netdev - Re: [PATCH net-next v2 2/7] usbnet: smsc95xx: Don't clear read-only PHY interrupt

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Message-ID: <YnGqtCDVHHpo/S+L@lunn.ch>
Date:   Wed, 4 May 2022 00:20:36 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Lukas Wunner <lukas@...ner.de>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-usb@...r.kernel.org,
        Steve Glendinning <steve.glendinning@...well.net>,
        UNGLinuxDriver@...rochip.com, Oliver Neukum <oneukum@...e.com>,
        Andre Edich <andre.edich@...rochip.com>,
        Oleksij Rempel <linux@...pel-privat.de>,
        Martyn Welch <martyn.welch@...labora.com>,
        Gabriel Hojda <ghojda@...urs.ro>,
        Christoph Fritz <chf.fritz@...glemail.com>,
        Lino Sanfilippo <LinoSanfilippo@....de>,
        Philipp Rosenberger <p.rosenberger@...bus.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Ferry Toth <fntoth@...il.com>
Subject: Re: [PATCH net-next v2 2/7] usbnet: smsc95xx: Don't clear read-only
 PHY interrupt

On Tue, May 03, 2022 at 03:15:02PM +0200, Lukas Wunner wrote:
> Upon receiving data from the Interrupt Endpoint, the SMSC LAN95xx driver
> attempts to clear the signaled interrupts by writing "all ones" to the
> Interrupt Status Register.
> 
> However the driver only ever enables a single type of interrupt, namely
> the PHY Interrupt.  And according to page 119 of the LAN950x datasheet,
> its bit in the Interrupt Status Register is read-only.  There's no other
> way to clear it than in a separate PHY register:
> 
> https://www.microchip.com/content/dam/mchp/documents/UNG/ProductDocuments/DataSheets/LAN950x-Data-Sheet-DS00001875D.pdf
> 
> Consequently, writing "all ones" to the Interrupt Status Register is
> pointless and can be dropped.
> 
> Tested-by: Oleksij Rempel <o.rempel@...gutronix.de> # LAN9514/9512/9500
> Tested-by: Ferry Toth <fntoth@...il.com> # LAN9514
> Signed-off-by: Lukas Wunner <lukas@...ner.de>

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

    Andrew