On Mon, Mar 11, 2019 at 6:11 PM Maxime Ripard [off-list ref] wrote:

On Fri, Mar 08, 2019 at 12:09:47AM +0800, Chen-Yu Tsai wrote:

quoted

On Thu, Mar 7, 2019 at 11:48 PM Maxime Ripard [off-list ref] wrote:

quoted

On Thu, Mar 07, 2019 at 05:15:20PM +0200, Georgi Djakov wrote:

quoted

Hi,

On 3/5/19 18:14, Robin Murphy wrote:

quoted

On 05/03/2019 15:53, Maxime Ripard wrote:

quoted

Hi,

On Fri, Mar 01, 2019 at 07:48:15PM +0200, Georgi Djakov wrote:

quoted

On 2/11/19 17:02, Maxime Ripard wrote:

quoted

The current DT bindings assume that the DMA will be performed by the
devices through their parent DT node, and rely on that assumption
for the
address translation using dma-ranges.

However, some SoCs have devices that will perform DMA through
another bus,
with separate address translation rules. We therefore need to
express that
relationship, through the special interconnect name "dma".

Signed-off-by: Maxime Ripard <redacted>
---
  Documentation/devicetree/bindings/interconnect/interconnect.txt |
3 +++
  1 file changed, 3 insertions(+)

diff --git
a/Documentation/devicetree/bindings/interconnect/interconnect.txt
b/Documentation/devicetree/bindings/interconnect/interconnect.txt
index 5a3c575b387a..e69fc2d992c3 100644

--- a/Documentation/devicetree/bindings/interconnect/interconnect.txt
+++ b/Documentation/devicetree/bindings/interconnect/interconnect.txt

@@ -51,6 +51,9 @@ interconnect-names : List of interconnect path

name strings sorted in the same
               interconnect-names to match interconnect paths with
interconnect
               specifier pairs.
  +                     Reserved interconnect names:
+                         * dma: Path from the device to the main
memory of the system

Bikeshed: As it's from the device to the main memory, maybe here we can
also denote this my calling the path dma-mem or dma-memory. For other
paths, we are trying to mention both the source and the destination and
maybe it would be good to be consistent although this is special one.

I'm not sure I understand what you mean. You'd like two interconnect
names, one called dma-memory, and one memory-dma?

Hmm, yes, it's not like "dma" describes an actual source or destination
either :/

IIUC, it's a path (bus) that a dma device use to access some memory
(read or/and write). So i have used source-destination above more in the
sense of initiator-target or master-slave. My suggestion was just to
change the reserved interconnect name from "dma" to "dma-mem" or
"dma-memory".

If dma is an issue in itself, maybe we can call it "device-memory" ?

Might I ask what happens if the device can both DMA to and from memory?

We can create another one called memory-device if that's needed?

Works for me as long as it doesn't get confusing. BTW I think it should be
X-to-Y, instead of X-Y, as the latter can be taken as a noun-phrase.

quoted

IIRC the display frontends, backends, and mixers all have writeback
capability, using the same interconnect port.

I think in both cases it's the same path. The camera driver also need
to have that offset, even though it's a producer and not a consumer,
and the VPU does too.

Yeah. The VPU is the obvious bi-directional example.

ChenYu

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