Hi, I have studied the booting sequence and boot modes of the OMAP5.
Basically we can simply use the standard order (0x1010) as set on the eval board:
1. SD 2. eMMC 3. USB
So I think there is no need for a trick as on the Beagle Board to press some AUX button to modify the boot order to get SD first if X-Loader in NAND is damaged.
What we *could* do is to add a 32 byte eeprom to I2C1 and then we can define the boot order ourselves. E.g. SD -> eMMC (boot partition) -> eMMC -> SATA -> UART3 -> USB
But I think this is overkill.
So my proposal is to have it simply as in the EVM: boot from SD (only one slot is boot capable!) and if no SD, boot from eMMC.
This means people can either have their full bootable system on SD. They can still boot from eMMC if they don't insert the SD. Or they always boot from eMMC because they use non-bootable SD card.
Unbricking is simply by booting from any bootable SD and restoring eMMC.
I think TI was able to change that from OMAP3 booting because the SD slot on the OMAP5 has an explicit card detect input. So the boot sequence is not slower if the SD card is not present but in the first position. This was probably the reason to boot from NAND by default and the need for the AUX button trick.
BTW: it appears that it is not possible to switch the sys_boot pins to GPIO mode and therefore read some AUX button.
BR, Nikolaus
Hello,
On Fri, Jan 31, 2014 at 11:20 AM, Dr. H. Nikolaus Schaller hns@goldelico.com wrote:
... So my proposal is to have it simply as in the EVM: boot from SD (only one slot is boot capable!) and if no SD, boot from eMMC.
This means people can either have their full bootable system on SD. They can still boot from eMMC if they don't insert the SD. Or they always boot from eMMC because they use non-bootable SD card.
Can it really fallback to eMMC if non-bootable card is inserted? Having to remove the card just to boot the system would be extremely annoying and confuse the users..
GraÅžvydas
Hi,
Am 31.01.2014 um 13:40 schrieb Grazvydas Ignotas:
Hello,
On Fri, Jan 31, 2014 at 11:20 AM, Dr. H. Nikolaus Schaller hns@goldelico.com wrote:
... So my proposal is to have it simply as in the EVM: boot from SD (only one slot is boot capable!) and if no SD, boot from eMMC.
This means people can either have their full bootable system on SD. They can still boot from eMMC if they don't insert the SD. Or they always boot from eMMC because they use non-bootable SD card.
Can it really fallback to eMMC if non-bootable card is inserted?
That is how I interpret the boot rom search sequence (try one after the other until successful). Otherwise it would not make sense to have a "sequence" at all.
And AFAIK the OMAP3 will also boot from NAND if the inserted SD card can't boot - even if we press the boot from SD button (to force the 1st SD 2nd NAND boot order). It may just take some milliseconds to find that the SD has no working system on it.
Having to remove the card just to boot the system would be extremely annoying and confuse the users..
But we should easily be able to test it on the EVM with the default switch settings. If we program the eMMC there it should boot with/without SD card. And only from the SD card if it has an MLO in the first partition.
BR, Nikolaus