On 20.09.2021 18:11, Florian Fainelli wrote:

On 9/20/21 5:34 AM, Rafał Miłecki wrote:

quoted

From: Rafał Miłecki <rafal@milecki.pl>

Check ethernet controller DT node for "mdio" subnode and use it with
of_mdiobus_register() when present. That allows specifying MDIO and its
PHY devices in a standard DT based way.

This is required for BCM53573 SoC support which has an MDIO attached
switch.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
---
  drivers/net/ethernet/broadcom/bgmac-bcma-mdio.c | 6 +++++-
  1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/broadcom/bgmac-bcma-mdio.c b/drivers/net/ethernet/broadcom/bgmac-bcma-mdio.c
index 6ce80cbcb48e..086739e4f40a 100644
--- a/drivers/net/ethernet/broadcom/bgmac-bcma-mdio.c
+++ b/drivers/net/ethernet/broadcom/bgmac-bcma-mdio.c

@@ -10,6 +10,7 @@
  
  #include <linux/bcma/bcma.h>
  #include <linux/brcmphy.h>
+#include <linux/of_mdio.h>
  #include "bgmac.h"
  
  static bool bcma_mdio_wait_value(struct bcma_device *core, u16 reg, u32 mask,

@@ -211,6 +212,7 @@ struct mii_bus *bcma_mdio_mii_register(struct bgmac *bgmac)
  {
  	struct bcma_device *core = bgmac->bcma.core;
  	struct mii_bus *mii_bus;
+	struct device_node *np;
  	int err;
  
  	mii_bus = mdiobus_alloc();

@@ -229,7 +231,9 @@ struct mii_bus *bcma_mdio_mii_register(struct bgmac *bgmac)
  	mii_bus->parent = &core->dev;
  	mii_bus->phy_mask = ~(1 << bgmac->phyaddr);
  
-	err = mdiobus_register(mii_bus);
+	np = of_get_child_by_name(core->dev.of_node, "mdio");

I believe this leaks np and the use case is not exactly clear to me
here. AFAICT the Northstar SoCs have two MDIO controllers: one for
internal PHYs and one for external PHYs which how you would attach a
switch to the chip (in chipcommonA). Is 53573 somewhat different here?
What is the MDIO bus driver that is being used?

of_get_child_by_name() doesn't seem to increase refcount or anything and
I think it's how most drivers handle it. I don't think it should leak.

BCM53573 is a built with some older blocks. Please check:

4ebd50472899 ("ARM: BCM53573: Initial support for Broadcom BCM53573 SoCs")
     BCM53573 series is a new family with embedded wireless. By marketing
     people it's sometimes called Northstar but it uses different CPU and has
     different architecture so we need a new symbol for it.
     Fortunately it shares some peripherals with other iProc based SoCs so we
     will be able to reuse some drivers/bindings.

e90d2d51c412 ("ARM: BCM5301X: Add basic dts for BCM53573 based Tenda AC9")
     BCM53573 seems to be low priced alternative for Northstar chipsts. It
     uses single core Cortex-A7 and doesn't have SDU or local (TWD) timer. It
     was also stripped out of independent SPI controller and 2 GMACs.

Northstar uses SRAB which is some memory based (0x18007000) access to
switch register space.
BCM53573 uses different blocks & mappings and it doesn't include SRAB at
0x18007000. Accessing switch registers is handled over MDIO.