eMMC Reset Line


I would like to disable the eMMC so I can use the additional GPIO lines. I was following these instructions as they were the most succinct I was able to find: https://github.com/modmaker/BeBoPr/wiki/BeBoPr-goes-Black. However I found that the rstn command is no longer supported. Looking at the U-boot code (I’m on the 2015.10.rc2 uboot) it appears that the rstn command has became rst-function and has been firewalled behind CONFIG_SUPPORT_EMMC_BOOT.

Is the best way for me to re-compile uboot with the CONFIG_SUPPORT_EMMC_BOOT (and where does it need to go?) Or am I going down the incorrect path?



I think you can also use mmc-utils from linux to enable the reset pin functionality in eMMC. Keep in mind this setting (ECSD byte 162, “RST_n_FUNCTION”), like disturbingly many of the eMMC’s settings, is one-time-programmable. No margin for mistakes or second thoughts here :stuck_out_tongue: (Unlike the author of the article you linked to I’m personally quite glad these settings were left in virgin state since there are security implications to enabling the reset line.)

Note BTW that as long as you leave mmc_clk alone you can safely use the remaining pins for other purposes, so unless you really need that last pin too I would leave reset alone.

Or, if you can briefly use the mmc_clk and mmc_cmd lines during boot, you
can command the eMMC enter inactive state (which makes it withdraw from the
bus until next power-up). You can then freely use all mmc lines.


在 2015年10月14日星期三 UTC+8上午5:41:01,Christopher Stack写道: