https://github.com/chewitt/linux/commit/8a4ebfb43a394e5dc5e9fafc92a50d5e81a4f258 If I boot any recent kernel without the above patch, the emmc module on the XU4 is not detected, see: Without: [ 3.227837] mmc0: tuning execution failed: -5 [ 3.231229] mmc0: error -5 whilst initialising MMC card [ 3.536450] mmc0: tuning execution failed: -5 [ 3.539680] mmc0: error -5 whilst initialising MMC card [ 3.794056] mmc0: tuning execution failed: -5 [ 3.794212] mmc0: error -5 whilst initialising MMC card [ 4.111097] mmc0: tuning execution failed: -5 [ 4.115356] mmc0: error -5 whilst initialising MMC card [ 4.426164] mmc0: tuning execution failed: -5 [ 4.429678] mmc0: error -5 whilst initialising MMC card [ 4.756226] mmc0: tuning execution failed: -5 [ 4.760641] mmc0: error -5 whilst initialising MMC card With: [ 3.305461] mmc0: new HS400 MMC card at address 0001 [ 3.307444] mmcblk0: mmc0:0001 8GME4R 7.28 GiB [ 3.308132] mmcblk0boot0: mmc0:0001 8GME4R 4.00 MiB [ 3.309172] mmcblk0boot1: mmc0:0001 8GME4R 4.00 MiB [ 3.310255] mmcblk0rpmb: mmc0:0001 8GME4R 512 KiB, chardev (246:0) [ 3.315963] mmcblk0: p1 p2 The patch is sourced from a Linux 5.4 patchset used by several retro gaming distros for XU4 images shared in the HardKernel forums. I would be happy to submit it, but the original patch has no description in the commit message. Not being a coding developer myself I cannot explain whether it is correct or what it’s doing to add one. All I can do is confirm that it works, and is needed. SD card boot is not an issue. I’ve CC’d the original author (Marian) in case he remembers the patch and can comment. It would be good to get this upstream. Christian
