[U-Boot] [PATCH v3] arm nomadik: use 1000 as HZ value and rewrite timer code
Alessandro Rubini
rubini-list at gnudd.com
Mon Jun 29 12:52:37 CEST 2009
From: Alessandro Rubini <rubini at 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 at unipv.it>
Acked-by: Andrea Gallo <andrea.gallo at 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 at sysgo.de>
- *
- * (C) Copyright 2002
- * Sysgo Real-Time Solutions, GmbH <www.elinos.com>
- * Alex Zuepke <azu at sysgo.de>
- *
- * (C) Copyright 2002-2004
- * Gary Jennejohn, DENX Software Engineering, <garyj at denx.de>
- *
- * (C) Copyright 2004
- * Philippe Robin, ARM Ltd. <philippe.robin at 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
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