Message-ID: <2feb1cf1-7597-9762-0864-87dc9c2c5559@linux.intel.com>
Date: Fri, 16 Aug 2024 16:56:24 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Andres Salomon <dilinger@...ued.net>
cc: LKML <linux-kernel@...r.kernel.org>, 
    Pali Rohár <pali@...nel.org>, 
    platform-driver-x86@...r.kernel.org, Matthew Garrett <mjg59@...f.ucam.org>, 
    Sebastian Reichel <sre@...nel.org>, Hans de Goede <hdegoede@...hat.com>, 
    linux-pm@...r.kernel.org, Dell.Client.Kernel@...l.com
Subject: Re: [PATCH v3 1/2] platform/x86:dell-laptop: Add knobs to change 
 battery charge settings

On Thu, 15 Aug 2024, Andres Salomon wrote:

> The Dell BIOS allows you to set custom charging modes, which is useful
> in particular for extending battery life. This adds support for tweaking
> those various settings from Linux via sysfs knobs. One might, for
> example, have their laptop plugged into power at their desk the vast
> majority of the time and choose fairly aggressive battery-saving
> settings (eg, only charging once the battery drops below 50% and only
> charging up to 80%). When leaving for a trip, it would be more useful
> to instead switch to a standard charging mode (top off at 100%, charge
> any time power is available). Rebooting into the BIOS to change the
> charging mode settings is a hassle.
> 
> For the Custom charging type mode, we reuse the common
> charge_control_{start,end}_threshold sysfs power_supply entries. The
> BIOS also has a bunch of other charging modes (with varying levels of
> usefulness), so this also adds a 'charge_type' sysfs entry that maps the
> standard values to Dell-specific ones and documents those mappings in
> sysfs-class-power-dell.
> 
> This work is based on a patch by Perry Yuan <perry_yuan@...l.com> and
> Limonciello Mario <Mario_Limonciello@...l.com> submitted back in 2020:
> https://lore.kernel.org/all/20200729065424.12851-1-Perry_Yuan@Dell.com/
> Both of their email addresses bounce, so I'm assuming they're no longer
> with the company. I've reworked most of the patch to make it smaller and
> cleaner.
> 
> Signed-off-by: Andres Salomon <dilinger@...ued.net>
> ---
> Changes in v3:
>     - switch tokenid and class types
>     - be stricter with results from both userspace and BIOS
>     - no longer allow failed BIOS reads
>     - rename/move dell_send_request_by_token_loc, and add helper function
>     - only allow registration for BAT0
>     - rename charge_type modes to match power_supply names
> Changes in v2, based on extensive feedback from Pali Rohár <pali@...nel.org>:
>     - code style changes
>     - change battery write API to use token->value instead of passed value
>     - stop caching current mode, instead querying SMBIOS as needed
>     - drop the separate list of charging modes enum
>     - rework the list of charging mode strings
>     - query SMBIOS for supported charging modes
>     - split dell_battery_custom_set() up
> ---
>  .../ABI/testing/sysfs-class-power-dell        |  33 ++
>  drivers/platform/x86/dell/Kconfig             |   1 +
>  drivers/platform/x86/dell/dell-laptop.c       | 316 ++++++++++++++++++
>  drivers/platform/x86/dell/dell-smbios.h       |   7 +
>  4 files changed, 357 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-class-power-dell
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-power-dell b/Documentation/ABI/testing/sysfs-class-power-dell
> new file mode 100644
> index 000000000000..d8c542177558
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-class-power-dell
> @@ -0,0 +1,33 @@
> +What:		/sys/class/power_supply/<supply_name>/charge_type
> +Date:		August 2024
> +KernelVersion:	6.12
> +Contact:	linux-pm@...r.kernel.org
> +Description:
> +		Select the charging algorithm to use for the (primary)
> +		battery.
> +
> +		Standard:
> +			Fully charge the battery at a moderate rate.
> +		Fast:
> +			Quickly charge the battery using fast-charge
> +			technology. This is harder on the battery than
> +			standard charging and may lower its lifespan.
> +			The Dell BIOS calls this ExpressCharge™.
> +		Trickle:
> +			Users who primarily operate the system while
> +			plugged into an external power source can extend
> +			battery life with this mode. The Dell BIOS calls
> +			this "Primarily AC Use".
> +		Adaptive:
> +			Automatically optimize battery charge rate based
> +			on typical usage pattern.
> +		Custom:
> +			Use the charge_control_* properties to determine
> +			when to start and stop charging. Advanced users
> +			can use this to drastically extend battery life.
> +
> +		Access: Read, Write
> +		Valid values:
> +			      "Standard", "Fast", "Trickle",
> +			      "Adaptive", "Custom"
> +
> diff --git a/drivers/platform/x86/dell/Kconfig b/drivers/platform/x86/dell/Kconfig
> index 85a78ef91182..02405793163c 100644
> --- a/drivers/platform/x86/dell/Kconfig
> +++ b/drivers/platform/x86/dell/Kconfig
> @@ -49,6 +49,7 @@ config DELL_LAPTOP
>  	default m
>  	depends on DMI
>  	depends on BACKLIGHT_CLASS_DEVICE
> +	depends on ACPI_BATTERY
>  	depends on ACPI_VIDEO || ACPI_VIDEO = n
>  	depends on RFKILL || RFKILL = n
>  	depends on DELL_WMI || DELL_WMI = n
> diff --git a/drivers/platform/x86/dell/dell-laptop.c b/drivers/platform/x86/dell/dell-laptop.c
> index 6552dfe491c6..8cc05f0fab91 100644
> --- a/drivers/platform/x86/dell/dell-laptop.c
> +++ b/drivers/platform/x86/dell/dell-laptop.c
> @@ -22,11 +22,13 @@
>  #include <linux/io.h>
>  #include <linux/rfkill.h>
>  #include <linux/power_supply.h>
> +#include <linux/sysfs.h>
>  #include <linux/acpi.h>
>  #include <linux/mm.h>
>  #include <linux/i8042.h>
>  #include <linux/debugfs.h>
>  #include <linux/seq_file.h>
> +#include <acpi/battery.h>
>  #include <acpi/video.h>
>  #include "dell-rbtn.h"
>  #include "dell-smbios.h"
> @@ -99,6 +101,18 @@ static bool force_rfkill;
>  static bool micmute_led_registered;
>  static bool mute_led_registered;
>  
> +static const struct {
> +	int token;
> +	const char *label;
> +} battery_modes[] = {

Please don't try to do this in one go but split it into two (define and 
then declaration of the variable).

> +	{ BAT_STANDARD_MODE_TOKEN, "Standard" },
> +	{ BAT_EXPRESS_MODE_TOKEN, "Fast" },
> +	{ BAT_PRI_AC_MODE_TOKEN, "Trickle" },
> +	{ BAT_ADAPTIVE_MODE_TOKEN, "Adaptive" },
> +	{ BAT_CUSTOM_MODE_TOKEN, "Custom" },

I suggest aligning the strings with tabs for better readability.

> +};
> +static u32 battery_supported_modes;
> +
>  module_param(force_rfkill, bool, 0444);
>  MODULE_PARM_DESC(force_rfkill, "enable rfkill on non whitelisted models");
>  
> @@ -353,6 +367,32 @@ static const struct dmi_system_id dell_quirks[] __initconst = {
>  	{ }
>  };
>  
> +/* -1 is a sentinel value, telling us to use token->value */
> +#define USE_TVAL ((u32) -1)
> +static int dell_send_request_for_tokenid(struct calling_interface_buffer *buffer,
> +					 u16 class, u16 select, u16 tokenid,
> +					 u32 val)
> +{
> +	struct calling_interface_token *token;
> +
> +	token = dell_smbios_find_token(tokenid);
> +	if (!token)
> +		return -ENODEV;
> +
> +	if (val == USE_TVAL)
> +		val = token->value;
> +
> +	dell_fill_request(buffer, token->location, val, 0, 0);
> +	return dell_send_request(buffer, class, select);
> +}
> +
> +static inline int dell_set_std_token_value(struct calling_interface_buffer *buffer,
> +		u16 tokenid, u32 value)
> +{
> +	return dell_send_request_for_tokenid(buffer, CLASS_TOKEN_WRITE,
> +			SELECT_TOKEN_STD, tokenid, value);
> +}
> +
>  /*
>   * Derived from information in smbios-wireless-ctl:
>   *
> @@ -2183,6 +2223,279 @@ static struct led_classdev mute_led_cdev = {
>  	.default_trigger = "audio-mute",
>  };
>  
> +static int dell_battery_set_mode(const u16 tokenid)
> +{
> +	struct calling_interface_buffer buffer;
> +
> +	return dell_set_std_token_value(&buffer, tokenid, USE_TVAL);
> +}
> +
> +static int dell_battery_read(const u16 tokenid)
> +{
> +	struct calling_interface_buffer buffer;
> +	int err;
> +
> +	err = dell_send_request_for_tokenid(&buffer, CLASS_TOKEN_READ,
> +			SELECT_TOKEN_STD, tokenid, 0);
> +	if (err)
> +		return err;
> +
> +	if (buffer.output[1] > INT_MAX)
> +		return -EIO;
> +
> +	return buffer.output[1];
> +}
> +
> +static bool dell_battery_mode_is_active(const u16 tokenid)
> +{
> +	struct calling_interface_token *token;
> +	int ret;
> +
> +	ret = dell_battery_read(tokenid);
> +	if (ret < 0)
> +		return false;
> +
> +	token = dell_smbios_find_token(tokenid);
> +	/* token's already verified by dell_battery_read() */
> +
> +	return token->value == (u16) ret;
> +}
> +
> +/*
> + * The rules: the minimum start charging value is 50%. The maximum
> + * start charging value is 95%. The minimum end charging value is
> + * 55%. The maximum end charging value is 100%. And finally, there
> + * has to be at least a 5% difference between start & end values.
> + */
> +#define CHARGE_START_MIN	50
> +#define CHARGE_START_MAX	95
> +#define CHARGE_END_MIN		55
> +#define CHARGE_END_MAX		100
> +#define CHARGE_MIN_DIFF		5
> +
> +static int dell_battery_set_custom_charge_start(int start)
> +{
> +	struct calling_interface_buffer buffer;
> +	int end;
> +
> +	if (start < CHARGE_START_MIN)
> +		start = CHARGE_START_MIN;
> +	else if (start > CHARGE_START_MAX)
> +		start = CHARGE_START_MAX;

We have clamp().

> +
> +	end = dell_battery_read(BAT_CUSTOM_CHARGE_END);
> +	if (end < 0)
> +		return end;
> +	if ((end - start) < CHARGE_MIN_DIFF)

Extra parenthesis.

> +		start = end - CHARGE_MIN_DIFF;
> +
> +	return dell_set_std_token_value(&buffer, BAT_CUSTOM_CHARGE_START,
> +			start);
> +}
> +
> +static int dell_battery_set_custom_charge_end(int end)
> +{
> +	struct calling_interface_buffer buffer;
> +	int start;
> +
> +	if (end < CHARGE_END_MIN)
> +		end = CHARGE_END_MIN;
> +	else if (end > CHARGE_END_MAX)
> +		end = CHARGE_END_MAX;

clamp.

> +	start = dell_battery_read(BAT_CUSTOM_CHARGE_START);
> +	if (start < 0)
> +		return start;
> +	if ((end - start) < CHARGE_MIN_DIFF)

Extra parenthesis.

> +		end = start + CHARGE_MIN_DIFF;
> +
> +	return dell_set_std_token_value(&buffer, BAT_CUSTOM_CHARGE_END, end);
> +}
> +
> +static ssize_t charge_type_show(struct device *dev,
> +		struct device_attribute *attr,
> +		char *buf)
> +{
> +	ssize_t count = 0;
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(battery_modes); i++) {
> +		bool active;
> +
> +		if (!(battery_supported_modes & BIT(i)))

Why not store this supported information into battery_modes itself?
What's the benefit of obfuscation it with the extra variable & BIT()?

-- 
 i.

> +			continue;
> +
> +		active = dell_battery_mode_is_active(battery_modes[i].token);
> +		count += sysfs_emit_at(buf, count, active ? "[%s] " : "%s ",
> +				battery_modes[i].label);
> +	}
> +
> +	/* convert the last space to a newline */
> +	if (count > 0)
> +		count--;
> +	count += sysfs_emit_at(buf, count, "\n");
> +
> +	return count;
> +}
> +
> +static ssize_t charge_type_store(struct device *dev,
> +		struct device_attribute *attr,
> +		const char *buf, size_t size)
> +{
> +	bool matched = false;
> +	int err, i;
> +
> +	for (i = 0; i < ARRAY_SIZE(battery_modes); i++) {
> +		if (!(battery_supported_modes & BIT(i)))
> +			continue;
> +
> +		if (sysfs_streq(battery_modes[i].label, buf)) {
> +			matched = true;
> +			break;
> +		}
> +	}
> +	if (!matched || !(battery_supported_modes & BIT(i)))
> +		return -EINVAL;
> +
> +	err = dell_battery_set_mode(battery_modes[i].token);
> +	if (err)
> +		return err;
> +
> +	return size;
> +}
> +
> +static ssize_t charge_control_start_threshold_show(struct device *dev,
> +		struct device_attribute *attr,
> +		char *buf)
> +{
> +	int start;
> +
> +	start = dell_battery_read(BAT_CUSTOM_CHARGE_START);
> +	if (start < 0)
> +		return start;
> +
> +	if (start > CHARGE_START_MAX)
> +		return -EIO;
> +
> +	return sysfs_emit(buf, "%d\n", start);
> +}
> +
> +static ssize_t charge_control_start_threshold_store(struct device *dev,
> +		struct device_attribute *attr,
> +		const char *buf, size_t size)
> +{
> +	int ret, start;
> +
> +	ret = kstrtoint(buf, 10, &start);
> +	if (ret)
> +		return ret;
> +	if (start < 0 || start > 100)
> +		return -EINVAL;
> +
> +	ret = dell_battery_set_custom_charge_start(start);
> +	if (ret)
> +		return ret;
> +
> +	return size;
> +}
> +
> +static ssize_t charge_control_end_threshold_show(struct device *dev,
> +		struct device_attribute *attr,
> +		char *buf)
> +{
> +	int end;
> +
> +	end = dell_battery_read(BAT_CUSTOM_CHARGE_END);
> +	if (end < 0)
> +		return end;
> +
> +	if (end > CHARGE_END_MAX)
> +		return -EIO;
> +
> +	return sysfs_emit(buf, "%d\n", end);
> +}
> +
> +static ssize_t charge_control_end_threshold_store(struct device *dev,
> +		struct device_attribute *attr,
> +		const char *buf, size_t size)
> +{
> +	int ret, end;
> +
> +	ret = kstrtouint(buf, 10, &end);
> +	if (ret)
> +		return ret;
> +	if (end < 0 || end > 100)
> +		return -EINVAL;
> +
> +	ret = dell_battery_set_custom_charge_end(end);
> +	if (ret)
> +		return ret;
> +
> +	return size;
> +}
> +
> +static DEVICE_ATTR_RW(charge_control_start_threshold);
> +static DEVICE_ATTR_RW(charge_control_end_threshold);
> +static DEVICE_ATTR_RW(charge_type);
> +
> +static struct attribute *dell_battery_attrs[] = {
> +	&dev_attr_charge_control_start_threshold.attr,
> +	&dev_attr_charge_control_end_threshold.attr,
> +	&dev_attr_charge_type.attr,
> +	NULL,
> +};
> +ATTRIBUTE_GROUPS(dell_battery);
> +
> +static int dell_battery_add(struct power_supply *battery,
> +		struct acpi_battery_hook *hook)
> +{
> +	/* this currently only supports the primary battery */
> +	if (strcmp(battery->desc->name, "BAT0") != 0)
> +		return -ENODEV;
> +
> +	return device_add_groups(&battery->dev, dell_battery_groups);
> +}
> +
> +static int dell_battery_remove(struct power_supply *battery,
> +		struct acpi_battery_hook *hook)
> +{
> +	device_remove_groups(&battery->dev, dell_battery_groups);
> +	return 0;
> +}
> +
> +static struct acpi_battery_hook dell_battery_hook = {
> +	.add_battery = dell_battery_add,
> +	.remove_battery = dell_battery_remove,
> +	.name = "Dell Primary Battery Extension",
> +};
> +
> +static u32 __init battery_get_supported_modes(void)
> +{
> +	u32 modes = 0;
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(battery_modes); i++) {
> +		if (dell_smbios_find_token(battery_modes[i].token))
> +			modes |= BIT(i);
> +	}
> +
> +	return modes;
> +}
> +
> +static void __init dell_battery_init(struct device *dev)
> +{
> +	battery_supported_modes = battery_get_supported_modes();
> +
> +	if (battery_supported_modes != 0)
> +		battery_hook_register(&dell_battery_hook);
> +}
> +
> +static void __exit dell_battery_exit(void)
> +{
> +	if (battery_supported_modes != 0)
> +		battery_hook_unregister(&dell_battery_hook);
> +}
> +
>  static int __init dell_init(void)
>  {
>  	struct calling_interface_token *token;
> @@ -2219,6 +2532,7 @@ static int __init dell_init(void)
>  		touchpad_led_init(&platform_device->dev);
>  
>  	kbd_led_init(&platform_device->dev);
> +	dell_battery_init(&platform_device->dev);
>  
>  	dell_laptop_dir = debugfs_create_dir("dell_laptop", NULL);
>  	debugfs_create_file("rfkill", 0444, dell_laptop_dir, NULL,
> @@ -2293,6 +2607,7 @@ static int __init dell_init(void)
>  	if (mute_led_registered)
>  		led_classdev_unregister(&mute_led_cdev);
>  fail_led:
> +	dell_battery_exit();
>  	dell_cleanup_rfkill();
>  fail_rfkill:
>  	platform_device_del(platform_device);
> @@ -2311,6 +2626,7 @@ static void __exit dell_exit(void)
>  	if (quirks && quirks->touchpad_led)
>  		touchpad_led_exit();
>  	kbd_led_exit();
> +	dell_battery_exit();
>  	backlight_device_unregister(dell_backlight_device);
>  	if (micmute_led_registered)
>  		led_classdev_unregister(&micmute_led_cdev);
> diff --git a/drivers/platform/x86/dell/dell-smbios.h b/drivers/platform/x86/dell/dell-smbios.h
> index ea0cc38642a2..77baa15eb523 100644
> --- a/drivers/platform/x86/dell/dell-smbios.h
> +++ b/drivers/platform/x86/dell/dell-smbios.h
> @@ -33,6 +33,13 @@
>  #define KBD_LED_AUTO_50_TOKEN	0x02EB
>  #define KBD_LED_AUTO_75_TOKEN	0x02EC
>  #define KBD_LED_AUTO_100_TOKEN	0x02F6
> +#define BAT_PRI_AC_MODE_TOKEN	0x0341
> +#define BAT_ADAPTIVE_MODE_TOKEN	0x0342
> +#define BAT_CUSTOM_MODE_TOKEN	0x0343
> +#define BAT_STANDARD_MODE_TOKEN	0x0346
> +#define BAT_EXPRESS_MODE_TOKEN	0x0347
> +#define BAT_CUSTOM_CHARGE_START	0x0349
> +#define BAT_CUSTOM_CHARGE_END	0x034A
>  #define GLOBAL_MIC_MUTE_ENABLE	0x0364
>  #define GLOBAL_MIC_MUTE_DISABLE	0x0365
>  #define GLOBAL_MUTE_ENABLE	0x058C
> 

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