AM335x xstal question

Sophia Kalibo

Intellectual 490 points

We are proposed to use 25MHz xstal with AM335x instead of 24Mhz.

Is there any necessary modification in linux BSP (AM335x EVM) ?
Or any thing I should take care?

Thanks.

over 12 years ago

0 Steve Kipisz over 12 years ago

TI__Genius 15510 points

In u-boot, you have to modify include/configs/am335x_evm.h and change

#define V_OSCK 24000000 /* Clock output from T2 */

#define V_OSCK 25000000 /* Clock output from T2 */

Steve K.

0 Sophia Kalibo over 12 years ago in reply to Steve Kipisz

Intellectual 490 points

OK, I see.

But is there any modification in Linux kernel setting with am335x_evm?

e.g., :in cm-regbits-33xx.h

#define AM33XX_CLKACTIVITY_CLK_24MHZ_GCLK_SHIFT 4

Or just change the u-boot setting?

Thank you.

0 Steve Kipisz over 12 years ago in reply to Sophia Kalibo

TI__Genius 15510 points

That #define is for a Peripheral clock

/* Used by CM_PER_CLK_24MHZ_CLKSTCTRL */
#define AM33XX_CLKACTIVITY_CLK_24MHZ_GCLK_SHIFT 4
#define AM33XX_CLKACTIVITY_CLK_24MHZ_GCLK_MASK (1 << 4)

So you do not need to modify that code. I think you might need to modify arch/arm/mach-omap2/clock33xx_data.c

/* sys_clk_in */
static struct clk sys_clkin_ck = {
          .name           = "sys_clkin_ck",
          .parent         = &virt_24m_ck,
          .init           = &omap2_init_clksel_parent,
          .clksel_reg     = AM33XX_CTRL_REGADDR(0x40),    /* CONTROL_STATUS *     /
          .clksel_mask    = (0x3 << 22),
          .clksel         = sys_clkin_sel,
          .ops            = &clkops_null,
          .recalc         = &omap2_clksel_recalc,
};

Change the 24 to a 25.

Steve K.

0 Sophia Kalibo over 12 years ago in reply to Steve Kipisz

Intellectual 490 points

Hi Steve,

Thanks for your reply.

As your mentioned, there is *only one* modification with 25MHz xstal.

I'll try for this.

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AM335x xstal question