3.2.2.18. MMC/SD
3.2.2.18.1. Introduction
The multimedia card high-speed/SDIO (MMC/SDIO) host controller provides an interface between a local host (LH) such as a microprocessor unit (MPU) or digital signal processor (DSP) and either MMC, SD® memory cards, or SDIO cards and handles MMC/SDIO transactions with minimal LH intervention.
The following image shows the MMC/SD Driver Architecture:
3.2.2.18.2. References
3.2.2.18.3. Acronyms & Definitions
Acronym |
Definition |
|---|---|
MMC |
Multimedia Card |
HS-MMC |
High Speed MMC |
SD |
Secure Digital |
SDHC |
SD High Capacity |
SDIO |
SD Input/Output |
3.2.2.18.4. Features
The SD/MMC driver supports the following features:
Support ADMA for DMA transfers
HS200 speed mode
Support for both built-in and module mode
ext2/ext3/ext4 file system support
3.2.2.18.5. SD: Supported High Speed Modes
SD
Platform |
SDR104 |
DDR50 |
SDR50 |
SDR25 |
SDR12 |
|---|---|---|---|---|---|
AM62* |
Y |
Y |
Y |
Y |
Y |
AM62ax |
Y |
Y |
Y |
Y |
Y |
am64x |
Y |
Y |
Y |
Y |
Y |
am62px |
Y |
Y |
Y |
Y |
Y |
eMMC
Platform |
DDR52 |
HS200 |
HS400 |
|---|---|---|---|
AM62* |
Y |
Y |
N |
AM62ax |
Y |
Y |
N |
am64x |
Y |
Y |
N |
am62px |
Y |
Y |
Y |
3.2.2.18.6. Driver Configuration
The default kernel configuration enables support for MMC/SD driver as built-in to kernel. TI SDHCI driver is used. Following options need to be configured in Linux Kernel for successfully selecting SDHCI driver for AM64x.
Enable SDHCI support (CONFIG_MMC_SDHCI)
Device Drivers -->
MMC/SD/SDIO card support -->
<*> Secure Digital Host Controller Interface support
Enable SDHCI platform helper (CONFIG_MMC_SDHCI_PLTFM)
Device Drivers -->
MMC/SD/SDIO card support -->
Secure Digital Host Controller Interface support -->
<*> SDHCI platform and OF driver helper
Enable SDHCI controller for TI device (CONFIG_MMC_SDHCI_AM654)
Device Drivers -->
MMC/SD/SDIO card support -->
<*> Support for the SDHCI Controller in TI's AM654 SOCs
3.2.2.18. Steps for working around SD card issues in Linux
In some cases, failures can be seen while using some SD cards:
Kernel fails to enumerate SD, thus failing to mount the root file system. This is the case when kernel hangs during boot with a message similar to the following:
[ 2.563279] Waiting for root device PARTUUID=835b171b-02...A lot of SDHCI register dumps logs getting printed continuously:
[ 10.811723] mmc1: Got data interrupt 0x00000002 even though no data operation was in progress. [ 10.820321] mmc1: sdhci: ============ SDHCI REGISTER DUMP =========== [ 10.826745] mmc1: sdhci: Sys addr: 0x00000080 | Version: 0x00001004 [ 10.833169] mmc1: sdhci: Blk size: 0x00007200 | Blk cnt: 0x00000080 [ 10.839593] mmc1: sdhci: Argument: 0x00000000 | Trn mode: 0x00000033 [ 10.846016] mmc1: sdhci: Present: 0x01f70000 | Host ctl: 0x0000001f [ 10.852440] mmc1: sdhci: Power: 0x0000000f | Blk gap: 0x00000080 [ 10.858864] mmc1: sdhci: Wake-up: 0x00000000 | Clock: 0x00000007 [ 10.865287] mmc1: sdhci: Timeout: 0x00000000 | Int stat: 0x00000000 [ 10.871711] mmc1: sdhci: Int enab: 0x03ff008b | Sig enab: 0x03ff008b [ 10.878134] mmc1: sdhci: ACmd stat: 0x00000000 | Slot int: 0x00000000 [ 10.884557] mmc1: sdhci: Caps: 0x3de8c801 | Caps_1: 0x18002407 [ 10.890981] mmc1: sdhci: Cmd: 0x00000c1a | Max curr: 0x00000000 [ 10.897404] mmc1: sdhci: Resp[0]: 0x00000b00 | Resp[1]: 0x0075cf7f [ 10.903828] mmc1: sdhci: Resp[2]: 0x32db7900 | Resp[3]: 0x00000900 [ 10.910251] mmc1: sdhci: Host ctl2: 0x0000000b [ 10.914682] mmc1: sdhci: ADMA Err: 0x00000000 | ADMA Ptr: 0x00000000a2e90200
Given below are the list of various workarounds that can be done in the device tree node to get SD card working. The workarounds are ordered from least to most performance impacting.
Note
All the changes mentioned below, are to be done in the MMCSD device tree node corresponding to the SD instance. This is usually the first (index starting from zero) instance.
Restricting to a given speed mode
By default the kernel driver tries to enumerate an SD card in the highest supported speed mode. Below is the order in which the driver tries to enumerate an SD card:
SDR104
DDR50
SDR50
SD HS
SD legacy
The sdhci-caps-mask can be added to the DT node to cap at a specific mode:
Limit to DDR50:
sdhci-caps-mask = <0x00000003 0x00000000>Limit to SD HS:
sdhci-caps-mask = <0x00000007 0x00000000>Limit to SD legacy:
sdhci-caps-mask = <0x00000007 0x00200000>
The following is an example DT node with the added sdhci-caps-mask:
&sdhci1 { /* SD/MMC */ vmmc-supply = <&vdd_mmc1>; vqmmc-supply = <&vdd_sd_dv>; pinctrl-names = "default"; pinctrl-0 = <&main_mmc1_pins_default>; ti,driver-strength-ohm = <50>; disable-wp; sdhci-caps-mask = <0x00000006 0x00000000>; /* Limiting to SDR50 speed mode */ };
Limiting to SD HS speed mode can also be done by using the property no-1-8-v. This disables switching to 1.8V which is required for UHS speed modes(SDR104, DDR50, SDR50, SDR25, SDR12):
&sdhci1 { /* SD/MMC */ vmmc-supply = <&vdd_mmc1>; vqmmc-supply = <&vdd_sd_dv>; pinctrl-names = "default"; pinctrl-0 = <&main_mmc1_pins_default>; ti,driver-strength-ohm = <50>; disable-wp; no-1-8-v; /* disabling all the UHS modes */ };
Reduce the bus width
The SD interface supports a bus width of 4. It can be reduced to 1 by changing the bus-width device tree property from 4 to 1.
diff --git a/arch/arm64/boot/dts/ti/k3-am62-main.dtsi b/arch/arm64/boot/dts/ti/k3-am62-main.dtsi index 7bbfcb158842..2ef974f7206f 100644 --- a/arch/arm64/boot/dts/ti/k3-am62-main.dtsi +++ b/arch/arm64/boot/dts/ti/k3-am62-main.dtsi @@ -424,7 +424,7 @@ ti,itap-del-sel-sdr12 = <0x0>; ti,itap-del-sel-sdr25 = <0x0>; ti,clkbuf-sel = <0x7>; - bus-width = <4>; + bus-width = <1>; }; sdhci2: mmc@fa20000 {
3.2.2.18.7. Create software partitions in eMMC UDA
In eMMC, the User Data Area (UDA) HW partition is the primary storage
space generally used to flash the rootfs. To prepare the UDA, use
the fdisk command. For ex: fdisk /dev/mmcblkN in
which N is 0 or 1. To find which integer is eMMC use the command
lsblk, like so:
root@<machine>:~# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
mmcblk0 179:0 0 14.8G 0 disk
mmcblk0boot0 179:32 0 31.5M 1 disk
mmcblk0boot1 179:64 0 31.5M 1 disk
mmcblk1 179:96 0 14.8G 0 disk
|-mmcblk1p1 179:97 0 128M 0 part /run/media/boot-mmcblk1p1
`-mmcblk1p2 179:98 0 1.9G 0 part /
Where the eMMC will have hardware partitions mmcblkNboot0
and mmcblkNboot1. The mmcblkN is the eMMC device.
Now we use fdisk /dev/mmcblk0 to create one software partition
in UDA. For documentation on using fdisk, please go to:
fdisk how-to.
3.2.2.18.8. Formatting eMMC partitions from Linux
After creating a partition/s, the partition can be formated with
the mkfs command. For ex: mkfs -t ext4 /dev/mmcblkN
where mmcblkN is the MMC device with the software partition to format.
The general syntax for formatting disk partitions in Linux is:
mkfs [options] [-t type fs-options] device [size]
For example, to format a partition in eMMC UDA to ext4 file system:
root@<machine>:~# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
mmcblk0 179:0 0 14.8G 0 disk
`-mmcblk0p1 179:1 0 14.8G 0 part /run/media/mmcblk0p1
mmcblk0boot0 179:32 0 31.5M 1 disk
mmcblk0boot1 179:64 0 31.5M 1 disk
mmcblk1 179:96 0 14.8G 0 disk
|-mmcblk1p1 179:97 0 128M 0 part /run/media/boot-mmcblk1p1
`-mmcblk1p2 179:98 0 8.8G 0 part /
root@<machine>:~# umount /run/media/mmcblk0p1
[ 43.648532] EXT4-fs (mmcblk0p1): unmounting filesystem f8ecc7b8-ab1a-4240-ab4b-470d242c0539.
root@<machine>:~# mkfs -t ext4 /dev/mmcblk0p1
mke2fs 1.47.0 (5-Feb-2023)
Discarding device blocks: done
Creating filesystem with 3884800 4k blocks and 972944 inodes
Filesystem UUID: 842929dd-4e57-47b6-afa1-c03abc3100b1
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208
Allocating group tables: done
Writing inode tables: done
Creating journal (16384 blocks): done
Writing superblocks and filesystem accounting information: done