2018-11-24 08:47:41

by Quentin Schulz

[permalink] [raw]
Subject: [PATCH net v3] net: phy: mscc: fix deadlock in vsc85xx_default_config

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 and phy_write and phy_read take and release the lock to write
or read to a PHY register.

Let's fix this deadlock by using phy_modify_paged which handles
correctly a read followed by a write in a non-standard page.

Fixes: 6a0bfbbe20b0 ("net: phy: mscc: migrate to phy_select/restore_page functions")

Signed-off-by: Quentin Schulz <[email protected]>
---

v3:
- remove useless goto label and condition,

v2:
- use phy_modify_paged instead of
phy_select_page -> __phy_read -> __phy_write -> phy_restore_page

drivers/net/phy/mscc.c | 14 +++++---------
1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/net/phy/mscc.c b/drivers/net/phy/mscc.c
index 62269e578718..cfe680f78a3f 100644
--- a/drivers/net/phy/mscc.c
+++ b/drivers/net/phy/mscc.c
@@ -810,17 +810,13 @@ static int vsc85xx_default_config(struct phy_device *phydev)

phydev->mdix_ctrl = ETH_TP_MDI_AUTO;
mutex_lock(&phydev->lock);
- rc = phy_select_page(phydev, MSCC_PHY_PAGE_EXTENDED_2);
- if (rc < 0)
- goto out_unlock;

- 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);
+ reg_val = RGMII_RX_CLK_DELAY_1_1_NS << RGMII_RX_CLK_DELAY_POS;
+
+ rc = phy_modify_paged(phydev, MSCC_PHY_PAGE_EXTENDED_2,
+ MSCC_PHY_RGMII_CNTL, RGMII_RX_CLK_DELAY_MASK,
+ reg_val);

-out_unlock:
- rc = phy_restore_page(phydev, rc, rc > 0 ? 0 : rc);
mutex_unlock(&phydev->lock);

return rc;
--
2.17.1



2018-11-24 08:46:59

by Andrew Lunn

[permalink] [raw]
Subject: Re: [PATCH net v3] net: phy: mscc: fix deadlock in vsc85xx_default_config

On Fri, Nov 23, 2018 at 07:01:51PM +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 and phy_write and phy_read take and release the lock to write
> or read to a PHY register.
>
> Let's fix this deadlock by using phy_modify_paged which handles
> correctly a read followed by a write in a non-standard page.
>
> Fixes: 6a0bfbbe20b0 ("net: phy: mscc: migrate to phy_select/restore_page functions")
>
> Signed-off-by: Quentin Schulz <[email protected]>

Reviewed-by: Andrew Lunn <[email protected]>

Andrew

2018-11-24 09:04:30

by David Miller

[permalink] [raw]
Subject: Re: [PATCH net v3] net: phy: mscc: fix deadlock in vsc85xx_default_config

From: Quentin Schulz <[email protected]>
Date: Fri, 23 Nov 2018 19:01:51 +0100

> 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 and phy_write and phy_read take and release the lock to write
> or read to a PHY register.
>
> Let's fix this deadlock by using phy_modify_paged which handles
> correctly a read followed by a write in a non-standard page.
>
> Fixes: 6a0bfbbe20b0 ("net: phy: mscc: migrate to phy_select/restore_page functions")
> Signed-off-by: Quentin Schulz <[email protected]>

Applied.