Merge branch 'net-phy-rust'

FUJITA Tomonori says:

====================
Rust abstractions for network PHY drivers

No functional change since v10; only comment and commit log updates.

This patchset adds Rust abstractions for phylib. It doesn't fully
cover the C APIs yet but I think that it's already useful. I implement
two PHY drivers (Asix AX88772A PHYs and Realtek Generic FE-GE). Seems
they work well with real hardware.

The first patch introduces Rust bindings for phylib.

The second patch adds a macro to declare a kernel module for PHYs
drivers.

The third adds the Rust ETHERNET PHY LIBRARY entry to MAINTAINERS
file; adds the binding file and me as a maintainer (as Andrew Lunn
suggested) with Trevor Gross as a reviewer.

The last patch introduces the Rust version of Asix PHY driver,
drivers/net/phy/ax88796b.c. The features are equivalent to the C
version. You can choose C (by default) or Rust version on kernel
configuration.

v11:
  - adds Andrew, Alice, and Trevor's Reviewed-by
  - comment update
v10: https://lore.kernel.org/netdev/20231210234924.1453917-1-fujita.tomonori@gmail.com/T/
  - adds Trevor's SoB to the third patch
  - adds Benno's Reviewed-by to the second patch
v9: https://lore.kernel.org/netdev/20231205.124531.842372711631366729.fujita.tomonori@gmail.com/T/
  - adds a workaround to access to a bit field in phy_device
  - fixes a comment typo
v8: https://lore.kernel.org/netdev/20231123050412.1012252-1-fujita.tomonori@gmail.com/
  - updates the safety comments on Device and its related code
  - uses _phy_start_aneg instead of phy_start_aneg
  - drops the patch for enum synchronization
  - moves Sync From Registration to DriverVTable
  - fixes doctest errors
  - minor cleanups
v7: https://lore.kernel.org/netdev/20231026001050.1720612-1-fujita.tomonori@gmail.com/T/
  - renames get_link() to is_link_up()
  - improves the macro format
  - improves the commit log in the third patch
  - improves comments
v6: https://lore.kernel.org/netdev/20231025.090243.1437967503809186729.fujita.tomonori@gmail.com/T/
  - improves comments
  - makes the requirement of phy_drivers_register clear
  - fixes Makefile of the third patch
v5: https://lore.kernel.org/all/20231019.094147.1808345526469629486.fujita.tomonori@gmail.com/T/
  - drops the rustified-enum option, writes match by hand; no *risk* of UB
  - adds Miguel's patch for enum checking
  - moves CONFIG_RUST_PHYLIB_ABSTRACTIONS to drivers/net/phy/Kconfig
  - adds a new entry for this abstractions in MAINTAINERS
  - changes some of Device's methods to take &mut self
  - comment improvment
v4: https://lore.kernel.org/netdev/20231012125349.2702474-1-fujita.tomonori@gmail.com/T/
  - split the core patch
  - making Device::from_raw() private
  - comment improvement with code update
  - commit message improvement
  - avoiding using bindings::phy_driver in public functions
  - using an anonymous constant in module_phy_driver macro
v3: https://lore.kernel.org/netdev/20231011.231607.1747074555988728415.fujita.tomonori@gmail.com/T/
  - changes the base tree to net-next from rust-next
  - makes this feature optional; only enabled with CONFIG_RUST_PHYLIB_BINDINGS=y
  - cosmetic code and comment improvement
  - adds copyright
v2: https://lore.kernel.org/netdev/20231006094911.3305152-2-fujita.tomonori@gmail.com/T/
  - build failure fix
  - function renaming
v1: https://lore.kernel.org/netdev/20231002085302.2274260-3-fujita.tomonori@gmail.com/T/
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 156 insertions, 1 deletions

diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
index 098d17d2d3f7..2e4667bf9ff5 100644
--- a/drivers/net/phy/Kconfig
+++ b/drivers/net/phy/Kconfig
@@ -60,6 +60,14 @@ config FIXED_PHY
 
 	  Currently tested with mpc866ads and mpc8349e-mitx.
 
+config RUST_PHYLIB_ABSTRACTIONS
+        bool "Rust PHYLIB abstractions support"
+        depends on RUST
+        depends on PHYLIB=y
+        help
+          Adds support needed for PHY drivers written in Rust. It provides
+          a wrapper around the C phylib core.
+
 config SFP
 	tristate "SFP cage support"
 	depends on I2C && PHYLINK
@@ -104,6 +112,14 @@ config AX88796B_PHY
 	  Currently supports the Asix Electronics PHY found in the X-Surf 100
 	  AX88796B package.
 
+config AX88796B_RUST_PHY
+	bool "Rust reference driver for Asix PHYs"
+	depends on RUST_PHYLIB_ABSTRACTIONS && AX88796B_PHY
+	help
+	  Uses the Rust reference driver for Asix PHYs (ax88796b_rust.ko).
+	  The features are equivalent. It supports the Asix Electronics PHY
+	  found in the X-Surf 100 AX88796B package.
+
 config BROADCOM_PHY
 	tristate "Broadcom 54XX PHYs"
 	select BCM_NET_PHYLIB
diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile
index 4ace41095ee2..e35ea69d9cb4 100644
--- a/drivers/net/phy/Makefile
+++ b/drivers/net/phy/Makefile
@@ -37,7 +37,11 @@ obj-$(CONFIG_ADIN1100_PHY)	+= adin1100.o
 obj-$(CONFIG_AMD_PHY)		+= amd.o
 obj-$(CONFIG_AQUANTIA_PHY)	+= aquantia/
 obj-$(CONFIG_AT803X_PHY)	+= at803x.o
-obj-$(CONFIG_AX88796B_PHY)	+= ax88796b.o
+ifdef CONFIG_AX88796B_RUST_PHY
+  obj-$(CONFIG_AX88796B_PHY)	+= ax88796b_rust.o
+else
+  obj-$(CONFIG_AX88796B_PHY)	+= ax88796b.o
+endif
 obj-$(CONFIG_BCM54140_PHY)	+= bcm54140.o
 obj-$(CONFIG_BCM63XX_PHY)	+= bcm63xx.o
 obj-$(CONFIG_BCM7XXX_PHY)	+= bcm7xxx.o
diff --git a/drivers/net/phy/ax88796b_rust.rs b/drivers/net/phy/ax88796b_rust.rs
new file mode 100644
index 000000000000..5c92572962dc
--- /dev/null
+++ b/drivers/net/phy/ax88796b_rust.rs
@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2023 FUJITA Tomonori <fujita.tomonori@gmail.com>
+
+//! Rust Asix PHYs driver
+//!
+//! C version of this driver: [`drivers/net/phy/ax88796b.c`](./ax88796b.c)
+use kernel::{
+    c_str,
+    net::phy::{self, DeviceId, Driver},
+    prelude::*,
+    uapi,
+};
+
+kernel::module_phy_driver! {
+    drivers: [PhyAX88772A, PhyAX88772C, PhyAX88796B],
+    device_table: [
+        DeviceId::new_with_driver::<PhyAX88772A>(),
+        DeviceId::new_with_driver::<PhyAX88772C>(),
+        DeviceId::new_with_driver::<PhyAX88796B>()
+    ],
+    name: "rust_asix_phy",
+    author: "FUJITA Tomonori <fujita.tomonori@gmail.com>",
+    description: "Rust Asix PHYs driver",
+    license: "GPL",
+}
+
+const MII_BMCR: u16 = uapi::MII_BMCR as u16;
+const BMCR_SPEED100: u16 = uapi::BMCR_SPEED100 as u16;
+const BMCR_FULLDPLX: u16 = uapi::BMCR_FULLDPLX as u16;
+
+// Performs a software PHY reset using the standard
+// BMCR_RESET bit and poll for the reset bit to be cleared.
+// Toggle BMCR_RESET bit off to accommodate broken AX8796B PHY implementation
+// such as used on the Individual Computers' X-Surf 100 Zorro card.
+fn asix_soft_reset(dev: &mut phy::Device) -> Result {
+    dev.write(uapi::MII_BMCR as u16, 0)?;
+    dev.genphy_soft_reset()
+}
+
+struct PhyAX88772A;
+
+#[vtable]
+impl Driver for PhyAX88772A {
+    const FLAGS: u32 = phy::flags::IS_INTERNAL;
+    const NAME: &'static CStr = c_str!("Asix Electronics AX88772A");
+    const PHY_DEVICE_ID: DeviceId = DeviceId::new_with_exact_mask(0x003b1861);
+
+    // AX88772A is not working properly with some old switches (NETGEAR EN 108TP):
+    // after autoneg is done and the link status is reported as active, the MII_LPA
+    // register is 0. This issue is not reproducible on AX88772C.
+    fn read_status(dev: &mut phy::Device) -> Result<u16> {
+        dev.genphy_update_link()?;
+        if !dev.is_link_up() {
+            return Ok(0);
+        }
+        // If MII_LPA is 0, phy_resolve_aneg_linkmode() will fail to resolve
+        // linkmode so use MII_BMCR as default values.
+        let ret = dev.read(MII_BMCR)?;
+
+        if ret & BMCR_SPEED100 != 0 {
+            dev.set_speed(uapi::SPEED_100);
+        } else {
+            dev.set_speed(uapi::SPEED_10);
+        }
+
+        let duplex = if ret & BMCR_FULLDPLX != 0 {
+            phy::DuplexMode::Full
+        } else {
+            phy::DuplexMode::Half
+        };
+        dev.set_duplex(duplex);
+
+        dev.genphy_read_lpa()?;
+
+        if dev.is_autoneg_enabled() && dev.is_autoneg_completed() {
+            dev.resolve_aneg_linkmode();
+        }
+
+        Ok(0)
+    }
+
+    fn suspend(dev: &mut phy::Device) -> Result {
+        dev.genphy_suspend()
+    }
+
+    fn resume(dev: &mut phy::Device) -> Result {
+        dev.genphy_resume()
+    }
+
+    fn soft_reset(dev: &mut phy::Device) -> Result {
+        asix_soft_reset(dev)
+    }
+
+    fn link_change_notify(dev: &mut phy::Device) {
+        // Reset PHY, otherwise MII_LPA will provide outdated information.
+        // This issue is reproducible only with some link partner PHYs.
+        if dev.state() == phy::DeviceState::NoLink {
+            let _ = dev.init_hw();
+            let _ = dev.start_aneg();
+        }
+    }
+}
+
+struct PhyAX88772C;
+
+#[vtable]
+impl Driver for PhyAX88772C {
+    const FLAGS: u32 = phy::flags::IS_INTERNAL;
+    const NAME: &'static CStr = c_str!("Asix Electronics AX88772C");
+    const PHY_DEVICE_ID: DeviceId = DeviceId::new_with_exact_mask(0x003b1881);
+
+    fn suspend(dev: &mut phy::Device) -> Result {
+        dev.genphy_suspend()
+    }
+
+    fn resume(dev: &mut phy::Device) -> Result {
+        dev.genphy_resume()
+    }
+
+    fn soft_reset(dev: &mut phy::Device) -> Result {
+        asix_soft_reset(dev)
+    }
+}
+
+struct PhyAX88796B;
+
+#[vtable]
+impl Driver for PhyAX88796B {
+    const NAME: &'static CStr = c_str!("Asix Electronics AX88796B");
+    const PHY_DEVICE_ID: DeviceId = DeviceId::new_with_model_mask(0x003b1841);
+
+    fn soft_reset(dev: &mut phy::Device) -> Result {
+        asix_soft_reset(dev)
+    }
+}