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ACPI / SBS: Fix GPE storm on recent MacBookPro's 

On Apple machines, plugging-in or unplugging the power triggers a GPE
for the EC. Since these machines expose an SBS device, this GPE ends
up triggering the acpi_sbs_callback(). This in turn tries to get the
status of the SBS charger. However, on MBP13,* and MBP14,* machines,
performing the smbus-read operation to get the charger's status triggers
the EC's GPE again. The result is an endless re-triggering and handling
of that GPE, consuming significant CPU resources (> 50% in irq).

In the end this is quite similar to commit 3031cddea6 (ACPI / SBS:
Don't assume the existence of an SBS charger), except that on the above
machines a status of all 1's is returned. And like there, we just want
ignore the charger here.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=198169
Signed-off-by: Ronald Tschalär <ronald@innovation.ch>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Ronald Tschalär 2018-09-30 19:52:51 -07:00 committed by Rafael J. Wysocki
parent 0238df646e
commit ca1721c5be
1 changed files with 6 additions and 2 deletions
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8
drivers/acpi/sbs.c
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@ -441,9 +441,13 @@ static int acpi_ac_get_present(struct acpi_sbs *sbs)
/* /*
* The spec requires that bit 4 always be 1. If it's not set, assume * The spec requires that bit 4 always be 1. If it's not set, assume
* that the implementation doesn't support an SBS charger * that the implementation doesn't support an SBS charger.
*
* And on some MacBooks a status of 0xffff is always returned, no
* matter whether the charger is plugged in or not, which is also
* wrong, so ignore the SBS charger for those too.
*/ */
if (!((status >> 4) & 0x1)) if (!((status >> 4) & 0x1) || status == 0xffff)
return -ENODEV; return -ENODEV;
sbs->charger_present = (status >> 15) & 0x1; sbs->charger_present = (status >> 15) & 0x1;