Re: [PATCH] acpi-cpufreq: Remove P-state read after a P-state write in normal path

[Dominik Brodowski <linux@dominikbrodowski.net>]

Hi,

On Fri, Aug 26, 2005 at 05:10:52PM -0700, Venkatesh Pallipadi wrote:
>  	/*
> -	 * Then we read the 'status_register' and compare the value with the
> -	 * target state's 'status' to make sure the transition was successful.
> -	 * Note that we'll poll for up to 1ms (100 cycles of 10us) before
> -	 * giving up.
> +	 * Assume the write went through when acpi_pstate_strict is not used.
> +	 * As read status_register is an expensive operation and there 
> +	 * are no specific error cases where an IO port write will fail.
>  	 */

Well, the IO port write itself might not fail, but the transition itself --
and we're reading the _status_ register here, not the control register where
we've written to. And 8.4.4.1 of ACPI-sepc 3.0 does specifically mention
that transitions _can_ fail, so I think we should handle this possibility.

	Dominik
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