Added SD Card page

docs/files/sdcard/helios4_dtb_sd_uhs_linux_stable.patch

@@ -0,0 +1,34 @@
+From 76fa8b1b9cd666312ade19e01de7c4a4103efe9b Mon Sep 17 00:00:00 2001
+Message-Id: <76fa8b1b9cd666312ade19e01de7c4a4103efe9b.1544609988.git.aditya@kobol.io>
+From: Aditya Prayoga <aditya@kobol.io>
+Date: Wed, 12 Dec 2018 15:02:16 +0800
+Subject: [PATCH] arm: dts: armada-388-helios4: Enable High Speed and UHS-I
+ support
+
+Enable High Speed and UHS-I mode support on SD card controller as
+specified by Functional Specification document.
+
+Signed-off-by: Aditya Prayoga <aditya@kobol.io>
+---
+ arch/arm/boot/dts/armada-388-helios4.dts | 5 +++++
+ 1 file changed, 5 insertions(+)
+
+diff --git a/arch/arm/boot/dts/armada-388-helios4.dts b/arch/arm/boot/dts/armada-388-helios4.dts
+index 705adfa..23785ec 100644
+--- a/arch/arm/boot/dts/armada-388-helios4.dts
++++ b/arch/arm/boot/dts/armada-388-helios4.dts
+@@ -253,6 +253,11 @@
+ 				status = "okay";
+ 				vmmc = <&reg_3p3v>;
+ 				wp-inverted;
++				cap-sd-highspeed;
++				sd-uhs-sdr12;
++				sd-uhs-sdr25;
++				sd-uhs-sdr50;
++				sd-uhs-ddr50;
+ 			};
+ 
+ 			usb@58000 {
+-- 
+2.7.4
+

docs/files/sdcard/run_sdcard_test.sh

@@ -0,0 +1,47 @@
+#!/bin/bash
+
+get_flash_information() {
+	# http://www.bunniestudios.com/blog/?page_id=1022
+	while read Device ; do
+		DeviceNode="${Device%/*}"
+		DeviceName="${DeviceNode##*/}"
+		echo -e "\n### ${DeviceName} info:\n"
+		find "${DeviceNode}" -maxdepth 1 -type f | while read ; do
+			NodeName="${REPLY##*/}"
+			echo -e "$(printf "%20s" ${NodeName}): $(cat "${DeviceNode}/${NodeName}" | tr '\n' " ")"
+		done
+
+		oem=$(cat ${DeviceNode}/name)
+		CardName="${DeviceName}-[${oem//[^a-zA-Z0-9]/_}]"
+	done <<< $(find /sys -name oemid)
+} # get_flash_information
+
+get_flash_information > card_info.txt
+LOGFILE="SD_test_${CardName}_$(date +%Y%m%d_%H%M%S).log"
+
+[[ -d /mnt/sdcard ]] || mkdir -p /mnt/sdcard
+mount /dev/mmcblk0p1 /mnt/sdcard
+result=$?
+
+if [[ $result -ne 0 ]]; then
+	echo "failed to mount SD card. Stopped the test"
+	exit 1
+fi
+
+cat card_info.txt | tee -a $LOGFILE
+rm -f card_info.txt
+
+echo -e "\n\n===============================\n\n" >> $LOGFILE
+
+echo "Start benchmarking ..." | tee -a ${LOGFILE}
+echo "Please wait"
+echo -e "\n\n1st run\n\n" | tee -a ${LOGFILE}
+iozone -e -I -a -s 100M -r 4k -r 16k -r 512k -r 1024k -r 16384k -i 0 -i 1 -i 2 -f /mnt/sdcard/iozone-test.dat | tee -a ${LOGFILE}
+echo -e "\n\n===============================\n\n" >> $LOGFILE
+
+echo -e "\n\n2nd run\n\n" | tee -a ${LOGFILE}
+iozone -e -I -a -s 100M -r 4k -r 16k -r 512k -r 1024k -r 16384k -i 0 -i 1 -i 2 -f /mnt/sdcard/iozone-test.dat | tee -a ${LOGFILE}
+echo -e "\n\n===============================\n\n" >> $LOGFILE
+
+umount /mnt/sdcard
+echo "Done" | tee -a ${LOGFILE}

docs/sdcard.md

@@ -0,0 +1,541 @@
+
+Helios4 SoC (Armada 388) SD card controller support up to UHS-I speed mode
+
+![Supported SD Card Speed](/img/sdcard/supported_sdcard_speed.png)
+
+However, it is not compatible with all card even though the cards are declared as UHS-I capable. To keep it compatible with most of card,
+Helios4 device tree only define [Normal Speed mode](https://www.sdcard.org/consumers/choices/speed_class/index.html).
+
+!!! Warning
+    Enabling High Speed and UHS-I support could lead the system unbootable on incompatible card.
+
+## Device Tree Modification
+
+To enable High Speed mode and UHS-I support, Helios4 device tree need to be modified. 
+The following instructions are executed under Helios4.
+
+### Prerequisites
+
+* Helios4 Linux Kernel Source Code
+* Build Essentials package
+
+Install the dependencies and extract the source into ~/src/linux
+
+```
+sudo apt-get -y install build-essential linux-source-next-mvebu
+mkdir -p ~/src/linux
+tar Jxf /usr/src/linux-source-*-mvebu.tar.xz -C ~/src/linux
+```
+
+### Patching and Compilation
+
+Download and apply [this patch](/files/sdcard/helios4_dtb_sd_uhs_linux_stable.patch) to Linux kernel source code.
+
+```
+cd ~/src/linux
+
+wget https://wiki.kobol.io/files/sdcard/helios4_dtb_sd_uhs_linux_stable.patch
+git apply --apply --verbose helios4_dtb_sd_uhs_linux_stable.patch
+```
+
+Compile the device tree into dtb
+
+```
+make armada-388-helios4.dtb
+cp arch/arm/boot/dts/armada-388-helios4.dtb armada-388-helios4.dtb.uhs
+```
+
+!!! Info
+    Precompiled dtb for Linux kernel 4.14 can be found [here](/files/sdcard/armada-388-helios4.dtb.uhs)
+
+Copy new dtb to /boot/dtb/, backup the original dtb and create symlink to new dtb
+
+```
+sudo cp armada-388-helios4.dtb.uhs /boot/dtb/
+cd /boot/dtb/
+sudo cp armada-388-helios4.dtb armada-388-helios4.dtb.ori
+sudo ln -sf armada-388-helios4.dtb.uhs armada-388-helios4.dtb
+```
+
+Reboot the system.
+
+
+## Recovery
+
+If the system become unbootable after applying modified dtb, recover the system by [connecting to Helios4 serial console](/install/#step-4-connect-to-helios4-serial-console)
+and run following commands
+
+```
+setenv fdt_addr 0x2040000
+setenv bootargs "console=ttyS0,115200 root=/dev/mmcblk0p1 rootwait rootfstype=ext4 ubootdev=mmc scandelay ignore_loglevel"
+
+load mmc 0:1 ${fdt_addr} /boot/dtb/armada-388-helios4.dtb.ori
+load mmc 0:1 ${ramdisk_addr_r} /boot/uInitrd
+load mmc 0:1 ${kernel_addr_r} /boot/zImage
+
+setenv fdt_high 0xffffffff
+setenv initrd_high 0xffffffff
+
+bootz ${kernel_addr_r} ${ramdisk_addr_r} ${fdt_addr}
+```
+
+After successfully boot to Linux, restore the original dtb and remove the modified one.
+
+```
+sudo mv -f /boot/dtb/armada-388-helios4.dtb.ori /boot/dtb/armada-388-helios4.dtb
+sudo rm /boot/dtb/armada-388-helios4.dtb.uhs
+```
+
+
+## Testing SD Card Performance
+
+The test methodology adapted from
+[SD card performance - Research guides & tutorials - Armbian forum](https://forum.armbian.com/topic/954-sd-card-performance/)
+with slightly modified parameter to run the test on SD card which mounted under /mnt/sdcard
+
+```
+iozone -e -I -a -s 100M -r 4k -r 16k -r 512k -r 1024k -r 16384k -i 0 -i 1 -i 2 -f /mnt/sdcard/iozone-test.dat
+```
+
+To automate the test, a test script named [run_sdcard_test.sh](/files/sdcard/run_sdcard_test.sh) was created.
+
+### Test Procedure
+
+**1.** Prepare the system to boot from SPI and Rootfs located on USB drive. See [SPI (NOR Flash) page](/spi/).
+
+**2.** Build and replace Helios4 dtb as instructed in [Device Tree Modification](#device-tree-modification).
+
+**3.** Install iozone and download the test script
+
+```
+sudo apt-get -y install iozone
+
+wget https://wiki.kobol.io/files/sdcard/run_sdcard_test.sh
+chmod 755 run_sdcard_test.sh
+
+```
+
+**4.** Override kernel loglevel on every boot
+
+```
+sudo sed -i 's/^exit 0/dmesg -n 8\nexit 0/g' /etc/rc.local
+```
+
+**5.** Make sure armada-388-helios4.dtb point to armada-388-helios4.dtb.uhs
+
+```
+cd /boot/dtb/
+sudo ln -sf armada-388-helios4.dtb.uhs armada-388-helios4.dtb
+```
+
+**6.** Reboot and cancel U-Boot autoboot.
+
+**7.** Read SD card info and boot to Linux
+
+```
+mmc rescan
+mmc info
+bootd
+```
+
+**8.** Observe whether any error/warning on sd card detection in console and check whether sdcard is detected.
+
+```
+dmesg | grep "mmc"
+lsblk
+```
+
+**9.** Run the test script
+
+```
+sudo ./run_sdcard_test.sh
+```
+
+It will display the test progress and also store into log file with filename format
+*SD_test_**<sdcard_address\>**\_[**<sdcard_name\>**]\_**<date_in_YYYYMMDD_HHMMSS\>**.log*
+
+Example filename: SD_test_mmc0:aaaa-[SU08G]_20181212_034241.log
+
+If the SD card is not detected, the test script would exit without saving any log file.
+
+**10.** Change armada-388-helios4.dtb to point back to armada-388-helios4.dtb.ori
+
+```
+cd /boot/dtb/
+sudo ln -sf armada-388-helios4.dtb.ori armada-388-helios4.dtb
+```
+
+**11.** Repeat step **6** until **9** to test in Normal Speed mode.
+
+**12.** Repeat step **5** until **11** for other card.
+
+**13.** Remove kernel loglevel override done in step **4**.
+
+```
+sudo sed -i '/^dmesg -n 8/d' /etc/rc.local
+```
+
+### Tested SD Card
+
+#### Kingston Mobile Card microSDHC (16GB)
+
+![Kingston microSDHC 16GB](/img/sdcard/kingston_16gb.jpg)
+
+*Specifications*
+
+|  |  |
+| -----|------|
+| Product Page | [https://www.kingston.com/en/flash/microsd_cards/sdcb](https://www.kingston.com/en/flash/microsd_cards/sdcb) |
+| Manufacture Id | 0x00009f |
+| OEM ID | 0x5449 |
+| Product Name | SD16G |
+| HW Revision | 0x3 |
+| FW Revision | 0x0 |
+| Serial Number | 0x5b3003c7 |
+| Manufacture Date | 07/2018 |
+| Capacity Standard | SDHC |
+| SD version^ | 1.0 |
+| Mode^ | SD Legacy |
+| Bus Speed^ | 25000000 |
+| Bus Width^ | 4-bit |
+
+!!! Notes
+    ^ Value taken from U-Boot "mmc info".
+
+*Test Result*
+
+Failed!
+
+```
+mmc0: new SDHC card at address 0001
+mmcblk0: mmc0:0001 SD16G 14.6 GiB
+ mmcblk0: p1
+```
+
+The card was detected by Linux but when the test runnning, kernel console constantly emits
+
+```
+mmcblk0: error -110 transferring data, sector 2433024, nr 1024, cmd response 0x900, card status 0xb00
+mmcblk0: retrying using single block read
+mmc0: Timeout waiting for hardware interrupt.
+mmc0: sdhci: ============ SDHCI REGISTER DUMP ===========
+mmc0: sdhci: Sys addr:  0x00000000 | Version:  0x00000202
+mmc0: sdhci: Blk size:  0x00007200 | Blk cnt:  0x00000030
+mmc0: sdhci: Argument:  0x00252400 | Trn mode: 0x00000033
+mmc0: sdhci: Present:   0x01e70206 | Host ctl: 0x00000011
+mmc0: sdhci: Power:     0x0000000f | Blk gap:  0x00000000
+mmc0: sdhci: Wake-up:   0x00000000 | Clock:    0x0000fa07
+mmc0: sdhci: Timeout:   0x00000003 | Int stat: 0x00000000
+mmc0: sdhci: Int enab:  0x02ff008b | Sig enab: 0x02ff008b
+mmc0: sdhci: AC12 err:  0x00000000 | Slot int: 0x00000000
+mmc0: sdhci: Caps:      0x25fcc8b2 | Caps_1:   0x00002f77
+mmc0: sdhci: Cmd:       0x0000123a | Max curr: 0x00000000
+mmc0: sdhci: Resp[0]:   0x00000900 | Resp[1]:  0x47305b30
+mmc0: sdhci: Resp[2]:   0x53443136 | Resp[3]:  0x009f5449
+mmc0: sdhci: Host ctl2: 0x00000008
+mmc0: sdhci: ADMA Err:  0x00000000 | ADMA Ptr: 0x7f0b95d0
+mmc0: sdhci: ============================================
+mmcblk0: error -110 transferring data, sector 2434048, nr 1024, cmd response 0x900, card status 0xb00
+mmc0: Timeout waiting for hardware interrupt.
+```
+
+And the still did not finished the test after 8 hours.
+
+---
+
+#### Sandisk Ultra microSD UHS-I Card For Smartphone (32GB)
+
+![Sandisk Ultra smartphone 32GB](/img/sdcard/sandisk_ultra_uhs-i_for_smartphone_32gb.jpg)
+
+*Specifications*
+
+|  |  |
+| -----|------|
+| Product Page | [https://www.sandisk.com/home/memory-cards/microsd-cards/ultra-microsd-for-smartphones](https://www.sandisk.com/home/memory-cards/microsd-cards/ultra-microsd-for-smartphones) |
+| Manufacture Id | 0x000003 |
+| OEM ID | 0x5344 |
+| Product Name | SL32G |
+| HW Revision | 0x8 |
+| FW Revision | 0x0 |
+| Serial Number | 0x0c9daa71 |
+| Manufacture Date | 04/2014 |
+| Capacity Standard | SDHC |
+| SD version^ | 3.0 |
+| Mode^ | SD High Speed (50MHz) |
+| Bus Speed^ | 50000000 |
+| Bus Width^ | 4-bit |
+
+!!! Notes
+    ^ Value taken from U-Boot "mmc info".
+
+*Test Result*
+
+```
+mmc0: new ultra high speed DDR50 SDHC card at address aaaa
+mmcblk0: mmc0:aaaa SL32G 29.7 GiB
+ mmcblk0: p1
+mmc0: Tuning failed, falling back to fixed sampling clock
+mmcblk0: error -84 transferring data, sector 62333824, nr 8, cmd response 0x900, card status 0xb00
+```
+
+Even though there are some errors, the test finished without much improvement.
+
+![Sandisk Ultra smartphone 32GB Test Result](/img/sdcard/test_result_sandisk_ultra_uhs-i_for_smartphone_32gb.png)
+
+---
+
+#### Sandisk Ultra microSD UHS-I Card For Smartphone (16GB)
+
+![Sandisk Ultra smartphone 16GB](/img/sdcard/sandisk_ultra_uhs-i_for_smartphone_16gb.jpg)
+
+*Specifications*
+
+|  |  |
+| -----|------|
+| Product Page | [https://www.sandisk.com/home/memory-cards/microsd-cards/ultra-microsd-for-smartphones](https://www.sandisk.com/home/memory-cards/microsd-cards/ultra-microsd-for-smartphones) |
+| Manufacture Id | 0x000003 |
+| OEM ID | 0x5344 |
+| Product Name | SL16G |
+| HW Revision | 0x8 |
+| FW Revision | 0x0 |
+| Serial Number | 0xa5253c77 |
+| Manufacture Date | 04/2017 |
+| Capacity Standard | SDHC |
+| SD version^ | 3.0 |
+| Mode^ | SD High Speed (50MHz) |
+| Bus Speed^ | 50000000 |
+| Bus Width^ | 4-bit |
+
+!!! Notes
+    ^ Value taken from U-Boot "mmc info".
+
+*Test Result*
+
+Failed!
+
+```
+mmc0: new ultra high speed DDR50 SDHC card at address aaaa
+mmcblk0: mmc0:aaaa SL16G 14.8 GiB
+mmcblk0: error -84 sending status command, retrying
+mmc0: Tuning failed, falling back to fixed sampling clock
+mmcblk0: error -84 sending status command, retrying
+mmc0: Tuning failed, falling back to fixed sampling clock
+mmcblk0: error -84 sending status command, aborting
+mmc0: Tuning failed, falling back to fixed sampling clock
+mmcblk0: unable to read partition table
+mmc0: card aaaa removed
+mmc0: new high speed SDHC card at address aaaa
+mmcblk0: mmc0:aaaa SL16G 14.8 GiB
+mmcblk0: error -84 sending status command, retrying
+mmcblk0: error -84 sending stop command, original cmd response 0x900, card status 0x900
+mmcblk0: error -84 transferring data, sector 0, nr 8, cmd response 0x900, card status 0x0
+mmcblk0: error -84 sending stop command, original cmd response 0x900, card status 0x900
+mmcblk0: error -84 transferring data, sector 0, nr 8, cmd response 0x900, card status 0x0
+```
+
+The card was not detected by Linux.
+
+---
+
+#### Sandisk Ultra microSD UHS-I Card 48MBps (16GB)
+
+![Sandisk Ultra 48MBps](/img/sdcard/sandisk_ultra_uhs-i_48mbps_16gb.jpg)
+
+*Specifications*
+
+|  |  |
+| -----|------|
+| Product Page | [https://www.sandisk.com/home/memory-cards/microsd-cards/ultra-microsd-48mbs](https://www.sandisk.com/home/memory-cards/microsd-cards/ultra-microsd-48mbs) |
+| Manufacture Id | 0x000003 |
+| OEM ID | 0x5344 |
+| Product Name | SL16G |
+| HW Revision | 0x8 |
+| FW Revision | 0x0 |
+| Serial Number | 0x349f2b91 |
+| Manufacture Date | 01/2016 |
+| Capacity Standard | SDHC |
+| SD version^ | 3.0 |
+| Mode^ | SD High Speed (50MHz) |
+| Bus Speed^ | 50000000 |
+| Bus Width^ | 4-bit |
+
+!!! Notes
+    ^ Value taken from U-Boot "mmc info".
+
+*Test Result*
+
+Failed!
+
+```
+mmc0: new ultra high speed DDR50 SDHC card at address aaaa
+mmcblk0: mmc0:aaaa SL16G 14.8 GiB
+mmc0: Tuning failed, falling back to fixed sampling clock
+mmcblk0: error -84 transferring data, sector 0, nr 8, cmd response 0x900, card status 0xb00
+ mmcblk0: p1
+mmcblk0: error -84 transferring data, sector 10240, nr 8, cmd response 0x900, card status 0xb00
+mmcblk0: error -84 transferring data, sector 8784, nr 72, cmd response 0x900, card status 0xb00
+mmcblk0: error -84 transferring data, sector 8784, nr 72, cmd response 0x900, card status 0xb00
+mmcblk0: retrying using single block read
+mmcblk0: error -84 transferring data, sector 8856, nr 360, cmd response 0x900, card status 0xb00
+mmcblk0: error -84 transferring data, sector 8856, nr 360, cmd response 0x900, card status 0xb00
+```
+
+The card was not detected by Linux.
+
+---
+
+#### Sandisk Ultra microSD UHS-I Card 30MBps (8GB)
+
+![Sandisk Ultra 30 MBps](/img/sdcard/sandisk_ultra_uhs-i_8gb.jpg)
+
+*Specifications*
+
+|  |  |
+| -----|------|
+| Product Page | [https://www.sandisk.com/home/memory-cards/microsd-cards/ultra-microsd-for-smartphones](https://www.sandisk.com/home/memory-cards/microsd-cards/ultra-microsd-for-smartphones) |
+| Manufacture Id | 0x000003 |
+| OEM ID | 0x5344 |
+| Product Name | SU08G |
+| HW Revision | 0x8 |
+| FW Revision | 0x0 |
+| Serial Number | 0x2369e07f |
+| Manufacture Date | 12/2013 |
+| Capacity Standard | SDHC |
+| SD version^ | 3.0 |
+| Mode^ | SD High Speed (50MHz) |
+| Bus Speed^ | 50000000 |
+| Bus Width^ | 4-bit |
+
+!!! Notes
+    ^ Value taken from U-Boot "mmc info".
+
+*Test Result*
+
+```
+mmc0: new ultra high speed DDR50 SDHC card at address aaaa
+mmcblk0: mmc0:aaaa SU08G 7.40 GiB
+mmc0: Tuning failed, falling back to fixed sampling clock
+mmcblk0: error -84 transferring data, sector 0, nr 8, cmd response 0x900, card status 0xb00
+ mmcblk0: p1
+```
+
+Even though there are some errors, the test finished. Many of test cases see performance reduction.
+
+![Sandisk Ultra 30 MBps Test Result](/img/sdcard/test_result_sandisk_ultra_uhs-i_8gb.png)
+
+---
+
+#### Strontium Nitro MicroSD Card (16GB)
+
+![Strontium](/img/sdcard/strontium_nitro_16gb.jpg)
+
+*Specifications*
+
+|  |  |
+| -----|------|
+| Product Page | [http://www.strontium.biz/products/memory-cards/mobile-memory-cards/#seven](http://www.strontium.biz/products/memory-cards/mobile-memory-cards/#seven) |
+| Manufacture Id | 0x000084 |
+| OEM ID | 0x5446 |
+| Product Name | SD |
+| HW Revision | 0x0 |
+| FW Revision | 0x0 |
+| Serial Number | 0x954b266b |
+| Manufacture Date | 09/2016 |
+| Capacity Standard | SDHC |
+| SD version^ | 3.0 |
+| Mode^ | SD High Speed (50MHz) |
+| Bus Speed^ | 50000000 |
+| Bus Width^ | 1-bit |
+
+!!! Notes
+    ^ Value taken from U-Boot "mmc info".
+
+*Test Result*
+
+```
+mmc0: Tuning failed, falling back to fixed sampling clock
+mmc0: new ultra high speed DDR50 SDHC card at address 0001
+mmcblk0: mmc0:0001 SD 14.6 GiB
+ mmcblk0: p1
+mmc0: Tuning failed, falling back to fixed sampling clock
+mmc0: Tuning failed, falling back to fixed sampling clock
+```
+
+Even though there are some warnings, the test finished.
+
+![Strontium Nitro Test Result](/img/sdcard/test_result_strontium_nitro_16gb.png)
+
+---
+
+#### Toshiba MicroSD Exceria Pro (16GB)
+
+
+![Toshiba Exceria Pro](/img/sdcard/toshiba_exceria_pro_16gb.jpg)
+
+*Specifications*
+
+|  |  |
+| -----|------|
+| Product Page | [https://www.toshiba-memory.com/products/toshiba-microsd-cards-exceria-pro-m401/](https://www.toshiba-memory.com/products/toshiba-microsd-cards-exceria-pro-m401/) |
+| Manufacture Id | 0x000002 |
+| OEM ID | 0x544d |
+| Product Name | UC0C5 |
+| HW Revision | 0x5 |
+| FW Revision | 0x0 |
+| Serial Number | 0xd2a0e6a3 |
+| Manufacture Date | 11/2016 |
+| Capacity Standard | SDHC |
+| SD version^ | 3.0 |
+| Mode^ | SD High Speed (50MHz) |
+| Bus Speed^ | 50000000 |
+| Bus Width^ | 4-bit |
+
+!!! Notes
+    ^ Value taken from U-Boot "mmc info".
+
+*Test Result*
+
+Failed!
+
+```
+mmc0: error -84 whilst initialising SD card
+```
+
+The card was not detected by Linux.
+
+---
+
+#### Transcend microSDHC Premium (8GB)
+
+![Transcend](/img/sdcard/transcend_premium_8gb.jpg)
+
+*Specifications*
+
+|  |  |
+| -----|------|
+| Product Page | [https://www.transcend-info.com/Products/No-320](https://www.transcend-info.com/Products/No-320) |
+| Manufacture Id | 0x000074 |
+| OEM ID | 0x4a45 |
+| Product Name | USD |
+| HW Revision | 0x1 |
+| FW Revision | 0x0 |
+| Serial Number | 0x4568e585 |
+| Manufacture Date | 06/2014 |
+| Capacity Standard | SDHC |
+| SD version^ | 3.0 |
+| Mode^ | SD High Speed (50MHz) |
+| Bus Speed^ | 50000000 |
+| Bus Width^ | 1-bit |
+
+!!! Notes
+    ^ Value taken from U-Boot "mmc info".
+
+*Test Result*
+
+```
+mmc0: new high speed SDHC card at address b368
+mmcblk0: mmc0:b368 USD   7.45 GiB
+ mmcblk0: p1
+```
+
+![Transcend Premium Test Result](/img/sdcard/test_result_transcend_premium_8gb.png)

mkdocs.yml

@@ -74,6 +74,7 @@ pages:
   - LED : 'led.md'
   - PWM (Fan) : 'pwm.md'
   - SPI (NOR Flash) : 'spi.md'
+  - SD Card : 'sdcard.md'
 - Development:
   - Armbian : 'armbian.md'
   - FreeBSD : 'freebsd.md'