[PATCH 3.16 155/192] Revert "ACPI / EC: Add support to disallow QR_EC to be issued before completing previous QR_EC"

Ben Hutchings
2017-10-09T13:18:05Z

From: Lv Zheng <lv.zheng@intel.com>

commit df9ff91801da603079018f21a9412385b62f0f8e upstream.

It is reported that the following commit breaks Samsung hardware:
Commit: 558e4736f2e1b0e6323adf7a5e4df77ed6cfc1a4.
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: 3afcf2ece453e1a8c2c6de19cdf06da3772a1b08
Subject: ACPI / EC: Add support to disallow QR_EC to be issued when
SCI_EVT isn't set
commit 558e4736f2e1b0e6323adf7a5e4df77ed6cfc1a4 can be reverted.

Fixes: 558e4736f2e1 (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>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/acpi/ec.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -299,11 +299,11 @@ static int acpi_ec_transaction_unlocked(
/* following two actions should be kept atomic */
ec->curr = t;
start_transaction(ec);
+ if (ec->curr->command == ACPI_EC_COMMAND_QUERY)
+ clear_bit(EC_FLAGS_QUERY_PENDING, &ec->flags);
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);
ec->curr = NULL;
spin_unlock_irqrestore(&ec->lock, tmp);
return ret;