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SubjectRe: [PATCH net] net: phy: mscc: fix deadlock in vsc85xx_default_config
On Thu, Nov 22, 2018 at 02:12:32PM +0100, Quentin Schulz wrote:
> The vsc85xx_default_config function called in the vsc85xx_config_init
> function which is used by VSC8530, VSC8531, VSC8540 and VSC8541 PHYs
> mistakenly calls phy_read and phy_write in-between phy_select_page and
> phy_restore_page.
>
> phy_select_page and phy_restore_page actually take and release the MDIO
> bus lock so __phy_write and __phy_read (which assume that you already
> have the MDIO bus lock unlike phy_write and phy_read) should be used for
> any call in between the two said functions.
>
> Let's fix this deadlock.
>
> Fixes: 6a0bfbbe20b0 ("net: phy: mscc: migrate to phy_select/restore_page functions")
>
> Signed-off-by: Quentin Schulz <quentin.schulz@bootlin.com>
> ---
> drivers/net/phy/mscc.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/phy/mscc.c b/drivers/net/phy/mscc.c
> index 62269e578718..6856fe4d1a60 100644
> --- a/drivers/net/phy/mscc.c
> +++ b/drivers/net/phy/mscc.c
> @@ -814,10 +814,10 @@ static int vsc85xx_default_config(struct phy_device *phydev)
> if (rc < 0)
> goto out_unlock;
>
> - reg_val = phy_read(phydev, MSCC_PHY_RGMII_CNTL);
> + reg_val = __phy_read(phydev, MSCC_PHY_RGMII_CNTL);
> reg_val &= ~(RGMII_RX_CLK_DELAY_MASK);
> reg_val |= (RGMII_RX_CLK_DELAY_1_1_NS << RGMII_RX_CLK_DELAY_POS);
> - phy_write(phydev, MSCC_PHY_RGMII_CNTL, reg_val);
> + __phy_write(phydev, MSCC_PHY_RGMII_CNTL, reg_val);

Hi Quentin

You appear to be only accessing a single register, read/modify/write.
I think you can use phy_modify_paged(), which will take care of all
the locking for you.

Andrew

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