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

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Message-id: <1467630195-6929-2-git-send-email-alim.akhtar@samsung.com>
Date:	Mon, 04 Jul 2016 16:33:14 +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
Subject: [RFC PATCH 2/2] rtc: s3c: Add s3c_rtc_{enable/disable}_clk in
 s3c_rtc_setfreq()

As per code flow it is possible that s3c_rtc_setfreq() might get called
with rtc clock disabled and in set_freq we perform h/w registers read/write,
which might results in a kernel crash while probing rtc driver.
Below is one such case:
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().

Signed-off-by: Alim Akhtar <alim.akhtar@...sung.com>
---
 drivers/rtc/rtc-s3c.c |    2 ++
 1 file changed, 2 insertions(+)

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