Linux Core MMC SD User's Guide

Linux Core MMC/SD User's Guide

LCPD

Introduction

TI devices have eMMC/SD/SDIO host controller to which either MMC, SD memory cards, or SDIO cards can be connected. The controller is programmed using omap_hsmmc driver.

This wiki page provides usage information of omap_hsmmc Linux driver.

Supported Features

• Speed:

mmc uhs sdr12

mmc uhs sdr25

mmc uhs sdr50

mmc uhs ddr50

mmc uhs sdr104

• ADMA2
• 4bit/8bit mode
• Max Frequency upto 192MHz

Features NOT supported

Following features are not supported currently:

• PIO mode

Supported Features in Board

Board	Instance	HS200	DDR	UHS SDR104	UHS DDR50	UHS SDR50	UHS SDR25	UHS SDR12
DRA7-EVM	MMC1	X	X	Y	Y	Y	Y	Y
Example	Example	Example	Example	Example	Example	Example	Example	Example
Example	Example	Example	Example	Example	Example	Example	Example	Example
Example	Example	Example	Example	Example	Example	Example	Example	Example
Example	Example	Example	Example	Example	Example	Example	Example	Example
Example	Example	Example	Example	Example	Example	Example	Example	Example
Example	Example	Example	Example	Example	Example	Example	Example	Example
Example	Example	Example	Example	Example	Example	Example	Example	Example
Example	Example	Example	Example	Example	Example	Example	Example	Example
Example	Example	Example	Example	Example	Example	Example	Example	Example

References

1. MMCA Homepage [https://www.jedec.org/]
2. SD ORG Homepage [http://www.sdcard.org/]

Features

The SD driver supports following features

• The driver is built in-kernel (part of vmlinux)
• SD cards including SD High Speed and SDHC cards
• Uses block bounce buffer to aggregate scattered blocks

Features NOT supported

Following features are not supported currently:

• PIO mode

Driver Configuration

The default kernel configuration enables support for MMC/SD(built-in to kernel). OMAP MMC/SD driver is reused for DM81xx.

The selection of MMC/SD/SDIO driver can be modified as follows: start Linux Kernel Configuration tool.

$ make menuconfig  ARCH=arm

• Select Device Drivers from the main menu.

...
...
Kernel Features  --->
Boot options  --->
CPU Power Management  --->
Floating point emulation  --->
Userspace binary formats  --->
Power management options  --->
[*] Networking support  --->
Device Drivers  --->
...
...

Building into Kernel

• Select MMC/SD/SDIO card support from the menu.

...
...
[*] USB support  --->
< > Ultra Wideband devices (EXPERIMENTAL)  --->
<*> MMC/SD/SDIO card support  --->
< > Sony MemoryStick card support (EXPERIMENTAL)  --->
...
...

• Select OMAP HS MMC driver

...
[ ] MMC debugging
[ ] Assume MMC/SD cards are non-removable (DANGEROUS) 
   *** MMC/SD/SDIO Card Drivers ***
<*> MMC block device driver
[*]  Use bounce buffer for simple hosts
...
<*>   TI OMAP High Speed Multimedia Card Interface support 
...

Building as Loadable Kernel Module

• To build the above components as modules, press 'M' key after navigating to config entries preceded with '< >' as shown below:

...
...
[*] USB support  --->
< > Ultra Wideband devices (EXPERIMENTAL)  --->
<M> MMC/SD/SDIO card support  --->
< > Sony MemoryStick card support (EXPERIMENTAL)  --->
...

• Select OMAP HS MMC driver to be built as module

...
[ ] MMC debugging
[ ] Assume MMC/SD cards are non-removable (DANGEROUS) 
   *** MMC/SD/SDIO Card Drivers ***
<*> MMC block device driver
[*]  Use bounce buffer for simple hosts
...
<*>   TI OMAP High Speed Multimedia Card Interface support 
...

• After doing module selection, exit and save the kernel configuration when prompted.
• Now build the kernel and modules form Linux build host as

$ make uImage
$ make modules

• Following modules will be built

mmc_core.ko
mmc_block.ko
omap_hsmmc.ko

• Boot the newly built kernel and transfer the above mentioned .ko files to the filesystem
• Navigate to the directory containing these modules and insert them form type the following commands in console to insert the modules in specified order:

# insmod mmc_core.ko
# insmod mmc_block.ko
# insmod omap_hsmmc.ko

• If 'udev' is running and the SD card is already inserted, the devices nodes will be created and filesystem will be automatically mounted if exists on the card.

Suspend to Memory support

This driver supports suspend to memory functionality. To use the same, the following steps need to be followed. Note that these are not enabled in the configuration by default. If this change is not made, suspend to memory might fail if I/O is happening on MMC/SD simultaneously.

• Select Device Drivers from the main menu.

...
...
Kernel Features  --->
Boot options  --->
CPU Power Management  --->
Floating point emulation  --->
Userspace binary formats  --->
Power management options  --->
[*] Networking support  --->
Device Drivers  --->
...
...

• Select MMC/SD/SDIO card support from the menu.

...
...
[*] USB support  --->
< > Ultra Wideband devices (EXPERIMENTAL)  --->
<*> MMC/SD/SDIO card support  --->
< > Sony MemoryStick card support (EXPERIMENTAL)  --->
...
...

• Select Assume MMC/SD cards are non-removable option.

...
[ ] MMC debugging
[*] Assume MMC/SD cards are non-removable (DANGEROUS) 
*** MMC/SD/SDIO Card Drivers ***
<*> MMC block device driver
[*]  Use bounce buffer for simple hosts
...
<*>   TI OMAP High Speed Multimedia Card Interface support 
...