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

[Robin Murphy <robin.murphy@arm.com>]

On 07/01/2020 5:46 am, Sriram Dash wrote:
>> From: Florian Fainelli <f.fainelli@gmail.com>
>> 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@sntech.de>
>> Reported-by: kernelci.org bot <bot@kernelci.org>
>> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> Nacked-by: Sriram Dash <Sriram.dash@samsung.com>
> 
>> ---
>> 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://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 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 "fixed-link" property is present.

Robin.

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