[L] Change in coreboot[main]: acpi: Add PPTT support

[Arthur Heymans (Code Review)]

Attention is currently required from: Cliff Huang, David Milosevic, Lance Zhao, Martin L Roth, Maximilian Brune, Nico Huber, Patrick Rudolph, Tim Wawrzynczak.

Arthur Heymans has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/78071?usp=email )

Change subject: acpi: Add PPTT support
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Patch Set 17:

(6 comments)

File src/acpi/acpi.c:

https://review.coreboot.org/c/coreboot/+/78071/comment/28a4e69d_7ce92372 :
PS17, Line 1204: /* --- header generation --- */
               : 
Useless comments?

File src/acpi/acpi_pptt.c:

https://review.coreboot.org/c/coreboot/+/78071/comment/b01f584e_7849976f :
PS17, Line 12: typedef
typedefs are against the style guide.

https://review.coreboot.org/c/coreboot/+/78071/comment/621eac02_06ec0928 :
PS17, Line 23:  = 0x0
static variables are always initialised at 0.

https://review.coreboot.org/c/coreboot/+/78071/comment/1cd4e6cb_f9b1b807 :
PS17, Line 74: u32 *n_caches
Do you need this? you memset cache_refs to 0. Just search for the first non 0 entry and make the function simpler? This works work well with the ideas below.

https://review.coreboot.org/c/coreboot/+/78071/comment/d861aa8c_1871fb59 :
PS17, Line 131: cache_reference_t cache_refs[CONFIG_ACPI_PPTT_MAX_CACHES];
Is this not more appropriate to declare this in setup_topology so that all siblings can reuse it? Now you create these references for each call of new_pptt_cpu. return reference_for_cache in pptt_cache if !0?

https://review.coreboot.org/c/coreboot/+/78071/comment/a9d0202d_31475423 :
PS17, Line 132: memset(cache_refs, 0x0, sizeof(cache_reference_t) * CONFIG_ACPI_PPTT_MAX_CACHES);
              : 
The ideomatic way in C is "= {}" in the declaration of the variable.