Re: Boot on eMMC

[Gary Thomas <gary@mlbassoc.com>]

On 2015-04-15 04:17, Thomas wrote:
> Gary Thomas <gary@...> writes:
>
>>
>> On 2015-04-14 08:28, Otavio Salvador wrote:
>>> On Tue, Apr 14, 2015 at 11:12 AM, Shanx <shanx@...> wrote:
>>>> Hello,
>>>> I've tried a lot of things, but I can't boot on eMMC. I've flashed it
> from
>>>> u-boot, or from the system (booted from the sdcard). For exemple, I've
> tried
>>>> : dd if=rootfs.sdcard of=/dev/mmcblk3
>>>> I've also tried to flash only u-boot.imx (with dd and seek=2)
>>>>
>>>> When booting on eMMC (with the boot switch setup given on the Linux
> User
>>>> Guide), nothing append. Any idea why ?
>>>
>>> eMMC has some details which differ from the uSD normal usage. Mainly
>>> regarding the use of Boot Partitions. So you must to write it to the
>>> boot partition otherwise it won't work.
>>>
>>
>> I'm not sure this is correct.  I have an i.MX6Q board which has
>> eMMC on SD4 and SD on SD3 and I can boot from either, using the
>> same command to install U-Boot
>>     dd if=/tmp/disk/${UBOOT_NAME} of=${DISK} seek=2 bs=512 conv=notrunc
>>
>> Maybe it's a difference in the eMMC device (mine is Sandisk SDIN5 (or7)C2-
> 32G-L)
>>
> Then you're actually booting in SD fallback mode (if your board is
> configured for emmc boot). To boot in emmc mode place u-boot on one of the
> boot partitions and enable the correct boot partition for boot via sysfs.
>
> First enable write to boot partition:
> echo 0 > /sys/block/mmcblk0boot0/force_ro
>
> Write uboot:
> dd if=u-boot.imx of=/dev/mmcblk0boot0 bs=512 seek=2
>
> Re-enable read-only access to the boot partition:
> echo 1 > /sys/block/mmcblk0boot0/force_ro
>
> Then boot partition (here 0) must be activated e.g. like this:
> echo 8 > /sys/devices/platform/sdhci-esdhc-
> imx.1/mmc_host/mmc0/mmc0:0001/boot_config
>
> Then set the fuses/gpio for emmc boot.
>
>

What is the advantage of this vs just using the SD fallback
method which seems to work just fine?  It seems to just make
life more complicated, especially my process for installing
the software to the unit.

-- 
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Gary Thomas                 |  Consulting for the
MLB Associates              |    Embedded world
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