[U-Boot] [PATCHv2] OMAP3: Avoid re-write to PRM_CLKSRC_CTRL

[Tom <Tom.Rix@windriver.com>]

Premi, Sanjeev wrote:
>> -----Original Message-----
>> From: Premi, Sanjeev 
>> Sent: Friday, January 29, 2010 6:44 PM
>> To: u-boot at lists.denx.de
>> Cc: Premi, Sanjeev; Hiremath, Vaibhav
>> Subject: [PATCHv2] OMAP3: Avoid re-write to PRM_CLKSRC_CTRL
>>
>> The function get_osc_clk_speed() is used to determine the master
>> clock. If SYS_CLK is being divided by 2, the divider is changed
>> to 1 - without following any sequence.
>>
>> Before reaching this function, some of the clocks have already
>> been set (by x-loader or equiv) OR power-on defaults are in use.
>> This change is too sudden, leading to instability beyond certain
>> tolerance zone.
>>
>> The problem was observed with DM3730 (silimar to OMAP3630), on
>> the OMAP3EVM.
>>
>> This patch removes the step to change clock divider. Instead,
>> uses a multiplication factor (if needed). Mathematically, the
>> formula is unchanged.
>>
>> Tested on OMAP3EVM with OMAP3530 and DM3730.
>>
>> Signed-off-by: Sanjeev Premi <premi@ti.com>
>> Signed-off-by: Hiremath Vaibhav <hvaibhav@ti.com>
>> ---
>>  cpu/arm_cortexa8/omap3/clock.c |   15 +++++++++++----
>>  1 files changed, 11 insertions(+), 4 deletions(-)
>>
>> diff --git a/cpu/arm_cortexa8/omap3/clock.c 
>> b/cpu/arm_cortexa8/omap3/clock.c
>> index 174c453..e8189b4 100644
>> --- a/cpu/arm_cortexa8/omap3/clock.c
>> +++ b/cpu/arm_cortexa8/omap3/clock.c
>> @@ -40,7 +40,7 @@
>>   
>> **************************************************************
>> ***************/
>>  u32 get_osc_clk_speed(void)
>>  {
>> -	u32 start, cstart, cend, cdiff, val;
>> +	u32 start, cstart, cend, cdiff, cdiv, val;
>>  	struct prcm *prcm_base = (struct prcm *)PRCM_BASE;
>>  	struct prm *prm_base = (struct prm *)PRM_BASE;
>>  	struct gptimer *gpt1_base = (struct gptimer *)OMAP34XX_GPT1;
>> @@ -48,9 +48,13 @@ u32 get_osc_clk_speed(void)
>>  
>>  	val = readl(&prm_base->clksrc_ctrl);
>>  
>> -	/* If SYS_CLK is being divided by 2, remove for now */
>> -	val = (val & (~SYSCLKDIV_2)) | SYSCLKDIV_1;
>> -	writel(val, &prm_base->clksrc_ctrl);
>> +	if (val & SYSCLKDIV_2)
>> +		cdiv = 2;
>> +	else if (val & SYSCLKDIV_1)
>> +		cdiv = 1;
>> +	else
>> +		/*Should never reach here! (Assume divider as 1) */
>> +		cdiv = 1;
>>  
>>  	/* enable timer2 */
>>  	val = readl(&prcm_base->clksel_wkup) | CLKSEL_GPT1;
>> @@ -83,6 +87,9 @@ u32 get_osc_clk_speed(void)
>>  	cend = readl(&gpt1_base->tcrr);		/* get end 
>> sys_clk count */
>>  	cdiff = cend - cstart;			/* get elapsed ticks */
>>  
>> +	if (cdiv == 2)
>> +		cdiff *= 2;
>> +
>>  	/* based on number of ticks assign speed */
>>  	if (cdiff > 19000)
>>  		return S38_4M;
>> -- 
>> 1.6.2.2
>>
>>
> 
> Tom, Sandeep,
> 
> Just wanted to check the status of this patch.
> 
I need to review and test it..
This will happen over the weekend.

> Best regards,
> Sanjeev
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