Change the SSP0 clock from max 28.8MHz to 50 MHz

[B_K_Ankur]

Hello Friends,

I am using imx28evk running linux kernel 3.10.29. I have found that the SSP0 (MMC slot 0) can only run maximum of clock 28.8MHz as mentioned in the

file: drivers/mmc/host/mxs-mmc.c

Line#666

   mmc->f_min = 400000;

  mmc->f_max = 288000000;

I want to plug the TI wifi module that runs on 50MHz. In this case, I would like to increase the clock frequency of SSP0 to 50 MHz. Is there any way I can change it?

Moreover, I found that "ref_io0" is set to 288 MHz below from file: drivers/clk/mxs/clk-imx28.c. Which code changes the frequency from 228 MHz to 28.8 MHz (maximum) ?

/*

118          * 480 MHz seems too high to be ssp clock source directly,

119          * so set frac0 to get a 288 MHz ref_io0 and ref_io1.

120          */

121         val = readl_relaxed(FRAC0);

122         val &= ~((0x3f << BP_FRAC0_IO0FRAC) | (0x3f << BP_FRAC0_IO1FRAC));

123         val |= (30 << BP_FRAC0_IO0FRAC) | (30 << BP_FRAC0_IO1FRAC);

124         writel_relaxed(val, FRAC0);

Any help is highly appreciated.

Thank you,

Ankur

[B_K_Ankur]

Hello Folks,

I got to know from the clock Hierarchy that ref_io0 is 288 MHz and the register values is also correct. But I don't able to know how the SSP0_DIV clock goes down to 57.6 MHz, I am sure that register  affects it as the divider value is 5.

Kernel: 3.10.29

root@imx28evk:~# cat /sys/kernel/debug/clk/clk_summary

      ssp0_sel              1          1            288000000

            ssp0_div      1          1            57600000

                    ssp0    1          1            57600000

I tried looking into drivers/clk/mxs/clk-imx28.c and drivers/clk/mxs/clk-div.c but didnt get any clue about how HW_CLKCTRL_SSP0 register gets divider value 5. Any hint will be appreciated.

Thank you,

Ankur

[B_K_Ankur · Accepted solution]

Hello Floks,

Found the Solution:

I just edited drivers/clk/mxs/clk-imx28.c and now the ssp0_div and ssp0 clock goes to 288 MHz.

Below are the additions to function clk_misc_init(void):

     val = readl_relaxed(SSP0);

    printk("Before Change ctrlssp0 0x%x\n",val);

    val = val & ~0x17;

    val = val | 0x1;

    writel_relaxed(val, SSP0);  

    val = readl_relaxed(SSP0);

    printk("After Change: ctrlssp0 0x%x\n",val);

Thanks all for support.

Have a Good One,

Ankur