[L] Change in coreboot[master]: drivers/smm_payload_interface: Add initial support for SMM payload

[Benjamin Doron (Code Review)]

Attention is currently required from: Arthur Heymans, Martin L Roth, Michał Żygowski, Patrick Rudolph.

Benjamin Doron has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/70378?usp=email )

Change subject: drivers/smm_payload_interface: Add initial support for SMM payload
......................................................................

Patch Set 14:

(1 comment)

File src/drivers/smm_payload_interface/ramstage.c:

https://review.coreboot.org/c/coreboot/+/70378/comment/421c5024_a453a48a :
PS14, Line 114: static void perform_save(void *unused)
              : {
              : 	uint32_t reg32;
              : 
              : 	// Payload does not enable sleep SMI
              : 	reg32 = inl(ACPI_BASE_ADDRESS + SMI_EN);
              : 	reg32 &= ~SLP_SMI_EN;
              : 	outl(reg32, ACPI_BASE_ADDRESS + SMI_EN);
              : 
              : 	// Enable SCI mode when there's no 'ACPI enable' SMI handler
              : 	reg32 = inl(ACPI_BASE_ADDRESS + PM1_CNT);
              : 	reg32 |= SCI_EN;
              : 	outl(reg32, ACPI_BASE_ADDRESS + PM1_CNT);
              : 
              : 	clear_s3_save_region();
              : }
              : 
              : static void perform_s3_restore(void *unused)
              : {
              : 	uint32_t reg32;
              : 
              : 	// Payload does not enable sleep SMI
              : 	reg32 = inl(ACPI_BASE_ADDRESS + SMI_EN);
              : 	reg32 &= ~SLP_SMI_EN;
              : 	outl(reg32, ACPI_BASE_ADDRESS + SMI_EN);
              : 
              : 	// Enable SCI mode when there's no 'ACPI enable' SMI handler
              : 	reg32 = inl(ACPI_BASE_ADDRESS + PM1_CNT);
              : 	reg32 |= SCI_EN;
              : 	outl(reg32, ACPI_BASE_ADDRESS + PM1_CNT);
              : 
              : 	trigger_payload_swsmi();
              : }
              : 
If we're already informing the payload where some registers are, maybe make it do this. Especially the "SLP_SMI_EN", that's highly implementation-specific. And creating these SMI handlers isn't a bad idea - depending on whether the payload can handle the interrupts as SMIs, or they should always go through ACPI instead.