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