[U-Boot] omap3: Is lowlevel_init() ever called?

[Premi, Sanjeev]

> -----Original Message-----
> From: u-boot-bounces at lists.denx.de 
> [mailto:u-boot-bounces at lists.denx.de] On Behalf Of Premi, Sanjeev
> Sent: Monday, November 30, 2009 11:41 PM
> To: u-boot at lists.denx.de
> Subject: [U-Boot] omap3: Is lowlevel_init() ever called?
> 
> Hi all,
> 
> I have been trying to debug 'strange' clock settings in the 
> omap3evm; that would
> surface quite infrequently. However, today I was able to get 
> them regularly.
> 
> Symptom: the MPU clock is set at 381MHz instead of expected 500MHz.
> 
> Tracing back from prcm_init() to s_init() to lowlevel_init() 
> and cpu_init_crit()
> I feel that lowlevel_init() is being skipped at together.
> 
> In the patch below, I am updating a flag on very beginning of 
> s_init() and later
> printing in print_cpuinfo(). To exclude any other (possible) 
> foul-play by stray
> pointer, I initialized this flag to 11 and expect it to be 55 
> after s_init() is
> called. But the value remains 11 - when printed in print_cpuinfo().
> 
> Also, CONFIG_SKIP_LOWLEVEL_INIT is not defined in omap3_evm_config.
> 
> Though I am at 2009.08, I did not see any differences in 
> start.S that could have
> an apparent effect.
> 
> Am I missing something completely?

Ok. I was misled by a portion of code+comment that states:
[quote]Copy DPLL code into SRAM[/quote] but goes on to copy
384*32 bytes.

I don't understand the startup bit of this code well, so
have few doubts:

1) What does the magic number #384 correspond to?
   384 * 32 = 12288 (0x3000)

2) Going by the comment, we possibly need to copy only the
   function _go_to_speed and constants used in it.

   Currently, we seem to be copying and relocating 0x3000 bytes.
   Isn't it an overhead?

3) While we are executing from SRAM, the variables are (possibly)
   being updated in relocated offsets, not 'in place' expected
   by the code.

   This goes with the behavior I described earlier.

I have made changes to u-boot to optimize the re-execution of the
code detecting silicon version for OMAP3. I have been able to make
it work by calling it twice - once when execution happens from
SRAM and then again in arch_cpu_init().

However, I feel we can optimize this - not just detecting si revision;
but amount of code copied and relocated.

Answers to 3 questions above will help me a lot.

Best regards,
Sanjeev

> 
> Best regards,
> Sanjeev
> 
> 
> 
> diff --git a/cpu/arm_cortexa8/omap3/board.c 
> b/cpu/arm_cortexa8/omap3/board.c
> index 939ed6c..5dfd8f3 100644
> --- a/cpu/arm_cortexa8/omap3/board.c
> +++ b/cpu/arm_cortexa8/omap3/board.c
> @@ -42,6 +42,8 @@ extern omap3_sysinfo sysinfo;
>  
>  extern u32 is_mem_sdr(void);
>  
> +int s_init_flag=11;
> +
>  
> /*************************************************************
> *****************
>   * Routine: delay
>   * Description: spinning delay to use before udelay works
> @@ -193,6 +195,8 @@ void s_init(void)
>  {
>  	int in_sdram = is_running_in_sdram();
>  
> +	s_init_flag=55;
> +
>  	watchdog_init();
>  
>  	try_unlock_memory();
> diff --git a/cpu/arm_cortexa8/omap3/lowlevel_init.S 
> b/cpu/arm_cortexa8/omap3/lowlevel_init.S
> index 73063ec..d83dd53 100644
> --- a/cpu/arm_cortexa8/omap3/lowlevel_init.S
> +++ b/cpu/arm_cortexa8/omap3/lowlevel_init.S
> @@ -174,7 +174,11 @@ lowlevel_init:
>  	ldr	sp, SRAM_STACK
>  	str	ip, [sp]	/* stash old link register */
>  	mov	ip, lr		/* save link reg across call */
> +	nop
> +	nop
>  	bl	s_init		/* go setup pll, mux, memory */
> +	nop
> +	nop
>  	ldr	ip, [sp]	/* restore save ip */
>  	mov	lr, ip		/* restore link reg */
>  
> diff --git a/cpu/arm_cortexa8/omap3/sys_info.c 
> b/cpu/arm_cortexa8/omap3/sys_info.c
> index 2fb6c10..2f29032 100644
> --- a/cpu/arm_cortexa8/omap3/sys_info.c
> +++ b/cpu/arm_cortexa8/omap3/sys_info.c
> @@ -31,6 +31,8 @@
>  #include <asm/arch/sys_proto.h>
>  #include <i2c.h>
>  
> +extern int s_init_flag;
> +
>  extern omap3_sysinfo sysinfo;
>  static struct sdrc *sdrc_base = (struct sdrc *)OMAP34XX_SDRC_BASE;
>  static struct ctrl *ctrl_base = (struct ctrl *)OMAP34XX_CTRL_BASE;
> @@ -414,6 +416,8 @@ int print_cpuinfo (void)
>  			cpu_s, sec_s, rev_s[get_cpu_rev()],
>  			(cpu_family == CPU_AM35XX) ? "" : " CPU-OPP2");
>  
> +	printf ("s_init_flag = %d\n", s_init_flag);
> +	
>  	return 0;
>  }
>  #endif	/* CONFIG_DISPLAY_CPUINFO */
> 
> ======================================
> 
> U-Boot 2009.08-00047-gd5ef5fe-dirty (Nov 30 2009 - 23:15:59)
> 
> OMAP3430/3530-GP ES3.1, CPU-OPP2 L3-165MHz
> s_init_flag = 11
> OMAP3 EVM board + LPDDR/NAND
> DRAM:  128 MB
> NAND:  256 MiB
> In:    serial
> Out:   serial
> Err:   serial
> Die ID #609200040000000004032d460c01201a
> Net:   smc911x-0
> Hit any key to stop autoboot:  0
> OMAP3_EVM #
> OMAP3_EVM #
> OMAP3_EVM #
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