[PATCH] Documentation: document dma device use for mcb
STALE2088d
LANDED
From: Johannes Thumshirn <hidden>
Date: 2020-12-18 15:37:08
Also in:
lkml
Subsystem:
documentation, men chameleon bus (mcb), the rest · Maintainers:
Jonathan Corbet, Johannes Thumshirn, Linus Torvalds
Landed in mainline as 7594bb08fb68 on 2021-01-11.
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 <redacted> Signed-off-by: Johannes Thumshirn <redacted> --- Documentation/driver-api/men-chameleon-bus.rst | 12 ++++++++++++ 1 file changed, 12 insertions(+)
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 */
--
2.26.2