h>
> +#include <linux/pm.h>
> +#include <linux/reboot.h>
> +#include <linux/regmap.h>
> +#include <linux/types.h>
> +#include <asm/unaligned.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;
> +	u8 buf[3] = { NTXEC_REG_POWEROFF };
> +	struct i2c_msg msgs[] = {
> +		{
> +			.addr = poweroff_restart_client->addr,
> +			.flags = 0,
> +			.len = sizeof(buf),
> +			.buf = buf,
> +		},
> +	};
> +
> +	put_unaligned_be16(NTXEC_POWEROFF_VALUE, buf + 1);
> +
> +	res = i2c_transfer(poweroff_restart_client->adapter, msgs, ARRAY_SIZE(msgs));
> +	if (res < 0)
> +		dev_warn(&poweroff_restart_client->dev,
> +			 "Failed to power off (err = %d)\n", res);
> +
> +	/*
> +	 * 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;
> +	u8 buf[3] = { NTXEC_REG_RESET };
> +	/*
> +	 * NOTE: The lower half of the reset value is not sent, because sending
> +	 * it causes an I2C error. (The reset handler in the downstream driver
> +	 * does send the full two-byte value, but doesn't check the result).
> +	 */
> +	struct i2c_msg msgs[] = {
> +		{
> +			.addr = poweroff_restart_client->addr,
> +			.flags = 0,
> +			.len = sizeof(buf) - 1,
> +			.buf = buf,
> +		},
> +	};
> +
> +	put_unaligned_be16(NTXEC_RESET_VALUE, buf + 1);
> +
> +	res = i2c_transfer(poweroff_restart_client->adapter, msgs, ARRAY_SIZE(msgs));
> +	if (res < 0)
> +		dev_warn(&poweroff_restart_client->dev,
> +			 "Failed to restart (err = %d)\n", res);
> +
> +	return NOTIFY_DONE;
> +}
> +
> +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 mfd_cell ntxec_subdevices[] = {
> +	{ .name = "ntxec-rtc" },
> +	{ .name = "ntxec-pwm" },
> +};
> +
> +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;
> +	}
> +
> +	/* Bail out if we encounter an unknown firmware version */
> +	switch (version) {
> +	case 0xd726: /* found in Kobo Aura */

No magic numbers.

Please submit a subsequent patch to define this.

> +		break;
> +	default:
> +		dev_err(ec->dev,
> +			"Netronix embedded controller version %04x is not supported.\n",
> +			version);
> +		return -ENODEV;
> +	}


Applied, thanks.

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