[PATCH 1/2] ide: pdc202xx_new: Replace mdelay with usleep_range in detect_pll_input_clock

[PATCH 1/2] ide: pdc202xx_new: Replace mdelay with usleep_range in detect_pll_input_clock

[Jia-Ju Bai]

detect_pll_input_clock() is never called in atomic context.

detect_pll_input_clock() is only called by init_chipset_pdcnew(), which 
is set as ".init_chipset" in struct ide_port_info.
This function is not called in atomic context.

Despite never getting called from atomic context, detect_pll_input_clock()
calls mdelay() to busily wait.
This is not necessary and can be replaced with usleep_range() to
avoid busy waiting.

This is found by a static analysis tool named DCNS written by myself.
And I also manually check it.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
 drivers/ide/pdc202xx_new.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/ide/pdc202xx_new.c b/drivers/ide/pdc202xx_new.c
index b33646b..6afa66d 100644
--- a/drivers/ide/pdc202xx_new.c
+++ b/drivers/ide/pdc202xx_new.c
@@ -258,7 +258,7 @@ static long detect_pll_input_clock(unsigned long dma_base)
 	outb(scr1 | 0x40, dma_base + 0x03);
 
 	/* Let the counter run for 10 ms. */
-	mdelay(10);
+	usleep_range(10);
 
 	end_count = read_counter(dma_base);
 	end_time = ktime_get();
-- 
1.9.1

Re: [PATCH 1/2] ide: pdc202xx_new: Replace mdelay with usleep_range in detect_pll_input_clock

[Sergei Shtylyov]

Hello!

On 4/11/2018 10:52 AM, Jia-Ju Bai wrote:

> detect_pll_input_clock() is never called in atomic context.
> 
> detect_pll_input_clock() is only called by init_chipset_pdcnew(), which
> is set as ".init_chipset" in struct ide_port_info.
> This function is not called in atomic context.
> 
> Despite never getting called from atomic context, detect_pll_input_clock()
> calls mdelay() to busily wait.
> This is not necessary and can be replaced with usleep_range() to
> avoid busy waiting.
> 
> This is found by a static analysis tool named DCNS written by myself.
> And I also manually check it.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
> ---
>   drivers/ide/pdc202xx_new.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/ide/pdc202xx_new.c b/drivers/ide/pdc202xx_new.c
> index b33646b..6afa66d 100644
> --- a/drivers/ide/pdc202xx_new.c
> +++ b/drivers/ide/pdc202xx_new.c
> @@ -258,7 +258,7 @@ static long detect_pll_input_clock(unsigned long dma_base)
>   	outb(scr1 | 0x40, dma_base + 0x03);
>   
>   	/* Let the counter run for 10 ms. */
> -	mdelay(10);
> +	usleep_range(10);

    This function takes 2 arguments.

[...]

MBR, Sergei

Re: [PATCH 1/2] ide: pdc202xx_new: Replace mdelay with usleep_range in detect_pll_input_clock

[Jia-Ju Bai]

On 2018/4/11 16:33, Sergei Shtylyov wrote:
> Hello!
>
> On 4/11/2018 10:52 AM, Jia-Ju Bai wrote:
>
>> detect_pll_input_clock() is never called in atomic context.
>>
>> detect_pll_input_clock() is only called by init_chipset_pdcnew(), which
>> is set as ".init_chipset" in struct ide_port_info.
>> This function is not called in atomic context.
>>
>> Despite never getting called from atomic context, 
>> detect_pll_input_clock()
>> calls mdelay() to busily wait.
>> This is not necessary and can be replaced with usleep_range() to
>> avoid busy waiting.
>>
>> This is found by a static analysis tool named DCNS written by myself.
>> And I also manually check it.
>>
>> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
>> ---
>>   drivers/ide/pdc202xx_new.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/ide/pdc202xx_new.c b/drivers/ide/pdc202xx_new.c
>> index b33646b..6afa66d 100644
>> --- a/drivers/ide/pdc202xx_new.c
>> +++ b/drivers/ide/pdc202xx_new.c
>> @@ -258,7 +258,7 @@ static long detect_pll_input_clock(unsigned long 
>> dma_base)
>>       outb(scr1 | 0x40, dma_base + 0x03);
>>         /* Let the counter run for 10 ms. */
>> -    mdelay(10);
>> +    usleep_range(10);
>
>    This function takes 2 arguments.
>
> [...]
>
> MBR, Sergei

Oops, sorry for my fault.
Thanks for telling me this :)
I will modify it and send V2.


Best wishes,
Jia-Ju Bai

Re: [PATCH 1/2] ide: pdc202xx_new: Replace mdelay with usleep_range in detect_pll_input_clock

[kbuild test robot]

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Hi Jia-Ju,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on ide/master]
[also build test ERROR on v4.16 next-20180411]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Jia-Ju-Bai/ide-pdc202xx_new-Replace-mdelay-with-usleep_range-in-detect_pll_input_clock/20180412-105416
base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/ide.git master
config: i386-randconfig-x015-201814 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

   drivers//ide/pdc202xx_new.c: In function 'detect_pll_input_clock':
>> drivers//ide/pdc202xx_new.c:261:2: error: too few arguments to function 'usleep_range'
     usleep_range(10);
     ^~~~~~~~~~~~
   In file included from drivers//ide/pdc202xx_new.c:21:0:
   include/linux/delay.h:60:6: note: declared here
    void usleep_range(unsigned long min, unsigned long max);
         ^~~~~~~~~~~~

vim +/usleep_range +261 drivers//ide/pdc202xx_new.c

   238	
   239	/**
   240	 * detect_pll_input_clock - Detect the PLL input clock in Hz.
   241	 * @dma_base: for the port address
   242	 * E.g. 16949000 on 33 MHz PCI bus, i.e. half of the PCI clock.
   243	 */
   244	static long detect_pll_input_clock(unsigned long dma_base)
   245	{
   246		ktime_t start_time, end_time;
   247		long start_count, end_count;
   248		long pll_input, usec_elapsed;
   249		u8 scr1;
   250	
   251		start_count = read_counter(dma_base);
   252		start_time = ktime_get();
   253	
   254		/* Start the test mode */
   255		outb(0x01, dma_base + 0x01);
   256		scr1 = inb(dma_base + 0x03);
   257		DBG("scr1[%02X]\n", scr1);
   258		outb(scr1 | 0x40, dma_base + 0x03);
   259	
   260		/* Let the counter run for 10 ms. */
 > 261		usleep_range(10);
   262	
   263		end_count = read_counter(dma_base);
   264		end_time = ktime_get();
   265	
   266		/* Stop the test mode */
   267		outb(0x01, dma_base + 0x01);
   268		scr1 = inb(dma_base + 0x03);
   269		DBG("scr1[%02X]\n", scr1);
   270		outb(scr1 & ~0x40, dma_base + 0x03);
   271	
   272		/*
   273		 * Calculate the input clock in Hz
   274		 * (the clock counter is 30 bit wide and counts down)
   275		 */
   276		usec_elapsed = ktime_us_delta(end_time, start_time);
   277		pll_input = ((start_count - end_count) & 0x3fffffff) / 10 *
   278			(10000000 / usec_elapsed);
   279	
   280		DBG("start[%ld] end[%ld]\n", start_count, end_count);
   281	
   282		return pll_input;
   283	}
   284	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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