Re: [PATCH v3 1/2] platform/x86:dell-laptop: Add knobs to change battery charge settings

Ilpo Järvinen
2024-08-16T13:56:32Z

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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@dell.com> and
> Limonciello Mario <Mario_Limonciello@Dell.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@queued.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@kernel.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@vger.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
>