[coreboot] fsp_baytrail smi_lock bit set

John Fastabend john.fastabend at gmail.com
Mon Sep 19 18:38:33 CEST 2016


I'm using the fsp_baytrail (minnowboard-max) code base with the Intel
provided FSP Gold4 binary for the platform.

Everything boots fine but I was looking at the SMI/smm code paths and
wanted to trigger an SMI from an I/O port write. It appears this is
being disabled the GBL_SMI_EN bit is disabled and can not be set because
the SMI_LOCK bit is being set.

I read through some of the code and it looks like other platforms such
as skylake have explicit control over this bit and clear/set it in the
coreboot source code. Even the baytrail platform (sans fsp) seems to
set/clear it directly.

For fsp_baytrail I don't see any coreboot code setting the SMI_LOCK bit
at all and some tracing seems to indicate it is being set in the FSP
parts of the code.

So two questions,

 1) Is my reading of the fsp_baytrail code correct and the SMI_LOCK bit
    is really being set by the FSP code paths.

 2) Anyone know how to _not_ set the bit either via coreboot change or
    FSP configuration maybe via BCT?

Sorry if this is really an FSP question I didn't see any good FSP
mailing list to CC or just send its own mail to.

For reference the SMI_LOCK bit is in this register,

	General PM Configuration 2 (GEN_PMCON2)—Offset 24h

at bit 4, and the GBL_SMI_EN is in this register,

	SMI_EN - SMI Control and Enable (SMI_EN)—Offset 30h

at bit 0. I use the following code snippets to add debugging into the
coreboot code paths,

+       pmc = inl(PMC_BASE_ADDRESS + 0x24);
+       printk(BIOS_INFO, "SMI# : PMC: 0x08x\n", pmc)

to read the smi_lock bit and the following to read/set the smi_enable
bit which fails due to the above bit being set,

+       outl(smi_en | 0x1, get_pmbase() + SMI_EN);
+       smi_en = inl(get_pmbase() + SMI_EN);
+       printk(BIOS_INFO, "post write SMI# : 0x08x\n", smi_en);

Any hints, help, comments would be appreciated at the moment I'm just
sort of scanning the FSP spec to try and glean something useful.


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