On Tue, Oct 13, 2015 at 3:03 AM, Lokesh Vutla a0131933@ti.com wrote:
On Tuesday 13 October 2015 01:14 PM, Heiko Schocher wrote:
Hello Lokesh,
Am 13.10.2015 um 08:46 schrieb Lokesh Vutla:
+Nishanth,
On Tuesday 13 October 2015 10:59 AM, Heiko Schocher wrote:
On embedded devices, often there is a combination of removable mmc devices (e.g. MMC/SD cards) and hard wired ones (e.g. eMMC). Depending on the hardware configuration, the 'mmcblkN' node might change if the removable device is available or not at boot time.
E.g. if the removable device is attached at boot time, it might become mmxblk0. And the hard wired one mmcblk1. But if the removable device isn't there at boot time, the hard wired one will become mmcblk0. This makes it somehow difficult to hard code the root device to the non-removable device and boot fast.
Why not use "root=PARTUUID=${uuid}" option instead of relying on mmcblk no? U-Boot can easily detect your partuuid. Refer to [1] on how TI platforms does this in u-boot.
Good tip ... I do not know, if it is possible to update U-Boot on this boards...
Current U-Boot says: U-Boot 2013.01.01_heads/master-gc7900a0 (2015-05-06 - 20:37:15)
I2C: ready DRAM: 512 MiB [...] U-Boot# mmc rescan U-Boot# mmc part
Partition Map for MMC device 0 -- Partition Type: DOS
Part Start Sector Num Sectors UUID Type 1 63 144522 000ce343-01 0e Boot 2 144585 659861 000ce343-02 83 U-Boot# part uuid mmc 0:2 uuid Unknown command 'part' - try 'help' U-Boot#
So, if this patch has no chance for mainline, please let me know it, thanks!
IIRC, Nishanth had posted a patch something similar but got rejected for some reason. Probably Nishanth can comment more here.
overall the feedback I received was for block devices, there is already an unique method(PARTUUID/uuid) of referencing required device and mmcxblky aliasing was not really needed - hence dropped my patch and switched over to partuuid.
CC Tom and u-boot list as well. for reference the current thread: http://marc.info/?t=144471421700002&r=1&w=2