From e6c40f62724c9d0157b5b102c01aade30bc4c47e Mon Sep 17 00:00:00 2001 From: Felix Held Date: Tue, 30 Jul 2024 15:24:08 +0200 Subject: soc/amd/common/psp_smm: add comments to psp_notify_smm The reasoning behind this and the positive side effects of this aren't too clear from the code, so point those out in a comment. Signed-off-by: Felix Held Change-Id: I4f4121031fc1ef600cdf5551f61f1ef4e03b56a5 Reviewed-on: https://review.coreboot.org/c/coreboot/+/83699 Tested-by: build bot (Jenkins) Reviewed-by: Matt DeVillier --- src/soc/amd/common/block/psp/psp_smm.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'src/soc/amd') diff --git a/src/soc/amd/common/block/psp/psp_smm.c b/src/soc/amd/common/block/psp/psp_smm.c index 114cf12add..eecdf02be7 100644 --- a/src/soc/amd/common/block/psp/psp_smm.c +++ b/src/soc/amd/common/block/psp/psp_smm.c @@ -47,6 +47,13 @@ static void clear_smm_flag(void) smm_flag = 0; } +/* + * The MBOX_BIOS_CMD_SMM_INFO PSP mailbox command doesn't necessarily need be sent from SMM, + * but doing so allows the linker to sort out the addresses of c2p_buffer, p2c_buffer and + * smm_flag without us needing to pass this info between ramstage and smm. In the PSP gen2 case + * this will also make sure that the PSP MMIO base will be cached in SMM before the OS takes + * over so no SMN accesses will be needed during OS runtime. + */ int psp_notify_smm(void) { msr_t msr; -- cgit v1.2.3