doc: man-page for mtest

Provide a man-page for the mtest command.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

doc/usage/cmd/mtest.rst

@@ -0,0 +1,66 @@
+.. SPDX-License-Identifier: GPL-2.0+
+.. Copyright 2022, Heinrich Schuchardt <xypron.glpk@gmx.de>
+
+mtest command
+=============
+
+Synopsis
+--------
+
+::
+
+    mtest [start [end [pattern [iterations]]]]
+
+Description
+-----------
+
+The *mtest* command tests the random access memory. It writes long values, reads
+them back and checks for differences. The test can be interrupted with CTRL+C.
+
+The default test uses *pattern* as first value to be written and varies it
+between memory addresses.
+
+An alternative test can be selected with CONFIG_SYS_ALT_MEMTEST=y. It uses
+multiple hard coded bit patterns.
+
+With CONFIGSYS_ALT_MEMTEST_BITFLIP=y a further test is executed. It writes long
+values offset by half the size of long and checks if writing to the one address
+causes bit flips at the other address.
+
+start
+	start address of the memory range tested, defaults to
+	CONFIG_SYS_MEMTEST_START
+
+end
+	end address of the memory range tested, defaults to
+	CONFIG_SYS_MEMTEST_END. If CONFIGSYS_ALT_MEMTEST_BITFLIP=y, a value will
+	be written to this address. Otherwise it is excluded from the range.
+
+pattern
+	pattern to be written to memory. This is a 64bit value on 64bit systems
+	and a 32bit value on 32bit systems. It defaults to 0. The value is
+	ignored if CONFIG_SYS_ALT_MEMTEST=y.
+
+iterations
+	number of test repetitions. If the value is not provided the test will
+	not terminate automatically. Enter CTRL+C instead.
+
+Examples
+--------
+
+::
+
+    => mtest 1000 2000 0x55aa55aa55aa55aa 10
+    Testing 00001000 ... 00002000:
+    Pattern AA55AA55AA55AA55  Writing...  Reading...
+    Tested 16 iteration(s) with 0 errors.
+
+Configuration
+-------------
+
+The mtest command is enabled by CONFIG_CMD_MEMTEST=y.
+
+Return value
+------------
+
+The return value $? is 0 (true) if the command succeeds, 1 (false) otherwise.

doc/usage/index.rst

@@ -63,6 +63,7 @@ Shell commands
    cmd/mbr
    cmd/md
    cmd/mmc
+   cmd/mtest
    cmd/part
    cmd/pause
    cmd/pinmux