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mb/google/bluey: Cache low battery mode check

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The function `google_chromeec_is_below_critical_threshold()`
communicates with the Embedded Controller (EC) via the eSPI bus or
similar interface. Calling this function multiple times during boot is
inefficient, as the battery state is static for the duration of the
current boot stage.

Introduce a new static inline wrapper function, `is_low_battery_mode()`,
which ensures that the EC is queried only once. This is achieved by
using a function-scope static variable initialized by the EC function,
leveraging C's guarantee that static local variables are initialized
only upon first call.

Replace the direct calls to the EC function in:
1. `lb_add_boot_mode()`
2. `mainboard_needs_pcie_init()`
3. `mainboard_init()`

This change optimizes boot time by eliminating redundant EC
communication checks and ensures non-boot critical componts are not
getting initialized during the low-battery or off-mode charging boot

BUG=b:460299891
TEST=Ensures non-boot critical componts are not getting initialized
during the low-battery or off-mode charging boot.

Change-Id: I05fa17866c4952c3f3ad552b969dbe0d023b30a6
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/90020
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kapil Porwal <kapilporwal@google.com>
This commit is contained in:
Subrata Banik 2025-11-13 07:53:05 +00:00
commit 486b1b51af
1 changed files with 33 additions and 1 deletions
Download patch file Download diff file Expand all files Collapse all files

34
src/mainboard/google/bluey/mainboard.c
View file

@ -12,6 +12,30 @@
#include "board.h"
#include <soc/usb/usb.h>
/*
* Check if the system is in low battery boot mode.
*
* This function calls the underlying EC function only once during the
* first execution and caches the result for all subsequent calls.
*
* Return `true` if system battery is below critical threshold, `false` otherwise.
*/
static inline bool is_low_battery_mode(void)
{
if (!CONFIG(EC_GOOGLE_CHROMEEC))
return false;
static bool low_battery_mode_cached = false;
static bool cached_low_battery_result = false;
if (!low_battery_mode_cached) {
cached_low_battery_result = google_chromeec_is_below_critical_threshold();
low_battery_mode_cached = true;
}
return cached_low_battery_result;
}
static void setup_usb(void)
{
setup_usb_host0();
@ -29,7 +53,7 @@ void lb_add_boot_mode(struct lb_header *header)
mode->size = sizeof(*mode);
mode->boot_mode = LB_BOOT_MODE_NORMAL;
if (google_chromeec_is_below_critical_threshold())
if (is_low_battery_mode())
mode->boot_mode = LB_BOOT_MODE_LOW_BATTERY;
/* Enable charging only during low-battery mode */
@ -39,6 +63,10 @@ void lb_add_boot_mode(struct lb_header *header)
bool mainboard_needs_pcie_init(void)
{
/* Skip PCIe initialization if boot mode is "low-battery" or "off-mode charging"*/
if (is_low_battery_mode())
return false;
return true;
}
@ -54,6 +82,10 @@ static void display_startup(void)
static void mainboard_init(struct device *dev)
{
/* Skip mainboard initialization if boot mode is "low-battery" or "off-mode charging"*/
if (is_low_battery_mode())
return;
gpi_firmware_load(QUP_0_GSI_BASE);
gpi_firmware_load(QUP_1_GSI_BASE);
gpi_firmware_load(QUP_2_GSI_BASE);