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

[ Upstream commit ca1721c5bee77105829cbd7baab8ee0eab85b06d ]

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 3031cddea633 (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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/acpi/sbs.c b/drivers/acpi/sbs.c
index ad0b13ad4bbb93b2b10da64b9607db809bdba39b..4a76000bcf7a47e7922539282fe100581c399d57 100644 (file)
--- a/drivers/acpi/sbs.c
+++ b/drivers/acpi/sbs.c
@@ -443,9 +443,13 @@ 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
-        * 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;
 
        sbs->charger_present = (status >> 15) & 0x1;