Commit df9ff918 authored Oct 29, 2014 by Lv Zheng Committed by Rafael J. Wysocki Oct 29, 2014

Revert "ACPI / EC: Add support to disallow QR_EC to be issued before completing previous QR_EC"

It is reported that the following commit breaks Samsung hardware:
 Commit: 558e4736.
 Subject: ACPI / EC: Add support to disallow QR_EC to be issued before
          completing previous QR_EC

Which means the Samsung behavior conflicts with the Acer behavior.

1. Samsung may behave like:
   [ +event 1 ] SCI_EVT set
   [ +event 2 ] SCI_EVT set
                              write QR_EC
                              read event
   [ -event 1 ] SCI_EVT clear
   Without the above commit, Samsung can work:
   [ +event 1 ] SCI_EVT set
   [ +event 2 ] SCI_EVT set
                              write QR_EC
                              CAN prepare next QR_EC as SCI_EVT=1
                              read event
   [ -event 1 ] SCI_EVT clear
                              write QR_EC
                              read event
   [ -event 2 ] SCI_EVT clear
   With the above commit, Samsung cannot work:
   [ +event 1 ] SCI_EVT set
   [ +event 2 ] SCI_EVT set
                              write QR_EC
                              read event
   [ -event 1 ] SCI_EVT clear
                              CANNOT prepare next QR_EC as SCI_EVT=0
2. Acer may behave like:
   [ +event 1 ] SCI_EVT set
   [ +event 2 ]
                              write QR_EC
                              read event
   [ -event 1 ] SCI_EVT clear
   [ +event 2 ] SCI_EVT set
   Without the above commit, Acer cannot work when there is only 1 event:
   [ +event 1 ] SCI_EVT set
                              write QR_EC
                              can prepared next QR_EC as SCI_EVT=1
                              read event
   [ -event 1 ] SCI_EVT clear
                              CANNOT write QR_EC as SCI_EVT=0
   With the above commit, Acer can work:
   [ +event 1 ] SCI_EVT set
   [ +event 2 ]
                              write QR_EC
                              read event
   [ -event 1 ] SCI_EVT set
                              can prepare next QR_EC because SCI_EVT=0
                              CAN write QR_EC as SCI_EVT=1

Since Acer can also work with only the following commit applied:
 Commit: 3afcf2ec
 Subject: ACPI / EC: Add support to disallow QR_EC to be issued when
          SCI_EVT isn't set
commit 558e4736 can be reverted.

Fixes: 558e4736 (ACPI / EC: Add support to disallow QR_EC to be issued ...)
Link: https://bugzilla.kernel.org/show_bug.cgi?id=44161


Reported-and-tested-by: Ortwin Glück <odi@odi.ch>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Cc: 3.17+ <stable@vger.kernel.org> # 3.17+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

parent cac7f242

drivers/acpi/ec.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -334,13 +334,13 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
		pr_debug("*** Command(%s) started ***\n",
		acpi_ec_cmd_string(t->command));
		start_transaction(ec);
		spin_unlock_irqrestore(&ec->lock, tmp);
		ret = ec_poll(ec);
		spin_lock_irqsave(&ec->lock, tmp);
		if (ec->curr->command == ACPI_EC_COMMAND_QUERY) {
		clear_bit(EC_FLAGS_QUERY_PENDING, &ec->flags);
		pr_debug("*** Event stopped ***\n");
		}
		spin_unlock_irqrestore(&ec->lock, tmp);
		ret = ec_poll(ec);
		spin_lock_irqsave(&ec->lock, tmp);
		pr_debug("*** Command(%s) stopped ***\n",
		acpi_ec_cmd_string(t->command));
		ec->curr = NULL;

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