netdev - Re: [PATCH net-next v2] net: phy: mdio_device: Reset device only when necessary

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Date: Thu, 30 Nov 2023 15:11:04 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Andrew Halaney <ahalaney@...hat.com>
Cc: Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Sagar Cheluvegowda <quic_scheluve@...cinc.com>
Subject: Re: [PATCH net-next v2] net: phy: mdio_device: Reset device only
 when necessary

On Mon, Nov 27, 2023 at 03:41:10PM -0600, Andrew Halaney wrote:
> Currently the phy reset sequence is as shown below for a
> devicetree described mdio phy on boot:
> 
> 1. Assert the phy_device's reset as part of registering
> 2. Deassert the phy_device's reset as part of registering
> 3. Deassert the phy_device's reset as part of phy_probe
> 4. Deassert the phy_device's reset as part of phy_hw_init
> 
> The extra two deasserts include waiting the deassert delay afterwards,
> which is adding unnecessary delay.
> 
> This applies to both possible types of resets (reset controller
> reference and a reset gpio) that can be used.
> 
> Here's some snipped tracing output using the following command line
> params "trace_event=gpio:* trace_options=stacktrace" illustrating
> the reset handling and where its coming from:

...
 
> Reported-by: Sagar Cheluvegowda <quic_scheluve@...cinc.com>
> Signed-off-by: Andrew Halaney <ahalaney@...hat.com>

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew