linux-kernel - Re: [PATCH RFC net-next v2 1/2] net: phy: allow a phy to opt-out of interrupt handling

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Message-ID: <f547b3b9-4c8f-b370-471a-0a7b5f025e50@gmail.com>
Date:   Wed, 28 Dec 2022 08:49:35 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Michael Walle <michael@...le.cc>, Xu Liang <lxu@...linear.com>,
        Andrew Lunn <andrew@...n.ch>,
        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>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC net-next v2 1/2] net: phy: allow a phy to opt-out of
 interrupt handling



On 12/28/2022 8:40 AM, Michael Walle wrote:
> Until now, it is not possible for a PHY driver to disable interrupts
> during runtime. If a driver offers the .config_intr() as well as the
> .handle_interrupt() ops, it is eligible for interrupt handling.
> Introduce a new flag for the dev_flags property of struct phy_device, which
> can be set by PHY driver to skip interrupt setup and fall back to polling
> mode.
> 
> At the moment, this is used for the MaxLinear PHY which has broken
> interrupt handling and there is a need to disable interrupts in some
> cases.
> 
> Signed-off-by: Michael Walle <michael@...le.cc>
> ---
>   drivers/net/phy/phy_device.c | 7 +++++++
>   include/linux/phy.h          | 2 ++
>   2 files changed, 9 insertions(+)
> 
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index 716870a4499c..e4562859ac00 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -1487,6 +1487,13 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
>   
>   	phydev->interrupts = PHY_INTERRUPT_DISABLED;
>   
> +	/* PHYs can request to use poll mode even though they have an
> +	 * associated interrupt line. This could be the case if they
> +	 * detect a broken interrupt handling.
> +	 */
> +	if (phydev->dev_flags & PHY_F_NO_IRQ)
> +		phydev->irq = PHY_POLL;

Cannot you achieve the same thing with the PHY driver mangling 
phydev->irq to a negative value, or is that too later already by the 
time your phy driver's probe function is running?

> +
>   	/* Port is set to PORT_TP by default and the actual PHY driver will set
>   	 * it to different value depending on the PHY configuration. If we have
>   	 * the generic PHY driver we can't figure it out, thus set the old
> diff --git a/include/linux/phy.h b/include/linux/phy.h
> index 71eeb4e3b1fd..f1566c7e47a8 100644
> --- a/include/linux/phy.h
> +++ b/include/linux/phy.h
> @@ -82,6 +82,8 @@ extern const int phy_10gbit_features_array[1];
>   #define PHY_POLL_CABLE_TEST	0x00000004
>   #define MDIO_DEVICE_IS_PHY	0x80000000
>   
> +#define PHY_F_NO_IRQ		0x80000000

Kudos for using the appropriate namespace for dev_flags :)
-- 
Florian