[U-Boot] [PATCH v3] arm nomadik: use 1000 as HZ value and rewrite timer code

[Alessandro Rubini <rubini-list@gnudd.com>]

From: Alessandro Rubini <rubini@unipv.it>

This sets CONFIG_SYS_HZ to 1000 as required, and completely rewrites
timer code, which is now both correct and much smaller.  Unused
functions like udelay_masked() have been removed as no driver uses
them, even the ones that are not currently active for this board.
mtu.h is copied literally from the kernel sources.

Signed-off-by: Alessandro Rubini <rubini@unipv.it>
Acked-by: Andrea Gallo <andrea.gallo@stericsson.com>
---

I've used mtu.h from kernel sources and done the other changes as requested
(the extra variable just to return it was a mishap from an earlier printf
I needed to find a misconfig).

> for the record what is its precision now?

it counts at 2.4MHz, so the 1000HZ tick has no approximation and udelay
is correct with sub-microsecond error. I'll use in soft_i2c, needed to
turn on the LCD light.

 cpu/arm926ejs/nomadik/mtu.h   |   45 +++++++++++
 cpu/arm926ejs/nomadik/timer.c |  166 +++++++----------------------------------
 include/configs/nhk8815.h     |    2 +-
 3 files changed, 73 insertions(+), 140 deletions(-)
 create mode 100644 cpu/arm926ejs/nomadik/mtu.h

diff --git a/cpu/arm926ejs/nomadik/mtu.h b/cpu/arm926ejs/nomadik/mtu.h
new file mode 100644
index 0000000..21b4a7a
--- /dev/null
+++ b/cpu/arm926ejs/nomadik/mtu.h
@@ -0,0 +1,45 @@
+
+#ifndef __ASM_ARCH_MTU_H
+#define __ASM_ARCH_MTU_H
+
+/*
+ * The MTU device hosts four different counters, with 4 set of
+ * registers. These are register names.
+ */
+
+#define MTU_IMSC	0x00	/* Interrupt mask set/clear */
+#define MTU_RIS		0x04	/* Raw interrupt status */
+#define MTU_MIS		0x08	/* Masked interrupt status */
+#define MTU_ICR		0x0C	/* Interrupt clear register */
+
+/* per-timer registers take 0..3 as argument */
+#define MTU_LR(x)	(0x10 + 0x10 * (x) + 0x00)	/* Load value */
+#define MTU_VAL(x)	(0x10 + 0x10 * (x) + 0x04)	/* Current value */
+#define MTU_CR(x)	(0x10 + 0x10 * (x) + 0x08)	/* Control reg */
+#define MTU_BGLR(x)	(0x10 + 0x10 * (x) + 0x0c)	/* At next overflow */
+
+/* bits for the control register */
+#define MTU_CRn_ENA		0x80
+#define MTU_CRn_PERIODIC	0x40	/* if 0 = free-running */
+#define MTU_CRn_PRESCALE_MASK	0x0c
+#define MTU_CRn_PRESCALE_1		0x00
+#define MTU_CRn_PRESCALE_16		0x04
+#define MTU_CRn_PRESCALE_256		0x08
+#define MTU_CRn_32BITS		0x02
+#define MTU_CRn_ONESHOT		0x01	/* if 0 = wraps reloading from BGLR*/
+
+/* Other registers are usual amba/primecell registers, currently not used */
+#define MTU_ITCR	0xff0
+#define MTU_ITOP	0xff4
+
+#define MTU_PERIPH_ID0	0xfe0
+#define MTU_PERIPH_ID1	0xfe4
+#define MTU_PERIPH_ID2	0xfe8
+#define MTU_PERIPH_ID3	0xfeC
+
+#define MTU_PCELL0	0xff0
+#define MTU_PCELL1	0xff4
+#define MTU_PCELL2	0xff8
+#define MTU_PCELL3	0xffC
+
+#endif /* __ASM_ARCH_MTU_H */
diff --git a/cpu/arm926ejs/nomadik/timer.c b/cpu/arm926ejs/nomadik/timer.c
index 2870d24..d0946ec 100644
--- a/cpu/arm926ejs/nomadik/timer.c
+++ b/cpu/arm926ejs/nomadik/timer.c
@@ -1,20 +1,5 @@
 /*
- * (C) Copyright 2003
- * Texas Instruments <www.ti.com>
- *
- * (C) Copyright 2002
- * Sysgo Real-Time Solutions, GmbH <www.elinos.com>
- * Marius Groeger <mgroeger@sysgo.de>
- *
- * (C) Copyright 2002
- * Sysgo Real-Time Solutions, GmbH <www.elinos.com>
- * Alex Zuepke <azu@sysgo.de>
- *
- * (C) Copyright 2002-2004
- * Gary Jennejohn, DENX Software Engineering, <garyj@denx.de>
- *
- * (C) Copyright 2004
- * Philippe Robin, ARM Ltd. <philippe.robin@arm.com>
+ * (C) Copyright 2009 Alessandro Rubini
  *
  * See file CREDITS for list of people who contributed to this
  * project.
@@ -37,146 +22,49 @@
 
 #include <common.h>
 #include <asm/io.h>
+#include "mtu.h"
 
-#define TIMER_LOAD_VAL 0xffffffff
-
-/* macro to read the 32 bit timer */
-#define READ_TIMER readl(CONFIG_SYS_TIMERBASE + 20)
+/*
+ * The timer is a decrementer, we'll left it free running at 2.4MHz.
+ * We have 2.4 ticks per microsecond and an overflow in almost 30min
+ */
+#define TIMER_CLOCK		(24 * 100 * 1000)
+#define COUNT_TO_USEC(x)	((x) * 5 / 12)	/* overflows at 6min */
+#define USEC_TO_COUNT(x)	((x) * 12 / 5)	/* overflows at 6min */
+#define TICKS_PER_HZ		(TIMER_CLOCK / CONFIG_SYS_HZ)
+#define TICKS_TO_HZ(x)		((x) / TICKS_PER_HZ)
 
-static ulong timestamp;
-static ulong lastdec;
+/* macro to read the 32 bit timer: since it decrements, we invert read value */
+#define READ_TIMER() (~readl(CONFIG_SYS_TIMERBASE + MTU_VAL(0)))
 
-/* nothing really to do with interrupts, just starts up a counter. */
+/* Configure a free-running, auto-wrap counter with no prescaler */
 int timer_init(void)
 {
-	/* Load timer with initial value */
-	writel(TIMER_LOAD_VAL, CONFIG_SYS_TIMERBASE + 16);
-
-	/*
-	 * Set timer to be enabled, free-running, no interrupts, 256 divider,
-	 * 32-bit, wrap-mode
-	 */
-	writel(0x8a, CONFIG_SYS_TIMERBASE + 24);
-
-	/* init the timestamp and lastdec value */
-	reset_timer_masked();
-
+	writel(MTU_CRn_ENA | MTU_CRn_PRESCALE_1 | MTU_CRn_32BITS,
+	       CONFIG_SYS_TIMERBASE + MTU_CR(0));
+	reset_timer();
 	return 0;
 }
 
-/*
- * timer without interrupts
- */
+/* Restart counting from 0 */
 void reset_timer(void)
 {
-	reset_timer_masked();
+	writel(0, CONFIG_SYS_TIMERBASE + MTU_LR(0)); /* Immediate effect */
 }
 
+/* Return how many HZ passed since "base" */
 ulong get_timer(ulong base)
 {
-	return get_timer_masked() - base;
+	return  TICKS_TO_HZ(READ_TIMER()) - base;
 }
 
-void set_timer(ulong t)
-{
-	timestamp = t;
-}
-
-/* delay x useconds AND perserve advance timstamp value */
+/* Delay x useconds */
 void udelay(unsigned long usec)
 {
-	ulong tmo, tmp;
-
-	if (usec >= 1000) {
-		/* if "big" number, spread normalization to seconds */
-		tmo = usec / 1000;	/* start to normalize */
-		tmo *= CONFIG_SYS_HZ;	/* find number of "ticks" */
-		tmo /= 1000;		/* finish normalize. */
-	} else {
-		/* small number, don't kill it prior to HZ multiply */
-		tmo = usec * CONFIG_SYS_HZ;
-		tmo /= (1000 * 1000);
-	}
-
-	tmp = get_timer(0);		/* get current timestamp */
-	if ((tmo + tmp + 1) < tmp)	/* will roll time stamp? */
-		reset_timer_masked();	/* reset to 0, set lastdec value */
-	else
-		tmo += tmp;
-
-	while (get_timer_masked() < tmo)
-		/* nothing */ ;
-}
-
-void reset_timer_masked(void)
-{
-	/* reset time */
-	lastdec = READ_TIMER;	/* capure current decrementer value time */
-	timestamp = 0;		/* start "advancing" time stamp from 0 */
-}
-
-ulong get_timer_masked(void)
-{
-	ulong now = READ_TIMER;		/* current tick value */
-
-	if (lastdec >= now) {		/* normal mode (non roll) */
-		/* move stamp fordward */
-		timestamp += lastdec - now;
-	} else {
-		/*
-		 * An overflow is expected.
-		 * nts = ts + ld + (TLV - now)
-		 * ts=old stamp, ld=time that passed before passing through -1
-		 * (TLV-now) amount of time after passing though -1
-		 * nts = new "advancing time stamp"...it could also roll
-		 */
-		timestamp += lastdec + TIMER_LOAD_VAL - now;
-	}
-	lastdec = now;
-
-	return timestamp;
-}
-
-/* waits specified delay value and resets timestamp */
-void udelay_masked(unsigned long usec)
-{
-	ulong tmo;
-
-	if (usec >= 1000) {
-		/* if "big" number, spread normalization to seconds */
-		tmo = usec / 1000;	/* start to normalize */
-		tmo *= CONFIG_SYS_HZ;	/* find number of "ticks" */
-		tmo /= 1000;		/* finish normalize. */
-	} else {
-		/* else small number, don't kill it prior to HZ multiply */
-		tmo = usec * CONFIG_SYS_HZ;
-		tmo /= (1000*1000);
-	}
-
-	reset_timer_masked();
-	/* set "advancing" timestamp to 0, set lastdec vaule */
-
-	while (get_timer_masked() < tmo)
-		/* nothing */ ;
-}
-
-/*
- * This function is derived from PowerPC code (read timebase as long long).
- * On ARM it just returns the timer value.
- */
-unsigned long long get_ticks(void)
-{
-	return get_timer(0);
-}
-
-/*
- * This function is derived from PowerPC code (timebase clock frequency).
- * On ARM it returns the number of timer ticks per second.
- */
-ulong get_tbclk(void)
-{
-	ulong tbclk;
+	ulong ini, end;
 
-	tbclk = CONFIG_SYS_HZ;
-	return tbclk;
+	ini = READ_TIMER();
+	end = ini + USEC_TO_COUNT(usec);
+	while ((signed)(end - READ_TIMER()) > 0)
+		;
 }
diff --git a/include/configs/nhk8815.h b/include/configs/nhk8815.h
index bf1a915..3e2e09f 100644
--- a/include/configs/nhk8815.h
+++ b/include/configs/nhk8815.h
@@ -96,7 +96,7 @@
 #define CONFIG_MISC_INIT_R	/* call misc_init_r during start up */
 
 /* timing informazion */
-#define CONFIG_SYS_HZ		(2400000 / 256)	/* Timer0: 2.4Mhz + divider */
+#define CONFIG_SYS_HZ		1000 /* Mandatory... */
 #define CONFIG_SYS_TIMERBASE	0x101E2000
 
 /* serial port (PL011) configuration */
-- 
1.5.6.5