[Intel-gfx] [RFC 2/4] i2c: designware-baytrail: Take punit lock on bus acquire

Hans de Goede hdegoede at redhat.com
Sun Jan 1 20:14:01 UTC 2017

Take the punit lock to stop others from accessing the punit while the
pmic i2c bus is in use. This is necessary because accessing the punit
from the kernel may result in the punit trying to access the pmic i2c
bus, which results in a hang when it happens while we own the pmic i2c
bus semaphore.

Signed-off-by: Hans de Goede <hdegoede at redhat.com>
 drivers/i2c/busses/i2c-designware-baytrail.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/i2c/busses/i2c-designware-baytrail.c b/drivers/i2c/busses/i2c-designware-baytrail.c
index 3effc9a..507875d 100644
--- a/drivers/i2c/busses/i2c-designware-baytrail.c
+++ b/drivers/i2c/busses/i2c-designware-baytrail.c
@@ -61,6 +61,8 @@ static void reset_semaphore(struct dw_i2c_dev *dev)
 		dev_err(dev->dev, "iosf failed to reset punit semaphore during write\n");
+	iosf_mbi_punit_unlock();
 	pm_qos_update_request(&dev->pm_qos, PM_QOS_DEFAULT_VALUE);
@@ -86,6 +88,8 @@ static int baytrail_i2c_acquire(struct dw_i2c_dev *dev)
 	pm_qos_update_request(&dev->pm_qos, 0);
+	iosf_mbi_punit_lock();
 	/* host driver writes to side band semaphore register */
 	ret = iosf_mbi_write(BT_MBI_UNIT_PMC, MBI_REG_WRITE, addr, sem);
 	if (ret) {

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