| Message ID | 20210914140515.2311548-1-vladimir.oltean@nxp.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2,net] Revert "net: phy: Uniform PHY driver access" | expand |
Hello: This patch was applied to netdev/net.git (refs/heads/master): On Tue, 14 Sep 2021 17:05:15 +0300 you wrote: > This reverts commit 3ac8eed62596387214869319379c1fcba264d8c6, which did > more than it said on the box, and not only it replaced to_phy_driver > with phydev->drv, but it also removed the "!drv" check, without actually > explaining why that is fine. > > That patch in fact breaks suspend/resume on any system which has PHY > devices with no drivers bound. > > [...] Here is the summary with links: - [v2,net] Revert "net: phy: Uniform PHY driver access" https://git.kernel.org/netdev/net/c/301de697d869 You are awesome, thank you! -- Deet-doot-dot, I am a bot. https://korg.docs.kernel.org/patchwork/pwbot.html
diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c index 9e2891d8e8dd..ba5ad86ec826 100644 --- a/drivers/net/phy/phy_device.c +++ b/drivers/net/phy/phy_device.c @@ -233,9 +233,11 @@ static DEFINE_MUTEX(phy_fixup_lock); static bool mdio_bus_phy_may_suspend(struct phy_device *phydev) { + struct device_driver *drv = phydev->mdio.dev.driver; + struct phy_driver *phydrv = to_phy_driver(drv); struct net_device *netdev = phydev->attached_dev; - if (!phydev->drv->suspend) + if (!drv || !phydrv->suspend) return false; /* PHY not attached? May suspend if the PHY has not already been
This reverts commit 3ac8eed62596387214869319379c1fcba264d8c6, which did more than it said on the box, and not only it replaced to_phy_driver with phydev->drv, but it also removed the "!drv" check, without actually explaining why that is fine. That patch in fact breaks suspend/resume on any system which has PHY devices with no drivers bound. The stack trace is: Unable to handle kernel NULL pointer dereference at virtual address 00000000000000e8 pc : mdio_bus_phy_suspend+0xd8/0xec lr : dpm_run_callback+0x38/0x90 Call trace: mdio_bus_phy_suspend+0xd8/0xec dpm_run_callback+0x38/0x90 __device_suspend+0x108/0x3cc dpm_suspend+0x140/0x210 dpm_suspend_start+0x7c/0xa0 suspend_devices_and_enter+0x13c/0x540 pm_suspend+0x2a4/0x330 Examples why that assumption is not fine: - There is an MDIO bus with a PHY device that doesn't have a specific PHY driver loaded, because mdiobus_register() automatically creates a PHY device for it but there is no specific PHY driver in the system. Normally under those circumstances, the generic PHY driver will be bound lazily to it (at phy_attach_direct time). But some Ethernet drivers attach to their PHY at .ndo_open time. Until then it, the to-be-driven-by-genphy PHY device will not have a driver. The blamed patch amounts to saying "you need to open all net devices before the system can suspend, to avoid the NULL pointer dereference". - There is any raw MDIO device which has 'plausible' values in the PHY ID registers 2 and 3, which is located on an MDIO bus whose driver does not set bus->phy_mask = ~0 (which prevents auto-scanning of PHY devices). An example could be a MAC's internal MDIO bus with PCS devices on it, for serial links such as SGMII. PHY devices will get created for those PCSes too, due to that MDIO bus auto-scanning, and although those PHY devices are not used, they do not bother anybody either. PCS devices are usually managed in Linux as raw MDIO devices. Nonetheless, they do not have a PHY driver, nor does anybody attempt to connect to them (because they are not a PHY), and therefore this patch breaks that. The goal itself of the patch is questionable, so I am going for a straight revert. to_phy_driver does not seem to have a need to be replaced by phydev->drv, in fact that might even trigger code paths which were not given too deep of a thought. For instance: phy_probe populates phydev->drv at the beginning, but does not clean it up on any error (including EPROBE_DEFER). So if the phydev driver requests probe deferral, phydev->drv will remain populated despite there being no driver bound. If a system suspend starts in between the initial probe deferral request and the subsequent probe retry, we will be calling the phydev->drv->suspend method, but _before_ any phydev->drv->probe call has succeeded. That is to say, if the phydev->drv is allocating any driver-private data structure in ->probe, it pretty much expects that data structure to be available in ->suspend. But it may not. That is a pretty insane environment to present to PHY drivers. In the code structure before the blamed patch, mdio_bus_phy_may_suspend would just say "no, don't suspend" to any PHY device which does not have a driver pointer _in_the_device_structure_ (not the phydev->drv). That would essentially ensure that ->suspend will never get called for a device that has not yet successfully completed probe. This is the code structure the patch is returning to, via the revert. Fixes: 3ac8eed62596 ("net: phy: Uniform PHY driver access") Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> --- v1->v2: reworded commit message. drivers/net/phy/phy_device.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)