soc/intel/fsp_broadwell_de: Check if memory is 'locked'

Under certain conditions TXT can "lock" memory controller for security
purpose. This manifests itself in IMC's SMbus controller failing all SPD
data read requests.  FSP does not detect error condition and fails boot
with "No memory found" issue.

TEST=tested on OCP monolake in 'locked' state

Change-Id: If4637e4293421794a89037ff107e87794c40114a
Signed-off-by: Andrey Petrov <anpetrov@fb.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42710
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-by: Christian Walter <christian.walter@9elements.com>

src/soc/intel/fsp_broadwell_de/include/soc/memory.h

@@ -27,4 +27,8 @@
 
 void save_dimm_info(void);
 
+/* Determine if memory configuration has been locked by TXT */
+bool memory_config_is_locked(void);
+
+
 #endif

src/soc/intel/fsp_broadwell_de/include/soc/msr.h

@@ -39,4 +39,9 @@
 #define MSR_PRMRR_PHYS_BASE	0x1f4
 #define MSR_PRMRR_PHYS_MASK	0x1f5
 
+/* EDS vol 2 */
+#define MSR_LT_MEMORY_LOCKED	0x2e7
+#define   MSR_MEM_LOCK_BIT1	(1 << 1)
+#define   MSR_MEM_LOCK_BIT2	(1 << 2)
+
 #endif /* _SOC_MSR_H_ */

src/soc/intel/fsp_broadwell_de/romstage/memory.c

@@ -13,6 +13,8 @@
  * GNU General Public License for more details.
  */
 
+#include <cpu/x86/msr.h>
+#include <soc/msr.h>
 #include <stddef.h>
 #include <device/pci_ops.h>
 #include <device/dram/ddr4.h>
@@ -85,3 +87,9 @@ void save_dimm_info(void)
 		}
 	}
 }
+
+bool memory_config_is_locked(void)
+{
+	msr_t msr = rdmsr(MSR_LT_MEMORY_LOCKED);
+	return (msr.lo & (MSR_MEM_LOCK_BIT1 | MSR_MEM_LOCK_BIT2));
+}