ACPI / EC: Remove duplicated ec_wait_ibf0() waiter

After we've added the first command byte write into advance_transaction(),
the IBF=0 waiter is duplicated with the command completion waiter
implemented in the ec_poll() because:
   If IBF=1 blocked the first command byte write invoked in the task
   context ec_poll(), it would be kicked off upon IBF=0 interrupt or timed
   out and retried again in the task context.

Remove this seperate and duplicate IBF=0 waiter.  By doing so we can
reduce the overall number of times to access the EC_SC(R) status
register.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=70891
Link: https://bugzilla.kernel.org/show_bug.cgi?id=63931
Link: https://bugzilla.kernel.org/show_bug.cgi?id=59911
Reported-and-tested-by: Gareth Williams <gareth@garethwilliams.me.uk>
Reported-and-tested-by: Hans de Goede <jwrdegoede@fedoraproject.org>
Reported-by: Barton Xu <tank.xuhan@gmail.com>
Tested-by: Steffen Weber <steffen.weber@gmail.com>
Tested-by: Arthur Chen <axchen@nvidia.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/ec.c

@@ -281,23 +281,6 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
 	return ret;
 }
 
-static int ec_check_ibf0(struct acpi_ec *ec)
-{
-	u8 status = acpi_ec_read_status(ec);
-	return (status & ACPI_EC_FLAG_IBF) == 0;
-}
-
-static int ec_wait_ibf0(struct acpi_ec *ec)
-{
-	unsigned long delay = jiffies + msecs_to_jiffies(ec_delay);
-	/* interrupt wait manually if GPE mode is not active */
-	while (time_before(jiffies, delay))
-		if (wait_event_timeout(ec->wait, ec_check_ibf0(ec),
-					msecs_to_jiffies(1)))
-			return 0;
-	return -ETIME;
-}
-
 static int acpi_ec_transaction(struct acpi_ec *ec, struct transaction *t)
 {
 	int status;
@@ -318,12 +301,6 @@ static int acpi_ec_transaction(struct acpi_ec *ec, struct transaction *t)
 			goto unlock;
 		}
 	}
-	if (ec_wait_ibf0(ec)) {
-		pr_err("input buffer is not empty, "
-				"aborting transaction\n");
-		status = -ETIME;
-		goto end;
-	}
 	pr_debug("transaction start (cmd=0x%02x, addr=0x%02x)\n",
 			t->command, t->wdata ? t->wdata[0] : 0);
 	/* disable GPE during transaction if storm is detected */
@@ -347,7 +324,6 @@ static int acpi_ec_transaction(struct acpi_ec *ec, struct transaction *t)
 		set_bit(EC_FLAGS_GPE_STORM, &ec->flags);
 	}
 	pr_debug("transaction end\n");
-end:
 	if (ec->global_lock)
 		acpi_release_global_lock(glk);
 unlock:
@@ -653,8 +629,7 @@ static u32 acpi_ec_gpe_handler(acpi_handle gpe_device,
 	spin_lock_irqsave(&ec->lock, flags);
 	advance_transaction(ec);
 	spin_unlock_irqrestore(&ec->lock, flags);
-	if (ec_transaction_completed(ec) &&
-	    (acpi_ec_read_status(ec) & ACPI_EC_FLAG_IBF) == 0) {
+	if (ec_transaction_completed(ec)) {
 		wake_up(&ec->wait);
 		ec_check_sci(ec, acpi_ec_read_status(ec));
 	}