[PATCH 3/6] gpio: dt-bindings: Add documentation for gpio controllers on Armada 7K/8K

Hi Rob,
 
 On mer., mai 31 2017, Gregory CLEMENT [off-list ref] wrote:

Hi Rob,
 
 On mer., mai 31 2017, Rob Herring [off-list ref] wrote:

quoted

quoted

 
 Required properties:
 
-- compatible : Should be "marvell,orion-gpio", "marvell,mv78200-gpio"
-  or "marvell,armadaxp-gpio". "marvell,orion-gpio" should be used for
-  Orion, Kirkwood, Dove, Discovery (except MV78200) and Armada
-  370. "marvell,mv78200-gpio" should be used for the Discovery
-  MV78200. "marvel,armadaxp-gpio" should be used for all Armada XP
-  SoCs (MV78230, MV78260, MV78460).
+- compatible : Should be "marvell,orion-gpio", "marvell,mv78200-gpio",
+  "marvell,armadaxp-gpio" or "marvell,armada-8k-gpio".
+
+    "marvell,orion-gpio" should be used for Orion, Kirkwood, Dove,
+    Discovery (except MV78200) and Armada 370. "marvell,mv78200-gpio"
+    should be used for the Discovery MV78200.
+
+    "marvel,armadaxp-gpio" should be used for all Armada XP SoCs
+    (MV78230, MV78260, MV78460).
+
+    "marvell,armada-8k-gpio" should be used for the Armada 7K and 8K
+    SoCs (either from AP or CP), see
+    Documentation/devicetree/bindings/arm/marvell/cp110-system-controller0.txt
+    and
+    Documentation/devicetree/bindings/arm/marvell/ap806-system-controller.txt
+    for specific details about the offset property.
 
 - reg: Address and length of the register set for the device. Only one
   entry is expected, except for the "marvell,armadaxp-gpio" variant
   for which two entries are expected: one for the general registers,
-  one for the per-cpu registers.
+  one for the per-cpu registers. Not used for marvell,armada-8k-gpio.

Why can't use you use reg instead of offset?

I looked for how the other syscon user did, and I found the offset
usage. So I assumed it was the way to do it. But if you wan I can use a
reg property.

I had a closer looked to the binding when syscon is used with several
subnodes. And actually the reg usage is very uncommon, I only find it in
drivers/regulator/pbias-regulator.c but for legacy.

I am not sure that we have any benefit with this reg property: we won't
use the length of the register and we need to add a range property in
the parent node.

An other way to pass this information is to have a different compatible
string which will match the different offset available. In this case the
reg property won't be used in a syscon node. However, while it makes
sens for the difference between AP806 and CP110, it would be strange to
have a different compatible string for gpio bank 1 and gpio bank 2.

So, in the end I would prefer to use the offset. From my point of view
it is better to not use the reg property for two different purposes:
mmio address vs offset in a syscon.

But if you think that from the point of view of the device tree
compliance we have to use the reg property, of course I will change it.

Thanks,

Gregory

Gregory

quoted

Rob

-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com

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-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com