Message-ID: <CAJ+vNU1GWFKv8f-ihhoVTWgD8G5UyupOek1fmBPaU0QXKC1qHw@mail.gmail.com>
Date:   Wed, 8 Apr 2020 08:36:26 -0700
From:   Tim Harvey <tharvey@...eworks.com>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     Linux HWMON List <linux-hwmon@...r.kernel.org>,
        Robert Jones <rjones@...eworks.com>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Device Tree Mailing List <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>
Subject: Re: [PATCH v8 2/3] mfd: add Gateworks System Controller core driver

On Fri, Mar 27, 2020 at 1:33 PM Tim Harvey <tharvey@...eworks.com> wrote:
>
> The Gateworks System Controller (GSC) is an I2C slave controller
> implemented with an MSP430 micro-controller whose firmware embeds the
> following features:
>  - I/O expander (16 GPIO's) using PCA955x protocol
>  - Real Time Clock using DS1672 protocol
>  - User EEPROM using AT24 protocol
>  - HWMON using custom protocol
>  - Interrupt controller with tamper detect, user pushbotton
>  - Watchdog controller capable of full board power-cycle
>  - Power Control capable of full board power-cycle
>
> see http://trac.gateworks.com/wiki/gsc for more details
>
> Cc: Randy Dunlap <rdunlap@...radead.org>
> Signed-off-by: Tim Harvey <tharvey@...eworks.com>
> ---
> v8:
> - whitespace fixes
> - describe sub-devices in Kconfig
> - add error print for invalid command
> - update copyright
> - use devm_of_platform_populate
> - use probe_new
> - move hwmon's regmap init to hwmon
>
> v7:
> - remove irq from private data struct
>
> v6:
> - remove duplicate signature and fix commit log
>
> v5:
> - simplify powerdown function
>
> v4:
> - remove hwmon max reg check/define
> - fix powerdown function
>
> v3:
> - rename gsc->gateworks-gsc
> - remove uncecessary include for linux/mfd/core.h
> - upercase I2C in comments
> - remove i2c debug
> - remove uncecessary comments
> - don't use KBUILD_MODNAME for name
> - remove unnecessary v1/v2/v3 tracking
> - unregister hwmon i2c adapter on remove
>
> v2:
> - change license comment block style
> - remove COMPILE_TEST (Randy)
> - fixed whitespace issues
> - replaced a printk with dev_err
> ---
>  MAINTAINERS                 |   8 ++
>  drivers/mfd/Kconfig         |  10 ++
>  drivers/mfd/Makefile        |   1 +
>  drivers/mfd/gateworks-gsc.c | 288 ++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/mfd/gsc.h     |  73 +++++++++++
>  5 files changed, 380 insertions(+)
>  create mode 100644 drivers/mfd/gateworks-gsc.c
>  create mode 100644 include/linux/mfd/gsc.h
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 56765f5..bb79b60 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -6839,6 +6839,14 @@ F:       tools/testing/selftests/futex/
>  F:     tools/perf/bench/futex*
>  F:     Documentation/*futex*
>
> +GATEWORKS SYSTEM CONTROLLER (GSC) DRIVER
> +M:     Tim Harvey <tharvey@...eworks.com>
> +M:     Robert Jones <rjones@...eworks.com>
> +S:     Maintained
> +F:     Documentation/devicetree/bindings/mfd/gateworks-gsc.yaml
> +F:     drivers/mfd/gateworks-gsc.c
> +F:     include/linux/mfd/gsc.h
> +
>  GCC PLUGINS
>  M:     Kees Cook <keescook@...omium.org>
>  R:     Emese Revfy <re.emese@...il.com>
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 4209008..d84725a 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -407,6 +407,16 @@ config MFD_EXYNOS_LPASS
>           Select this option to enable support for Samsung Exynos Low Power
>           Audio Subsystem.
>
> +config MFD_GATEWORKS_GSC
> +       tristate "Gateworks System Controller"
> +       depends on (I2C && OF)
> +       select MFD_CORE
> +       select REGMAP_I2C
> +       select REGMAP_IRQ
> +       help
> +         Enable support for the Gateworks System Controller found
> +         on Gateworks Single Board Computers.
> +
>  config MFD_MC13XXX
>         tristate
>         depends on (SPI_MASTER || I2C)
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index aed99f0..c82b442 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -15,6 +15,7 @@ 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_EXYNOS_LPASS) += exynos-lpass.o
> +obj-$(CONFIG_MFD_GATEWORKS_GSC)        += gateworks-gsc.o
>
>  obj-$(CONFIG_HTC_PASIC3)       += htc-pasic3.o
>  obj-$(CONFIG_HTC_I2CPLD)       += htc-i2cpld.o
> diff --git a/drivers/mfd/gateworks-gsc.c b/drivers/mfd/gateworks-gsc.c
> new file mode 100644
> index 00000000..020e1e1
> --- /dev/null
> +++ b/drivers/mfd/gateworks-gsc.c
> @@ -0,0 +1,288 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * The Gateworks System Controller (GSC) is a multi-function
> + * device designed for use in Gateworks Single Board Computers.
> + * The control interface is I2C, with an interrupt. The device supports
> + * system functions such as pushbutton monitoring, multiple ADC's for
> + * voltage and temperature, fan controller, and watchdog monitor.
> + *
> + * Copyright (C) 2020 Gateworks Corporation
> + */
> +#include <linux/device.h>
> +#include <linux/i2c.h>
> +#include <linux/interrupt.h>
> +#include <linux/mfd/gsc.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/of.h>
> +#include <linux/of_platform.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +
> +/*
> + * The GSC suffers from an errata where occasionally during
> + * ADC cycles the chip can NAK I2C transactions. To ensure we have reliable
> + * register access we place retries around register access.
> + */
> +#define I2C_RETRIES    3
> +
> +static int gsc_regmap_regwrite(void *context, unsigned int reg,
> +                              unsigned int val)
> +{
> +       struct i2c_client *client = context;
> +       int retry, ret;
> +
> +       for (retry = 0; retry < I2C_RETRIES; retry++) {
> +               ret = i2c_smbus_write_byte_data(client, reg, val);
> +               /*
> +                * -EAGAIN returned when the i2c host controller is busy
> +                * -EIO returned when i2c device is busy
> +                */
> +               if (ret != -EAGAIN && ret != -EIO)
> +                       break;
> +       }
> +
> +       return 0;
> +}
> +
> +static int gsc_regmap_regread(void *context, unsigned int reg,
> +                             unsigned int *val)
> +{
> +       struct i2c_client *client = context;
> +       int retry, ret;
> +
> +       for (retry = 0; retry < I2C_RETRIES; retry++) {
> +               ret = i2c_smbus_read_byte_data(client, reg);
> +               /*
> +                * -EAGAIN returned when the i2c host controller is busy
> +                * -EIO returned when i2c device is busy
> +                */
> +               if (ret != -EAGAIN && ret != -EIO)
> +                       break;
> +       }
> +       *val = ret & 0xff;
> +
> +       return 0;
> +}
> +
> +/*
> + * gsc_powerdown - API to use GSC to power down board for a specific time
> + *
> + * secs - number of seconds to remain powered off
> + */
> +static int gsc_powerdown(struct gsc_dev *gsc, unsigned long secs)
> +{
> +       int ret;
> +       unsigned char regs[4];
> +
> +       dev_info(&gsc->i2c->dev, "GSC powerdown for %ld seconds\n",
> +                secs);
> +
> +       regs[0] = secs & 0xff;
> +       regs[1] = (secs >> 8) & 0xff;
> +       regs[2] = (secs >> 16) & 0xff;
> +       regs[3] = (secs >> 24) & 0xff;
> +
> +       ret = regmap_bulk_write(gsc->regmap, GSC_TIME_ADD, regs, 4);
> +       if (ret)
> +               return ret;
> +
> +       regs[0] = 1 << GSC_CTRL_1_LATCH_SLEEP_ADD;
> +
> +       ret = regmap_update_bits(gsc->regmap, GSC_CTRL_1, regs[0], regs[0]);
> +       if (ret)
> +               return ret;
> +
> +       regs[0] = (1 << GSC_CTRL_1_ACTIVATE_SLEEP) |
> +               (1 << GSC_CTRL_1_SLEEP_ENABLE);
> +
> +       ret = regmap_update_bits(gsc->regmap, GSC_CTRL_1, regs[0], regs[0]);
> +
> +       return ret;
> +}
> +
> +static ssize_t gsc_show(struct device *dev, struct device_attribute *attr,
> +                       char *buf)
> +{
> +       struct gsc_dev *gsc = dev_get_drvdata(dev);
> +       const char *name = attr->attr.name;
> +       int rz = 0;
> +
> +       if (strcasecmp(name, "fw_version") == 0)
> +               rz = sprintf(buf, "%d\n", gsc->fwver);
> +       else if (strcasecmp(name, "fw_crc") == 0)
> +               rz = sprintf(buf, "0x%04x\n", gsc->fwcrc);
> +       else
> +               dev_err(dev, "invalid command: '%s'\n", name);
> +
> +       return rz;
> +}
> +
> +static ssize_t gsc_store(struct device *dev, struct device_attribute *attr,
> +                        const char *buf, size_t count)
> +{
> +       struct gsc_dev *gsc = dev_get_drvdata(dev);
> +       const char *name = attr->attr.name;
> +       long value;
> +
> +       if (strcasecmp(name, "powerdown") == 0) {
> +               if (kstrtol(buf, 0, &value) == 0)
> +                       gsc_powerdown(gsc, value);
> +       } else {
> +               dev_err(dev, "invalid command: '%s\n", name);
> +       }
> +
> +       return count;
> +}
> +
> +static struct device_attribute attr_fwver =
> +       __ATTR(fw_version, 0440, gsc_show, NULL);
> +static struct device_attribute attr_fwcrc =
> +       __ATTR(fw_crc, 0440, gsc_show, NULL);
> +static struct device_attribute attr_pwrdown =
> +       __ATTR(powerdown, 0220, NULL, gsc_store);
> +
> +static struct attribute *gsc_attrs[] = {
> +       &attr_fwver.attr,
> +       &attr_fwcrc.attr,
> +       &attr_pwrdown.attr,
> +       NULL,
> +};
> +
> +static struct attribute_group attr_group = {
> +       .attrs = gsc_attrs,
> +};
> +
> +static const struct of_device_id gsc_of_match[] = {
> +       { .compatible = "gw,gsc", },
> +       { }
> +};
> +MODULE_DEVICE_TABLE(of, gsc_of_match);
> +
> +static const struct regmap_config gsc_regmap_config = {
> +       .reg_bits = 8,
> +       .val_bits = 8,
> +       .cache_type = REGCACHE_NONE,
> +       .max_register = 0xf,
> +};
> +
> +static const struct regmap_irq gsc_irqs[] = {
> +       REGMAP_IRQ_REG(GSC_IRQ_PB, 0, BIT(GSC_IRQ_PB)),
> +       REGMAP_IRQ_REG(GSC_IRQ_KEY_ERASED, 0, BIT(GSC_IRQ_KEY_ERASED)),
> +       REGMAP_IRQ_REG(GSC_IRQ_EEPROM_WP, 0, BIT(GSC_IRQ_EEPROM_WP)),
> +       REGMAP_IRQ_REG(GSC_IRQ_RESV, 0, BIT(GSC_IRQ_RESV)),
> +       REGMAP_IRQ_REG(GSC_IRQ_GPIO, 0, BIT(GSC_IRQ_GPIO)),
> +       REGMAP_IRQ_REG(GSC_IRQ_TAMPER, 0, BIT(GSC_IRQ_TAMPER)),
> +       REGMAP_IRQ_REG(GSC_IRQ_WDT_TIMEOUT, 0, BIT(GSC_IRQ_WDT_TIMEOUT)),
> +       REGMAP_IRQ_REG(GSC_IRQ_SWITCH_HOLD, 0, BIT(GSC_IRQ_SWITCH_HOLD)),
> +};
> +
> +static const struct regmap_irq_chip gsc_irq_chip = {
> +       .name = "gateworks-gsc",
> +       .irqs = gsc_irqs,
> +       .num_irqs = ARRAY_SIZE(gsc_irqs),
> +       .num_regs = 1,
> +       .status_base = GSC_IRQ_STATUS,
> +       .mask_base = GSC_IRQ_ENABLE,
> +       .mask_invert = true,
> +       .ack_base = GSC_IRQ_STATUS,
> +       .ack_invert = true,
> +};
> +
> +static int gsc_probe(struct i2c_client *client)
> +{
> +       struct device *dev = &client->dev;
> +       struct gsc_dev *gsc;
> +       int ret;
> +       unsigned int reg;
> +
> +       gsc = devm_kzalloc(dev, sizeof(*gsc), GFP_KERNEL);
> +       if (!gsc)
> +               return -ENOMEM;
> +
> +       gsc->dev = &client->dev;
> +       gsc->i2c = client;
> +       i2c_set_clientdata(client, gsc);
> +
> +       gsc->bus.reg_write = gsc_regmap_regwrite;
> +       gsc->bus.reg_read = gsc_regmap_regread;
> +       gsc->regmap = devm_regmap_init(dev, &gsc->bus, client,
> +                                      &gsc_regmap_config);
> +       if (IS_ERR(gsc->regmap))
> +               return PTR_ERR(gsc->regmap);
> +
> +       if (regmap_read(gsc->regmap, GSC_FW_VER, &reg))
> +               return -EIO;
> +       gsc->fwver = reg;
> +
> +       regmap_read(gsc->regmap, GSC_FW_CRC, &reg);
> +       gsc->fwcrc = reg;
> +       regmap_read(gsc->regmap, GSC_FW_CRC + 1, &reg);
> +       gsc->fwcrc |= reg << 8;
> +
> +       gsc->i2c_hwmon = i2c_new_dummy_device(client->adapter, GSC_HWMON);
> +       if (!gsc->i2c_hwmon) {
> +               dev_err(dev, "Failed to allocate I2C device for HWMON\n");
> +               return -ENODEV;
> +       }
> +       i2c_set_clientdata(gsc->i2c_hwmon, gsc);
> +
> +       ret = devm_regmap_add_irq_chip(dev, gsc->regmap, client->irq,
> +                                      IRQF_ONESHOT | IRQF_SHARED |
> +                                      IRQF_TRIGGER_FALLING, 0,
> +                                      &gsc_irq_chip, &gsc->irq_chip_data);
> +       if (ret)
> +               goto err_regmap;
> +
> +       dev_info(dev, "Gateworks System Controller v%d: fw 0x%04x\n",
> +                gsc->fwver, gsc->fwcrc);
> +
> +       ret = sysfs_create_group(&dev->kobj, &attr_group);
> +       if (ret)
> +               dev_err(dev, "failed to create sysfs attrs\n");
> +
> +       ret = devm_of_platform_populate(dev);
> +       if (ret)
> +               goto err_sysfs;
> +
> +       return 0;
> +
> +err_sysfs:
> +       sysfs_remove_group(&dev->kobj, &attr_group);
> +err_regmap:
> +       i2c_unregister_device(gsc->i2c_hwmon);
> +
> +       return ret;
> +}
> +
> +static int gsc_remove(struct i2c_client *client)
> +{
> +       struct gsc_dev *gsc = i2c_get_clientdata(client);
> +
> +       sysfs_remove_group(&client->dev.kobj, &attr_group);
> +       i2c_unregister_device(gsc->i2c_hwmon);
> +
> +       return 0;
> +}
> +
> +static const struct i2c_device_id gsc_id_table[] = {
> +       {"gsc", GSC_MISC },
> +       { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(i2c, gsc_id_table);
> +
> +static struct i2c_driver gsc_driver = {
> +       .driver = {
> +               .name   = "gateworks-gsc",
> +               .of_match_table = gsc_of_match,
> +       },
> +       .id_table       = gsc_id_table,
> +       .probe_new      = gsc_probe,
> +       .remove         = gsc_remove,
> +};
> +
> +module_i2c_driver(gsc_driver);
> +
> +MODULE_AUTHOR("Tim Harvey <tharvey@...eworks.com>");
> +MODULE_DESCRIPTION("I2C Core interface for GSC");
> +MODULE_LICENSE("GPL v2");
> diff --git a/include/linux/mfd/gsc.h b/include/linux/mfd/gsc.h
> new file mode 100644
> index 00000000..fc33647
> --- /dev/null
> +++ b/include/linux/mfd/gsc.h
> @@ -0,0 +1,73 @@
> +/* SPDX-License-Identifier: GPL-2.0
> + *
> + * Copyright (C) 2020 Gateworks Corporation
> + */
> +#ifndef __LINUX_MFD_GSC_H_
> +#define __LINUX_MFD_GSC_H_
> +
> +#include <linux/regmap.h>
> +
> +/* Device Addresses */
> +#define GSC_MISC       0x20
> +#define GSC_UPDATE     0x21
> +#define GSC_GPIO       0x23
> +#define GSC_HWMON      0x29
> +#define GSC_EEPROM0    0x50
> +#define GSC_EEPROM1    0x51
> +#define GSC_EEPROM2    0x52
> +#define GSC_EEPROM3    0x53
> +#define GSC_RTC                0x68
> +
> +/* Register offsets */
> +#define GSC_CTRL_0     0x00
> +#define GSC_CTRL_1     0x01
> +#define GSC_TIME       0x02
> +#define GSC_TIME_ADD   0x06
> +#define GSC_IRQ_STATUS 0x0A
> +#define GSC_IRQ_ENABLE 0x0B
> +#define GSC_FW_CRC     0x0C
> +#define GSC_FW_VER     0x0E
> +#define GSC_WP         0x0F
> +
> +/* Bit definitions */
> +#define GSC_CTRL_0_PB_HARD_RESET       0
> +#define GSC_CTRL_0_PB_CLEAR_SECURE_KEY 1
> +#define GSC_CTRL_0_PB_SOFT_POWER_DOWN  2
> +#define GSC_CTRL_0_PB_BOOT_ALTERNATE   3
> +#define GSC_CTRL_0_PERFORM_CRC         4
> +#define GSC_CTRL_0_TAMPER_DETECT       5
> +#define GSC_CTRL_0_SWITCH_HOLD         6
> +
> +#define GSC_CTRL_1_SLEEP_ENABLE                0
> +#define GSC_CTRL_1_ACTIVATE_SLEEP      1
> +#define GSC_CTRL_1_LATCH_SLEEP_ADD     2
> +#define GSC_CTRL_1_SLEEP_NOWAKEPB      3
> +#define GSC_CTRL_1_WDT_TIME            4
> +#define GSC_CTRL_1_WDT_ENABLE          5
> +#define GSC_CTRL_1_SWITCH_BOOT_ENABLE  6
> +#define GSC_CTRL_1_SWITCH_BOOT_CLEAR   7
> +
> +#define GSC_IRQ_PB                     0
> +#define GSC_IRQ_KEY_ERASED             1
> +#define GSC_IRQ_EEPROM_WP              2
> +#define GSC_IRQ_RESV                   3
> +#define GSC_IRQ_GPIO                   4
> +#define GSC_IRQ_TAMPER                 5
> +#define GSC_IRQ_WDT_TIMEOUT            6
> +#define GSC_IRQ_SWITCH_HOLD            7
> +
> +struct gsc_dev {
> +       struct device *dev;
> +
> +       struct i2c_client *i2c;         /* 0x20: interrupt controller, WDT */
> +       struct i2c_client *i2c_hwmon;   /* 0x29: hwmon, fan controller */
> +
> +       struct regmap *regmap;
> +       struct regmap_bus bus;
> +       struct regmap_irq_chip_data *irq_chip_data;
> +
> +       unsigned int fwver;
> +       unsigned short fwcrc;
> +};
> +
> +#endif /* __LINUX_MFD_GSC_H_ */
> --
> 2.7.4
>

Lee,

Do you have time to look at this? Rob has reviewed the dt-bindings and
Guenter has reviewed the hwmon driver so this is the only patch
remaining in the series that needs review/sign-off.

Best Regards,

Tim

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