Re: [PATCH v8 07/13] drivers: base cacheinfo: Add support for ACPI based firmware tables

[Jeremy Linton]

Hi,

On 04/26/2018 06:05 AM, Sudeep Holla wrote:
> On 26/04/18 00:31, Jeremy Linton wrote:
> > Call ACPI cache parsing routines from base cacheinfo code if ACPI
> > is enable. Also stub out cache_setup_acpi() so that individual
> > architectures can enable ACPI topology parsing.
>
> [...]
>
> > +#ifndef CONFIG_ACPI
> > +static inline int acpi_find_last_cache_level(unsigned int cpu)
> > +{
> > +	/* ACPI kernels should be built with PPTT support */
>
> This sounds incorrect for x86. But I understand why you have it there.
> Does it makes sense to change above to .. ?
>
> #if !defined(CONFIG_ACPI) || (defined(CONFIG_ACPI) && !(CONFIG_ACPI_PPTT))
I'm not sure what that buys us, if anything you want more non-users of 
the function to be falling through to the function prototype rather than 
the static inline. The only place any of this matters (as long as the 
compiler/linker is tossing the static inline) is arm64 because its the 
only arch making a call to acpi_find_last_cache_level(). ACPI_PPTT is 
also only visible on arm64 at the moment due to being wrapped in a if 
ARM64 in the Kconfig

Put another way, I wouldn't expect an arch to have a 'user' visible 
option to enable/disable parsing the PPTT. If an arch can handle 
ACPI/PPTT topology then I would expect it to be fixed to the CONFIG_ACPI 
state. What happens when acpi_find_last_cache_level() is called should 
only be dependent on whether ACPI is enabled, the PPTT parser itself 
will handle the cases of a missing table.