linux-kernel - [PATCH v2 2/2] rtc: s3c: Add s3c_rtc_{enable/disable}_clk in s3c_rtc

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Date:	Tue, 05 Jul 2016 15:28:53 +0530
From:	Alim Akhtar <alim.akhtar@...sung.com>
To:	rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org
Cc:	alexandre.belloni@...e-electrons.com, k.kozlowski@...sung.com,
	javier@....samsung.com, pankaj.dubey@...sung.com,
	alim.akhtar@...sung.com, stable@...r.kernel.org
Subject: [PATCH v2 2/2] rtc: s3c: Add s3c_rtc_{enable/disable}_clk in
 s3c_rtc_setfreq()

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")

Cc: <stable@...r.kernel.org>
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>
---
 drivers/rtc/rtc-s3c.c |    2 ++
 1 file changed, 2 insertions(+)

* Changes from v1
   -updated commit message as suggested by Krzysztof.
   -updated reviewed-by, tested-by tags

diff --git a/drivers/rtc/rtc-s3c.c b/drivers/rtc/rtc-s3c.c
index b083840..1168814 100644
--- a/drivers/rtc/rtc-s3c.c
+++ b/drivers/rtc/rtc-s3c.c
@@ -149,12 +149,14 @@ static int s3c_rtc_setfreq(struct s3c_rtc *info, int freq)
 	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;
 }
-- 
1.7.10.4