linux-kernel - [PATCH 1/3] power: clock_ops.c: fixup clk prepare/unprepare count

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Date:	Sat, 11 Jan 2014 13:05:38 +0000
From:	Ben Dooks <ben.dooks@...ethink.co.uk>
To:	linux-kernel@...ts.codethink.co.uk
Cc:	Ben Dooks <ben.dooks@...ethink.co.uk>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Pavel Machek <pavel@....cz>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-pm@...r.kernel.org, linux-sh@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] power: clock_ops.c: fixup clk prepare/unprepare count

The drivers/base/power/clock_ops.c file is causing warnings from
the clock driver (as shown below) due to failing to do a clk_prepare()
call before enabling a clock. It also fails to check the balance of
prepare/unprepare as __pm_clk_remove() do clk_disable_unprepare() call.

This bug has probably been in since commit b2476490e ("clk: introduce
the common clock framework") as the warning was part of the original
commit. It is strange that it has not been noticed (although this has
also been coupled with a failure for certain SH builds to not build the
necessary glue to use this method of controlling the clocks).

In summary, this is probably needed in several stable branches but need
advice on which ones.

On the Renesas Lager board, this causes numerous warnings of the following
and even worse the clock system will not enable clocks, causing drivers
that are in development to fail to work:

WARNING: CPU: 0 PID: 1 at drivers/clk/clk.c:883 __clk_enable+0x2c/0xa0()

Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Pavel Machek <pavel@....cz>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-pm@...r.kernel.org
Cc: linux-sh@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Ben Dooks <ben.dooks@...ethink.co.uk>
Reviewed-by: Ian Molton <ian.molton@...ethink.co.uk>
---
 drivers/base/power/clock_ops.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/base/power/clock_ops.c b/drivers/base/power/clock_ops.c
index 9d8fde7..b9dd8fa 100644
--- a/drivers/base/power/clock_ops.c
+++ b/drivers/base/power/clock_ops.c
@@ -43,6 +43,7 @@ static void pm_clk_acquire(struct device *dev, struct pm_clock_entry *ce)
 	if (IS_ERR(ce->clk)) {
 		ce->status = PCE_STATUS_ERROR;
 	} else {
+		clk_prepare(ce->clk);
 		ce->status = PCE_STATUS_ACQUIRED;
 		dev_dbg(dev, "Clock %s managed by runtime PM.\n", ce->con_id);
 	}
@@ -99,10 +100,12 @@ static void __pm_clk_remove(struct pm_clock_entry *ce)
 
 	if (ce->status < PCE_STATUS_ERROR) {
 		if (ce->status == PCE_STATUS_ENABLED)
-			clk_disable_unprepare(ce->clk);
+			clk_disable(ce->clk);
 
-		if (ce->status >= PCE_STATUS_ACQUIRED)
+		if (ce->status >= PCE_STATUS_ACQUIRED) {
+			clk_unprepare(ce->clk);
 			clk_put(ce->clk);
+		}
 	}
 
 	kfree(ce->con_id);
-- 
1.8.5.2

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