[U-Boot] [PATCH] mx35 timer: Switch to 32-kHz source

[Stefano Babic]

On 14/08/2012 21:53, Benoît Thébaudeau wrote:
> Switch the mx35 timer driver to the 32-kHz clock source to avoid calling
> mxc_get_clock() again and again, and to be consistent with the timer drivers of
> other i.MX SoCs.
> 
> Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau at advansee.com>
> Cc: Stefano Babic <sbabic at denx.de>
> ---

Hi Benoît,

just some minor points:

>  .../arch/arm/cpu/arm1136/mx35/timer.c              |   43 ++++++++++++--------
>  .../include/configs/flea3.h                        |    1 +
>  .../include/configs/mx35pdk.h                      |    1 +
>  3 files changed, 27 insertions(+), 18 deletions(-)
> 
> diff --git u-boot-4d3c95f.orig/arch/arm/cpu/arm1136/mx35/timer.c u-boot-4d3c95f/arch/arm/cpu/arm1136/mx35/timer.c
> index 04937a1..25057af 100644
> --- u-boot-4d3c95f.orig/arch/arm/cpu/arm1136/mx35/timer.c
> +++ u-boot-4d3c95f/arch/arm/cpu/arm1136/mx35/timer.c
> @@ -27,7 +27,7 @@
>  #include <asm/io.h>
>  #include <div64.h>
>  #include <asm/arch/imx-regs.h>
> -#include <asm/arch/clock.h>
> +#include <asm/arch/crm_regs.h>
>  
>  DECLARE_GLOBAL_DATA_PTR;
>  
> @@ -37,43 +37,50 @@ DECLARE_GLOBAL_DATA_PTR;
>  /* General purpose timers bitfields */
>  #define GPTCR_SWR       (1<<15)	/* Software reset */
>  #define GPTCR_FRR       (1<<9)	/* Freerun / restart */
> -#define GPTCR_CLKSOURCE_32   (0x100<<6)	/* Clock source */
> -#define GPTCR_CLKSOURCE_IPG (0x001<<6)	/* Clock source */
> +#define GPTCR_CLKSOURCE_32   (4<<6)	/* Clock source */
>  #define GPTCR_TEN       (1)	/* Timer enable */
>  
> -#define	TIMER_FREQ_HZ	mxc_get_clock(MXC_IPG_CLK)
> -
> +/*
> + * "time" is measured in 1 / CONFIG_SYS_HZ seconds,
> + * "tick" is internal timer period
> + */
> +/* ~0.4% error - measured with stop-watch on 100s boot-delay */
>  static inline unsigned long long tick_to_time(unsigned long long tick)
>  {
>  	tick *= CONFIG_SYS_HZ;
> -	do_div(tick, TIMER_FREQ_HZ);
> +	do_div(tick, CONFIG_MX35_CLK32);
>  
>  	return tick;
>  }
>  
> -static inline unsigned long long us_to_tick(unsigned long long usec)
> +static inline unsigned long long us_to_tick(unsigned long long us)
>  {
> -	usec *= TIMER_FREQ_HZ;
> -	do_div(usec, 1000000);
> +	us = us * CONFIG_MX35_CLK32 + 999999;
> +	do_div(us, 1000000);
>  
> -	return usec;
> +	return us;
>  }
>  
> +/* nothing really to do with interrupts, just starts up a counter. */
> +/* The 32KHz 32-bit timer overruns in 134217 seconds */

Wrong multiline comment. A multiline comment must be in the form:

/*
 * blah blah blah
 * blah blah blah
 */

>  int timer_init(void)
>  {
>  	int i;
>  	struct gpt_regs *gpt = (struct gpt_regs *)GPT1_BASE_ADDR;
> +	struct ccm_regs *ccm = (struct ccm_regs *)CCM_BASE_ADDR;
>  
>  	/* setup GP Timer 1 */
>  	writel(GPTCR_SWR, &gpt->ctrl);
> -	for (i = 0; i < 100; i++)
> -		writel(0, &gpt->ctrl);	/* We have no udelay by now */
>  
> -	writel(0, &gpt->pre);
> -	/* Freerun Mode, PERCLK1 input */
> -	writel(readl(&gpt->ctrl) |
> -		GPTCR_CLKSOURCE_IPG | GPTCR_TEN,
> -		&gpt->ctrl);
> +	writel(readl(&ccm->cgr1) | 3 << MXC_CCM_CGR1_GPT_OFFSET, &ccm->cgr1);
> +
> +	for (i = 0; i < 100; i++)
> +		writel(0, &gpt->ctrl); /* We have no udelay by now */
> +	writel(0, &gpt->pre); /* prescaler = 1 */
> +	/* Freerun Mode, 32KHz input */
> +	writel(readl(&gpt->ctrl) | GPTCR_CLKSOURCE_32 | GPTCR_FRR,
> +			&gpt->ctrl);
> +	writel(readl(&gpt->ctrl) | GPTCR_TEN, &gpt->ctrl);
>  
>  	return 0;
>  }
> @@ -132,5 +139,5 @@ void __udelay(unsigned long usec)
>   */
>  ulong get_tbclk(void)
>  {
> -	return TIMER_FREQ_HZ;
> +	return CONFIG_MX35_CLK32;
>  }
> diff --git u-boot-4d3c95f.orig/include/configs/flea3.h u-boot-4d3c95f/include/configs/flea3.h
> index 46939d4..26f1b3e 100644
> --- u-boot-4d3c95f.orig/include/configs/flea3.h
> +++ u-boot-4d3c95f/include/configs/flea3.h
> @@ -32,6 +32,7 @@
>  #define CONFIG_ARM1136	/* This is an arm1136 CPU core */
>  #define CONFIG_MX35
>  #define CONFIG_MX35_HCLK_FREQ	24000000
> +#define CONFIG_MX35_CLK32	32768

I know the example in the tx25, but on all MX35 they share the same
value and I doubt we will have a different one. And if we will had, it
will be the exception that should be handled.

So set it inside timer.c and do not add it to the board configuartion files.

Best regards,
Stefano Babic


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