[U-Boot] [PATCH v2] arm, imx6: add support for SD/MMC Manufacture Mode

[Stefano Babic]

Hi Jay,

On 22/06/2018 07:16, Jay Carlson wrote:
> This patch adds support for booting blank i.MX6 devices in SD/MMC Manufacture
> Mode: a fallback mode which the boot ROM enters when no fuses or boot mode 
> pins have been set, the USB serial downloader connection is inactive, and there
> is an SD card inserted into uSDHC1. The i.MX7 and i.MX8, which both have 
> a Boot_SW_Info data structure which can be parsed to determine boot source, is
> unaffected by this patch.
> 
> Signed-off-by: Jay Carlson <jay.d.carlson at gmail.com>
> ---
>  arch/arm/mach-imx/spl.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/arch/arm/mach-imx/spl.c b/arch/arm/mach-imx/spl.c
> index a20b30d154..8ecae8605c 100644
> --- a/arch/arm/mach-imx/spl.c
> +++ b/arch/arm/mach-imx/spl.c
> @@ -43,6 +43,16 @@ u32 spl_boot_device(void)
>  	 */
>  	if (is_usbotg_phy_active())
>  		return BOOT_DEVICE_BOARD;
> +	
> +	/**
> +	 * To support SD/MMC Manufacture Mode, we check that BOOT_MODE == 0
> +	 * and that BT_FUSE_SEL == 0. If this was disabled via
> +	 * blowing DISABLE_SDMMC_MFG, or if SDMMC MFG mode failed,
> +	 * we would be in USB download mode, which the previous line would 
> +	 * have detected.
> +	 */
> +	if (((bmode >> 24) & 0x03) == 0x00 && (bmode >> 4) == 0x00)
> +		return BOOT_DEVICE_MMC1;
>  
>  	/* BOOT_CFG1[7:4] - see IMX6DQRM Table 8-8 */
>  	switch ((reg & IMX6_BMODE_MASK) >> IMX6_BMODE_SHIFT) {
> 

This looks to me a fix for a custom board, but it does not seem that can
be applied general for all devices. I understand that this works in your
use case, where you have soldered eMMC and in factory you install the
software via SD card. But this is one use case.

Your change goes into general code (mach-imx/spl.c), and then it can
breaks many projects. You coul write your board_boot_order() in your
boot code to set the order of the device to be booted.

Best regards,
Stefano Babic

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