[G 2014 Q&A, Help & Troubleshooting] devsk:
<3>[ 418.504575,0] mmc0: Timeout waiting for hardware interrupt.
<6>[ 418.504738,0] sdhci: =========== REGISTER DUMP (mmc0)===========
<6>[ 418.504825,0] sdhci: Sys addr: 0x4000f001 | Version: 0x00003802
<6>[ 418.504975,0] sdhci: Blk size: 0x00007200 | Blk cnt: 0x00001600
<6>[ 418.505060,0] sdhci: Argument: 0x00573c00 | Trn mode: 0x0000002b
<6>[ 418.505224,0] sdhci: Present: 0x01e80106 | Host ctl: 0x00000035
<6>[ 418.505309,0] sdhci: Power: 0x0000000b | Blk gap: 0x00000000
<6>[ 418.505459,0] sdhci: Wake-up: 0x00000000 | Clock: 0x00000007
<6>[ 418.505544,0] sdhci: Timeout: 0x0000000a | Int stat: 0x00000000
<6>[ 418.505694,0] sdhci: Int enab: 0x03ff800b | Sig enab: 0x03ff800b
<6>[ 418.505777,0] sdhci: AC12 err: 0x00000000 | Slot int: 0x00000000
<6>[ 418.505925,0] sdhci: Caps: 0x642dc8b2 | Caps_1: 0x00008004
<6>[ 418.506009,0] sdhci: Cmd: 0x0000193a | Max curr: 0x00000000
<6>[ 418.506094,0] sdhci: Resp 1: 0x454d3038 | Resp 0: 0x00000900
<6>[ 418.506243,0] sdhci: Resp 3: 0x00000900 | Resp 2: 0x47070e0f
<6>[ 418.506326,0] sdhci: Host ctl2: 0x00000004
<6>[ 418.506408,0] sdhci: ADMA Err: 0x00000003 | ADMA Ptr: 0x23f4b490
<6>[ 418.506557,0] mmc0: clk: 50000000 clk-gated: 0 claimer: mmcqd/0 pwr: 10
<6>[ 418.506704,0] mmc0: rpmstatus[pltfm](runtime-suspend:usage_count:disable_depth)(0:0:0)
<6>[ 418.506787,0] sdhci: ===========================================
<6>[ 418.506935,0] mmc0: bytes to transfer: 31457792 transferred: 2883584
<3>[ 418.539062,0] mmcblk0: error -110 transferring data, sector 5716992, nr 1024, cmd response 0x900, card status 0xc00
<3>[ 418.544473,0] end_request: I/O error, dev mmcblk0, sector 5716992
<3>[ 418.544922,0] end_request: I/O error, dev mmcblk0, sector 5718016
<3>[ 418.545214,0] end_request: I/O error, dev mmcblk0, sector 5719040
<3>[ 418.545529,0] end_request: I/O error, dev mmcblk0, sector 5719848
<3>[ 418.545811,0] end_request: I/O error, dev mmcblk0, sector 5720872
<3>[ 418.546161,0] end_request: I/O error, dev mmcblk0, sector 5721896
<3>[ 418.546378,0] end_request: I/O error, dev mmcblk0, sector 5730304
<3>[ 418.546656,0] end_request: I/O error, dev mmcblk0, sector 5731328
<3>[ 418.547002,0] end_request: I/O error, dev mmcblk0, sector 5732352
<3>[ 418.547284,0] end_request: I/O error, dev mmcblk0, sector 5733376
<3>[ 426.584573,0] mmc0: Timeout waiting for hardware interrupt.
<6>[ 426.584668,0] sdhci: =========== REGISTER DUMP (mmc0)===========
<6>[ 426.584819,0] sdhci: Sys addr: 0x00000310 | Version: 0x00003802
<6>[ 426.584904,0] sdhci: Blk size: 0x00007200 | Blk cnt: 0x00000310
<6>[ 426.585054,0] sdhci: Argument: 0x0058bc00 | Trn mode: 0x0000002b
<6>[ 426.585139,0] sdhci: Present: 0x01f80000 | Host ctl: 0x00000035
<6>[ 426.585287,0] sdhci: Power: 0x0000000b | Blk gap: 0x00000000
<6>[ 426.585371,0] sdhci: Wake-up: 0x00000000 | Clock: 0x00000007
<6>[ 426.585519,0] sdhci: Timeout: 0x0000000a | Int stat: 0x00000000
<6>[ 426.585605,0] sdhci: Int enab: 0x03ff800b | Sig enab: 0x03ff800b
<6>[ 426.585754,0] sdhci: AC12 err: 0x00000000 | Slot int: 0x00000000
<6>[ 426.585839,0] sdhci: Caps: 0x642dc8b2 | Caps_1: 0x00008004
<6>[ 426.585987,0] sdhci: Cmd: 0x0000193a | Max curr: 0x00000000
<6>[ 426.586136,0] sdhci: Resp 1: 0x00000000 | Resp 0: 0x00000900
<6>[ 426.586219,0] sdhci: Resp 3: 0x00000900 | Resp 2: 0x00000000
<6>[ 426.586365,0] sdhci: Host ctl2: 0x00000004
<6>[ 426.586448,0] sdhci: ADMA Err: 0x00000007 | ADMA Ptr: 0x23f40320
<6>[ 426.586597,0] mmc0: clk: 50000000 clk-gated: 0 claimer: mmcqd/0 pwr: 10
<6>[ 426.586681,0] mmc0: rpmstatus[pltfm](runtime-suspend:usage_count:disable_depth)(0:0:0)
<6>[ 426.586829,0] sdhci: ===========================================
<6>[ 426.586914,0] mmc0: bytes to transfer: 401408 transferred: 401408
<3>[ 426.591186,0] mmcblk0: error -110 sending stop command, original cmd response 0x900, card status 0x400900
<3>[ 426.591384,0] mmcblk0: error -110 transferring data, sector 5815296, nr 784, cmd response 0x900, card status 0x0
<4>[ 426.592095,0] blk_update_request: 53 callbacks suppressed
<3>[ 426.592180,0] end_request: I/O error, dev mmcblk0, sector 5815296
<3>[ 426.592481,0] end_request: I/O error, dev mmcblk0, sector 5816080
<3>[ 426.592738,0] end_request: I/O error, dev mmcblk0, sector 5817104
<3>[ 426.593064,0] end_request: I/O error, dev mmcblk0, sector 5818128
<3>[ 426.593321,0] end_request: I/O error, dev mmcblk0, sector 5819152
<3>[ 426.593635,0] end_request: I/O error, dev mmcblk0, sector 5820176
<3>[ 426.593762,0] end_request: I/O error, dev mmcblk0, sector 5824512
<3>[ 426.594080,0] end_request: I/O error, dev mmcblk0, sector 5825536
<3>[ 426.594283,0] end_request: I/O error, dev mmcblk0, sector 15094616

Those IO errors are write requests going to mmcblk0, which is the internal memory. Does this mean the end of the phone? I just have had this phone for less than 2 months and haven't flashed a whole lot (2 times so far). How can the internal memory start going bad so fast? Does anybody know if this is SLC NAND or MLC NAND that they use for internal memory?

I have a full TWRP backup of the phone which I can use to restore. Is it possible to "TRIM" or "ERASE" the NAND somehow to reset it completely? Just like SSDs.

The phone is seeing some weird behaviour during boot where it boot loops during the early boot some times and then eventually boots up fine. But most of the time works fine after that.