Re: Re: Linux ACPI processor driver patch: user-definable power state limit

[Jos Delbar <jos.delbar-Cru1EgDzd7c@public.gmane.org>]

On Saturday 06 November 2004 01:29, Dominik Brodowski wrote:
> If that is the case, my patch is "overkill". If there's a chance to do more
> fine-tuned disabling of C3, my patch seems to be better.

Maybe you could reduce the overkill by using a counter instead of a linked 
list to keep track of the limits imposed by other modules. I don't think you 
need any extra code in the idle handler, Len's additions should be enough to 
handle a limit change. The only possible danger that I can see is one or more 
extra idle cycles with an outdated limit.

As it is, is there a way for a module such as ipw2100 to detect when its limit 
request has been commited? Does the processor module export the current C 
state, or should the module rely on the /proc file?

Anyway, here is some code to illustrate the counter. And now I'm going to stop 
spending time on workarounds! ;-)

static unsigned int cstate_limit_counter[ACPI_C_STATES_MAX];
static spinlock_t cstate_limit_lock = SPIN_LOCK_UNLOCKED;

inline void acpi_update_cstate_limit(unsigned int limit, int gain)
{
 unsigned long flags;
 int c;

 if(new_limit >= ACPI_C_STATES_MAX)
  return;

 spin_lock_irqsave(&cstate_limit_lock, flags);
 if (gain > 0)
  cstate_limit_counter[limit]++;
 else if (cstate_limit_counter[limit] > 0)
  cstate_limit_counter[limit]--;

 for (c = 0; c < ACPI_C_STATES_MAX; c++) {
  if (cstate_limit_counter[c]) {
   acpi_cstate_limit = c;
   spin_unlock_irqrestore(&cstate_limit_lock, flags);
   return;
  }
 }
 acpi_cstate_limit = ACPI_C_STATES_MAX;
 spin_unlock_irqrestore(&cstate_limit_lock, flags);
}

static void acpi_remove_cstate_limit(unsigned int limit)
{
 acpi_update_cstate_limit(limit, -1);
}

static void acpi_set_cstate_limit(unsigned int limit)
{
 acpi_update_cstate_limit(limit, 1);
}

-- 

Jos Delbar
jos.delbar-Cru1EgDzd7c@public.gmane.org


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