cmd/dma: documentation

This explains how
to use the new U-Boot command 'dmareset'.

Signed-off-by: Brian Sune <briansune@gmail.com>
Reviewed-by: Tom Rini <trini@konsulko.com>

doc/usage/cmd/dmareset.rst

@@ -0,0 +1,55 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+.. index::
+   single: dmareset (command)
+
+dmareset command
+================
+
+Synopsis
+--------
+
+::
+
+    Usage: dmareset <channel 0-7> [<channel 0-7> ...]
+    dmareset - Release PL330 DMA channel reset(s) for SoCFPGA
+
+    Usage:
+    dmareset <channel 0-7> [<channel 0-7> ...]  - release reset for one or more DMA channels
+
+Description
+-----------
+
+Release the DMA channel reset *channel*.
+
+Parameters
+----------
+
+channel
+    DMA channel number
+
+Example
+-------
+
+Release DMA channel(s)::
+
+    => dmareset 0
+    PL330 DMA channel 0 reset released
+    => dmareset 1
+    PL330 DMA channel 1 reset released
+    => dmareset 0 1
+    PL330 DMA channel 0 reset released
+    PL330 DMA channel 1 reset released
+
+
+Configuration
+-------------
+
+The dmareset command is only available if CONFIG_CMD_C5_PL330_DMA=y in
+"Shell scripting commands".
+
+Return value
+------------
+
+If the command succeeds, the return value $? is set to 0 (true).
+If an error occurs, the return value $? is set to 1 (false).

doc/usage/index.rst

@@ -57,6 +57,7 @@ Shell commands
    cmd/cpu
    cmd/cpuid
    cmd/cyclic
+   cmd/dmareset
    cmd/dm
    cmd/ebtupdate
    cmd/echo