[PATCH] ARM: pxa: fix GPIO double shifts

[PATCH] ARM: pxa: fix GPIO double shifts

[Robert Jarzmik]

The commit 9bf448c66d4b ("ARM: pxa: use generic gpio operation instead of
gpio register") from Oct 17, 2011, leads to the following static checker
warning:
  arch/arm/mach-pxa/spitz_pm.c:172 spitz_charger_wakeup()
  warn: double left shift '!gpio_get_value(SPITZ_GPIO_KEY_INT)
        << (1 << ((SPITZ_GPIO_KEY_INT) & 31))'

As Dan reported, the value is shifted three times :
 - once by gpio_get_value(), which returns either 0 or BIT(gpio)
 - once by the shift operation '<<'
 - a last time by GPIO_bit(gpio) which is BIT(gpio)

Therefore the calculation lead to a chained or operator of :
 - (1 << gpio) << (1 << gpio) = (2^gpio)^gpio = 2 ^ (gpio * gpio)

It is be sheer luck the former statement works, only because each gpio
used is strictly smaller than 6, and therefore 2^(gpio^2) never
overflows a 32 bits value, and because it is used as a boolean value to
check a gpio activation.

Fixes: 9bf448c66d4b ("ARM: pxa: use generic gpio operation instead of
gpio register")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
---
 arch/arm/mach-pxa/corgi_pm.c | 8 +++-----
 arch/arm/mach-pxa/spitz_pm.c | 5 ++---
 2 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/arch/arm/mach-pxa/corgi_pm.c b/arch/arm/mach-pxa/corgi_pm.c
index d9206811be9b..a7bc7e18158e 100644
--- a/arch/arm/mach-pxa/corgi_pm.c
+++ b/arch/arm/mach-pxa/corgi_pm.c
@@ -135,11 +135,9 @@ static unsigned long corgi_charger_wakeup(void)
 {
 	unsigned long ret;
 
-	ret = (!gpio_get_value(CORGI_GPIO_AC_IN) << GPIO_bit(CORGI_GPIO_AC_IN))
-		| (!gpio_get_value(CORGI_GPIO_KEY_INT)
-		<< GPIO_bit(CORGI_GPIO_KEY_INT))
-		| (!gpio_get_value(CORGI_GPIO_WAKEUP)
-		<< GPIO_bit(CORGI_GPIO_WAKEUP));
+	ret = !gpio_get_value(CORGI_GPIO_AC_IN)
+		| !gpio_get_value(CORGI_GPIO_KEY_INT)
+		| !gpio_get_value(CORGI_GPIO_WAKEUP);
 	return ret;
 }
 
diff --git a/arch/arm/mach-pxa/spitz_pm.c b/arch/arm/mach-pxa/spitz_pm.c
index ea9f9034cb54..5a4c45b5a526 100644
--- a/arch/arm/mach-pxa/spitz_pm.c
+++ b/arch/arm/mach-pxa/spitz_pm.c
@@ -168,9 +168,8 @@ static int spitz_should_wakeup(unsigned int resume_on_alarm)
 static unsigned long spitz_charger_wakeup(void)
 {
 	unsigned long ret;
-	ret = ((!gpio_get_value(SPITZ_GPIO_KEY_INT)
-		<< GPIO_bit(SPITZ_GPIO_KEY_INT))
-		| gpio_get_value(SPITZ_GPIO_SYNC));
+	ret = !gpio_get_value(SPITZ_GPIO_KEY_INT)
+		| gpio_get_value(SPITZ_GPIO_SYNC);
 	return ret;
 }
 
-- 
2.1.4

Re: [PATCH] ARM: pxa: fix GPIO double shifts

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 2020 bytes --]

Hi,

[auto build test WARNING on arm-soc/for-next]
[also build test WARNING on v4.7-rc7 next-20160715]
[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/Robert-Jarzmik/ARM-pxa-fix-GPIO-double-shifts/20160716-163032
base:   https://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc.git for-next
config: arm-spitz_defconfig (attached as .config)
compiler: arm-linux-gnueabi-gcc (Debian 5.3.1-8) 5.3.1 20160205
reproduce:
        wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=arm 

All warnings (new ones prefixed by >>):

   arch/arm/mach-pxa/spitz_pm.c: In function 'spitz_charger_wakeup':
>> arch/arm/mach-pxa/spitz_pm.c:171:8: warning: suggest parentheses around operand of '!' or change '|' to '||' or '!' to '~' [-Wparentheses]
     ret = !gpio_get_value(SPITZ_GPIO_KEY_INT)
           ^

vim +171 arch/arm/mach-pxa/spitz_pm.c

   155		if (PEDR & GPIO_bit(SPITZ_GPIO_KEY_INT))
   156			is_resume |= GPIO_bit(SPITZ_GPIO_KEY_INT);
   157	
   158		if (PKSR & GPIO_bit(SPITZ_GPIO_SYNC))
   159			is_resume |= GPIO_bit(SPITZ_GPIO_SYNC);
   160	
   161		if (resume_on_alarm && (PEDR & PWER_RTC))
   162			is_resume |= PWER_RTC;
   163	
   164		dev_dbg(sharpsl_pm.dev, "is_resume: %x\n", is_resume);
   165		return is_resume;
   166	}
   167	
   168	static unsigned long spitz_charger_wakeup(void)
   169	{
   170		unsigned long ret;
 > 171		ret = !gpio_get_value(SPITZ_GPIO_KEY_INT)
   172			| gpio_get_value(SPITZ_GPIO_SYNC);
   173		return ret;
   174	}
   175	
   176	unsigned long spitzpm_read_devdata(int type)
   177	{
   178		switch (type) {
   179		case SHARPSL_STATUS_ACIN:

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

[-- Attachment #2: .config.gz --]
[-- Type: application/octet-stream, Size: 19249 bytes --]