[coreboot-gerrit] [S] Change in coreboot[main]: ec/google/chromeec: Add function to detect barrel charger

[Subrata Banik (Code Review)]

Subrata Banik has submitted this change. ( https://review.coreboot.org/c/coreboot/+/85765?usp=email )

Change subject: ec/google/chromeec: Add function to detect barrel charger
......................................................................

ec/google/chromeec: Add function to detect barrel charger

This commit introduces a new function,
google_chromeec_is_barrel_charger_present(), which checks if a barrel
charger is present.

The function uses the following logic to determine if a barrel charger
is present:

- If both a barrel charger and USB-C PD are present, then the barrel
charger takes precedence over USB-C PD. As a result,
google_chromeec_is_usb_pd_attached() will return false. This logic can
be used to deterministically say if a barrel charger is present even
when both a barrel charger and USB-C PD are attached.

- If an AC charger is detected and USB-C PD is not present, then a
barrel charger must be present.

This change allows the EC to accurately detect the presence of a barrel
charger, even when a USB-C PD charger is also attached.

BUG=b:377798581
TEST=Able to read the charger status correctly while booting
google/fatcat.

Experiment #1:
- USB-C PD Attached = yes
- Barrel Attached = No
- Charger Detected = Yes

```
fatcat-rev257 ~ # cbmem -c | grep -5 "ac_charger_present"
[INFO ]  ac_charger_present: yes
[INFO ]  usb_pd_present: yes
[INFO ]  baseboard_devtree_update: Barrel Absent
```

Experiment #2:
- USB-C PD Attached = No
- Barrel Attached = Yes
- Charger Detected = Yes

```
[INFO ]  ac_charger_present: yes
[INFO ]  usb_pd_present: no
[INFO ]  baseboard_devtree_update: Barrel Present
```

Experiment #3:
- USB-C PD Attached = Yes
- Barrel Attached = Yes
- Charger Detected = Yes

```
[INFO ]  ac_charger_present: yes
[INFO ]  usb_pd_present: no
[INFO ]  baseboard_devtree_update: Barrel Present
```

Experiment #4:
- USB-C PD Attached = No
- Barrel Attached = No
- Charger Detected = No

```
[INFO ]  ac_charger_present: no
[INFO ]  usb_pd_present: no
[INFO ]  baseboard_devtree_update: Barrel Absent
```

Change-Id: I9644f0dec057f95bb0a22cdc18edc1a0234ee3a9
Signed-off-by: Subrata Banik 
Reviewed-on: https://review.coreboot.org/c/coreboot/+/85765
Tested-by: build bot (Jenkins) 
Reviewed-by: Jérémy Compostella 
---
M src/ec/google/chromeec/ec.c
M src/ec/google/chromeec/ec.h
2 files changed, 32 insertions(+), 0 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Jérémy Compostella: Looks good to me, approved

diff --git a/src/ec/google/chromeec/ec.c b/src/ec/google/chromeec/ec.c
index 1ee242b..2e8961f 100644
--- a/src/ec/google/chromeec/ec.c
+++ b/src/ec/google/chromeec/ec.c
@@ -1002,6 +1002,30 @@
    return false;
 }

+/*
+ * Using below scenarios to conclude if device has a barrel charger attached.
+ * +-----------+-----------------+------------------+---------------------------------+
+ * | Scenarios | Charger Present | USB-C PD Present | Conclusion: Barrel Present ?    |
+ * +-----------+-----------------+------------------+---------------------------------+
+ * |  #1       | Yes             | Yes              | Non Conclusive (comments below) |
+ * |  #2       | No              | Yes              | Not possible                    |
+ * |  #3       | Yes             | No               | Must be barrel charger          |
+ * |  #4       | No              | No               | Barrel not present              |
+ * +-----------+-----------------+------------------+---------------------------------+
+ */
+bool google_chromeec_is_barrel_charger_present(void)
+{
+	/*
+	 * If both the barrel charger and USB-C PD are connected, the barrel charger takes
+	 * precedence over USB-C PD. This means google_chromeec_is_usb_pd_attached()
+	 * will return false in such a scenario.
+	 *
+	 * This behavior allows us to reliably detect the presence of a barrel
+	 * charger, even when a USB-C PD charger is also connected.
+	 */
+	return google_chromeec_is_charger_present() && !google_chromeec_is_usb_pd_attached();
+}
+
 int google_chromeec_override_dedicated_charger_limit(uint16_t current_lim,
    					     uint16_t voltage_lim)
 {
diff --git a/src/ec/google/chromeec/ec.h b/src/ec/google/chromeec/ec.h
index a50c311..b11b7a8 100644
--- a/src/ec/google/chromeec/ec.h
+++ b/src/ec/google/chromeec/ec.h
@@ -148,6 +148,14 @@
  */
 bool google_chromeec_is_charger_present(void);

+/**
+ * Check if barrel charger is present.
+ *
+ * @return		true: if the barrel charger is present
+ *			false: if the barrel charger is not present
+ */
+bool google_chromeec_is_barrel_charger_present(void);
+
 /*
  * Set max current and voltage of a dedicated charger.
  *