On 01.10.2021 01:04, Florian Fainelli wrote:

On 9/30/21 7:29 AM, Rafał Miłecki wrote:

quoted

On 20.09.2021 19:57, Rafał Miłecki wrote:

quoted

On 20.09.2021 18:11, Florian Fainelli wrote:

quoted

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.

Florian: did my explanations help reviewing this patch? Would you ack it
now?

Thanks for providing the background.

You still appear to be needing an of_node_put() after
of_mdiobus_register() because that function does increase the reference
count.

I really can't find code increasing refcount.

I even attempted to runtime test it and I still can't see a leaking ref. See:

[    1.168863] bgmac_bcma bcma0:5: [bcma_mdio_mii_register] BEFORE count:2
[    1.176235] libphy: bcma_mdio mii bus: probed
[    1.181513] bcm53xx bcma_mdio-0-0:1e: found switch: BCM53125, rev 4
[    1.187936] bcm53xx bcma_mdio-0-0:1e: failed to register switch: -517
[    1.194610] bgmac_bcma bcma0:5: [bcma_mdio_mii_register]  AFTER count:2

diff --git a/drivers/net/ethernet/broadcom/bgmac-bcma-mdio.c b/drivers/net/ethernet/broadcom/bgmac-bcma-mdio.c
index 086739e4f..e52a3d8b7 100644
--- a/drivers/net/ethernet/broadcom/bgmac-bcma-mdio.c
+++ b/drivers/net/ethernet/broadcom/bgmac-bcma-mdio.c

@@ -233,11 +233,14 @@ struct mii_bus *bcma_mdio_mii_register(struct bgmac *bgmac)

         np = of_get_child_by_name(core->dev.of_node, "mdio");

+
+       dev_info(&core->dev, "[%s] BEFORE count:%d\n", __func__, refcount_read(&np->kobj.kref.refcount));
         err = of_mdiobus_register(mii_bus, np);
         if (err) {
                 dev_err(&core->dev, "Registration of mii bus failed\n");
                 goto err_free_bus;
         }
+       dev_info(&core->dev, "[%s]  AFTER count:%d\n", __func__, refcount_read(&np->kobj.kref.refcount));

         return mii_bus;