From 3bd554e03ef412438b42862cb088ddc4e2a2561b Mon Sep 17 00:00:00 2001 From: Armin Wolf Date: Fri, 24 Mar 2023 21:26:28 +0100 Subject: ACPI: SBS: Fix handling of Smart Battery Selectors The "Smart Battery Selector" standard says that when writing SelectorState (0x1), the nibbles which should not be modified need to be masked with 0xff. This is necessary since in contrast to a "Smart Battery Manager", the last three nibbles are writable. Failing to do so might trigger the following cycle: 1. Host accidentally changes power source of the system (3rd nibble) when selecting a battery. 2. Power source is invalid, Selector changes to another power source. 3. Selector notifies host that it changed the power source. 4. Host re-reads some batteries. 5. goto 1 for each re-read battery. This loop might also be entered when a battery which is not present is selected for SMBus access. In the end some workqueues fill up, which causes the system to lockup upon suspend/shutdown. Fix this by correctly masking the value to be written, and avoid selecting batteries which are absent. Tested on a Acer Travelmate 4002WLMi. Signed-off-by: Armin Wolf Signed-off-by: Rafael J. Wysocki --- drivers/acpi/sbs.c | 27 ++++++++++++++++++--------- 1 file changed, 18 insertions(+), 9 deletions(-) (limited to 'drivers/acpi') diff --git a/drivers/acpi/sbs.c b/drivers/acpi/sbs.c index e90752d4f488..94e3c000df2e 100644 --- a/drivers/acpi/sbs.c +++ b/drivers/acpi/sbs.c @@ -473,23 +473,32 @@ static const struct device_attribute alarm_attr = { -------------------------------------------------------------------------- */ static int acpi_battery_read(struct acpi_battery *battery) { - int result = 0, saved_present = battery->present; + int result, saved_present = battery->present; u16 state; if (battery->sbs->manager_present) { result = acpi_smbus_read(battery->sbs->hc, SMBUS_READ_WORD, ACPI_SBS_MANAGER, 0x01, (u8 *)&state); - if (!result) - battery->present = state & (1 << battery->id); - state &= 0x0fff; + if (result) + return result; + + battery->present = state & (1 << battery->id); + if (!battery->present) + return 0; + + /* Masking necessary for Smart Battery Selectors */ + state = 0x0fff; state |= 1 << (battery->id + 12); acpi_smbus_write(battery->sbs->hc, SMBUS_WRITE_WORD, ACPI_SBS_MANAGER, 0x01, (u8 *)&state, 2); - } else if (battery->id == 0) - battery->present = 1; - - if (result || !battery->present) - return result; + } else { + if (battery->id == 0) { + battery->present = 1; + } else { + if (!battery->present) + return 0; + } + } if (saved_present != battery->present) { battery->update_time = 0; -- cgit v1.2.3