linux-kernel - [PATCH 4.2.y-ckt 248/305] i2c: rcar: disable runtime PM correctly in slave mode

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Message-Id: <1452902519-2754-249-git-send-email-kamal@canonical.com>
Date:	Fri, 15 Jan 2016 16:01:02 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Wolfram Sang <wsa@...-dreams.de>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 248/305] i2c: rcar: disable runtime PM correctly in slave mode

4.2.8-ckt2 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Wolfram Sang <wsa+renesas@...g-engineering.com>

commit b4cd08aa1f53c831e67dc5c6bc9f9acff27abcba upstream.

When we also are I2C slave, we need to disable runtime PM because the
address detection mechanism needs to be active all the time. However, we
can reenable runtime PM once the slave instance was unregistered. So,
use pm_runtime_get_sync/put to achieve this, since it has proper
refcounting. pm_runtime_allow/forbid is like a global knob controllable
from userspace which is unsuitable here.

Signed-off-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
Signed-off-by: Wolfram Sang <wsa@...-dreams.de>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/i2c/busses/i2c-rcar.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index d8b5a8f..3191dd9 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -575,7 +575,7 @@ static int rcar_reg_slave(struct i2c_client *slave)
 	if (slave->flags & I2C_CLIENT_TEN)
 		return -EAFNOSUPPORT;
 
-	pm_runtime_forbid(rcar_i2c_priv_to_dev(priv));
+	pm_runtime_get_sync(rcar_i2c_priv_to_dev(priv));
 
 	priv->slave = slave;
 	rcar_i2c_write(priv, ICSAR, slave->addr);
@@ -597,7 +597,7 @@ static int rcar_unreg_slave(struct i2c_client *slave)
 
 	priv->slave = NULL;
 
-	pm_runtime_allow(rcar_i2c_priv_to_dev(priv));
+	pm_runtime_put(rcar_i2c_priv_to_dev(priv));
 
 	return 0;
 }
-- 
1.9.1