What is the reason for this reading mmc in linux

Question

What is the cause of this problem reading mmc in linux ..? please help solve this ...? please check my kernel boot log below, help me solve this problem.

I included the appropriate drivers for mmc, compiled and loaded using the newly created kernel image. I get kernel boot loogs as shown below.

mmc0: card lacks mandatory switch function, performance might suffer. mmc0: host does not support reading read-only switch. assuming write-enable. mmc0: new SD card at address b368 mmcblk0: mmc0:b368 SMI-S 8.00 MiB mmcblk0: mmcblk0: retrying using single block read mmcblk0: error -110 transferring data, sector 0, nr 8, card status 0xb00 end_request: I/O error, dev mmcblk0, sector 0 mmcblk0: error -110 sending read/write command, response 0xb00, card status 0x40 end_request: I/O error, dev mmcblk0, sector 1 mmcblk0: error -110 sending read/write command, response 0x400b00, card status 0 end_request: I/O error, dev mmcblk0, sector 2 mmcblk0: error -110 sending read/write command, response 0x400b00, card status 0 end_request: I/O error, dev mmcblk0, sector 3 mmcblk0: error -110 sending read/write command, response 0x400b00, card status 0 end_request: I/O error, dev mmcblk0, sector 4 mmcblk0: error -110 sending read/write command, response 0x400b00, card status 0 end_request: I/O error, dev mmcblk0, sector 5 mmcblk0: error -110 sending read/write command, response 0x400b00, card status 0 end_request: I/O error, dev mmcblk0, sector 6 mmcblk0: error -110 sending read/write command, response 0x400b00, card status 0 end_request: I/O error, dev mmcblk0, sector 7 Buffer I/O error on device mmcblk0, logical block 0 mmcblk0: retrying using single block read mmcblk0: error -110 sending read/write command, response 0x400b00, card status 0 end_request: I/O error, dev mmcblk0, sector 0 mmcblk0: error -110 sending read/write command, response 0x400b00, card status 0 end_request: I/O error, dev mmcblk0, sector 1 mmcblk0: error -110 sending read/write command, response 0x400b00, card status 0 end_request: I/O error, dev mmcblk0, sector 2 mmcblk0: error -110 sending read/write command, response 0x400b00, card status 0 end_request: I/O error, dev mmcblk0, sector 3 mmcblk0: error -110 sending read/write command, response 0x400b00, card status 0 end_request: I/O error, dev mmcblk0, sector 4 mmcblk0: error -110 sending read/write command, response 0x400b00, card status 0 end_request: I/O error, dev mmcblk0, sector 5 mmcblk0: error -110 sending read/write command, response 0x400b00, card status 0 end_request: I/O error, dev mmcblk0, sector 6 mmcblk0: error -110 sending read/write command, response 0x400b00, card status 0 end_request: I/O error, dev mmcblk0, sector 7 Buffer I/O error on device mmcblk0, logical block 0 unable to read partition table 

Answer 1

Error -110 means timeout. Basically, your MMC controller cannot speak correctly with your SD card. This usually happens when your card is inserted incorrectly into the slot (for example, spring drops your card too much) or you may be using a micro SD card and inserted incorrectly into the SD card adapter. It may also happen that your SD card adapter is slightly broken and some connections are incorrect (for example, your card has a consistent 4-bit mode and some lines are not actually connected).