How to change the DSP clock in TI816x

Hi Gabi,

We can chagne the DSP frequency in u-boot (code), in kernel we have a provision to change the DSP clock rate runtime.

Details can get from http://processors.wiki.ti.com/index.php?title=TI81XX_PSP_PM_Clock_Framework_User_Guide

Regards

AnilKumar

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Hi Anil, 

Thank you very much for your answer, i have read the wiki you have sent me carefully, i have a few questions, where exactly is the file that i need to modify in order to change the DSP frequency? since i couldn't find it at the wiki, it is explained only how to do it.
Which device_id should i use for changing the DSP clock frequency?

Thanks,
Gabi 

Hi Gabi,

Generally frequency modification required for a module, so we can add it in driver or driver initialization code. In case of DSP you can add to "ti8168_evm_init()" in arch/arm/mach-omap2/board-ti8168evm.c file. Refer the same document for adding the necessary clk APIs.

Regards

AnilKumar

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Hi Anil,

Thank you very much for your answer, now i know that i have to add the code 

clk = clk_get(dev_id,clk_name);
rate = clk_get_rate(clk);
ret = clk_set_rate(clk, new_clk_rate);

in the function "ti8168_evm_init()" in the file arch/arm/mach-omap2/board-ti8168evm.c
but i still don't know what are the values for  dev_id and clk_name that i need to put in order to change the DSP clock rate, can you please help with that?

Thanks,
Gabi 

Hi Gabi,

Steps for change the DSP frequency.

clk = clk_get(NULL, "gem_ick");
rate = clk_get_rate(clk);
ret = clk_set_rate(clk, new_clk_rate);

Regards

AnilKumar

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Hi Anil,

I have changed the fuction "ti8168_evm_init()" as listed below, recompiled the kernel and checked and there is no change in DSP clock rate, please advice.

static void __init ti8168_evm_init(void)
{
  
struct clk *clk;
unsigned long rate;

	ti81xx_mux_init(board_mux);
	omap_serial_init();
	ti816x_evm_i2c_init();
	i2c_add_driver(&ti816xevm_cpld_driver);
	ti81xx_register_mcasp(0, &ti8168_evm_snd_data);
	ti816x_spi_init();
	/* initialize usb */
	usb_musb_init(&musb_board_data);
	board_nand_init(ti816x_nand_partitions,
		ARRAY_SIZE(ti816x_nand_partitions), 0, NAND_BUSWIDTH_16);
	omap2_hsmmc_init(mmc);
	board_nor_init(ti816x_evm_norflash_partitions,
		ARRAY_SIZE(ti816x_evm_norflash_partitions), 0);
	ti816x_vpss_init();
	ti816x_gpio_vr_init();
	ti816x_hdmi_init();
	regulator_has_full_constraints();
	regulator_use_dummy_regulator();
	
// change DSP clock rate
clk = clk_get(NULL, "gem_ick");
rate = clk_get_rate(clk);
ret = clk_set_rate(clk, 990000000);

}

Thanks,
Gabi 

Hi Gabi,

What is the error message you are seeing?

Lookat "dmesg"

$ dmesg | tail

Regards

AnilKumar

Hi Anil,

Thanks for your reply, there is no error in the dmesg, i have looked on all of it.
It is just that the DSP performances stay the same so i guess that there is no change in the DSP clock.

Thanks,
Gabi 

Hi Anil,

Can you please refer?

Thanks,
Gabi 

Hi Gabi,

Sorry for delay in response

Can you add clk_enable(); before clk_set_rate(), so that you can able to change the rate. Wiki page will be updated with a note.

// change DSP clock rate
clk = clk_get(NULL, "gem_ick");
clk_enable(clk);
rate = clk_get_rate(clk);
ret = clk_set_rate(clk, 990000000);

Regards

AnilKumar

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Hi Anil,

It didn't help, DSP clock doesn't change.

Gabi

Hi Gabi,

Which kernel version are you using? I tried with the latest one and its worked for me, I am able to change the rate.

If you are on the old kernel, can you change it to new one

http://software-dl.ti.com/dsps/dsps_public_sw/psp/LinuxPSP/TI81XX_04_04/04_04_00_01/index_FDS.html

Regards

AnilKumar

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Hi Anil,

I have linux-2.6.37-psp04.00.01.13.patch2, shouldn't it work on this version as well?

Gabi

Hi Gabi,

I had tested recently, that is the reason why I asked you to test on the same.

If you don't have any other dependencies can you try with recent kernel, mean while I will check with "psp04.00.01.13.patch2" also

Regards

AnilKumar

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Hi Anil,

Thank you very much for your effort, i am sorry but i have other dependencies, therefore it is impossible for me to update the kernel.

Gabi 

Hi Gabi,

I have checked, its working, can you follow these steps?

// change DSP clock rate

rrate = 990000000;
clk = clk_get(NULL, "gem_ick");
ret = clk_set_rate(clk, rrate);

if (ret)

pr_err("Failed to set the requested rate %lu and dsp running at %lu", rrate, clk_get_rate(clk));

Recent kernel versions clk_enable(clk); is required to change the rate, and not required in your case.

Regards

AnilKumar

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Anil said:

We can chagne the DSP frequency in u-boot (code),

How is the DSP clock set in u-boot?  The referenced document says nothing about this.

By the way, I have located the clock settings in u-boot for the ARM.

Lee

Hi Lee,

Better go throgh the TRM of DM8168 for pll configuration. section "1.10.3 Flying Adder PLL"

Regards

AnilKumar

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Hi Lee,

MAIN_*1 (u-boot, evm.c, main_pll_init_ti816x) macros are coresponding to DSP clock out rate values, change to required values. Make sure that you are not exceeding the limits.

Regards

AnilKumar

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Hi Anil,

Anil said:

// change DSP clock rate

rrate = 990000000;
clk = clk_get(NULL, "gem_ick");
ret = clk_set_rate(clk, rrate);

if (ret)

pr_err("Failed to set the requested rate %lu and dsp running at %lu", rrate, clk_get_rate(clk));

I have done what you have written above, i saw no error, but the clock frequency doesn't change, i am working with an OMX application could it be that some where else the clock frequency is set back to 800MHz?

Thanks,
Gabi 

Hi Gabi,

I am not aware of OMX application, Can you print the rate after setting to new value? We can conclude at this position setrate on your setup is working/not.

Another option is you can write some kernel module application, after kernel boots up you can control the clock rate using some sysfs/debugfs entries.

Regards

AnilKumar

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