topic Re: 4bits bus width emmc prebuild image for sabresd in i.MX Processors

4bits bus width emmc prebuild image for sabresd

xaviercarcelle — Tue, 20 Sep 2016 21:47:02 GMT

hi there,

for production issues, we are looking for a prebuild linux image for 4bits-bus-width emmc used my MfgTool.

This prebuild image is used to be loaded in ocram and then writing uboot in emmc using dd commands.

The available images for sabre-sd and others boards seem to be built for 8bits-bus-width emmc.

Much regards,

Xavier.

Re: 4bits bus width emmc prebuild image for sabresd

igorpadykov — Wed, 21 Sep 2016 06:00:12 GMT

Hi Xavier

emmc bus width can be changed in *.dts file:

&usdhc.. {
   pinctrl-names = "default";
   pinctrl-0 = <&pinctrl_usdhc..>;
   bus-width = <8>;..

one can refer to attached Yocto Guide for building

procedures. Please elevate additional requirements

through local fae channel.

Best regards
igor
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Re: 4bits bus width emmc prebuild image for sabresd

xaviercarcelle — Wed, 21 Sep 2016 07:00:09 GMT

Dear Igor,

thanks a lot for your reply. Due to urgent matter with this issue, could it be possible that you could build a uImage based on the 4bits width emmc so I can try it on custom board ?

Much regards,

Xavier.

Re: 4bits bus width emmc prebuild image for sabresd

xaviercarcelle — Wed, 21 Sep 2016 08:04:18 GMT

Dear Igor,

could it be possible to use the archive "IMX6_M6.0.1_2.1.0_MFG_TOOL"

This archive uses in "files", uboot/zImage/dtb that can be recompilable from dts for 4bits emmc ?

Much regards,

Xavier.

Re: 4bits bus width emmc prebuild image for sabresd

xaviercarcelle — Thu, 22 Sep 2016 15:43:04 GMT

Dear Igor,

using "MFGTool (v2.3.2)" + UCL/UTP scripts (available with that tarsal) a kernel is loader in imx6 cram (Linux version 3.0.35-2666-gbdde708), we were unable to write into /dev/mmcblk0 as the emmc on our custom boards is 4bits bus-width. The kernel does not detect the emmc on 4bits as we guess this kernel is configured for 8bits bus-width.

However, after a few seconds, the EMMC appears in the kernel and we detect /dev/mmcblk0 and are able to read it.

Our technical understanding is that the kernel is firstly accessing the emmc in 8bits mode but after some retries, it falls-back in 4bits mode ? Coud it be a good hypothesis ?

Much regards,

Xavier.

Re: 4bits bus width emmc prebuild image for sabresd

igorpadykov — Fri, 23 Sep 2016 01:07:55 GMT

Hi Xavier

in general yes, kernel can check EXT_CSD[BUS_WIDTH] and

continue with changed bit mode.

Best regards
igor

Re: 4bits bus width emmc prebuild image for sabresd

xaviercarcelle — Fri, 23 Sep 2016 08:13:32 GMT

Hi Igor,

do you know where the code snippet in the kernel for this EXT_CSD configuration usage and timeout for 8bits and 4bits ?

We are trying to rebuild a kernel image based on the sha1 of the kernel we use :

Linux version 3.0.35-2666-gbdde708 (r65388@shlinux3) (gcc version 4.6.2 20110630 (prerelease)

but when rebuilding this kernel with 4bits emmc we have a kernel panic :

"Unable to handle kernel paging request at virtual address e1a01000 / pgd = 80004000"

Do you have some hints to rebuild a fresh kernel from the sha1 gbdde708 ?

Best regards,

Xavier.

Re: 4bits bus width emmc prebuild image for sabresd

igorpadykov — Fri, 23 Sep 2016 09:43:00 GMT

Hi Xavier

please post this to kernel mail list, as this is generic linux question.

Best regards
igor