Message-ID: <20240722202504.jgz6tcc247mjxq4f@pali>
Date: Mon, 22 Jul 2024 22:25:04 +0200
From: Pali Rohár <pali@...nel.org>
To: Andres Salomon <dilinger@...ued.net>
Cc: linux-kernel@...r.kernel.org, platform-driver-x86@...r.kernel.org,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Sebastian Reichel <sre@...nel.org>,
	Hans de Goede <hdegoede@...hat.com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	linux-pm@...r.kernel.org, Dell.Client.Kernel@...l.com,
	Mario Limonciello <mario.limonciello@....com>
Subject: Re: [PATCH] platform/x86:dell-laptop: Add knobs to change battery
 charge settings

On Monday 22 July 2024 20:41:32 Pali Rohár wrote:
> On Monday 22 July 2024 14:34:32 Andres Salomon wrote:
> > On Mon, 22 Jul 2024 09:18:45 +0200
> > Pali Rohár <pali@...nel.org> wrote:
> > 
> > > On Sunday 21 July 2024 19:58:51 Andres Salomon wrote:
> > > > On Mon, 22 Jul 2024 01:40:37 +0200
> > > > Pali Rohár <pali@...nel.org> wrote:
> > > >   
> > > > > On Sunday 21 July 2024 19:37:16 Andres Salomon wrote:  
> > > > > > On Sun, 21 Jul 2024 11:02:38 +0200
> > > > > > Pali Rohár <pali@...nel.org> wrote:
> > > > > >     
> > > > > > > On Saturday 20 July 2024 22:06:06 Andres Salomon wrote:    
> > > > > > > > On Sat, 20 Jul 2024 11:55:07 +0200
> > > > > > > > Pali Rohár <pali@...nel.org> wrote:
> > > > > > > >       
> > > > > > > > > On Saturday 20 July 2024 05:24:19 Andres Salomon wrote:      
> > > > > > > > > > Thanks for the quick feedback! Responses below.
> > > > > > > > > > 
> > > > > > > > > > On Sat, 20 Jul 2024 10:40:19 +0200
> > > > > > > > > > Pali Rohár <pali@...nel.org> wrote:
> > > > > > > > > >         
> > > > > > 
> > > > > > [...]
> > > > > >     
> > > > > > > > > > > > +
> > > > > > > > > > > > +static void __init dell_battery_init(struct device *dev)
> > > > > > > > > > > > +{
> > > > > > > > > > > > +	enum battery_charging_mode current_mode = DELL_BAT_MODE_NONE;
> > > > > > > > > > > > +
> > > > > > > > > > > > +	dell_battery_read_req(BAT_CUSTOM_MODE_TOKEN, (int *) &current_mode);
> > > > > > > > > > > > +	if (current_mode != DELL_BAT_MODE_NONE) {          
> > > > > > > > > > > 
> > > > > > > > > > > I quite do not understand how is this code suppose to work.
> > > > > > > > > > > 
> > > > > > > > > > > Why is there mix of custom kernel enum battery_charging_mode and return
> > > > > > > > > > > value from Dell's API?        
> > > > > > > > > > 
> > > > > > > > > > This is from the original patch from Dell; tbh, I'm not sure. It does
> > > > > > > > > > work, though. That is, current_mode ends up holding the correct value
> > > > > > > > > > based on what was previously set, even if the charging mode is set from
> > > > > > > > > > the BIOS.
> > > > > > > > > > 
> > > > > > > > > > I just scanned through the libsmbios code to see what it's doing, and
> > > > > > > > > > it appears to loop through every charging mode to check if its active.
> > > > > > > > > > I'm not really sure that makes much more sense, so I'll try some more
> > > > > > > > > > tests.        
> > > > > > > > > 
> > > > > > > > > Keyboard backlight code (kbd_get_first_active_token_bit) is doing also
> > > > > > > > > this type scan. If I remember correctly, for every keyboard backlight
> > > > > > > > > token we just know the boolean value - if the token is set or not.
> > > > > > > > > 
> > > > > > > > > It would really nice to see what (raw) value is returned by the
> > > > > > > > > dell_battery_read_req(token) function for every battery token and for
> > > > > > > > > every initial state.      
> > > > > > > > 
> > > > > > > > I checked this. The BIOS sets the mode value in every related token
> > > > > > > > location. I'm still not really sure what libsmbios is doing, but the
> > > > > > > > kernel code seems to arbitrarily choose one of the token locations
> > > > > > > > to read from. This makes sense to me now.
> > > > > > > > 
> > > > > > > > In the BIOS when I set the mode to "ExpressCharge",
> > > > > > > > this what I pulled for each token location:
> > > > > > > > 
> > > > > > > > [    5.704651] dell-laptop dell-laptop: BAT_CUSTOM_MODE_TOKEN value: 2
> > > > > > > > [    5.707015] dell-laptop dell-laptop: BAT_PRI_AC_MODE_TOKEN value: 2
> > > > > > > > [    5.709114] dell-laptop dell-laptop: BAT_ADAPTIVE_MODE_TOKEN value: 2
> > > > > > > > [    5.711041] dell-laptop dell-laptop: BAT_STANDARD_MODE_TOKEN value: 2
> > > > > > > > [    5.713705] dell-laptop dell-laptop: BAT_EXPRESS_MODE_TOKEN value: 2
> > > > > > > > 
> > > > > > > > Similar story when I set it to Custom (all were '5'), or Standard ('1').
> > > > > > > > When I set it from linux as well, it changed all location values.      
> > > > > > > 
> > > > > > > Interesting... Anyway, I still think that the API could be similar to
> > > > > > > what is used in keyboard backlight.
> > > > > > > 
> > > > > > > Could you please dump all information about each token? They are in
> > > > > > > struct calling_interface_token returned by dell_smbios_find_token.
> > > > > > > 
> > > > > > > I'm interesting in tokenID, location and value.
> > > > > > > 
> > > > > > > Ideally to compare what is in token->value and then in buffer.output[1]
> > > > > > > (in case dell_send_request does not fail).    
> > > > > > 
> > > > > > 
> > > > > > Alright, here's what I see:
> > > > > > 
> > > > > > [    5.904775] dell_laptop: dell_battery_read_req: token requested: 0x343, tokenID=0x343, location=0x343, value=5
> > > > > > [    5.908675] dell_laptop: dell_battery_read_req: buffer.output[1]=3
> > > > > > [    5.908680] dell_laptop: dell_battery_init: BAT_CUSTOM_MODE_TOKEN value: 3
> > > > > > [    5.908682] dell_laptop: dell_battery_read_req: token requested: 0x341, tokenID=0x341, location=0x341, value=3
> > > > > > [    5.910922] dell_laptop: dell_battery_read_req: buffer.output[1]=3
> > > > > > [    5.910926] dell_laptop: dell_battery_init: BAT_PRI_AC_MODE_TOKEN value: 3
> > > > > > [    5.910928] dell_laptop: dell_battery_read_req: token requested: 0x342, tokenID=0x342, location=0x342, value=4
> > > > > > [    5.913042] dell_laptop: dell_battery_read_req: buffer.output[1]=3
> > > > > > [    5.913046] dell_laptop: dell_battery_init: BAT_ADAPTIVE_MODE_TOKEN value: 3
> > > > > > [    5.913048] dell_laptop: dell_battery_read_req: token requested: 0x346, tokenID=0x346, location=0x346, value=1
> > > > > > [    5.914996] dell_laptop: dell_battery_read_req: buffer.output[1]=3
> > > > > > [    5.914999] dell_laptop: dell_battery_init: BAT_STANDARD_MODE_TOKEN value: 3
> > > > > > [    5.915000] dell_laptop: dell_battery_read_req: token requested: 0x347, tokenID=0x347, location=0x347, value=2
> > > > > > [    5.916723] dell_laptop: dell_battery_read_req: buffer.output[1]=3
> > > > > > [    5.916724] dell_laptop: dell_battery_init: BAT_EXPRESS_MODE_TOKEN value: 3
> > > > > > [    5.916725] dell_laptop: dell_battery_read_req: token requested: 0x349, tokenID=0x349, location=0x349, value=65535
> > > > > > [    5.918727] dell_laptop: dell_battery_read_req: buffer.output[1]=65
> > > > > > [    5.918731] dell_laptop: dell_battery_init: BAT_CUSTOM_CHARGE_START value: 65
> > > > > > [    5.918734] dell_laptop: dell_battery_read_req: token requested: 0x34a, tokenID=0x34a, location=0x34a, value=65535
> > > > > > [    5.920864] dell_laptop: dell_battery_read_req: buffer.output[1]=85
> > > > > > [    5.920867] dell_laptop: dell_battery_init: BAT_CUSTOM_CHARGE_END value: 85    
> > > > > 
> > > > > Perfect. And can you check dumps when the mode is set to some other than BAT_PRI_AC_MODE_TOKEN?  
> > > > 
> > > > Here's Express:
> > > > 
> > > > [    5.880090] dell_laptop: dell_battery_read_req: token requested: 0x343, tokenID=0x343, location=0x343, value=5
> > > > [    5.882011] dell_laptop: dell_battery_read_req: buffer.output[1]=2
> > > > [    5.882014] dell_laptop: dell_battery_init: BAT_CUSTOM_MODE_TOKEN value: 2
> > > > [    5.882016] dell_laptop: dell_battery_read_req: token requested: 0x341, tokenID=0x341, location=0x341, value=3
> > > > [    5.894513] dell_laptop: dell_battery_read_req: buffer.output[1]=2
> > > > [    5.894518] dell_laptop: dell_battery_init: BAT_PRI_AC_MODE_TOKEN value: 2
> > > > [    5.894520] dell_laptop: dell_battery_read_req: token requested: 0x342, tokenID=0x342, location=0x342, value=4
> > > > [    5.913870] dell_laptop: dell_battery_read_req: buffer.output[1]=2
> > > > [    5.913874] dell_laptop: dell_battery_init: BAT_ADAPTIVE_MODE_TOKEN value: 2
> > > > [    5.913875] dell_laptop: dell_battery_read_req: token requested: 0x346, tokenID=0x346, location=0x346, value=1
> > > > [    5.915622] dell_laptop: dell_battery_read_req: buffer.output[1]=2
> > > > [    5.915625] dell_laptop: dell_battery_init: BAT_STANDARD_MODE_TOKEN value: 2
> > > > [    5.915626] dell_laptop: dell_battery_read_req: token requested: 0x347, tokenID=0x347, location=0x347, value=2
> > > > [    5.917349] dell_laptop: dell_battery_read_req: buffer.output[1]=2
> > > > [    5.917351] dell_laptop: dell_battery_init: BAT_EXPRESS_MODE_TOKEN value: 2
> > > > [    5.917352] dell_laptop: dell_battery_read_req: token requested: 0x349, tokenID=0x349, location=0x349, value=65535
> > > > [    5.919068] dell_laptop: dell_battery_read_req: buffer.output[1]=65
> > > > [    5.919070] dell_laptop: dell_battery_init: BAT_CUSTOM_CHARGE_START value: 65
> > > > [    5.919071] dell_laptop: dell_battery_read_req: token requested: 0x34a, tokenID=0x34a, location=0x34a, value=65535
> > > > [    5.920780] dell_laptop: dell_battery_read_req: buffer.output[1]=85
> > > > [    5.920782] dell_laptop: dell_battery_init: BAT_CUSTOM_CHARGE_END value: 85
> > > > 
> > > > And here's Adaptive:
> > > > 
> > > > [    5.945319] dell_laptop: dell_battery_read_req: token requested: 0x343, tokenID=0x343, location=0x343, value=5
> > > > [    5.973685] dell_laptop: dell_battery_read_req: buffer.output[1]=4
> > > > [    5.973690] dell_laptop: dell_battery_init: BAT_CUSTOM_MODE_TOKEN value: 4
> > > > [    5.973692] dell_laptop: dell_battery_read_req: token requested: 0x341, tokenID=0x341, location=0x341, value=3
> > > > [    5.976533] dell_laptop: dell_battery_read_req: buffer.output[1]=4
> > > > [    5.976538] dell_laptop: dell_battery_init: BAT_PRI_AC_MODE_TOKEN value: 4
> > > > [    5.976540] dell_laptop: dell_battery_read_req: token requested: 0x342, tokenID=0x342, location=0x342, value=4
> > > > [    5.981013] dell_laptop: dell_battery_read_req: buffer.output[1]=4
> > > > [    5.981018] dell_laptop: dell_battery_init: BAT_ADAPTIVE_MODE_TOKEN value: 4
> > > > [    5.981020] dell_laptop: dell_battery_read_req: token requested: 0x346, tokenID=0x346, location=0x346, value=1
> > > > [    5.983474] dell_laptop: dell_battery_read_req: buffer.output[1]=4
> > > > [    5.983479] dell_laptop: dell_battery_init: BAT_STANDARD_MODE_TOKEN value: 4
> > > > [    5.983481] dell_laptop: dell_battery_read_req: token requested: 0x347, tokenID=0x347, location=0x347, value=2
> > > > [    5.985881] dell_laptop: dell_battery_read_req: buffer.output[1]=4
> > > > [    5.985885] dell_laptop: dell_battery_init: BAT_EXPRESS_MODE_TOKEN value: 4
> > > > [    5.985887] dell_laptop: dell_battery_read_req: token requested: 0x349, tokenID=0x349, location=0x349, value=65535
> > > > [    5.988332] dell_laptop: dell_battery_read_req: buffer.output[1]=65
> > > > [    5.988337] dell_laptop: dell_battery_init: BAT_CUSTOM_CHARGE_START value: 65
> > > > [    5.988339] dell_laptop: dell_battery_read_req: token requested: 0x34a, tokenID=0x34a, location=0x34a, value=65535
> > > > [    5.990769] dell_laptop: dell_battery_read_req: buffer.output[1]=85
> > > > [    5.990774] dell_laptop: dell_battery_init: BAT_CUSTOM_CHARGE_END value: 85
> > > > 
> > > > 
> > > > 
> > > > -- 
> > > > I'm available for contract & employment work, see:
> > > > https://spindle.queued.net/~dilinger/resume-tech.pdf  
> > > 
> > > Nice! So it is exactly same as API of keyboard backlight tokens. Thanks.
> > > 
> > > In dell_battery_write_req function you can drop second "val" argument
> > > and replace it by token->value. So the dell_fill_request call in that
> > > function would look like:
> > > 
> > >     dell_fill_request(&buffer, token->location, token->value, 0, 0);
> > 
> > 
> > Well, except that we use dell_battery_write_req for writing the charge
> > start/end values as well (in dell_battery_custom_set). Those can't be
> > obtained from token->value.
> > 
> > We could have two separate functions for that, or set 'val' to a
> > sentinel value (0) that, if detected, we set val=token->value. I'm
> > still not really understanding the point, though.
> 
> I think that two separate functions would be needed. One which set
> battery mode (enum) and which set custom thresholds.
> 
> > > 
> > > And then you can mimic the usage as it is done in keyboard backlight
> > > functions (kbd_get_first_active_token_bit).
> > > 
> > > If you do not know what I mean then later (today or tomorrow) I can
> > > write code example of the functionality.
> > 
> > Sorry, I still don't understand what the goal is here. Is the goal to
> > not pull from a random location to determine the current charging mode?
> > Is the goal to determine what charging modes are currently supported
> > (and if so, I don't see how)? Is the goal to avoid having the kernel
> > hardcode a list of enums that the BIOS might have different values
> > for? Is the goal to merge the keyboard backlight and battery setting
> > functions?
> 
> Avoid having the kernel hardcoded values for enums which SMBIOS
> provides. Future (or maybe also older) modes may have different enum
> values. So we should use what SMBIOS provides to us.
> 
> Also to determinate which charging modes are supported by the current HW
> configuration. If BIOS does not support some mode or does not allow to
> set some mode, kernel should not export this as supported option.
> 
> If you do not see how to do it, please give me some time, I will send
> you an example. Going to look at it right now.
> 
> Merging keyboard backlight and battery code is bonus, not required.
> But I thought that it would be easier to build a new code from common
> blocks.

Here is very quick & hacky example of what I mean (completely untested):

--- dell-laptop.c
+++ dell-laptop.c
@@ -353,6 +353,105 @@ static const struct dmi_system_id dell_q
 	{ }
 };
 
+static int dell_read_token_value(u16 tokenid, u32 *value)
+{
+	struct calling_interface_buffer buffer;
+	struct calling_interface_token *token;
+	int ret;
+
+	token = dell_smbios_find_token(tokenid);
+	if (!token)
+		return -ENODEV;
+
+	dell_fill_request(&buffer, token->location, 0, 0, 0);
+	ret = dell_send_request(&buffer, CLASS_TOKEN_READ, SELECT_TOKEN_STD);
+	if (ret)
+		return ret;
+
+	*value = buffer.output[1];
+	return 0;
+}
+
+static int dell_write_token_value(u16 tokenid, u32 value)
+{
+	struct calling_interface_buffer buffer;
+	struct calling_interface_token *token;
+
+	token = dell_smbios_find_token(type);
+	if (!token)
+		return -ENODEV;
+
+	dell_fill_request(&buffer, token->location, value, 0, 0);
+	return dell_send_request(&buffer, CLASS_TOKEN_WRITE, SELECT_TOKEN_STD);
+}
+
+static int dell_is_enum_token_active(u16 tokenid)
+{
+	struct calling_interface_buffer buffer;
+	struct calling_interface_token *token;
+	int ret;
+
+	token = dell_smbios_find_token(tokenid);
+	if (!token)
+		return -EINVAL;
+
+	if (token->value == (u16)-1)
+		return -EINVAL;
+
+	dell_fill_request(&buffer, token->location, 0, 0, 0);
+	ret = dell_send_request(&buffer, CLASS_TOKEN_READ, SELECT_TOKEN_STD);
+	if (ret)
+		return ret;
+
+	return (buffer.output[1] == token->value);
+}
+
+static int dell_activate_enum_token(u16 tokenid)
+{
+	struct calling_interface_buffer buffer;
+	struct calling_interface_token *token;
+	int ret;
+
+	token = dell_smbios_find_token(tokenid);
+	if (!token)
+		return -EINVAL;
+
+	if (token->value == (u16)-1)
+		return -EINVAL;
+
+	dell_fill_request(&buffer, token->location, token->value, 0, 0);
+	return dell_send_request(&buffer, CLASS_TOKEN_WRITE, SELECT_TOKEN_STD);
+}
+
+static u32 dell_get_supported_enum_tokens(const u16 *tokenids, u32 count)
+{
+	u32 supported_mask = 0;
+	u32 i;
+
+	for (i = 0; i < count; i++) {
+		if (dell_smbios_find_token(tokenids[i]))
+			supported_mask |= BIT(i);
+	}
+
+	return supported_mask;
+}
+
+static int dell_get_active_enum_token(const u16 *tokenids, u32 count, u32 supported_mask)
+{
+	int ret;
+	u32 i;
+
+	for (i = 0; i < count; i++) {
+		if (!(supported_mask & BIT(i)))
+			continue;
+		ret = dell_is_enum_token_active(tokenids[i]);
+		if (ret == 1)
+			return i;
+	}
+
+	return -EINVAL;
+}
+
 /*
  * Derived from information in smbios-wireless-ctl:
  *
@@ -2183,6 +2282,144 @@ static struct led_classdev mute_led_cdev
 	.default_trigger = "audio-mute",
 };
 
+static const u16 battery_mode_tokens[] = {
+	BAT_STANDARD_MODE_TOKEN,
+	BAT_EXPRESS_MODE_TOKEN,
+	BAT_PRI_AC_MODE_TOKEN,
+	BAT_ADAPTIVE_MODE_TOKEN,
+	BAT_CUSTOM_MODE_TOKEN,
+};
+
+static const char * const battery_mode_names[] = {
+	"standard",
+	"express",
+	"primarily_ac",
+	"adaptive",
+	"custom",
+};
+
+static u32 battery_mode_token_mask;
+
+static int dell_battery_read_custom_charge(u16 token)
+{
+	u32 value;
+	int ret;
+
+	ret = dell_read_token_value(token, &value);
+	if (ret)
+		return ret;
+	if (value > 100)
+		return -EINVAL;
+	return value;
+}
+
+#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 val)
+{
+	int end;
+
+	if (val < CHARGE_START_MIN)
+		val = CHARGE_START_MIN;
+	else if (val > CHARGE_START_MAX)
+		val = CHARGE_START_MAX;
+
+	end = dell_battery_get_custom_charge(BAT_CUSTOM_CHARGE_END);
+	if (end < 0)
+		return end;
+
+	if (end - val < CHARGE_MIN_DIFF)
+		val = end - CHARGE_MIN_DIFF;
+
+	return dell_write_token_value(BAT_CUSTOM_CHARGE_START, val);
+}
+
+static int dell_battery_set_custom_charge_end(int val)
+{
+	int start;
+
+	if (val < CHARGE_END_MIN)
+		val = CHARGE_END_MIN;
+	else if (val > CHARGE_END_MAX)
+		val = CHARGE_END_MAX;
+
+	start = dell_battery_get_custom_charge(BAT_CUSTOM_CHARGE_START);
+	if (start < 0)
+		return start;
+
+	if (val - start < CHARGE_MIN_DIFF)
+		val = start + CHARGE_MIN_DIFF;
+
+	return dell_write_token_value(BAT_CUSTOM_CHARGE_END, val);
+}
+
+static ssize_t charge_type_show(struct device *dev,
+				struct device_attribute *attr,
+				char *buf)
+{
+	int active;
+	ssize_t count;
+
+	active = dell_get_active_enum_token(battery_mode_tokens, ARRAY_SIZE(battery_mode_tokens), battery_mode_token_mask);
+	if (active < 0)
+		return ret;
+
+	for (count = 0, i = 0; i < ARRAY_SIZE(battery_mode_names); i++) {
+		if (!(BIT(i) & battery_mode_token_mask))
+			continue;
+		count += sysfs_emit_at(buf, count, i == active ? "[%s] " : "%s ", battery_mode_names[mode]);
+	}
+
+	/* convert the last space to a newline */
+	/* battery_mode_names is non-empty and battery_mode_token_mask is non-zero, so count is also non-zero */
+	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)
+{
+	size_t i;
+	int ret;
+
+	for (i = 0; i < ARRAY_SIZE(battery_mode_names); i++) {
+		if (sysfs_streq(battery_mode_names[i], buf))
+			break;
+	}
+
+	if (i >= ARRAY_SIZE(battery_mode_names))
+		return -EINVAL;
+
+	if (!(BIT(i) & battery_mode_token_mask))
+		return -EINVAL;
+
+	ret = dell_activate_enum_token(battery_mode_tokens[i]);
+	if (ret)
+		return ret;
+
+	return size;
+}
+
+static void __init dell_battery_init(struct device *dev)
+{
+	battery_mode_token_mask = dell_get_supported_enum_tokens(battery_mode_tokens, ARRAY_SIZE(battery_mode_tokens));
+	if (battery_mode_token_mask != 0)
+		battery_hook_register(&dell_battery_hook);
+}
+
+static void __exit dell_battery_exit(void)
+{
+	if (battery_mode_token_mask != 0)
+		battery_hook_unregister(&dell_battery_hook);
+}
+
 static int __init dell_init(void)
 {
 	struct calling_interface_token *token;

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