[U-Boot] problem to boot i.MX28 custom platform

[Fabio Estevam <fabio.estevam@freescale.com>]

Hi Hector,

Hector Palacios wrote:

> Apparently the problem was due to my platform suffering a hardware
> specific VDDD brownout during the initialization.
> 
> Just in case it helps anybody, the reason why I was not able to see
> anything on the DUART port during SPL initialization, despite having
> enabled CONFIG_SPL_SERIAL_SUPPORT and having serial_puts() on the SPL
> code, was that my platform uses alternate pins for the DUART than the
> default used by the BOOT ROM and the EVK, so apart from configuring the
> correct IOMUX, I needed to unconfigure the pins used by BOOT ROM for the
> DUART (on board/<vendor>/iomux.c):
> 
> @@ -33,8 +33,12 @@
> 
>  const iomux_cfg_t iomux_setup[] = {
>         /* DUART */
> -       MX28_PAD_PWM0__DUART_RX,
> -       MX28_PAD_PWM1__DUART_TX,
> +       /* Unconfigure BOOT ROM default DUART */
> +       MX28_PAD_PWM0__GPIO_3_16,
> +       MX28_PAD_PWM1__GPIO_3_17,
> +       /* Configure DUART on alternate pins */
> +       MX28_PAD_I2C0_SCL__DUART_RX,
> +       MX28_PAD_I2C0_SDA__DUART_TX,
> 
>         /* MMC0 */
>         MX28_PAD_SSP0_DATA0__SSP0_D0 | MUX_CONFIG_SSP0,
> @@ -159,9 +163,6 @@ const iomux_cfg_t iomux_setup[] = {
>         MX28_PAD_SSP2_MISO__SSP2_D0 | MUX_CONFIG_SSP2,
>         MX28_PAD_SSP2_SS0__SSP2_D3 |
>                 (MXS_PAD_3V3 | MXS_PAD_8MA | MXS_PAD_PULLUP),
> -       /* I2C */
> -       MX28_PAD_I2C0_SCL__I2C0_SCL,
> -       MX28_PAD_I2C0_SDA__I2C0_SDA,
>  };
> 
>  #define HW_DRAM_CTL29  (0x74 >> 2)

Thanks for sharing your solution. It seems that the other mx28 boards we currently have all use
MX28_PAD_PWM0__DUART_RX / MX28_PAD_PWM1__DUART_TX for DUART and then we never faced this issue.

It would be great if you can submit a patch for adding support to your board in U-boot.

Regards,

Fabio Estevam