Re: [PATCHv2] dt: bindings: Add support for CSI1 bus

Hi Ivaylo,

On Fri, Jan 20, 2017 at 09:59:13AM +0200, Ivaylo Dimitrov wrote:

Hi,

On 19.01.2017 23:49, Sakari Ailus wrote:

quoted

Hi Pavel,

On Wed, Jan 11, 2017 at 11:53:35PM +0100, Pavel Machek wrote:

quoted

From: Sakari Ailus <redacted>

In the vast majority of cases the bus type is known to the driver(s)
since a receiver or transmitter can only support a single one. There
are cases however where different options are possible.

The existing V4L2 OF support tries to figure out the bus type and
parse the bus parameters based on that. This does not scale too well
as there are multiple serial busses that share common properties.

Some hardware also supports multiple types of busses on the same
interfaces.

Document the CSI1/CCP2 property strobe. It signifies the clock or
strobe mode.

Signed-off-by: Sakari Ailus <redacted>
Signed-off-by: Ivaylo Dimitrov <redacted>
Signed-off-by: Pavel Machek <redacted>

diff --git a/Documentation/devicetree/bindings/media/video-interfaces.txt b/Documentation/devicetree/bindings/media/video-interfaces.txt
index 9cd2a36..08c4498 100644
--- a/Documentation/devicetree/bindings/media/video-interfaces.txt
+++ b/Documentation/devicetree/bindings/media/video-interfaces.txt

@@ -76,6 +76,11 @@ Optional endpoint properties
  mode horizontal and vertical synchronization signals are provided to the
  slave device (data source) by the master device (data sink). In the master
  mode the data source device is also the source of the synchronization signals.
+- bus-type: data bus type. Possible values are:
+  0 - MIPI CSI2
+  1 - parallel / Bt656
+  2 - MIPI CSI1
+  3 - CCP2

Actually, thinking about this again --- we only need to explictly specify
busses if we're dealing with either CCP2 or CSI-1. The vast majority of the
actual busses are and continue to be CSI-2 or either parallel or Bt.656. As
they can be implicitly detected, we would have an option to just drop values
0 and 1 from above, i.e. only leave CSI-1 and CCP2. For now, specifying
CSI-2 or parallel / Bt.656 adds no value as the old DT binaries without
bus-type will need to be supported anyway.

quoted

- bus-width: number of data lines actively used, valid for the parallel busses.
- data-shift: on the parallel data busses, if bus-width is used to specify the
  number of data lines, data-shift can be used to specify which data lines are

@@ -112,7 +117,8 @@ Optional endpoint properties
  should be the combined length of data-lanes and clock-lanes properties.
  If the lane-polarities property is omitted, the value must be interpreted
  as 0 (normal). This property is valid for serial busses only.
-
+- strobe: Whether the clock signal is used as clock or strobe. Used
+  with CCP2, for instance.

How about the "ti,strobe-clock-inv" I proposed? No-one seems to know what
this really truly means... or just drop it if it's not really needed.

Not really :), see https://www.spinics.net/lists/linux-media/msg99802.html
and https://www.spinics.net/lists/linux-media/msg99800.html

"clock/strobe", and "strobe-inv" are two distinct properties, see CSI1B_CTRL
description in OMAP TRM. BTW there is another property that is needed for
both n900 cameras to operate correctly (VP_CLK_POL, bit 12 from the same
reg), but that can be added later on when we have the other bits in place.

Oh, indeed, my mistake. Please ignore that comment.

-- 
Sakari Ailus
e-mail: sakari.ailus-X3B1VOXEql0@public.gmane.org	XMPP: sailus-PCDdDYkjdNMDXYZnReoRVg@public.gmane.org
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