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Date:   Thu, 30 Nov 2023 15:11:04 +0100
From:   Andrew Lunn <andrew@lunn.ch>
To:     Andrew Halaney <ahalaney@redhat.com>
Cc:     Heiner Kallweit <hkallweit1@gmail.com>,
        Russell King <linux@armlinux.org.uk>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Sagar Cheluvegowda <quic_scheluve@quicinc.com>
Subject: Re: [PATCH net-next v2] net: phy: mdio_device: Reset device only
 when necessary
Message-ID: <760c746a-5469-4f26-8fd9-5f48affe44a4@lunn.ch>
References: <20231127-net-phy-reset-once-v2-1-448e8658779e@redhat.com>
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In-Reply-To: <20231127-net-phy-reset-once-v2-1-448e8658779e@redhat.com>
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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@quicinc.com>
> Signed-off-by: Andrew Halaney <ahalaney@redhat.com>

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

    Andrew