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ACPI / EC: Add support to disallow QR_EC to be issued when SCI_EVT is…
…n't set There is a platform refusing to respond QR_EC when SCI_EVT isn't set (Acer Aspire V5-573G). Currently, we rely on the behaviour that the EC firmware can respond something (for example, 0x00 to indicate "no outstanding events") to QR_EC even when SCI_EVT is not set, but the reporter has complained about AC/battery pluging/unpluging and video brightness change delay on that platform. This is because the work item that has issued QR_EC has to wait until timeout in this case, and the _Qxx method evaluation work item queued after QR_EC one is delayed. It sounds reasonable to fix this issue by: 1. Implementing SCI_EVT sanity check before issuing QR_EC in the EC driver's main state machine. 2. Moving QR_EC issuing out of the work queue used by _Qxx evaluation to a seperate IRQ handling thread. This patch fixes this issue using solution 1. By disallowing QR_EC to be issued when SCI_EVT isn't set, we are able to handle such platform in the EC driver's main state machine. This patch enhances the state machine in this way to survive with such malfunctioning EC firmware. Note that this patch can also fix CLEAR_ON_RESUME quirk which also relies on the assumption that the platforms are able to respond even when SCI_EVT isn't set. Fixes: c0d6534 ACPI / EC: Fix race condition in ec_transaction_completed() Link: https://bugzilla.kernel.org/show_bug.cgi?id=82611 Reported-and-tested-by: Alexander Mezin <firstname.lastname@example.org> Signed-off-by: Lv Zheng <email@example.com> Cc: 3.16+ <firstname.lastname@example.org> # 3.16+ Signed-off-by: Rafael J. Wysocki <email@example.com>
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