1 files changed, 45 insertions, 0 deletions
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);
+}