2014-03-12 6:20 GMT+08:00 Matthew Garrett <matthew.garrett@xxxxxxxxxx>:
The existing SBS code explicitly sets the selected battery in the SBSHi Matthew:
manager regardless of whether the battery in question is already selected.
This causes bus timeouts on Apple hardware. Check for this case and avoid
it.
This patch is to avoid a redundant battery select operation when
the battery is selected. But the symptom "bus timeouts" is a bus transaction
issue, right? Will this happen during other SBS write/read operations? Do we
need to increase the wait time of SMBUS transaction?
Signed-off-by: Matthew Garrett <matthew.garrett@xxxxxxxxxx>
---
drivers/acpi/sbs.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)
diff --git a/drivers/acpi/sbs.c b/drivers/acpi/sbs.c
index dbd4849..c386505 100644
--- a/drivers/acpi/sbs.c
+++ b/drivers/acpi/sbs.c
@@ -470,17 +470,25 @@ static struct device_attribute alarm_attr = {
static int acpi_battery_read(struct acpi_battery *battery)
{
int result = 0, saved_present = battery->present;
- u16 state;
+ u16 state, selected, desired;
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;
- state |= 1 << (battery->id + 12);
- acpi_smbus_write(battery->sbs->hc, SMBUS_WRITE_WORD,
- ACPI_SBS_MANAGER, 0x01, (u8 *)&state, 2);
+ /*
+ * Don't switch battery if the correct one is already selected
+ */
+ selected = state & 0xf000;
+ desired = 1 << (battery->id + 12);
+ if (selected != desired) {
+ state &= 0x0fff;
+ state |= desired;
+ 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)
--
1.8.5.3
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