From 432516586e7f646aa2a8ac0cbdf8e80ac44f97d0 Mon Sep 17 00:00:00 2001
From: Kyösti Mälkki <kyosti.malkki@gmail.com>
Date: Thu, 31 Oct 2019 13:25:23 +0200
Subject: cpu/x86: Move calibrate_tsc_with_pit() to drivers/pc80
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Change-Id: Ia8d8dc23ee0b51d62c83f5ba640b3a9aea4e744b
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/36507
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>
---
 src/drivers/pc80/pc/Makefile.inc |  8 ++++-
 src/drivers/pc80/pc/i8254.c      | 76 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 83 insertions(+), 1 deletion(-)

(limited to 'src/drivers/pc80/pc')

diff --git a/src/drivers/pc80/pc/Makefile.inc b/src/drivers/pc80/pc/Makefile.inc
index 8c348e323e..bd56cd43a1 100644
--- a/src/drivers/pc80/pc/Makefile.inc
+++ b/src/drivers/pc80/pc/Makefile.inc
@@ -1,7 +1,6 @@
 ifeq ($(CONFIG_ARCH_X86),y)
 
 ramstage-y += isa-dma.c
-ramstage-y += i8254.c
 ramstage-y += i8259.c
 ramstage-$(CONFIG_UDELAY_IO) += udelay_io.c
 romstage-$(CONFIG_UDELAY_IO) += udelay_io.c
@@ -9,4 +8,11 @@ ramstage-y += keyboard.c
 ramstage-$(CONFIG_SPKMODEM) += spkmodem.c
 romstage-$(CONFIG_SPKMODEM) += spkmodem.c
 
+bootblock-y += i8254.c
+verstage-y += i8254.c
+romstage-y += i8254.c
+ramstage-y += i8254.c
+postcar-y += i8254.c
+smm-y += i8254.c
+
 endif
diff --git a/src/drivers/pc80/pc/i8254.c b/src/drivers/pc80/pc/i8254.c
index 53d880cc79..8e15d4ded1 100644
--- a/src/drivers/pc80/pc/i8254.c
+++ b/src/drivers/pc80/pc/i8254.c
@@ -12,6 +12,8 @@
  */
 
 #include <arch/io.h>
+#include <commonlib/helpers.h>
+#include <cpu/x86/tsc.h>
 #include <pc80/i8254.h>
 
 /* Initialize i8254 timers */
@@ -46,3 +48,77 @@ void udelay(int usecs)
 		;
 }
 #endif
+
+#define CLOCK_TICK_RATE	1193180U /* Underlying HZ */
+
+/* ------ Calibrate the TSC -------
+ * Too much 64-bit arithmetic here to do this cleanly in C, and for
+ * accuracy's sake we want to keep the overhead on the CTC speaker (channel 2)
+ * output busy loop as low as possible. We avoid reading the CTC registers
+ * directly because of the awkward 8-bit access mechanism of the 82C54
+ * device.
+ */
+
+#define CALIBRATE_INTERVAL ((2*CLOCK_TICK_RATE)/1000) /* 2ms */
+#define CALIBRATE_DIVISOR  (2*1000) /* 2ms / 2000 == 1usec */
+
+unsigned long calibrate_tsc_with_pit(void)
+{
+	/* Set the Gate high, disable speaker */
+	outb((inb(0x61) & ~0x02) | 0x01, 0x61);
+
+	/*
+	 * Now let's take care of CTC channel 2
+	 *
+	 * Set the Gate high, program CTC channel 2 for mode 0,
+	 * (interrupt on terminal count mode), binary count,
+	 * load 5 * LATCH count, (LSB and MSB) to begin countdown.
+	 */
+	outb(0xb0, 0x43);	/* binary, mode 0, LSB/MSB, Ch 2 */
+
+	outb(CALIBRATE_INTERVAL	& 0xff, 0x42);	/* LSB of count */
+	outb(CALIBRATE_INTERVAL	>> 8, 0x42);	/* MSB of count */
+
+	{
+		tsc_t start;
+		tsc_t end;
+		unsigned long count;
+
+		start = rdtsc();
+		count = 0;
+		do {
+			count++;
+		} while ((inb(0x61) & 0x20) == 0);
+		end = rdtsc();
+
+		/* Error: ECTCNEVERSET */
+		if (count <= 1)
+			goto bad_ctc;
+
+		/* 64-bit subtract - gcc just messes up with long longs */
+		__asm__("subl %2,%0\n\t"
+			"sbbl %3,%1"
+			: "=a" (end.lo), "=d" (end.hi)
+			: "g" (start.lo), "g" (start.hi),
+			 "0" (end.lo), "1" (end.hi));
+
+		/* Error: ECPUTOOFAST */
+		if (end.hi)
+			goto bad_ctc;
+
+
+		/* Error: ECPUTOOSLOW */
+		if (end.lo <= CALIBRATE_DIVISOR)
+			goto bad_ctc;
+
+		return DIV_ROUND_UP(end.lo, CALIBRATE_DIVISOR);
+	}
+
+	/*
+	 * The CTC wasn't reliable: we got a hit on the very first read,
+	 * or the CPU was so fast/slow that the quotient wouldn't fit in
+	 * 32 bits..
+	 */
+bad_ctc:
+	return 0;
+}
-- 
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