[Fire TV General] YourNameInHere:
looks like i'm on the right way :D

[...]
Nov 20 19:58:58 kernel: [45074.287457] mmc0: req done (CMD3): 0: 00000500 00000000 00000000 00000000
Nov 20 19:58:58 kernel: [45074.287471] mmc0: clock 400000Hz busmode 2 powermode 2 cs 0 Vdd 21 width 0 timing 0
Nov 20 19:58:58 kernel: [45074.287473] OWN DEBUG: 2 (1=MMC_BUSMODE_OPENDRAIN, 2=MMC_BUSMODE_PUSHPULL)
Nov 20 19:58:58 kernel: [45074.287473] OWN DEBUG: 0 (0=MMC_CS_DONTCARE, 1=MMC_CS_HIGH, 2=MMC_CS_LOW)
Nov 20 19:58:58 kernel: [45074.287473] OWN DEBUG: 2 (0=MMC_POWER_OFF, 1=MMC_POWER_UP, 2=MMC_POWER_ON)
Nov 20 19:58:58 kernel: [45074.287473] OWN DEBUG: 0 (0=MMC_BUS_WIDTH_1, 2=MMC_BUS_WIDTH_4, 3=MMC_BUS_WIDTH_8)
Nov 20 19:58:58 kernel: [45074.287473] OWN DEBUG: 1 (0=MMC_SIGNAL_VOLTAGE_330, 1=MMC_SIGNAL_VOLTAGE_180, 2=MMC_SIGNAL_VOLTAGE_120)
Nov 20 19:58:58 kernel: [45074.287493] mmc0: starting CMD9 arg 00010000 flags 00000007
Nov 20 19:58:58 kernel: [45074.287502] rtsx_pci_sdmmc rtsx_pci_sdmmc.0: sd_send_cmd_get_rsp: SD/MMC CMD 9, arg = 0x00010000
Nov 20 19:58:58 kernel: [45074.288417] rtsx_pci_sdmmc rtsx_pci_sdmmc.0: cmd->resp[0] = 0xd00f0032
Nov 20 19:58:58 kernel: [45074.288419] rtsx_pci_sdmmc rtsx_pci_sdmmc.0: cmd->resp[1] = 0x0f5903ff
Nov 20 19:58:58 kernel: [45074.288421] rtsx_pci_sdmmc rtsx_pci_sdmmc.0: cmd->resp[2] = 0xffffffff
Nov 20 19:58:58 kernel: [45074.288422] rtsx_pci_sdmmc rtsx_pci_sdmmc.0: cmd->resp[3] = 0x8a404000
Nov 20 19:58:58 kernel: [45074.288423] mmc0: req done (CMD9): 0: d00f0032 0f5903ff ffffffff 8a404000
Nov 20 19:58:58 kernel: [45074.288425] mmc0: starting CMD7 arg 00010000 flags 00000015
Nov 20 19:58:58 kernel: [45074.288434] rtsx_pci_sdmmc rtsx_pci_sdmmc.0: sd_send_cmd_get_rsp: SD/MMC CMD 7, arg = 0x00010000
Nov 20 19:58:58 kernel: [45074.288990] rtsx_pci_sdmmc rtsx_pci_sdmmc.0: cmd->resp[0] = 0x00000700
Nov 20 19:58:58 kernel: [45074.288991] mmc0: req done (CMD7): 0: 00000700 00000000 00000000 00000000
Nov 20 19:58:58 kernel: [45074.288993] mmc0: starting CMD8 arg 00000000 flags 000000b5
Nov 20 19:58:58 kernel: [45074.288995] mmc0: blksz 512 blocks 1 flags 00000200 tsac 100 ms nsac 0
Nov 20 19:58:58 kernel: [45074.289005] rtsx_pci_sdmmc rtsx_pci_sdmmc.0: sd_read_data: SD/MMC CMD8
Nov 20 19:58:58 kernel: [45074.289674] mmc0: req done (CMD8): 0: 00000000 00000000 00000000 00000000
Nov 20 19:58:58 kernel: [45074.289676] mmc0: 512 bytes transferred: 0
Nov 20 19:58:58 kernel: [45074.289678] mmc0: clock 25000000Hz busmode 2 powermode 2 cs 0 Vdd 21 width 0 timing 0
Nov 20 19:58:58 kernel: [45074.289680] OWN DEBUG: 2 (1=MMC_BUSMODE_OPENDRAIN, 2=MMC_BUSMODE_PUSHPULL)
Nov 20 19:58:58 kernel: [45074.289680] OWN DEBUG: 0 (0=MMC_CS_DONTCARE, 1=MMC_CS_HIGH, 2=MMC_CS_LOW)
Nov 20 19:58:58 kernel: [45074.289680] OWN DEBUG: 2 (0=MMC_POWER_OFF, 1=MMC_POWER_UP, 2=MMC_POWER_ON)
Nov 20 19:58:58 kernel: [45074.289680] OWN DEBUG: 0 (0=MMC_BUS_WIDTH_1, 2=MMC_BUS_WIDTH_4, 3=MMC_BUS_WIDTH_8)
Nov 20 19:58:58 kernel: [45074.289680] OWN DEBUG: 1 (0=MMC_SIGNAL_VOLTAGE_330, 1=MMC_SIGNAL_VOLTAGE_180, 2=MMC_SIGNAL_VOLTAGE_120)
Nov 20 19:58:58 kernel: [45074.289718] mmc0: new MMC card at address 0001
Nov 20 19:58:58 kernel: [45074.289803] mmcblk0: mmc0:0001 SEM08G 0 B
[...]

at this moment i saw the block device but it wasn't accessible. :crying:

Sadly this happens only once while testing yesterday - maybe due to suboptimal vccq voltage.

I will do further testing at weekend and post the results.

P.S. Box is still alive :victory: