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    Subject[PATCH 5.15 695/779] usbnet: smsc95xx: Dont clear read-only PHY interrupt
    Date
    From: Lukas Wunner <lukas@wunner.de>

    [ Upstream commit 3108871f19221372b251f7da1ac38736928b5b3a ]

    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@pengutronix.de> # LAN9514/9512/9500
    Tested-by: Ferry Toth <fntoth@gmail.com> # LAN9514
    Signed-off-by: Lukas Wunner <lukas@wunner.de>
    Reviewed-by: Andrew Lunn <andrew@lunn.ch>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/net/usb/smsc95xx.c | 4 ----
    1 file changed, 4 deletions(-)

    diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
    index 4e39e4345084..c33089168880 100644
    --- a/drivers/net/usb/smsc95xx.c
    +++ b/drivers/net/usb/smsc95xx.c
    @@ -570,10 +570,6 @@ static int smsc95xx_link_reset(struct usbnet *dev)
    unsigned long flags;
    int ret;

    - ret = smsc95xx_write_reg(dev, INT_STS, INT_STS_CLEAR_ALL_);
    - if (ret < 0)
    - return ret;
    -
    spin_lock_irqsave(&pdata->mac_cr_lock, flags);
    if (pdata->phydev->duplex != DUPLEX_FULL) {
    pdata->mac_cr &= ~MAC_CR_FDPX_;
    --
    2.35.1


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