Patchwork [U-Boot] Update s3c24x0 timer implementation

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Submitter Mark Norman
Date Oct. 23, 2011, 11:52 a.m.
Message ID <CAJtrzLOvjswmuww+xNLXxeSH4QxOBZww3JrZGKCgLq5w6B=y3w@mail.gmail.com>
Download mbox | patch
Permalink /patch/121225/
State Changes Requested
Headers show

Comments

Mark Norman - Oct. 23, 2011, 11:52 a.m.
I have been doing some work to get U-Boot running on a samsung S3C2440
based SBC (QQ2440).  I experienced several issues getting the board
running including "raise: Signal # 8 caught" errors being printed to
the console.  After a bit of debugging with a JTAG debugger I found
the problems were due to arch/arm/cpu/arm920t/s3c24x0/timer.c using
several global variables prior to relocation to RAM.  I noticed that
the global variable .bss section is shared with the .rel.text section.
 Since the .rel.text section is required by the relocation code, I
assume that .bss global variables cannot be used until after
relocation?

After studying several other timer.c files I developed the following
patch which uses the global data struct to store the global variables.
 I also restructured some of the code based on structure of the other
timer.c files.  I have confirmed it works correctly on the SBC I have.

Regards

Mark Norman



The s3c24x0 timer has been updated to use the global_data struct.
Restructured code based on other timer.c files.
Updated comments and several parameters.

Signed-off-by: Mark Norman <mpnorman@gmail.com>
---
 arch/arm/cpu/arm920t/s3c24x0/timer.c |  158 +++++++++++++--------------------
 arch/arm/include/asm/global_data.h   |   12 +--
 2 files changed, 66 insertions(+), 104 deletions(-)
Wolfgang Denk - Oct. 23, 2011, 5:22 p.m.
Dear Mark Norman,

In message <CAJtrzLOvjswmuww+xNLXxeSH4QxOBZww3JrZGKCgLq5w6B=y3w@mail.gmail.com> you wrote:
>
>  Since the .rel.text section is required by the relocation code, I
> assume that .bss global variables cannot be used until after
> relocation?

Why do you have to make such assumptions?  That's documented
behaviour.  Didn't you RTFM?

> After studying several other timer.c files I developed the following
> patch which uses the global data struct to store the global variables.
>  I also restructured some of the code based on structure of the other
> timer.c files.  I have confirmed it works correctly on the SBC I have.

Then please submit a proper patch - these introductury comments don;lt
belong intot he commit message and shouldbemoved into the comment
section (below the "---" line).


...
> +	/* Use PWM Timer 4 because it has no output.
> +	 * Prescaler is hard fixed at 250, divider at 2.
> +	 * This generates a Timer clock frequency of 100kHz (@PCLK=50MHz) and
> +	 * therefore 10us timer ticks.
> +	 */

Incorrect multiline comment format; please fix globally.

> +	/* Prescaler for Timer 4 is 250 */
> +	const ulong prescaler = 250;
> +	writel((prescaler-1) << 8, &timers->tcfg0);

Please move declarations up.  Don't split declarations by comment
lines.  Add a blank line between declarations and code.

...
> --- a/arch/arm/include/asm/global_data.h
> +++ b/arch/arm/include/asm/global_data.h
> @@ -38,9 +38,6 @@ typedef	struct	global_data {
>  	unsigned long	flags;
>  	unsigned long	baudrate;
>  	unsigned long	have_console;	/* serial_init() was called */
> -#ifdef CONFIG_PRE_CONSOLE_BUFFER
> -	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
> -#endif

Make sure not to add such unrelated, incorrect changes!

> -#if defined(CONFIG_POST) || defined(CONFIG_LOGBUFFER)
> -	unsigned long	post_log_word; /* Record POST activities */
> -	unsigned long	post_log_res; /* success of POST test */
> -	unsigned long	post_init_f_time; /* When post_init_f started */
> -#endif

Ditto.

Best regards,

Wolfgang Denk

Patch

diff --git a/arch/arm/cpu/arm920t/s3c24x0/timer.c
b/arch/arm/cpu/arm920t/s3c24x0/timer.c
index 9571870..1552345 100644
--- a/arch/arm/cpu/arm920t/s3c24x0/timer.c
+++ b/arch/arm/cpu/arm920t/s3c24x0/timer.c
@@ -35,146 +35,112 @@ 
 #include <asm/io.h>
 #include <asm/arch/s3c24x0_cpu.h>

-int timer_load_val = 0;
-static ulong timer_clk;
+DECLARE_GLOBAL_DATA_PTR;

-/* macro to read the 16 bit timer */
-static inline ulong READ_TIMER(void)
+/* Read the 16 bit timer */
+static inline ulong read_timer(void)
 {
 	struct s3c24x0_timers *timers = s3c24x0_get_base_timers();
-
 	return readl(&timers->tcnto4) & 0xffff;
 }

-static ulong timestamp;
-static ulong lastdec;
-
 int timer_init(void)
 {
 	struct s3c24x0_timers *timers = s3c24x0_get_base_timers();
 	ulong tmr;

-	/* use PWM Timer 4 because it has no output */
-	/* prescaler for Timer 4 is 16 */
-	writel(0x0f00, &timers->tcfg0);
-	if (timer_load_val == 0) {
-		/*
-		 * for 10 ms clock period @ PCLK with 4 bit divider = 1/2
-		 * (default) and prescaler = 16. Should be 10390
-		 * @33.25MHz and 15625 @ 50 MHz
-		 */
-		timer_load_val = get_PCLK() / (2 * 16 * 100);
-		timer_clk = get_PCLK() / (2 * 16);
-	}
-	/* load value for 10 ms timeout */
-	lastdec = timer_load_val;
-	writel(timer_load_val, &timers->tcntb4);
-	/* auto load, manual update of timer 4 */
+	/* Use PWM Timer 4 because it has no output.
+	 * Prescaler is hard fixed at 250, divider at 2.
+	 * This generates a Timer clock frequency of 100kHz (@PCLK=50MHz) and
+	 * therefore 10us timer ticks.
+	 */
+
+	/* Prescaler for Timer 4 is 250 */
+	const ulong prescaler = 250;
+	writel((prescaler-1) << 8, &timers->tcfg0);
+
+	/* Calculate timer freq, approx 100kHz @ PCLK=50MHz. */
+	gd->timer_rate_hz = get_PCLK() / (2 * prescaler);
+
+	/* Set timer for 0.5s timeout (50000 ticks @ 10us ticks). */
+	gd->timer_reset_value = 50000;
+	writel(gd->timer_reset_value, &timers->tcntb4);
+	gd->lastdec = gd->timer_reset_value;
+
+	/* Load the initial timer 4 count value using the manual update bit. */
 	tmr = (readl(&timers->tcon) & ~0x0700000) | 0x0600000;
 	writel(tmr, &timers->tcon);
-	/* auto load, start timer 4 */
+
+	/* Configure timer 4 for auto reload and start it. */
 	tmr = (tmr & ~0x0700000) | 0x0500000;
 	writel(tmr, &timers->tcon);
-	timestamp = 0;
+
+	gd->timestamp = 0;

 	return (0);
 }

 /*
- * timer without interrupts
+ * Get the number of ticks (in CONFIG_SYS_HZ resolution)
  */
-ulong get_timer(ulong base)
+unsigned long long get_ticks(void)
 {
-	return get_timer_masked() - base;
+	return get_timer(0);
 }

-void __udelay (unsigned long usec)
+unsigned long get_timer_raw(void)
 {
-	ulong tmo;
-	ulong start = get_ticks();
+	ulong now = read_timer();

-	tmo = usec / 1000;
-	tmo *= (timer_load_val * 100);
-	tmo /= 1000;
+	if (gd->lastdec >= now) {
+		/* normal mode */
+		gd->timestamp += gd->lastdec - now;
+	} else {
+		/* we have an overflow ... */
+		gd->timestamp += gd->lastdec + gd->timer_reset_value - now;
+	}
+	gd->lastdec = now;

-	while ((ulong) (get_ticks() - start) < tmo)
-		/*NOP*/;
+	return gd->timestamp;
 }

-ulong get_timer_masked(void)
+/*
+ * 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 tmr = get_ticks();
-
-	return tmr / (timer_clk / CONFIG_SYS_HZ);
+	return CONFIG_SYS_HZ;
 }

-void udelay_masked(unsigned long usec)
+ulong get_timer_masked(void)
 {
-	ulong tmo;
-	ulong endtime;
-	signed long diff;
-
-	if (usec >= 1000) {
-		tmo = usec / 1000;
-		tmo *= (timer_load_val * 100);
-		tmo /= 1000;
-	} else {
-		tmo = usec * (timer_load_val * 100);
-		tmo /= (1000 * 1000);
-	}
+	unsigned long tmr = get_timer_raw();

-	endtime = get_ticks() + tmo;
+	return (tmr * CONFIG_SYS_HZ) / gd->timer_rate_hz;
+}

-	do {
-		ulong now = get_ticks();
-		diff = endtime - now;
-	} while (diff >= 0);
+ulong get_timer(ulong base)
+{
+	return get_timer_masked() - base;
 }

-/*
- * 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)
+void __udelay(unsigned long usec)
 {
-	ulong now = READ_TIMER();
+	unsigned long tmp;
+	unsigned long tmo;

-	if (lastdec >= now) {
-		/* normal mode */
-		timestamp += lastdec - now;
-	} else {
-		/* we have an overflow ... */
-		timestamp += lastdec + timer_load_val - now;
-	}
-	lastdec = now;
+	/* convert usec to ticks. */
+	tmo = ((gd->timer_rate_hz / 1000) * usec) / 1000;

-	return timestamp;
-}
+	tmp = get_timer_raw() + tmo;	/* get current timestamp */

-/*
- * 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;
-
-#if defined(CONFIG_SMDK2400)
-	tbclk = timer_load_val * 100;
-#elif defined(CONFIG_SBC2410X) || \
-      defined(CONFIG_SMDK2410) || \
-	defined(CONFIG_S3C2440) || \
-      defined(CONFIG_VCMA9)
-	tbclk = CONFIG_SYS_HZ;
-#else
-#	error "tbclk not configured"
-#endif
-
-	return tbclk;
+	while (get_timer_raw() < tmp)   /* loop till event */
+		/*NOP*/;
 }

 /*
- * reset the cpu by setting up the watchdog timer and let him time out
+ * Reset the cpu by setting up the watchdog timer and let him time out
  */
 void reset_cpu(ulong ignored)
 {
diff --git a/arch/arm/include/asm/global_data.h
b/arch/arm/include/asm/global_data.h
index fac98d5..a20a9f7 100644
--- a/arch/arm/include/asm/global_data.h
+++ b/arch/arm/include/asm/global_data.h
@@ -38,9 +38,6 @@  typedef	struct	global_data {
 	unsigned long	flags;
 	unsigned long	baudrate;
 	unsigned long	have_console;	/* serial_init() was called */
-#ifdef CONFIG_PRE_CONSOLE_BUFFER
-	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
-#endif
 	unsigned long	env_addr;	/* Address  of Environment struct */
 	unsigned long	env_valid;	/* Checksum of Environment valid? */
 	unsigned long	fb_base;	/* base address of frame buffer */
@@ -67,6 +64,10 @@  typedef	struct	global_data {
 #ifdef CONFIG_IXP425
 	unsigned long	timestamp;
 #endif
+#ifdef CONFIG_S3C24X0
+	unsigned long	lastdec;
+	unsigned long	timestamp;
+#endif
 	unsigned long	relocaddr;	/* Start address of U-Boot in RAM */
 	phys_size_t	ram_size;	/* RAM size */
 	unsigned long	mon_len;	/* monitor len */
@@ -78,11 +79,6 @@  typedef	struct	global_data {
 #endif
 	void		**jt;		/* jump table */
 	char		env_buf[32];	/* buffer for getenv() before reloc. */
-#if defined(CONFIG_POST) || defined(CONFIG_LOGBUFFER)
-	unsigned long	post_log_word; /* Record POST activities */
-	unsigned long	post_log_res; /* success of POST test */
-	unsigned long	post_init_f_time; /* When post_init_f started */
-#endif
 } gd_t;

 /*