Re: [PATCH] phy: micrel: add of configuration for LED mode

On Tuesday 18 March 2014 17:21:04 Ben Dooks wrote:

On 18/03/14 17:11, Laurent Pinchart wrote:

quoted

On Tuesday 18 March 2014 16:56:06 Laurent Pinchart wrote:

quoted

On Thursday 27 February 2014 10:30:51 Ben Dooks wrote:

quoted

On 27/02/14 09:15, Mark Rutland wrote:

quoted

On Wed, Feb 26, 2014 at 11:48:00AM +0000, Ben Dooks wrote:

quoted

Add support for the led-mode property for the following PHYs
which have a single LED mode configuration value.

KSZ8001 and KSZ8041 which both use register 0x1e bits 15,14 and
KSZ8021, KSZ8031 and KSZ8051 which use register 0x1f bits 5,4
to control the LED configuration.

Signed-off-by: Ben Dooks <redacted>
---

  Documentation/devicetree/bindings/net/micrel.txt | 18 +++++++++
  drivers/net/phy/micrel.c                         | 49
  ++++++++++++++--
  2 files changed, 63 insertions(+), 4 deletions(-)
  create mode 100644 Documentation/devicetree/bindings/net/micrel.txt

diff --git a/Documentation/devicetree/bindings/net/micrel.txt

b/Documentation/devicetree/bindings/net/micrel.txt new file mode
100644
index 0000000..98a3e61

--- /dev/null
+++ b/Documentation/devicetree/bindings/net/micrel.txt

@@ -0,0 +1,18 @@
+Micrel PHY properties.
+
+These properties cover the base properties Micrel PHYs.
+
+Optional properties:
+
+ - micrel,led-mode : LED mode value to set for PHYs with configurable

LEDs.
+
+              Configure the LED mode with single value. The list of
PHYs and
+	      the bits that are currently supported:
+
+	      KSZ8001: register 0x1e, bits 15..14
+	      KSZ8041: register 0x1e, bits 15..14
+	      KSZ8021: register 0x1f, bits 5..4
+	      KSZ8031: register 0x1f, bits 5..4
+	      KSZ8051: register 0x1f, bits 5..4
+
+              See the respective PHY datasheet for the mode values.

What do these mean, roughly,, and why can the kernel not decide how to
cnofigure these?

Board specific, in the case of the Lager one of the LEDs is connected
to the ethernet mac block to indicate link, however the default mode
is not for just "Link" so we have to change it.

quoted

In general we prefer to not place raw register values in the DT, and
I'd
like to know why we'd have to here.

I could copy out stuff from the data-sheet, but I was trying to avoid a
copy and paste job.

I quite agree with Mark here, I would prefer not to list register values
in
DT bindings. However, the hardware hardware diversity doesn't help us
abstracting LED modes.

The following table summarizes LED usage options.

Device              Mode LED usage
-------------------------------------------------------------------------

--- 8001 (LED[3:0])     00   Collision / Full-Duplex / Speed /

Link/Activity>> 
                     01   Activity / Full-Duplex/Collision / Speed / Link
                     10   Activity / Full-Duplex / 100Mbps Link / 10Mbps
                     Link
                     11   Reserved

80[23]1 (LED[0])    00   Link/Activity
                     01   Link
                     10   Reserved
                     11   Reserved

80[45]1 (LED[1:0])  00   Speed / Link/Activity
                     01   Activity / Link
                     10   Reserved
                     11   Reserved

While LED mode could be described by LED0 mode using "link-activity" or
"link" strings for the 80[2345]1 chips, the 8001 makes that slightly more
complex and shows that future chips might not conform to any scheme we
come up with now.

I thus have no strong preference for a string-based mode description over
using an integer. However, if we keep the integer value, I wouldn't use
the register value directly, but would instead use the mode field value
as an integer in the 0-3 range. This would remove knowledge of the PHY
control register layout from the DT node content, and bring more
consistency to the values.

And I realize that this is what you've done already in the implementation
:-/ I'll send a patch to clarify the DT bindings documentation if you
don't mind, after hearing Mark's opinion on the issue.

Do we need strings for what is basically a single-setup post reset which it
makes no sense for the user to ever update?

If it was a standard setting I would have voted to try and standardize the 
values. As it isn't, we probably don't.

What would you think about defining macros for the LED mode values somewhere 
in include/dt-bindings/ ?

-- 
Regards,

Laurent Pinchart

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