RE: [PATCH net] Revert "net: stmmac: platform: Fix MDIO init for platforms without PHY"

[Sriram Dash]

> From: Robin Murphy <robin.murphy@xxxxxxx>
> Subject: Re: [PATCH net] Revert "net: stmmac: platform: Fix MDIO init for
> platforms without PHY"
> 
> On 07/01/2020 5:46 am, Sriram Dash wrote:
> >> From: Florian Fainelli <f.fainelli@xxxxxxxxx>
> >> Subject: [PATCH net] Revert "net: stmmac: platform: Fix MDIO init for
> > platforms
> >> without PHY"
> >>
> >> This reverts commit d3e014ec7d5ebe9644b5486bc530b91e62bbf624 ("net:
> >> stmmac: platform: Fix MDIO init for platforms without PHY") because
> >> it
> > breaks
> >> existing systems with stmmac which do not have a MDIO bus sub-node
> >> nor a 'phy-handle' property declared in their Device Tree. On those
> >> systems, the stmmac MDIO bus is expected to be created and then
> >> scanned by
> >> of_mdiobus_register() to create PHY devices.
> >>
> >> While these systems should arguably make use of a more accurate
> >> Device
> > Tree
> >> reprensentation with the use of the MDIO bus sub-node an appropriate
> >> 'phy- handle', we cannot break them, therefore restore the behavior
> >> prior to the
> > said
> >> commit.
> >>
> >> Fixes: d3e014ec7d5e ("net: stmmac: platform: Fix MDIO init for
> >> platforms without PHY")
> >> Reported-by: Heiko Stuebner <heiko@xxxxxxxxx>
> >> Reported-by: kernelci.org bot <bot@xxxxxxxxxxxx>
> >> Signed-off-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
> > Nacked-by: Sriram Dash <Sriram.dash@xxxxxxxxxxx>
> >
> >> ---
> >> Heiko,
> >>
> >> I did not add the Tested-by because the patch is a little bit
> >> different
> > from what
> >> you tested, even if you most likely were not hitting the other part
> >> that I
> > was
> >> changing. Thanks!
> >>
> >>   drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c | 2 +-
> >>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> >> b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> >> index cc8d7e7bf9ac..bedaff0c13bd 100644
> >> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> >> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> >> @@ -320,7 +320,7 @@ static int stmmac_mtl_setup(struct
> >> platform_device *pdev,  static int stmmac_dt_phy(struct
> plat_stmmacenet_data *plat,
> >>   			 struct device_node *np, struct device *dev)  {
> >> -	bool mdio = false;
> >> +	bool mdio = true;
> >
> >
> > This is breaking for the platforms with fixed-link.
> > stih418-b2199.dts and 169445.dts to name a few.
> >
> > For the newer platforms, they should provide the mdio/ snps,dwmac-mdio
> > property in the device tree as we are checking the mdio/
> > snps,dwmac-mdio property in the stmmac_platform driver for the mdio bus
> memory allocation.
> > For existing platforms, I agree we should not break them, but we
> > should make the code correct. And make the existing platforms adapt to the
> proper code.
> > There is a proposed solution.
> > https://protect2.fireeye.com/url?k=d075c0fc-8da69942-d0744bb3-0cc47a31
> > ba82-60be9f5a0fb38a27&u=https://lkml.org/lkml/2020/1/7/14
> >
> > What do you think?
> 
> The binding says that the phy handle and mdio child node are optional, so
> "update all of the DTBs!" is not a viable solution. I'm far from an expert here, but

I get your point Robin. Because the mdio child or snps,dwmac-mdio is not mandatory,
there has been this problem.

> AFAICS the fault of the current code is that it assumes the lack of a phy handle
> implies a fixed link, so the obvious answer is to actually check whether the

Kind of. 

> "fixed-link" property is present.


I agree to have a fixed link check. Possibly this can be done:

--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
@@ -320,7 +320,9 @@ static int stmmac_mtl_setup(struct platform_device *pdev,
 static int stmmac_dt_phy(struct plat_stmmacenet_data *plat,
                         struct device_node *np, struct device *dev)
 {
-       bool mdio = false;
+       bool mdio = true;
+       struct device_node *fixed_link;
+
        static const struct of_device_id need_mdio_ids[] = {
                { .compatible = "snps,dwc-qos-ethernet-4.10" },
                {},
@@ -340,9 +342,8 @@ static int stmmac_dt_phy(struct plat_stmmacenet_data *plat,
                }
        }

-       if (plat->mdio_node) {
-               dev_dbg(dev, "Found MDIO subnode\n");
-               mdio = true;
+       if (of_get_child_by_name(np, "fixed-link")) {
+               mdio = false;
        }

        if (mdio) {

Neil and Heiko,

Can you guys please test this on your platforms?
We can post a more cleaner version of the patch if all agree to it.

> 
> Robin.
> 
> >
> >>   	static const struct of_device_id need_mdio_ids[] = {
> >>   		{ .compatible = "snps,dwc-qos-ethernet-4.10" },
> >>   		{},
> >> --
> >> 2.19.1
> >
> >
> >
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