enable the spread spectrum

[#1]

Hi,

         Here is the document about how to enable spread spectrum in imx6.

best regards

Jack

[jack_mao]

correct some word in the documents  change "before switch to OSC_CLK, it need power down the PLL2 " to "after switch to OSC_CLK, power down the PLL2 "

[Wlodek_D_]

Dear Junping Mao,

Thank you for your post, however please consider moving it to the right community place for better visibility.

For details please see general advice https://community.freescale.com/docs/DOC-99909

Thank you for using Freescale Community.

Regards,

Wlodek_D.

[timjaacks]

Hello Jumping Mao,

thanks for your document. You say "To enable the spread spectrum, the PLL2 need reconfigure, it need be shut down and enable/setting the spread spectrum  and power on back again". Where did you get this information from? I cannot find anything like this in the i.MX6 reference manual (IMX6DQ-RefMan-RM-r2-2014-06.pdf). In my understanding, it should be possible to enable spread spectrum on-the-fly. Am I correct? Is there anyone from Freescale who can confirm this?

Best Regards,

Tim

[jack_mao]

Hi Tim,

     The info is from SOC owner, it's the required sequence, can't set on the fly

[timjaacks]

Thanks, Jumping Mao. Freescale, can you please confirm this? Is there an official document where this sequence is described? We enable the spread spectrum on-the-fly here on our i.MX6 based systems, and it seems to work (change is immediately visible in measured frequency spectrum). Do we have to expect any side effects?

[uwebeyer]

Hi Jumping Mao,

many thanks for providing this artice and the boot loader changes to set up the PLL2 in spread spectrum mode.

I following this guidance but run into boot problems when running it on my i.MX6D system. Finally I figured out that the plugin was rejected and could fix it.

At this discussion Enable the PLL2 spread spectrum feature on a i.MX6D

I uploaded my flash_header.S in case other users might have the same trouble.

I also changed the sequence where PLL2 us powered down/up. Using the PLL2 register description of the MX6D the bit for BYPASS mode was set (0x00010000) instead of Power Down (0x00001000).

Cheers,

Uwe

[rajendrabaniyav]

Hello Tim,

Can you please provide instruction to enable spread spectrum on-the-fly? I am writing below two registers from kernel board init file but I don't see any changes.

0x20c 8060 = 0x1770

0x20c 8040 = 0x05dc8006

Is there anything else needs to be done?

regards

Rajendra

[rajendrabaniyav]

Hello Uwe,

I see all absolute address in IVT section (e.g. app_code_jump_v:        .long 0x00907458), but in my old code we have label based address assignment (app_code_jump_v:  .word _start).

Does it work for solo too? I am using uboot 2009 and with the given changes my board is not booting up.

regards

Rajendra

[timjaacks]

See the following snippet from my code:

/* Disable spread spectrum mode */

__raw_writel((__raw_readl(anatop_base + PLL2_528_OFFSET + PLL_528_SS_OFFSET) & ~ANADIG_PLL_528_SYS_SS_ENABLE), anatop_base + PLL2_528_OFFSET +  PLL_528_SS_OFFSET);

/* Write new values */

__raw_writel(sys_ss, anatop_base + PLL2_528_OFFSET + PLL_528_SS_OFFSET);

__raw_writel(denom, anatop_base + PLL2_528_OFFSET + PLL_528_DENOM_DIV_OFFSET);

/* Enable spread spectrum mode */

if (enabled)

        __raw_writel((__raw_readl(anatop_base + PLL2_528_OFFSET + PLL_528_SS_OFFSET) | ANADIG_PLL_528_SYS_SS_ENABLE), anatop_base + PLL2_528_OFFSET +  PLL_528_SS_OFFSET);

Tried with denom=0x190, sys_ss=0xFA0001 and enabled=1 (which gives a spread spectrum range of 15 MHz, modulation frequency of 48 kHz and frequency step of 60 kHz).

I use this code at runtime after the kernel has booted by writing to a procfs entry.

[rajendrabaniyav]

Thanks Tim, it works for us!

[PKZ]

Hi Tim Jaacks,

It seems you modified other file than flash_header.S. Which BSP version was that and which file did you modify?

I am using Linux BSP L3.10.17_1.0.2 and I don't see flash_header.S.

Regards

PK

[PKZ]

Dear Junping Mao,

Do you have details on which files to be modified in Linux BSP L3.10.17_1.0.2?

Regards,

PK

[john9]

Hi Jumping Mao,

I was using a 2015 version of the uboot for imx6 and the plugin support did not work. I would like to know which repo should I use in order to test the patches for the spread spectrum?.

Regards,

John

[jack_mao]

The code loaded is missing a line, please add the line in your code.

before_calling_rom___pu_irom_hwcnfg_setup:
    ldr r3, =ROM_VERSION_OFFSET
    ldr r4, [r3]
    ldr r3, =ROM_VERSION_TO12
    cmp r4, r3
    ldrge r3, =ROM_API_TABLE_BASE_ADDR_MX6DL_TO12
    ldrlt r3, =ROM_API_TABLE_BASE_ADDR_LEGACY
    ldr r4, [r3, #ROM_API_HWCNFG_SETUP_OFFSET]              //missing line
    blx r4 /* This address might change in future ROM versions */
after_calling_rom___pu_irom_hwcnfg_setup:

[petertseng]

Dear Jack Mao,

How do I implement this feature in UBOOT 2016 ?

regards

Peter Tseng

[csoapy]

jackmao‌

I'm confused about attached "spread spectrum.docx"

1. Why CCM_ANALOG_PLL_SYS_NUM is not used in your scripts & document? and how to used it?
2. ssc_top should be ssc_stop in page 4?
3. In page 3:

              the modulation frequency is controlled about 48k.

       In Page 4:

              the formula "Modulation frequency = Fref * (ssc_step) / (2 * ssc_top)" is not matched with demo code: 24000 ≠ 48000 

       

[csoapy]

1. Enable U-Boot Plugin by CONFIG_USE_PLUGIN (v16.03) or CONFIG_USE_IMXIMG_PLUGIN (v18.03)
2. Translate your DCD data into assembly language script in macro imx6_XXX_ddr_setting in plugin.S
3. Copy macro spreadspectrum definition, in following url, to plugin.S, Spread Spectrum in i.mx6 | Reference Designer 
4. Modify #60 & #40 registers in macro spreadspectrum
5. Call macro spreadspectrum at the first line in your imx6_XXX_ddr_setting in plugin.S
6. Build & Flash & Test

[jack_mao]

please refer to the new doc  attached on the top

[csoapy]

Please fix the typo "ssc_top" --> "ssc_stop" in spread spectrum.docx