net: dsa: mv88e6xxx: Support LED control

This adds control over the hardware LEDs in the Marvell
MV88E6xxx DSA switch and enables it for MV88E6352.

This fixes an imminent problem on the Inteno XG6846 which
has a WAN LED that simply do not work with hardware
defaults: driver amendment is necessary.

The patch is modeled after Christian Marangis LED support
code for the QCA8k DSA switch, I got help with the register
definitions from Tim Harvey.

After this patch it is possible to activate hardware link
indication like this (or with a similar script):

  cd /sys/class/leds/Marvell\ 88E6352:05:00:green:wan/
  echo netdev > trigger
  echo 1 > link

This makes the green link indicator come up on any link
speed. It is also possible to be more elaborate, like this:

  cd /sys/class/leds/Marvell\ 88E6352:05:00:green:wan/
  echo netdev > trigger
  echo 1 > link_1000
  cd /sys/class/leds/Marvell\ 88E6352:05:01:amber:wan/
  echo netdev > trigger
  echo 1 > link_100

Making the green LED come on for a gigabit link and the
amber LED come on for a 100 mbit link.

Each port has 2 LED slots (the hardware may use just one or
none) and the hardware triggers are specified in four bits per
LED, and some of the hardware triggers are only available on the
SFP (fiber) uplink. The restrictions are described in the
port.h header file where the registers are described. For
example, selector 1 set for LED 1 on port 5 or 6 will indicate
Fiber 1000 (gigabit) and activity with a blinking LED, but
ONLY for an SFP connection. If port 5/6 is used with something
not SFP, this selector is a noop: something else need to be
selected.

After the previous series rewriting the MV88E6xxx DT
bindings to use YAML a "leds" subnode is already valid
for each port, in my scratch device tree it looks like
this:

   leds {
     #address-cells = <1>;
     #size-cells = <0>;

     led@0 {
       reg = <0>;
       color = <LED_COLOR_ID_GREEN>;
       function = LED_FUNCTION_LAN;
       default-state = "off";
       linux,default-trigger = "netdev";
     };
     led@1 {
       reg = <1>;
       color = <LED_COLOR_ID_AMBER>;
       function = LED_FUNCTION_LAN;
       default-state = "off";
     };
   };

This DT config is not yet configuring everything: when the netdev
default trigger is assigned the hw acceleration callbacks are
not called, and there is no way to set the netdev sub-trigger
type (such as link_1000) from the device tree, such as if you want
a gigabit link indicator. This has to be done from userspace at
this point.

We add LED operations to all switches in the 6352 family:
6172, 6176, 6240 and 6352.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20241001-mv88e6xxx-leds-v4-1-cc11c4f49b18@linaro.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/net/dsa/mv88e6xxx/Kconfig b/drivers/net/dsa/mv88e6xxx/Kconfig
index e3181d5471df..64ae3882d17c 100644
--- a/drivers/net/dsa/mv88e6xxx/Kconfig
+++ b/drivers/net/dsa/mv88e6xxx/Kconfig
@@ -17,3 +17,13 @@ config NET_DSA_MV88E6XXX_PTP
 	help
 	  Say Y to enable PTP hardware timestamping on Marvell 88E6xxx switch
 	  chips that support it.
+
+config NET_DSA_MV88E6XXX_LEDS
+	bool "LED support for Marvell 88E6xxx"
+	default y
+	depends on NET_DSA_MV88E6XXX
+	depends on LEDS_CLASS=y || LEDS_CLASS=NET_DSA_MV88E6XXX
+	depends on LEDS_TRIGGERS
+	help
+	  This enabled support for controlling the LEDs attached to the
+	  Marvell 88E6xxx switch chips.