diff options
| author | Johannes Thumshirn | 2020-12-19 00:35:25 +0900 |
|---|---|---|
| committer | Jonathan Corbet | 2021-01-11 13:26:13 -0700 |
| commit | 7594bb08fb68ffe7e77c2e77ecc33c1e21631ead (patch) | |
| tree | ca28fad089ff59fd187b9045a59ebcf84a5ed01e /Documentation/driver-api/men-chameleon-bus.rst | |
| parent | 7178b4a7d69ca96db6e0bb3593c202c2dd323089 (diff) | |
Documentation: document dma device use for mcb
Hannes reported a problem with setting up dma transfers on a mcb device.
The problem boiled down to the use of a wrong 'device' for the dma
functions.
Document how to setup dma transfers for a IP core on a mcb carrier.
Reported-by: Hannes Duerr <Hannes.Duerr@duagon.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/3bdc8f76b30c2b0e2a2bfab06c2e73797ddc9384.1608305690.git.johannes.thumshirn@wdc.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/driver-api/men-chameleon-bus.rst')
| -rw-r--r-- | Documentation/driver-api/men-chameleon-bus.rst | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/Documentation/driver-api/men-chameleon-bus.rst b/Documentation/driver-api/men-chameleon-bus.rst index 1b1f048aa748..6f0b9ee47595 100644 --- a/Documentation/driver-api/men-chameleon-bus.rst +++ b/Documentation/driver-api/men-chameleon-bus.rst @@ -18,6 +18,7 @@ MEN Chameleon Bus 4.1 The driver structure 4.2 Probing and attaching 4.3 Initializing the driver + 4.4 Using DMA Introduction @@ -173,3 +174,14 @@ module at the MCB core:: The module_mcb_driver() macro can be used to reduce the above code:: module_mcb_driver(foo_driver); + +Using DMA +--------- + +To make use of the kernel's DMA-API's function, you will need to use the +carrier device's 'struct device'. Fortunately 'struct mcb_device' embeds a +pointer (->dma_dev) to the carrier's device for DMA purposes:: + + ret = dma_set_mask_and_coherent(&mdev->dma_dev, DMA_BIT_MASK(dma_bits)); + if (rc) + /* Handle errors */ |