[PATCH v2 2/2] rtc: s3c: Add s3c_rtc_{enable/disable}_clk in s3c_rtc_setfreq()

[PATCH v2 2/2] rtc: s3c: Add s3c_rtc_{enable/disable}_clk in s3c_rtc_setfreq()

[Alim Akhtar]

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@vger.kernel.org>
Signed-off-by: Alim Akhtar <alim.akhtar@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Pankaj Dubey <pankaj.dubey@samsung.com>
Tested-by: Pankaj Dubey <pankaj.dubey@samsung.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

Re: [PATCH v2 2/2] rtc: s3c: Add s3c_rtc_{enable/disable}_clk in s3c_rtc_setfreq()

[Alexandre Belloni]

On 05/07/2016 at 15:28:53 +0530, Alim Akhtar wrote :
> 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@vger.kernel.org>
> Signed-off-by: Alim Akhtar <alim.akhtar@samsung.com>
> Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> Reviewed-by: Pankaj Dubey <pankaj.dubey@samsung.com>
> Tested-by: Pankaj Dubey <pankaj.dubey@samsung.com>
> ---
>  drivers/rtc/rtc-s3c.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
Applied, thanks.

-- 
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com