Subject: [PATCH] ARM:OMAP2: an issue about curr_pwrst, u8 is never < 0

From: [email-masked] (Chen Gang)
Date: Mon, 01 Apr 2013 18:41:11 +0800

On 2013?04?01? 18:25, Paul Walmsley wrote:
> Hi,
> 
> On Thu, 14 Mar 2013, Chen Gang wrote:
> 
>>
>>   if pwrdm_read_pwrst returns negative number, curr_pwrst can not notice it.
>>   since really need check curr_pwrst whether is negative,
>>     need let the check valid in _pwrdm_save_clkdm_state_and_activate.
>>     and also better to check the return value of pwrdm_read_pwrst, firstly.
>>
>> Signed-off-by: Chen Gang <[email-masked]>
> 
> thanks for reporting this and sending a suggested fix.  The following 
> patch is what I've queued here, which should deal with the root cause 
> without the casts.
> 
> 

  yours (patch below) is simpler and clearer than mine.

  thanks.

  :-)

> - Paul
> 
> From: Paul Walmsley <[email-masked]>
> Date: Sun, 31 Mar 2013 20:22:22 -0600
> Subject: [PATCH] ARM: OMAP2+: powerdomain: avoid testing whether an unsigned
>  char is less than 0
> 
> _pwrdm_save_clkdm_state_and_activate() tried to test one of its
> unsigned arguments to determine whether it was less than zero.  Fix by
> moving the error test to the caller.
> 
> Reported-by: Chen Gang <[email-masked]>
> Signed-off-by: Paul Walmsley <[email-masked]>
> ---
>  arch/arm/mach-omap2/powerdomain.c |   18 ++++++++----------
>  1 file changed, 8 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm/mach-omap2/powerdomain.c b/arch/arm/mach-omap2/powerdomain.c
> index 8e61d80..89cad4a 100644
> --- a/arch/arm/mach-omap2/powerdomain.c
> +++ b/arch/arm/mach-omap2/powerdomain.c
> @@ -52,7 +52,6 @@ enum {
>  #define ALREADYACTIVE_SWITCH		0
>  #define FORCEWAKEUP_SWITCH		1
>  #define LOWPOWERSTATE_SWITCH		2
> -#define ERROR_SWITCH			3
>  
>  /* pwrdm_list contains all registered struct powerdomains */
>  static LIST_HEAD(pwrdm_list);
> @@ -233,10 +232,7 @@ static u8 _pwrdm_save_clkdm_state_and_activate(struct powerdomain *pwrdm,
>  {
>  	u8 sleep_switch;
>  
> -	if (curr_pwrst < 0) {
> -		WARN_ON(1);
> -		sleep_switch = ERROR_SWITCH;
> -	} else if (curr_pwrst < PWRDM_POWER_ON) {
> +	if (curr_pwrst < PWRDM_POWER_ON) {
>  		if (curr_pwrst > pwrst &&
>  		    pwrdm->flags & PWRDM_HAS_LOWPOWERSTATECHANGE &&
>  		    arch_pwrdm->pwrdm_set_lowpwrstchange) {
> @@ -1091,7 +1087,8 @@ int pwrdm_post_transition(struct powerdomain *pwrdm)
>   */
>  int omap_set_pwrdm_state(struct powerdomain *pwrdm, u8 pwrst)
>  {
> -	u8 curr_pwrst, next_pwrst, sleep_switch;
> +	u8 next_pwrst, sleep_switch;
> +	int curr_pwrst;
>  	int ret = 0;
>  	bool hwsup = false;
>  
> @@ -1107,16 +1104,17 @@ int omap_set_pwrdm_state(struct powerdomain *pwrdm, u8 pwrst)
>  	pwrdm_lock(pwrdm);
>  
>  	curr_pwrst = pwrdm_read_pwrst(pwrdm);
> +	if (curr_pwrst < 0) {
> +		ret = -EINVAL;
> +		goto osps_out;
> +	}
> +
>  	next_pwrst = pwrdm_read_next_pwrst(pwrdm);
>  	if (curr_pwrst == pwrst && next_pwrst == pwrst)
>  		goto osps_out;
>  
>  	sleep_switch = _pwrdm_save_clkdm_state_and_activate(pwrdm, curr_pwrst,
>  							    pwrst, &hwsup);
> -	if (sleep_switch == ERROR_SWITCH) {
> -		ret = -EINVAL;
> -		goto osps_out;
> -	}
>  
>  	ret = pwrdm_set_next_pwrst(pwrdm, pwrst);
>  	if (ret)
> 

-- 
Chen Gang

Asianux Corporation