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

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.

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