Re: [net-next: PATCH v3 2/6] net: mdiobus: Introduce fwnode_mdbiobus_register()

Hi,

czw., 24 cze 2021 o 00:10 Marcin Wojtas [off-list ref] napisał(a):

Hi,

śr., 23 cze 2021 o 22:22 Andrew Lunn [off-list ref] napisał(a):

quoted

On Mon, Jun 21, 2021 at 07:30:24PM +0200, Marcin Wojtas wrote:

quoted

This patch introduces a new helper function that
wraps acpi_/of_ mdiobus_register() and allows its
usage via common fwnode_ interface.

Fall back to raw mdiobus_register() in case CONFIG_FWNODE_MDIO
is not enabled, in order to satisfy compatibility
in all future user drivers.

Signed-off-by: Marcin Wojtas <redacted>
---
 include/linux/fwnode_mdio.h    | 12 +++++++++++
 drivers/net/mdio/fwnode_mdio.c | 22 ++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/include/linux/fwnode_mdio.h b/include/linux/fwnode_mdio.h
index faf603c48c86..13d4ae8fee0a 100644
--- a/include/linux/fwnode_mdio.h
+++ b/include/linux/fwnode_mdio.h

@@ -16,6 +16,7 @@ int fwnode_mdiobus_phy_device_register(struct mii_bus *mdio,
 int fwnode_mdiobus_register_phy(struct mii_bus *bus,
                              struct fwnode_handle *child, u32 addr);

+int fwnode_mdiobus_register(struct mii_bus *bus, struct fwnode_handle *fwnode);
 #else /* CONFIG_FWNODE_MDIO */
 int fwnode_mdiobus_phy_device_register(struct mii_bus *mdio,
                                     struct phy_device *phy,

@@ -30,6 +31,17 @@ static inline int fwnode_mdiobus_register_phy(struct mii_bus *bus,
 {
      return -EINVAL;
 }
+
+static inline int fwnode_mdiobus_register(struct mii_bus *bus,
+                                       struct fwnode_handle *fwnode)
+{
+     /*
+      * Fall back to mdiobus_register() function to register a bus.
+      * This way, we don't have to keep compat bits around in drivers.
+      */
+
+     return mdiobus_register(mdio);
+}
 #endif

I looked at this some more, and in the end i decided it was O.K.

quoted

+/**
+ * fwnode_mdiobus_register - bring up all the PHYs on a given MDIO bus and
+ *   attach them to it.
+ * @bus: Target MDIO bus.
+ * @fwnode: Pointer to fwnode of the MDIO controller.
+ *
+ * Return values are determined accordingly to acpi_/of_ mdiobus_register()
+ * operation.
+ */
+int fwnode_mdiobus_register(struct mii_bus *bus, struct fwnode_handle *fwnode)
+{
+     if (is_acpi_node(fwnode))
+             return acpi_mdiobus_register(bus, fwnode);
+     else if (is_of_node(fwnode))
+             return of_mdiobus_register(bus, to_of_node(fwnode));
+     else
+             return -EINVAL;

I wounder if here you should call mdiobus_register(mdio), rather than
-EINVAL?

I don't have a strong opinion.

Currently (and in foreseeable future) we support only DT/ACPI as a
firmware description, reaching the last "else" means something really
wrong. The case of lack of DT/ACPI and the fallback is handled on the
include/linux/fwnode_mdio.h level.

quoted

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

Unfortunately I have to withdraw this patch, as well as xgmac_mdio
one. In case the fwnode_/of_/acpi_mdio are built as modules, we get a
cycle dependency during depmod phase of modules_install, eg.:

depmod: ERROR: Cycle detected: fwnode_mdio -> of_mdio -> fwnode_mdio
depmod: ERROR: Found 2 modules in dependency cycles!

OR:

depmod: ERROR: Cycle detected: acpi_mdio -> fwnode_mdio -> acpi_mdio
depmod: ERROR: Found 2 modules in dependency cycles!

The proper solution would be to merge contents of
acpi_mdiobus_register and of_mdiobus_register inside the common
fwnode_mdiobus_register (so that the former would only call the
latter). However this change seems feasible, but I'd expect it to be a
patchset bigger than this one alone and deserves its own thorough
review and testing, as it would affect huge amount of current
of_mdiobus_register users.

Given above, for now I will resubmit this patchset in the shape as
proposed in v1, i.e. using the 'if' condition explicitly in mvmdio
driver.

Best regards,
Marcin