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Commit 3349fb64 authored by Chris Bainbridge's avatar Chris Bainbridge Committed by Rafael J. Wysocki
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ACPI / SBS: Add 5 us delay to fix SBS hangs on MacBook 

Commit 7bc5a2ba '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: 7bc5a2ba 'ACPI: Support _OSI("Darwin") correctly'
Link: https://bugzilla.kernel.org/show_bug.cgi?id=94651


Signed-off-by: default avatarChris Bainbridge <chris.bainbridge@gmail.com>
Cc: 3.18+ <stable@vger.kernel.org> # 3.18+
[ rjw: Subject and changelog ]
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 61f8ff69

drivers/acpi/sbshc.c

+22 −0
Original line number Diff line number Diff line
@@ -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;