intel i945 gm45 x4x post-car: Use postcar_frame for MTRR setup

Adapt implementation from skylake to prepare for removal of
HIGH_MEMORY_SAVE and moving on to RELOCATABLE_RAMSTAGE.
With this change, CBMEM region is set early-on as WRBACK
with MTRRs and romstage ram stack is moved to CBMEM.

Change-Id: Idee5072fd499aa3815b0d78f54308c273e756fd1
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/15791
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

2 files changed, 65 insertions, 24 deletions

diff --git a/src/cpu/intel/car/cache_as_ram_ht.inc b/src/cpu/intel/car/cache_as_ram_ht.inc
index 210d3566c7..d8a4fd9a83 100644
--- a/src/cpu/intel/car/cache_as_ram_ht.inc
+++ b/src/cpu/intel/car/cache_as_ram_ht.inc
@@ -337,10 +337,9 @@ before_romstage:
 	post_code(0x2f)
 	/* Call romstage.c main function. */
 	call	romstage_main
-
 	/* Save return value from romstage_main. It contains the stack to use
-	 * after cache-as-ram is torn down.
-	 */
+	 * after cache-as-ram is torn down. It also contains the information
+	 * for setting up MTRRs. */
 	movl	%eax, %esp
 
 	post_code(0x30)
@@ -378,27 +377,48 @@ before_romstage:
 
 	post_code(0x38)
 
-	/* Enable Write Back and Speculative Reads for low RAM. */
+	/* Clear all of the variable MTRRs. */
+	popl	%ebx
 	movl	$MTRR_PHYS_BASE(0), %ecx
-	movl	$(0x00000000 | MTRR_TYPE_WRBACK), %eax
-	xorl	%edx, %edx
-	wrmsr
-	movl	$MTRR_PHYS_MASK(0), %ecx
-	rdmsr
-	movl	$(~(CACHE_TMP_RAMTOP - 1) | MTRR_PHYS_MASK_VALID), %eax
-	wrmsr
+	clr	%eax
+	clr	%edx
+
+1:
+	testl	%ebx, %ebx
+	jz	1f
+	wrmsr			/* Write MTRR base. */
+	inc	%ecx
+	wrmsr			/* Write MTRR mask. */
+	inc	%ecx
+	dec	%ebx
+	jmp	1b
 
-#if CACHE_ROM_SIZE
-	/* Enable caching and Speculative Reads for Flash ROM device. */
-	movl	$MTRR_PHYS_BASE(1), %ecx
-	movl	$(CACHE_ROM_BASE | MTRR_TYPE_WRPROT), %eax
-	xorl	%edx, %edx
+1:
+	/* Get number of MTRRs. */
+	popl	%ebx
+	movl	$MTRR_PHYS_BASE(0), %ecx
+2:
+	testl	%ebx, %ebx
+	jz	2f
+
+	/* Low 32 bits of MTRR base. */
+	popl	%eax
+	/* Upper 32 bits of MTRR base. */
+	popl	%edx
+	/* Write MTRR base. */
 	wrmsr
-	movl	$MTRR_PHYS_MASK(1), %ecx
-	rdmsr
-	movl	$(~(CACHE_ROM_SIZE - 1) | MTRR_PHYS_MASK_VALID), %eax
+	inc	%ecx
+	/* Low 32 bits of MTRR mask. */
+	popl	%eax
+	/* Upper 32 bits of MTRR mask. */
+	popl	%edx
+	/* Write MTRR mask. */
 	wrmsr
-#endif
+	inc	%ecx
+
+	dec	%ebx
+	jmp	2b
+2:
 
 	post_code(0x39)
 
diff --git a/src/cpu/intel/car/romstage.c b/src/cpu/intel/car/romstage.c
index 4f600342ec..14f841c08b 100644
--- a/src/cpu/intel/car/romstage.c
+++ b/src/cpu/intel/car/romstage.c
@@ -14,6 +14,7 @@
 #include <arch/cpu.h>
 #include <console/console.h>
 #include <cpu/intel/romstage.h>
+#include <cpu/x86/mtrr.h>
 #include <program_loading.h>
 
 #define DCACHE_RAM_ROMSTAGE_STACK_SIZE 0x2000
@@ -41,10 +42,7 @@ void * asmlinkage romstage_main(unsigned long bist)
 	}
 
 	/* Get the stack to use after cache-as-ram is torn down. */
-	if (IS_ENABLED(CONFIG_LATE_CBMEM_INIT))
-		romstage_stack_after_car = (void*)CONFIG_RAMTOP;
-	else
-		romstage_stack_after_car = setup_stack_and_mtrrs();
+	romstage_stack_after_car = setup_stack_and_mtrrs();
 
 	return romstage_stack_after_car;
 }
@@ -54,3 +52,26 @@ void asmlinkage romstage_after_car(void)
 	/* Load the ramstage. */
 	run_ramstage();
 }
+
+#if IS_ENABLED(CONFIG_LATE_CBMEM_INIT)
+/* setup_stack_and_mtrrs() determines the stack to use after
+ * cache-as-ram is torn down as well as the MTRR settings to use. */
+void *setup_stack_and_mtrrs(void)
+{
+	struct postcar_frame pcf;
+
+	postcar_frame_init_lowmem(&pcf);
+
+	/* Cache the ROM as WP just below 4GiB. */
+	postcar_frame_add_mtrr(&pcf, -CACHE_ROM_SIZE, CACHE_ROM_SIZE,
+		MTRR_TYPE_WRPROT);
+
+	/* Cache RAM as WB from 0 -> CACHE_TMP_RAMTOP. */
+	postcar_frame_add_mtrr(&pcf, 0, CACHE_TMP_RAMTOP, MTRR_TYPE_WRBACK);
+
+	/* Save the number of MTRRs to setup. Return the stack location
+	 * pointing to the number of MTRRs.
+	 */
+	return postcar_commit_mtrrs(&pcf);
+}
+#endif /* CONFIG_LATE_CBMEM_INIT */