commit 3b621ccabdccb34891bb58865a9654a09c2b7279
author Bin Meng <bmeng.cn@gmail.com> Thu Jan 22 11:29:41 2015 +0800
committer Simon Glass <sjg@chromium.org> Fri Jan 23 17:24:55 2015 -0700
tree 8c9321d4657a4154867bd77d92d4d5dad851dbc3
parent 49491669065c1c718d8dc0b0ebc151b3d010c17b

x86: Test mtrr support flag before accessing mtrr msr

On some x86 processors (like Intel Quark) the MTRR registers are not
supported. This is reflected by the CPUID (EAX 01H) result EDX[12].
Accessing the MTRR registers on such processors will cause #GP so we
must test the support flag before accessing MTRR MSRs.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>

arch/x86/cpu/mtrr.c

diff --git a/arch/x86/cpu/mtrr.c b/arch/x86/cpu/mtrr.c
index ac8765f..5d36b3e 100644
--- a/arch/x86/cpu/mtrr.c
+++ b/arch/x86/cpu/mtrr.c
@@ -22,6 +22,9 @@
 /* Prepare to adjust MTRRs */
 void mtrr_open(struct mtrr_state *state)
 {
+	if (!gd->arch.has_mtrr)
+		return;
+
 	state->enable_cache = dcache_status();
 
 	if (state->enable_cache)
@@ -33,6 +36,9 @@
 /* Clean up after adjusting MTRRs, and enable them */
 void mtrr_close(struct mtrr_state *state)
 {
+	if (!gd->arch.has_mtrr)
+		return;
+
 	wrmsrl(MTRR_DEF_TYPE_MSR, state->deftype | MTRR_DEF_TYPE_EN);
 	if (state->enable_cache)
 		enable_caches();
@@ -45,6 +51,9 @@
 	uint64_t mask;
 	int i;
 
+	if (!gd->arch.has_mtrr)
+		return -ENOSYS;
+
 	mtrr_open(&state);
 	for (i = 0; i < gd->arch.mtrr_req_count; i++, req++) {
 		mask = ~(req->size - 1);
@@ -66,6 +75,9 @@
 	struct mtrr_request *req;
 	uint64_t mask;
 
+	if (!gd->arch.has_mtrr)
+		return -ENOSYS;
+
 	if (gd->arch.mtrr_req_count == MAX_MTRR_REQUESTS)
 		return -ENOSPC;
 	req = &gd->arch.mtrr_req[gd->arch.mtrr_req_count++];

arch/x86/include/asm/mtrr.h

diff --git a/arch/x86/include/asm/mtrr.h b/arch/x86/include/asm/mtrr.h
index 3c11740..fda4eae 100644
--- a/arch/x86/include/asm/mtrr.h
+++ b/arch/x86/include/asm/mtrr.h
@@ -65,7 +65,6 @@
  *
  * @state:	Structure from mtrr_open()
  */
-/*  */
 void mtrr_close(struct mtrr_state *state);
 
 /**
@@ -76,6 +75,8 @@
  * @type:	Requested type (MTRR_TYPE_)
  * @start:	Start address
  * @size:	Size
+ *
+ * @return:	0 on success, non-zero on failure
  */
 int mtrr_add_request(int type, uint64_t start, uint64_t size);
 
@@ -86,6 +87,8 @@
  * It must be called with caches disabled.
  *
  * @do_caches:	true if caches are currently on
+ *
+ * @return:	0 on success, non-zero on failure
  */
 int mtrr_commit(bool do_caches);
 

arch/x86/lib/init_helpers.c

diff --git a/arch/x86/lib/init_helpers.c b/arch/x86/lib/init_helpers.c
index fc211d9..5097ca2 100644
--- a/arch/x86/lib/init_helpers.c
+++ b/arch/x86/lib/init_helpers.c
@@ -7,6 +7,7 @@
 #include <common.h>
 #include <fdtdec.h>
 #include <spi.h>
+#include <asm/errno.h>
 #include <asm/mtrr.h>
 #include <asm/sections.h>
 
@@ -71,7 +72,8 @@
 	int ret;
 
 	ret = mtrr_commit(false);
-	if (ret)
+	/* If MTRR MSR is not implemented by the processor, just ignore it */
+	if (ret && ret != -ENOSYS)
 		return ret;
 #endif
 	/* Initialise the CPU cache(s) */