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

On 07/04/2016 01:03 PM, Alim Akhtar wrote:

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

The indentation suggests levels of calls (chain) not sequence. This
should be:
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().

What I don't get is that you wrote "it is *possible* that
s3c_rtc_setfreq() *might* get called". From my understanding this will
happen always because src_rtc_gettime() always disables the clocks.

Why it does not happen always?

Best regards,
Krzysztof

-- 
You received this message because you are subscribed to "rtc-linux".
Membership options at http://groups.google.com/group/rtc-linux .
Please read http://groups.google.com/group/rtc-linux/web/checklist
before submitting a driver.
--- 
You received this message because you are subscribed to the Google Groups "rtc-linux" group.
To unsubscribe from this group and stop receiving emails from it, send an email to rtc-linux+unsubscribe@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.