How to correctly set CONFIG_SYS_LDB_CLOCK

marcosal — Tue, 31 Jul 2018 19:35:35 GMT

Hi, sorry if the question is dummy, I started to work on embedded systems some weeks ago =).

I'm working with an IMX6 Dual .

I would like to know how to set the correct value for the define "#define CONFIG_SYS_LDB_CLOCK 65000000" in the file ipu_common.c in the spl.

the settings for the display are (in both spl setup file and ldb.c kernel file):

struct fb_videomode mode_display= {
.name = "1920x720",
.refresh = 60,
.xres = 1920,
.yres = 720,

/*
LVDS-Clock:
1 / (48,7MHz * 2)
10267
*/
.pixclock = 10267,
.left_margin = 40,
.right_margin = 48,
.upper_margin = 2,
.lower_margin = 3,
.hsync_len = 40,
.vsync_len = 4,
.sync = FB_SYNC_EXT,
.vmode = FB_VMODE_NONINTERLACED
};

The setup_display (spl) performs the following operations (I use smooth transition since I'm displaying a splash screen):

void setup_display(void)
{
struct mxc_ccm_reg *mxc_ccm = (struct mxc_ccm_reg *)CCM_BASE_ADDR;

  reg = readl(&mxc_ccm->CCGR3);
  reg |= MXC_CCM_CCGR3_IPU2_IPU_MASK;
  writel(reg, &mxc_ccm->CCGR3);

  reg = readl(&mxc_ccm->CCGR3);
  reg &= ~MXC_CCM_CCGR3_LDB_DI1_MASK;
  reg |= MXC_CCM_CCGR3_LDB_DI0_MASK;
  writel(reg, &mxc_ccm->CCGR3);

#ifdef MAN_IMX_SPREAD_SPRECTRUM_ENABLED

  reg = readl(&mxc_ccm->analog_pfd_528);
  reg &= ~(BM_ANADIG_PFD_528_PFD2_FRAC);
  reg |= BF_ANADIG_PFD_528_PFD2_FRAC(0x1C);
  writel(reg, &mxc_ccm->analog_pfd_528);

  /* Spread spectrum numerator */
  reg =BF_ANADIG_PLL_528_DENOM_B(MAN_SPREAD_SPECTRUM_DENOM_B);
  writel(reg, &mxc_ccm->analog_pll_528_denom);

  reg = readl(&mxc_ccm->analog_pll_528_ss);
  reg |= BF_ANADIG_PLL_528_SS_STEP(MAN_SPREAD_SPECTRUM_STEP);
  reg |= BF_ANADIG_PLL_528_SS_STOP(MAN_SPREAD_SPECTRUM_STOP);
  reg |= BM_ANADIG_PLL_528_SS_ENABLE; /* Enable Spread Spectrum*/
  writel(reg, &mxc_ccm->analog_pll_528_ss);

  reg = readl(&mxc_ccm->cs2cdr);
  // Select PLL2 for ldb_diX_clk_sel
  reg &= ~(MXC_CCM_CS2CDR_LDB_DI0_CLK_SEL_MASK);
  reg |= (MXC_CCM_CS2CDR_LDB_DI0_CLK_SEL_PLL2_396M_PFD <<   MXC_CCM_CS2CDR_LDB_DI0_CLK_SEL_OFFSET);
  writel(reg, &mxc_ccm->cs2cdr);
#else

.... // code doesn't enter here

#endif

  //Divider for 3.5
  reg = readl(&mxc_ccm->cscmr2);
  reg &= ~(MXC_CCM_CSCMR2_LDB_DI0_IPU_DIV);
  writel(reg, &mxc_ccm->cscmr2);

//Clocks for IPU2
reg = readl(&mxc_ccm->cscdr2);

  /* Use ipu2 root clock from LDB_DI0 */
  reg &= ~(MXC_CCM_CHSCCDR_IPU2_DI0_CLK_SEL_MASK);
  reg |= (CHSCCDR_CLK_SEL_LDB_DI0 << MXC_CCM_CHSCCDR_IPU2_DI0_CLK_SEL_OFFSET);
  writel(reg, &mxc_ccm->cscdr2);

}

the ipu_common.c has:

#if !defined CONFIG_SYS_LDB_CLOCK
#define CONFIG_SYS_LDB_CLOCK 65000000
#endif

static struct clk ldb_clk = {
.name = "ldb_clk",
.rate = CONFIG_SYS_LDB_CLOCK,
.usecount = 0,
};

Thanks for any solution or advise.

Re: How to correctly set CONFIG_SYS_LDB_CLOCK

igorpadykov — Tue, 31 Jul 2018 23:13:55 GMT

Hi Marcos

one can look at below examples for configuring ldb clocks

Patch to support uboot logo keep from uboot to kernel for NXP Linux and Android BSP (HDMI, LCD and LVDS)

Best regards
igor
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How to correctly set CONFIG_SYS_LDB_CLOCK

Re: How to correctly set CONFIG_SYS_LDB_CLOCK