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SubjectRe: [PATCH v7 2/3] mfd: add Gateworks System Controller core driver
On Fri, 20 Mar 2020, Tim Harvey 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@infradead.org>
> Signed-off-by: Tim Harvey <tharvey@gateworks.com>
> ---
> 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 | 291 ++++++++++++++++++++++++++++++++++++++++++++
> include/linux/mfd/gsc.h | 71 +++++++++++
> 5 files changed, 381 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@gateworks.com>
> +M: Robert Jones <rjones@gateworks.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@chromium.org>
> R: Emese Revfy <re.emese@gmail.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.

Please describe which sub-devices are attached.

> 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..8566123
> --- /dev/null
> +++ b/drivers/mfd/gateworks-gsc.c
> @@ -0,0 +1,291 @@
> +// 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.

When are you planning on adding support for the other devices?

> + * Copyright (C) 2020 Gateworks Corporation
> + *

Superfluous '\n'.

> + */
> +#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;
> +}
> +
> +static struct regmap_bus regmap_gsc = {
> + .reg_write = gsc_regmap_regwrite,
> + .reg_read = gsc_regmap_regread,
> +};
> +
> +/*
> + * 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];

No error checking? Could be down for a very long time.

> + dev_info(&gsc->i2c->dev, "GSC powerdown for %ld seconds\n",
> + secs);

Nit: '\n' here.

> + regs[0] = secs & 0xff;
> + regs[1] = (secs >> 8) & 0xff;
> + regs[2] = (secs >> 16) & 0xff;
> + regs[3] = (secs >> 24) & 0xff;

Nit: '\n' here.

> + ret = regmap_bulk_write(gsc->regmap, GSC_TIME_ADD, regs, 4);
> + if (ret)
> + return ret;

Nit: '\n' here.

> + regs[0] = 1 << GSC_CTRL_1_LATCH_SLEEP_ADD;

Nit: '\n' here.

> + ret = regmap_update_bits(gsc->regmap, GSC_CTRL_1, regs[0], regs[0]);
> + if (ret)
> + return ret;

Nit: '\n' here.

> + regs[0] = (1 << GSC_CTRL_1_ACTIVATE_SLEEP) |
> + (1 << GSC_CTRL_1_SLEEP_ENABLE);

Nit: '\n' here.

> + 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);

No error message for non-matched commands?

> + 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 name '%s\n", name);
> + }

Name? Isn't it more of a command?

> + 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", },
> + { }
> +};
> +
> +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_config gsc_regmap_hwmon_config = {
> + .reg_bits = 8,
> + .val_bits = 8,
> + .cache_type = REGCACHE_NONE,
> +};
> +
> +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

Break the arguments instead.

> +gsc_probe(struct i2c_client *client, const struct i2c_device_id *id)
> +{
> + 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->regmap = devm_regmap_init(dev, &regmap_gsc, 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;

You not checking this for a valid value?

> + 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);
> +
> + gsc->regmap_hwmon = devm_regmap_init(dev, &regmap_gsc, gsc->i2c_hwmon,
> + &gsc_regmap_hwmon_config);
> + if (IS_ERR(gsc->regmap_hwmon)) {
> + ret = PTR_ERR(gsc->regmap_hwmon);
> + dev_err(dev, "failed to allocate register map: %d\n", ret);
> + goto err_regmap;
> + }

Why can't the HWMON driver fetch its own Regmap?

> + 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 = of_platform_populate(dev->of_node, NULL, NULL, dev);

devm_*?

> + 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 struct i2c_driver gsc_driver = {
> + .driver = {
> + .name = "gateworks-gsc",
> + .of_match_table = of_match_ptr(gsc_of_match),
> + },
> + .probe = gsc_probe,

I think you need to use .probe_new OR supply an I2C device table. Not
sure why/how this is working for you currently.

> + .remove = gsc_remove,
> +};
> +
> +module_i2c_driver(gsc_driver);
> +
> +MODULE_AUTHOR("Tim Harvey <tharvey@gateworks.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..a04e613
> --- /dev/null
> +++ b/include/linux/mfd/gsc.h
> @@ -0,0 +1,71 @@
> +/* SPDX-License-Identifier: GPL-2.0
> + *
> + * Copyright (C) 2018 Gateworks Corporation

This is out of date.

> + */
> +#ifndef __LINUX_MFD_GSC_H_
> +#define __LINUX_MFD_GSC_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 *regmap_hwmon;
> + struct regmap_irq_chip_data *irq_chip_data;
> +
> + unsigned int fwver;
> + unsigned short fwcrc;
> +};
> +
> +#endif /* __LINUX_MFD_GSC_H_ */

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