linux-kernel - [PATCH 4.4 135/138] rtc: s3c: Add s3c_rtc_{enable/disable}_clk in s3c_rtc

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Message-Id: <20160818135613.608105144@linuxfoundation.org>
Date:	Thu, 18 Aug 2016 15:59:05 +0200
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Alim Akhtar <alim.akhtar@...sung.com>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Pankaj Dubey <pankaj.dubey@...sung.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Subject: [PATCH 4.4 135/138] rtc: s3c: Add s3c_rtc_{enable/disable}_clk in s3c_rtc_setfreq()

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

------------------

From: Alim Akhtar <alim.akhtar@...sung.com>

commit 70c96dfac0e231424e17743bd52f6cd2ff1f2439 upstream.

As per code flow s3c_rtc_setfreq() will get called with rtc clock disabled
and in set_freq we perform h/w registers read/write, which results in a
kernel crash on exynos7 platform while probing rtc driver.
Below is code flow:
s3c_rtc_probe()
    clk_prepare_enable(info->rtc_clk) // rtc clock enabled
    s3c_rtc_gettime() // will enable clk if not done, and disable it upon exit
    s3c_rtc_setfreq() //then this will be called with clk disabled

This patch take cares of such issue by adding s3c_rtc_{enable/disable}_clk in
s3c_rtc_setfreq().

Fixes: 24e1455493da ("drivers/rtc/rtc-s3c.c: delete duplicate clock control")
Signed-off-by: Alim Akhtar <alim.akhtar@...sung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
Reviewed-by: Pankaj Dubey <pankaj.dubey@...sung.com>
Tested-by: Pankaj Dubey <pankaj.dubey@...sung.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/rtc/rtc-s3c.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/rtc/rtc-s3c.c
+++ b/drivers/rtc/rtc-s3c.c
@@ -149,12 +149,14 @@ static int s3c_rtc_setfreq(struct s3c_rt
 	if (!is_power_of_2(freq))
 		return -EINVAL;
 
+	s3c_rtc_enable_clk(info);
 	spin_lock_irq(&info->pie_lock);
 
 	if (info->data->set_freq)
 		info->data->set_freq(info, freq);
 
 	spin_unlock_irq(&info->pie_lock);
+	s3c_rtc_disable_clk(info);
 
 	return 0;
 }