netdev - Re: [PATCH 3/9] net: mdio: ipq4019: Enable GPIO reset for ipq5332 platform

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Date: Thu, 16 Nov 2023 12:19:30 +0100
From: Robert Marko <robert.marko@...tura.hr>
To: Jie Luo <quic_luoj@...cinc.com>
Cc: Andrew Lunn <andrew@...n.ch>, agross@...nel.org, andersson@...nel.org, 
	konrad.dybcio@...aro.org, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, robh+dt@...nel.org, 
	krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org, hkallweit1@...il.com, 
	linux@...linux.org.uk, linux-arm-msm@...r.kernel.org, netdev@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	quic_srichara@...cinc.com
Subject: Re: [PATCH 3/9] net: mdio: ipq4019: Enable GPIO reset for ipq5332 platform

On Thu, Nov 16, 2023 at 12:14 PM Jie Luo <quic_luoj@...cinc.com> wrote:
>
>
>
> On 11/15/2023 11:11 PM, Andrew Lunn wrote:
> > On Wed, Nov 15, 2023 at 11:25:09AM +0800, Luo Jie wrote:
> >> Before doing GPIO reset on the MDIO slave devices, the common clock
> >> output to MDIO slave device should be enabled, and the related GCC
> >> clocks also need to be configured.
> >>
> >> Because of these extra configurations, the MDIO bus level GPIO and
> >> PHY device level GPIO can't be leveraged.
> >
> > Its not clear to me why the normal reset cannot be used. The MBIO bus
> > driver can probe, setup the clocks, and then register the MDIO bus to
> > the core. The core can then use the GPIO resets.
> >
> > What am i missing?
> >
> >       Andrew
>
> Hi Andrew,
> Looks we can leverage the MDIO bus GPIO to reset qca8084 PHY, but the
> mdio bus gpio only supports one GPIO number.

But, you can specify a PHY specific reset-gpio under the PHY subnode.
However, you must specify the PHY ID via compatible then, please look at:
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/Documentation/devicetree/bindings/net/ethernet-phy.yaml?h=next-20231116#n36

I do this commonly when there are multiple reset GPIO-s for different ethernet
PHY-s.

Regards,
Robert
>
> Here are the reasons i put the GPIO reset here.
> 1. Currently one MDIO bus instance only connects one qca8084 PHY as
> MDIO slave device on IPQ5332 platform, since the MDIO address
> occupied by qca8084. if the other type PHY also needs to use MDIO
> bus GPIO reset, then we can't cover this case.
>
> 2. Before doing the GPIO reset on qca8084, we need to enable the clock
> output to qca8084 by configuring eth_ldo_rdy register, and the mdio
> bus->reset is called after the mdio bus level reset.
>
> 3. program the mdio address of qca8084 PHY and the initialization
> configurations needed before the registers of qca8084 can be accessed.
> if we take the PHY level GPIO reset for qca8084, there is no call point
> to do the initialization configurations and programing PHY address in
> the MDIO driver code.
>
> i will check the feasibility of taking the PHY level GPIO reset and do
> the initial configurations in the PHY probe function.
>
> FYI, here is the sequence to bring up qca8084.
> a. enable clock output to qca8084.
> b. do gpio reset of qca8084.
> c. customize MDIO address and initialization configurations.
> d. the PHY ID can be acquired.
>
>
> Thanks,
> Jie.



-- 
Robert Marko
Staff Embedded Linux Engineer
Sartura Ltd.
Lendavska ulica 16a
10000 Zagreb, Croatia
Email: robert.marko@...tura.hr
Web: www.sartura.hr