summaryrefslogtreecommitdiff
path: root/src/cpu
diff options
context:
space:
mode:
Diffstat (limited to 'src/cpu')
-rw-r--r--src/cpu/amd/agesa/family15tn/Makefile.inc2
-rw-r--r--src/cpu/amd/agesa/family15tn/udelay.c45
2 files changed, 47 insertions, 0 deletions
diff --git a/src/cpu/amd/agesa/family15tn/Makefile.inc b/src/cpu/amd/agesa/family15tn/Makefile.inc
index 19a2f0f298..a8f644d241 100644
--- a/src/cpu/amd/agesa/family15tn/Makefile.inc
+++ b/src/cpu/amd/agesa/family15tn/Makefile.inc
@@ -20,6 +20,8 @@
ramstage-y += chip_name.c
ramstage-y += model_15_init.c
+smm-$(CONFIG_HAVE_SMI_HANDLER) += udelay.c
+
subdirs-y += ../../mtrr
subdirs-y += ../../smm
subdirs-y += ../../../x86/tsc
diff --git a/src/cpu/amd/agesa/family15tn/udelay.c b/src/cpu/amd/agesa/family15tn/udelay.c
new file mode 100644
index 0000000000..5873237b0c
--- /dev/null
+++ b/src/cpu/amd/agesa/family15tn/udelay.c
@@ -0,0 +1,45 @@
+/*
+ * udelay() impementation for SMI handlers
+ * This is neat in that it never writes to hardware registers, and thus does not
+ * modify the state of the hardware while servicing SMIs.
+ *
+ * Copyright (C) 2014 Alexandru Gagniuc <mr.nuke.me@gmail.com>
+ * Subject to the GNU GPL v2, or (at your option) any later version.
+ */
+
+#include <cpu/x86/msr.h>
+#include <cpu/x86/tsc.h>
+#include <delay.h>
+#include <stdint.h>
+
+void udelay(uint32_t us)
+{
+ uint8_t fid, did, pstate_idx;
+ uint64_t tsc_clock, tsc_start, tsc_now, tsc_wait_ticks;
+ msr_t msr;
+ const uint64_t tsc_base = 100000000;
+
+ /* Get initial timestamp before we do the math */
+ tsc_start = rdtscll();
+
+ /* Get the P-state. This determines which MSR to read */
+ msr = rdmsr(0xc0010063);
+ pstate_idx = msr.lo & 0x07;
+
+ /* Get FID and VID for current P-State */
+ msr = rdmsr(0xc0010064 + pstate_idx);
+
+ /* Extract the FID and VID values */
+ fid = msr.lo & 0x3f;
+ did = (msr.lo >> 6) & 0x7;
+
+ /* Calculate the CPU clock (from base freq of 100MHz) */
+ tsc_clock = tsc_base * (fid + 0x10) / (1 << did);
+
+ /* Now go on and wait */
+ tsc_wait_ticks = (tsc_clock / 1000000) * us;
+
+ do {
+ tsc_now = rdtscll();
+ } while (tsc_now - tsc_wait_ticks < tsc_start);
+}