[U-Boot] [PATCH] imx_common: check for Serial Downloader in spl_boot_device

[Eric Nelson <eric@nelint.com>]

Hi Stefano,

On 12/04/2015 02:02 AM, Stefano Babic wrote:
> Check for bmode before reading the boot device
> to check if a serial downloader is started,
> and returns UART if the serial downloader is set,
> letting SPL to wait for an image if
> CONFIG_SPL_YMODEM_SUPPORT is set.
> 
> This allows to load again a SPL based board
> with imx_usb_loader together with a tool
> such as kermit.
> 
> Signed-off-by: Stefano Babic <sbabic@denx.de>
> CC: Tim Harvey <tharvey@gateworks.com>
> CC: Fabio Estevam <Fabio.Estevam@freescale.com>
> CC: Eric Nelson <eric.nelson@boundarydevices.com>
> ---
> 
> Note: I know we have already discussed more complicated solution
> 	for adding multilple files to imx_usb_loader.
> 	However, fixing ymodem support for i.MX6
> 	was trivial and imx_usb_loader is working
> 	again.
> 
>  arch/arm/imx-common/spl.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/arch/arm/imx-common/spl.c b/arch/arm/imx-common/spl.c
> index ac6e40e..28217d2 100644
> --- a/arch/arm/imx-common/spl.c
> +++ b/arch/arm/imx-common/spl.c
> @@ -20,7 +20,14 @@ u32 spl_boot_device(void)
>  	struct src *psrc = (struct src *)SRC_BASE_ADDR;
>  	unsigned int gpr10_boot = readl(&psrc->gpr10) & (1 << 28);
>  	unsigned reg = gpr10_boot ? readl(&psrc->gpr9) : readl(&psrc->sbmr1);
> +	unsigned int bmode = readl(&psrc->sbmr2);
>  
> +	/*
> +	 * Check for BMODE if serial downloader is enabled
> +	 * BOOT_MODE - see IMX6DQRM Table 8-1
> +	 */

I think you may need to check only bits 24 and 25 here.

> +	if ((bmode >> 24) == 0x01) /* Serial Downloader */
> +		return BOOT_DEVICE_UART;

Even though the data sheet says the high bits should be zero,
I'm seeing some other bits set on an i.MX6SL:

	=> mm 0x020d801c
	020d801c: 22000001 ? x

Separately, what's your thought about enabling this when the
system is reset through "bmode usb"?

http://git.denx.de/?p=u-boot.git;a=blob;f=arch/arm/cpu/armv7/mx6/soc.c;h=bf5ae8cdffd8b0887291249332b06f66dc644832;hb=HEAD#l389

Since the gpr9 value in this mode is 0x00000001, the switch
statement currently falls into the NOR/OneNAND block, which
is pretty useless.