Re: [PATCH v4.1] phylib: Add device reset GPIO support

On 12/07/2017 08:20 PM, Sergei Shtylyov wrote:

quoted

The PHY devices sometimes do have their reset signal (maybe even power
supply?) tied to some GPIO and sometimes it also does happen that a boot
loader does not leave it deasserted. So far this issue has been attacked
from (as I believe) a wrong angle: by teaching the MAC driver to manipulate
the GPIO in question; that solution, when applied to the device trees, led
to adding the PHY reset GPIO properties to the MAC device node, with one
exception: Cadence MACB driver which could handle the "reset-gpios" prop
in a PHY device subnode. I believe that the correct approach is to teach
the 'phylib' to get the MDIO device reset GPIO from the device tree node
corresponding to this device -- which this patch is doing...

Note that I had to modify the AT803x PHY driver as it would stop working
otherwise -- it made use of the reset GPIO for its own purposes...

Signed-off-by: Sergei Shtylyov <sergei.shtylyov-M4DtvfQ/ZS1MRgGoP+s0PdBPR1lH4CV8@public.gmane.org>
Acked-by: Rob Herring <redacted>
[geert: Propagate actual errors from fwnode_get_named_gpiod()]
[geert: Avoid destroying initial setup]
[geert: Consolidate GPIO descriptor acquiring code]
Signed-off-by: Geert Uytterhoeven <redacted>

[...]

quoted

diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 2df7b62c1a36811e..8f8b7747c54bc478 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c

[...]

quoted

@@ -48,9 +49,26 @@
  int mdiobus_register_device(struct mdio_device *mdiodev)
  {
+    struct gpio_desc *gpiod = NULL;
+
      if (mdiodev->bus->mdio_map[mdiodev->addr])
          return -EBUSY;
+    /* Deassert the optional reset signal */

    Umm, but why deassert it here for such a short time?

quoted

+    if (mdiodev->dev.of_node)
+        gpiod = fwnode_get_named_gpiod(&mdiodev->dev.of_node->fwnode,
+                           "reset-gpios", 0, GPIOD_OUT_LOW,
+                           "PHY reset");
+    if (PTR_ERR(gpiod) == -ENOENT)
+        gpiod = NULL;
+    else if (IS_ERR(gpiod))
+        return PTR_ERR(gpiod);

    Hm, returning on error with reset deasserted?

   Oops, error means we couldn't drive the GPIO at all...
   The 1st question remains though...

[...]

MBR, Sergei
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