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* [rtc-linux] [bug report] rtc: add STM32 RTC driver
@ 2017-01-16 12:13 Dan Carpenter
  2017-01-16 12:19 ` [rtc-linux] " Amelie DELAUNAY
  2017-01-16 12:21 ` [rtc-linux] " Dan Carpenter
  0 siblings, 2 replies; 5+ messages in thread
From: Dan Carpenter @ 2017-01-16 12:13 UTC (permalink / raw)
  To: amelie.delaunay; +Cc: rtc-linux

Hello Amelie Delaunay,

The patch 4e64350f42e2: "rtc: add STM32 RTC driver" from Jan 11,
2017, leads to the following static checker warning:

	drivers/rtc/rtc-stm32.c:514 stm32_rtc_init()
	warn: always true condition '(pred_a >= 0) => (0-u32max >= 0)'

drivers/rtc/rtc-stm32.c
   499  static int stm32_rtc_init(struct platform_device *pdev,
   500                            struct stm32_rtc *rtc)
   501  {
   502          unsigned int prer, pred_a, pred_s, pred_a_max, pred_s_max, cr;
   503          unsigned int rate;
   504          int ret = 0;
   505  
   506          rate = clk_get_rate(rtc->ck_rtc);
   507  
   508          /* Find prediv_a and prediv_s to obtain the 1Hz calendar clock */
   509          pred_a_max = STM32_RTC_PRER_PRED_A >> STM32_RTC_PRER_PRED_A_SHIFT;
   510          pred_s_max = STM32_RTC_PRER_PRED_S >> STM32_RTC_PRER_PRED_S_SHIFT;
   511  
   512          for (pred_a = pred_a_max; pred_a >= 0; pred_a--) {
                                          ^^^^^^^^^^^
We should probably make pred_a, pred_s, pred_a_max and pred_s_max
signed.

   513                  pred_s = (rate / (pred_a + 1)) - 1;
   514  
   515                  if (((pred_s + 1) * (pred_a + 1)) == rate)
   516                          break;
   517          }
   518  

regards,
dan carpenter

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^ permalink raw reply	[flat|nested] 5+ messages in thread
* [rtc-linux] RE: [bug report] rtc: add STM32 RTC driver
  2017-01-16 12:13 [rtc-linux] [bug report] rtc: add STM32 RTC driver Dan Carpenter
@ 2017-01-16 12:19 ` Amelie DELAUNAY
  2017-01-16 12:21 ` [rtc-linux] " Dan Carpenter
  1 sibling, 0 replies; 5+ messages in thread
From: Amelie DELAUNAY @ 2017-01-16 12:19 UTC (permalink / raw)
  To: Dan Carpenter; +Cc: rtc-linux

Hi Dan,

Thanks for reporting this issue.
I've already send a fix ("rtc: stm32: fix comparison warnings"): https://patchwork.kernel.org/patch/9518411/.

Regards,
Amelie

> -----Original Message-----
> From: Dan Carpenter [mailto:dan.carpenter@oracle.com]
> Sent: lundi 16 janvier 2017 13:14
> To: Amelie DELAUNAY <amelie.delaunay@st.com>
> Cc: rtc-linux@googlegroups.com
> Subject: [bug report] rtc: add STM32 RTC driver
> 
> Hello Amelie Delaunay,
> 
> The patch 4e64350f42e2: "rtc: add STM32 RTC driver" from Jan 11, 2017, leads
> to the following static checker warning:
> 
> 	drivers/rtc/rtc-stm32.c:514 stm32_rtc_init()
> 	warn: always true condition '(pred_a >= 0) => (0-u32max >= 0)'
> 
> drivers/rtc/rtc-stm32.c
>    499  static int stm32_rtc_init(struct platform_device *pdev,
>    500                            struct stm32_rtc *rtc)
>    501  {
>    502          unsigned int prer, pred_a, pred_s, pred_a_max, pred_s_max, cr;
>    503          unsigned int rate;
>    504          int ret = 0;
>    505
>    506          rate = clk_get_rate(rtc->ck_rtc);
>    507
>    508          /* Find prediv_a and prediv_s to obtain the 1Hz calendar clock */
>    509          pred_a_max = STM32_RTC_PRER_PRED_A >>
> STM32_RTC_PRER_PRED_A_SHIFT;
>    510          pred_s_max = STM32_RTC_PRER_PRED_S >>
> STM32_RTC_PRER_PRED_S_SHIFT;
>    511
>    512          for (pred_a = pred_a_max; pred_a >= 0; pred_a--) {
>                                           ^^^^^^^^^^^ We should probably make pred_a,
> pred_s, pred_a_max and pred_s_max signed.
> 
>    513                  pred_s = (rate / (pred_a + 1)) - 1;
>    514
>    515                  if (((pred_s + 1) * (pred_a + 1)) == rate)
>    516                          break;
>    517          }
>    518
> 
> regards,
> dan carpenter

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^ permalink raw reply	[flat|nested] 5+ messages in thread
* [rtc-linux] Re: [bug report] rtc: add STM32 RTC driver
  2017-01-16 12:13 [rtc-linux] [bug report] rtc: add STM32 RTC driver Dan Carpenter
  2017-01-16 12:19 ` [rtc-linux] " Amelie DELAUNAY
@ 2017-01-16 12:21 ` Dan Carpenter
  2017-01-16 12:26   ` Amelie DELAUNAY
  1 sibling, 1 reply; 5+ messages in thread
From: Dan Carpenter @ 2017-01-16 12:21 UTC (permalink / raw)
  To: amelie.delaunay; +Cc: rtc-linux

Oh.  That still won't fix this:

drivers/rtc/rtc-stm32.c
   519          /*
   520           * Can't find a 1Hz, so give priority to RTC power consumption
   521           * by choosing the higher possible value for prediv_a
   522           */
   523          if ((pred_s > pred_s_max) || (pred_a > pred_a_max)) {
   524                  pred_a = pred_a_max;
   525                  pred_s = (rate / (pred_a + 1)) - 1;
   526  
   527                  dev_warn(&pdev->dev, "ck_rtc is %s\n",
   528                           (rate - ((pred_a + 1) * (pred_s + 1)) < 0) ?

This is type promoted to unsigned int < 0.

   529                           "fast" : "slow");
   530          }

regards,
dan carpenter

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^ permalink raw reply	[flat|nested] 5+ messages in thread
* [rtc-linux] Re: [bug report] rtc: add STM32 RTC driver
  2017-01-16 12:21 ` [rtc-linux] " Dan Carpenter
@ 2017-01-16 12:26   ` Amelie DELAUNAY
  2017-01-16 12:29     ` Dan Carpenter
  0 siblings, 1 reply; 5+ messages in thread
From: Amelie DELAUNAY @ 2017-01-16 12:26 UTC (permalink / raw)
  To: Dan Carpenter; +Cc: rtc-linux

I've changed the comparison:
@@ -525,7 +525,7 @@  static int stm32_rtc_init(struct platform_device *pdev,
  		pred_s = (rate / (pred_a + 1)) - 1;

  		dev_warn(&pdev->dev, "ck_rtc is %s\n",
-			 (rate - ((pred_a + 1) * (pred_s + 1)) < 0) ?
+			 (rate < ((pred_a + 1) * (pred_s + 1))) ?
  			 "fast" : "slow");
  	}
Now, rate (unsigned) is compared to ((pred_a + 1) * (pred_s + 1)) 
(unsigned), so no further "unsigned expression < 0 is always false".

Regards,
Amelie
On 01/16/2017 01:21 PM, Dan Carpenter wrote:
> Oh.  That still won't fix this:
>
> drivers/rtc/rtc-stm32.c
>    519          /*
>    520           * Can't find a 1Hz, so give priority to RTC power consumption
>    521           * by choosing the higher possible value for prediv_a
>    522           */
>    523          if ((pred_s > pred_s_max) || (pred_a > pred_a_max)) {
>    524                  pred_a = pred_a_max;
>    525                  pred_s = (rate / (pred_a + 1)) - 1;
>    526
>    527                  dev_warn(&pdev->dev, "ck_rtc is %s\n",
>    528                           (rate - ((pred_a + 1) * (pred_s + 1)) < 0) ?
>
> This is type promoted to unsigned int < 0.
>
>    529                           "fast" : "slow");
>    530          }
>
> regards,
> dan carpenter
>

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^ permalink raw reply	[flat|nested] 5+ messages in thread
* [rtc-linux] Re: [bug report] rtc: add STM32 RTC driver
  2017-01-16 12:26   ` Amelie DELAUNAY
@ 2017-01-16 12:29     ` Dan Carpenter
  0 siblings, 0 replies; 5+ messages in thread
From: Dan Carpenter @ 2017-01-16 12:29 UTC (permalink / raw)
  To: Amelie DELAUNAY; +Cc: rtc-linux

Yeah.  I just read your patch now.  Thanks.

regards,
dan carpenter

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^ permalink raw reply	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2017-01-16 12:29 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-01-16 12:13 [rtc-linux] [bug report] rtc: add STM32 RTC driver Dan Carpenter
2017-01-16 12:19 ` [rtc-linux] " Amelie DELAUNAY
2017-01-16 12:21 ` [rtc-linux] " Dan Carpenter
2017-01-16 12:26   ` Amelie DELAUNAY
2017-01-16 12:29     ` Dan Carpenter

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