Spartan-6 / OMAP-L138 Co-Processing Kit

[pankaj2701]

Hello,

What files should be modified to change the EMIF clk frequency. In my OMAP spartan6 board after startup the default EMIF clk frequency is being set at 25 MHz. I want to increase it to 100 Mhz.

Regards

Pankaj

[AlbertaBeef]

Pankaj,

This is documented in the OMAP-L138 datasheet.

The EMIFA clock frequency can be either:

- SYSCLK3

- PLL0 output clock divided by 4.5

The attached image illustrates this.

Regards,

Mario.

[pankaj2701]

Hi,

Sorry I didn't make my question clear.  I am able to change the frequency by modifying the PLL registers through command line of u-boot. But I am unable to do so in Linux. I wanted to know the location of source code where the clocks are being initialized in linux.

Regards

Pankaj

[JohnW]

Pankaj,

You need to get really comfortable with the Linux kernel.  Don't be afraid to explore.

Our kernel is essentially the same kernel as the one in the OMAP-L138 EVM and eXperimenter kit.  I haven't tried changing the clock myself, but I hope that I can point you to the right files and some code and you can do the rest for yourself.

Look at the following files:

arch/arm/mach-davinci/board-da850-evm.c

arch/arm/mach-davinci/da580.c

These files contain some low-level initialization code for the chip and board.

If you do a search for 'emif' in these files, it will lead you to the following.

In da850.c:

static struct clk emif3_clk = {
        .name           = "emif3",
        .parent         = &pll0_sysclk5,
        .lpsc           = DA8XX_LPSC1_EMIF3C,
        .gpsc           = 1,
        .flags          = ALWAYS_ENABLED,
};

....further down in the file:

static struct clk aemif_clk = {
        .name           = "aemif",
        .parent         = &pll0_sysclk3,
        .lpsc           = DA8XX_LPSC0_EMIF25,
};

These structs get plugged into a big clock table, that in turn gets plugged into a larger structure that is used to initialize the chip.  Look at arch/arm/mach-davinci/clock.c (contains the clock init code that loops through the big clock table and inits/registers the clocks) and arch/arm/mach-davinci/common.c  (contains the common DaVinci init routine) in this directory as well.

John