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ACPI / SBS: Add 5 us delay to fix SBS hangs on MacBook

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Commit 7bc5a2bad0 'ACPI: Support _OSI("Darwin") correctly' caused
the MacBook firmware to expose the SBS, resulting in intermittent
hangs of several minutes on boot, and failure to detect or report
the battery.  Fix this by adding a 5 us delay to the start of each
SMBUS transaction.  This timing is the result of experimentation -
hangs were observed with 3 us but never with 5 us.

Fixes: 7bc5a2bad0 'ACPI: Support _OSI("Darwin") correctly'
Link: https://bugzilla.kernel.org/show_bug.cgi?id=94651
Signed-off-by: Chris Bainbridge <chris.bainbridge@gmail.com>
Cc: 3.18+ <stable@vger.kernel.org> # 3.18+
[ rjw: Subject and changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Chris Bainbridge 2015-04-29 21:21:40 +01:00 committed by Rafael J. Wysocki
parent 61f8ff6939
commit 3349fb64b2
1 changed files with 22 additions and 0 deletions
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22
drivers/acpi/sbshc.c
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@ -14,6 +14,7 @@
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/dmi.h>
#include "sbshc.h"
#define PREFIX "ACPI: "
@ -87,6 +88,8 @@ enum acpi_smb_offset {
ACPI_SMB_ALARM_DATA = 0x26, /* 2 bytes alarm data */
};
static bool macbook;
static inline int smb_hc_read(struct acpi_smb_hc *hc, u8 address, u8 *data)
{
return ec_read(hc->offset + address, data);
@ -132,6 +135,8 @@ static int acpi_smbus_transaction(struct acpi_smb_hc *hc, u8 protocol,
}
mutex_lock(&hc->lock);
if (macbook)
udelay(5);
if (smb_hc_read(hc, ACPI_SMB_PROTOCOL, &temp))
goto end;
if (temp) {
@ -257,12 +262,29 @@ extern int acpi_ec_add_query_handler(struct acpi_ec *ec, u8 query_bit,
acpi_handle handle, acpi_ec_query_func func,
void *data);
static int macbook_dmi_match(const struct dmi_system_id *d)
{
pr_debug("Detected MacBook, enabling workaround\n");
macbook = true;
return 0;
}
static struct dmi_system_id acpi_smbus_dmi_table[] = {
{ macbook_dmi_match, "Apple MacBook", {
DMI_MATCH(DMI_BOARD_VENDOR, "Apple"),
DMI_MATCH(DMI_PRODUCT_NAME, "MacBook") },
},
{ },
};
static int acpi_smbus_hc_add(struct acpi_device *device)
{
int status;
unsigned long long val;
struct acpi_smb_hc *hc;
dmi_check_system(acpi_smbus_dmi_table);
if (!device)
return -EINVAL;