ACPI: EC: Restore udelay in poll mode

This fixes keyboard event handling on some systems.

Note that this delay was thought unnecessary, and removed
from linux-2.6.20 with 50c1e1138cb94f6aca0f8555777edbcefe0324e2
'ACPI: ec: Drop udelay() from poll mode. Loop by reading status field instead.'

Signed-off-by: Alexey Starikovskiy <astarikovskiy@suse.de>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 7222a18a0319..828c75292cf6 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -73,6 +73,7 @@ enum ec_event {
 
 #define ACPI_EC_DELAY           500     /* Wait 500ms max. during EC ops */
 #define ACPI_EC_UDELAY_GLK      1000    /* Wait 1ms max. to get global lock */
+#define ACPI_EC_UDELAY          100     /* Wait 100us before polling EC again */
 
 enum {
         EC_FLAGS_WAIT_GPE = 0,          /* Don't check status until GPE arrives */
@@ -227,6 +228,7 @@ static int acpi_ec_wait(struct acpi_ec *ec, enum ec_event event, int force_poll)
                 while (time_before(jiffies, delay)) {
                         if (acpi_ec_check_status(ec, event))
                                 goto end;
+                        udelay(ACPI_EC_UDELAY);
                 }
         }
         pr_err(PREFIX "acpi_ec_wait timeout,"