[Galaxy S 4 i9505 Original Android Development] webmaster33:
I found the following external sd relevant log information in kmsg.log file:

[ 12.435272] mblog: 1 fstab entries for the external SD
[ 12.435394] mblog: [Attempt 1/10] Finding and mounting external SD
[ 12.435607] mblog: Matching devices against pattern: /devices/platform/msm_sdcc.2/mmc_host/mmc2*
[ 13.163726] [SSP] Updated 88487 bytes / 107440 bytes
[ 13.340209] synaptics_rmi4_i2c 3-0020: synaptics_init_power_on: until lcd does not turn on.
[ 13.435913] mblog: [Attempt 2/10] Finding and mounting external SD
[ 13.436035] mblog: Matching devices against pattern: /devices/platform/msm_sdcc.2/mmc_host/mmc2*
[ 13.924163] max77693-muic max77693-muic: func:max77693_muic_usb_detect info->muic_data->sw_path:0
[ 14.197753] [SSP] Updated 103374 bytes / 107440 bytes
[ 14.349060] synaptics_rmi4_i2c 3-0020: synaptics_init_power_on: until lcd does not turn on.
[ 14.436370] mblog: [Attempt 3/10] Finding and mounting external SD
[ 14.436553] mblog: Matching devices against pattern: /devices/platform/msm_sdcc.2/mmc_host/mmc2*
[ 14.957031] [SSP] Firmware download is success.(107440 bytes)
[ 15.080261] [SSP]: debug_work_func(0) - Sensor state: 0x0, RC: 0, MS: 0
[ 15.080383] [SSP] : debug_work_func firmware downloading state = 3
[ 15.340240] synaptics_rmi4_i2c 3-0020: synaptics_init_power_on: until lcd does not turn on.
[ 15.436828] mblog: [Attempt 4/10] Finding and mounting external SD
[ 15.436950] mblog: Matching devices against pattern: /devices/platform/msm_sdcc.2/mmc_host/mmc2*
[ 16.340209] synaptics_rmi4_i2c 3-0020: synaptics_init_power_on: until lcd does not turn on.
[ 16.437255] mblog: [Attempt 5/10] Finding and mounting external SD
[ 16.437377] mblog: Matching devices against pattern: /devices/platform/msm_sdcc.2/mmc_host/mmc2*
[ 17.340209] synaptics_rmi4_i2c 3-0020: synaptics_init_power_on: until lcd does not turn on.
[ 17.437683] mblog: [Attempt 6/10] Finding and mounting external SD
[ 17.437866] mblog: Matching devices against pattern: /devices/platform/msm_sdcc.2/mmc_host/mmc2*
[ 17.960235] [SSP] forced_to_download_binary, DL state = 4
[ 17.962554] [SSP] MCU device ID = 85, reading ID = 85
[ 17.962707] [SSP] Sensor Posision A : 3, G : 3, M: 5, P: 0
[ 17.963592] ssp_enable, enable = 1, old enable = 1
[ 17.964355] [SSP]: Proximity Threshold - 0, 0
[ 17.964874] [SSP]: set_hw_offset: x: 0, y: 0, z: 0
[ 17.964965] ssp_sensorhub_report_notice: reset
[ 17.965057] [SSP] forced_to_download_binary, DL state = 5
[ 17.965698] [SSP] MCU Firm Rev : New = 14111200
[ 18.340240] synaptics_rmi4_i2c 3-0020: synaptics_init_power_on: until lcd does not turn on.
[ 18.438110] mblog: [Attempt 7/10] Finding and mounting external SD
[ 18.438293] mblog: Matching devices against pattern: /devices/platform/msm_sdcc.2/mmc_host/mmc2*
[ 19.340240] synaptics_rmi4_i2c 3-0020: synaptics_init_power_on: until lcd does not turn on.
[ 19.438537] mblog: [Attempt 8/10] Finding and mounting external SD
[ 19.438720] mblog: Matching devices against pattern: /devices/platform/msm_sdcc.2/mmc_host/mmc2*
[ 20.340240] synaptics_rmi4_i2c 3-0020: synaptics_init_power_on: until lcd does not turn on.
[ 20.438964] mblog: [Attempt 9/10] Finding and mounting external SD
[ 20.439147] mblog: Matching devices against pattern: /devices/platform/msm_sdcc.2/mmc_host/mmc2*
[ 21.340240] synaptics_rmi4_i2c 3-0020: synaptics_init_power_on: until lcd does not turn on.
[ 21.439392] mblog: [Attempt 10/10] Finding and mounting external SD
[ 21.439575] mblog: Matching devices against pattern: /devices/platform/msm_sdcc.2/mmc_host/mmc2*
[ 21.439788] mblog: Failed to mount /raw/extsd
[ 21.439910] mblog: Failed to mount fstab

Note the "Failed to mount /raw/extsd" line after 10 attempts.

I think this is a bug available since about 2016 November or December. [MENTION=4277844]chenxiaolong[/MENTION]: could you check this issue?