MMC Test Framework¶

Overview¶

The mmc_test framework is designed to test the performance and reliability of host controller drivers and all devices handled by the MMC subsystem. This includes not only MMC devices but also SD cards and other devices supported by the subsystem.

The framework provides a variety of tests to evaluate different aspects of the host controller and device interactions, such as read and write performance, data integrity, and error handling. These tests help ensure that the host controller drivers and devices operate correctly under various conditions.

The mmc_test framework is particularly useful for:

Verifying the functionality and performance of MMC and SD host controller drivers.
Ensuring compatibility and reliability of MMC and SD devices.
Identifying and diagnosing issues in the MMC subsystem.

The results of the tests are logged in the kernel log, providing detailed information about the test outcomes and any encountered issues.

Note: whatever is on your card will be overwritten by these tests.

Initialization¶

To use the mmc_test framework, follow these steps:

Enable the MMC Test Framework:

Ensure that the CONFIG_MMC_TEST kernel configuration option is enabled. This can be done by configuring the kernel:
```
make menuconfig
```
Navigate to:

Device Drivers --->

<*> MMC/SD/SDIO card support --->
[*] MMC host test driver

Alternatively, you can enable it directly in the kernel configuration file:
```
echo "CONFIG_MMC_TEST=y" >> .config
```
Rebuild and install the kernel if necessary.
Load the MMC Test Module:

If the mmc_test framework is built as a module, you need to load it using modprobe:
```
modprobe mmc_test
```

Binding the MMC Card for Testing¶

To enable MMC testing, you need to unbind the MMC card from the mmcblk driver and bind it to the mmc_test driver. This allows the mmc_test framework to take control of the MMC card for testing purposes.

Identify the MMC card:
```
ls /sys/bus/mmc/devices/
```
This will list the MMC devices, such as mmc0:0001.

Unbind the MMC card from the mmcblk driver:

echo 'mmc0:0001' > /sys/bus/mmc/drivers/mmcblk/unbind

Bind the MMC card to the mmc_test driver:

echo 'mmc0:0001' > /sys/bus/mmc/drivers/mmc_test/bind

After binding, you should see a line in the kernel log indicating that the card has been claimed for testing:

mmc_test mmc0:0001: Card claimed for testing.

Usage - Debugfs Entries¶

Once the mmc_test framework is enabled, you can interact with the following debugfs entries located in /sys/kernel/debug/mmc0/mmc0:0001:

test:

This file is used to run specific tests. Write the test number to this file to execute a test.
```
echo <test_number> > /sys/kernel/debug/mmc0/mmc0:0001/test
```
The test result is indicated in the kernel log info. You can view the kernel log using the dmesg command or by checking the log file in /var/log/.
```
dmesg | grep mmc0
```
Example:

To run test number 4 (Basic read with data verification):
```
echo 4 > /sys/kernel/debug/mmc0/mmc0:0001/test
```
Check the kernel log for the result:
```
dmesg | grep mmc0
```
testlist:

This file lists all available tests. You can read this file to see the list of tests and their corresponding numbers.
```
cat /sys/kernel/debug/mmc0/mmc0:0001/testlist
```
The available tests are listed in the table below:

Test	Test Name	Test Description
0	Run all tests	Runs all available tests
1	Basic write	Performs a basic write operation of a single 512-Byte block to the MMC card without data verification.
2	Basic read	Same for read
3	Basic write (with data verification)	Performs a basic write operation of a single 512-Byte block to the MMC card with data verification by reading back the written data and comparing it.
4	Basic read (with data verification)	Same for read
5	Multi-block write	Performs a multi-block write operation of 8 blocks (each 512 bytes) to the MMC card.
6	Multi-block read	Same for read
7	Power of two block writes	Performs write operations with block sizes that are powers of two, starting from 1 byte up to 256 bytes, to the MMC card.
8	Power of two block reads	Same for read
9	Weird sized block writes	Performs write operations with varying block sizes starting from 3 bytes and increasing by 7 bytes each iteration, up to 511 bytes, to the MMC card.
10	Weird sized block reads	same for read
11	Badly aligned write	Performs write operations with buffers starting at different alignments (0 to 7 bytes offset) to test how the MMC card handles unaligned data transfers.
12	Badly aligned read	same for read
13	Badly aligned multi-block write	same for multi-write
14	Badly aligned multi-block read	same for multi-read
15	Proper xfer_size at write (Start failure)	intentionally create a broken transfer by modifying the MMC request in a way that it will not perform as expected, e.g. use MMC_WRITE_BLOCK for a multi-block transfer
16	Proper xfer_size at read (Start failure)	same for read
17	Proper xfer_size at write (Midway failure)	same for 2 blocks
18	Proper xfer_size at read (Midway failure)	same for read
19	Highmem write	use a high memory page
20	Highmem read	same for read
21	Multi-block highmem write	same for multi-write
22	Multi-block highmem read	same for mult-read
23	Best-case read performance	Performs 512K sequential read (non sg)
24	Best-case write performance	same for write
25	Best-case read performance (Into scattered pages)	Same using sg
26	Best-case write performance (From scattered pages)	same for write
27	Single read performance	By transfer size
28	Single write performance	By transfer size
29	Single trim performance	By transfer size
30	Consecutive read performance	By transfer size
31	Consecutive write performance	By transfer size
32	Consecutive trim performance	By transfer size
33	Random read performance	By transfer size
34	Random write performance	By transfer size
35	Large sequential read	Into scattered pages
36	Large sequential write	From scattered pages
37	Write performance	With blocking req 4k to 4MB
38	Write performance	With non-blocking req 4k to 4MB
39	Read performance	With blocking req 4k to 4MB
40	Read performance	With non-blocking req 4k to 4MB
41	Write performance	Blocking req 1 to 512 sg elems
42	Write performance	Non-blocking req 1 to 512 sg elems
43	Read performance	Blocking req 1 to 512 sg elems
44	Read performance	Non-blocking req 1 to 512 sg elems
45	Reset test
46	Commands during read	No Set Block Count (CMD23)
47	Commands during write	No Set Block Count (CMD23)
48	Commands during read	Use Set Block Count (CMD23)
49	Commands during write	Use Set Block Count (CMD23)
50	Commands during non-blocking	Read - use Set Block Count (CMD23)
51	Commands during non-blocking	Write - use Set Block Count (CMD23)

Test Results¶

The results of the tests are logged in the kernel log. Each test logs the start, end, and result of the test. The possible results are:

OK: The test completed successfully.
FAILED: The test failed.
UNSUPPORTED (by host): The test is unsupported by the host.
UNSUPPORTED (by card): The test is unsupported by the card.
ERROR: An error occurred during the test.

Example Kernel Log Output¶

When running a test, you will see log entries similar to the following in the kernel log:

[ 1234.567890] mmc0: Starting tests of card mmc0:0001...
[ 1234.567891] mmc0: Test case 4. Basic read (with data verification)...
[ 1234.567892] mmc0: Result: OK
[ 1234.567893] mmc0: Tests completed.

In this example, test case 4 (Basic read with data verification) was executed, and the result was OK.

Contributing¶

Contributions to the mmc_test framework are welcome. Please follow the standard Linux kernel contribution guidelines and submit patches to the appropriate maintainers.

Contact¶

For more information or to report issues, please contact the MMC subsystem maintainers.