intel/braswell: allow dirty cache line evictions for SMRAM to stick

The BUNIT controls the policy for read/write access to physical
memory. For the SMRAM range the policy was not allowing dirty
evictions to the SMRAM when the core causing the eviction was not
in SMM mode. This could happen when the SMM handler dirtied a line
and then RSM'd back into non-SMM mode. The cache line was dirtied
while in SMM mode, but when that particular cache line was evicted
it would be silently dropped. Fix this by allowing the BUNIT to honor
writes to the SMRAM range while the evicting core is not in SMM mode.
The core SMRR msr provides the mechanism for disallowing general access
to the SMRAM region while it is not in SMM mode.

BUG=chrome-os-partner:43091
BRANCH=None
TEST=Run suspend_stress_test and ensure there is no hang SMI handler
on suspend-path.
Signed-off-by: Chiranjeevi Rapolu <chiranjeevi.rapolu@intel.com>

Change-Id: Ie794aa3afd54b5e21d0d59a2a7388d507f233537
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Original-Commit-Id: 9c481ab339b4e5ab063e2c32b1f0a48b521142b2
Original-Change-Id: I3e7d41c794c6168eb2ad4eb047675bdb1728f72f
Original-Reviewed-on: https://chromium-review.googlesource.com/292890
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Original-Commit-Queue: Hannah Williams <hannah.williams@intel.com>
Original-Tested-by: Hannah Williams <hannah.williams@intel.com>
Reviewed-on: http://review.coreboot.org/11412
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/soc/intel/braswell/cpu.c

@@ -30,6 +30,7 @@
 #include <cpu/x86/smm.h>
 #include <soc/intel/common/memmap.h>
 #include <reg_script.h>
+#include <soc/iosf.h>
 #include <soc/msr.h>
 #include <soc/pattrs.h>
 #include <soc/ramstage.h>
@@ -86,6 +87,7 @@ void soc_init_cpus(device_t dev)
 	const struct pattrs *pattrs = pattrs_get();
 	struct mp_params mp_params;
 	void *default_smm_area;
+	uint32_t bsmrwac;
 
 	printk(BIOS_SPEW, "%s/%s ( %s )\n",
 			__FILE__, __func__, dev_name(dev));
@@ -104,6 +106,14 @@ void soc_init_cpus(device_t dev)
 
 	default_smm_area = backup_default_smm_area();
 
+	/*
+	 * Configure the BUNIT to allow dirty cache line evictions in non-SMM
+	 * mode for the lines that were dirtied while in SMM mode. Otherwise
+	 * the writes would be silently dropped.
+	 */
+	bsmrwac = iosf_bunit_read(BUNIT_SMRWAC) | SAI_IA_UNTRUSTED;
+	iosf_bunit_write(BUNIT_SMRWAC, bsmrwac);
+
 	/* Set package MSRs */
 	reg_script_run(package_msr_script);
 

src/soc/intel/braswell/include/soc/iosf.h

@@ -131,9 +131,15 @@ void reg_script_write_iosf(struct reg_script_context *ctx);
 #define BUNIT_MMCONF_REG	0x27
 #define BUNIT_BMISC		0x28
 /* The SMMRR registers define the SMM region in MiB granularity. */
+#define BUNIT_SMRWAC	0x2d
 #define BUNIT_SMRRL		0x2e
 #define BUNIT_SMRRH		0x2f
 
+/* SA ID bits. */
+#define SAI_IA_UNTRUSTED	(1 << 0)
+#define SAI_IA_SMM			(1 << 2)
+#define SAI_IA_BOOT			(1 << 4)
+
 /*
  * LPSS Registers
  */