On 06/24/2016 10:10 AM, Rob Herring wrote:

On Wed, Jun 22, 2016 at 02:46:14PM +0200, Thierry Reding wrote:

quoted

On Wed, Jun 22, 2016 at 05:17:22PM +0530, Laxman Dewangan wrote:

quoted

Tegra186 has 8 different PWM controller and each controller has only
one output. Earlier generation SoCs have the 4 PWM output per controller.

Add DT node compatible for Tegra186.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
---
  Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.txt | 10 ++++++----
  1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.txt b/Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.txt
index c52f03b..2851b2d 100644
--- a/Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.txt
+++ b/Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.txt

@@ -1,10 +1,12 @@
  Tegra SoC PWFM controller

  Required properties:
-- compatible: For Tegra20, must contain "nvidia,tegra20-pwm".  For Tegra30,
-  must contain "nvidia,tegra30-pwm".  Otherwise, must contain
-  "nvidia,<chip>-pwm", plus one of the above, where <chip> is tegra114,
-  tegra124, tegra132, or tegra210.
+- compatible: For Tegra20, must contain "nvidia,tegra20-pwm".
+	      For Tegra30, must contain "nvidia,tegra30-pwm".
+	      For Tegra114, Tegra124, Tegra132, Tegra210 must contain
+	      "nvidia,<chip>-pwm", plus one of the above, where <chip> is
+	      tegra114, tegra124, tegra132, or tegra210.
+	      For Tegra186, must contain "nvidia,tegra186-pwm".

Rob, I recall discussing this with you a couple of weeks ago, but fail
to remember the outcome and can't find a link to the discussion either.
Wasn't there a new standard way of documenting this kind of compatible
string list?

We did? This is fine for me. However, "plus one of the above" is not
clear. That means either is valid? If all are "the same" I would expect
that only nvidia,tegra20-pwm is the fallback. I'm guessing this is
docuemnting what happened in practice though. Probably should update the
doc and dts files to reflect desired practice rather than what may be in
the wild.

FWIW, I've started listing the legal values as explicit separate bullet 
items rather than prose. See the example below - all those entries are 
just one string simply due to the HW design it represents, but each 
entry could be a list (i.e. is a complete compatible value):

- compatible
     Array of strings.
     One of:
     - "nvidia,tegra186-gpio".
     - "nvidia,tegra186-gpio-aon".

could be expanded as e.g.

     - "nvidia,tegra999-gpio", "nvidia,tegra186-gpio"
     ...