net: phy: add Rust Asix PHY driver

This is the Rust implementation of drivers/net/phy/ax88796b.c. The
features are equivalent. You can choose C or Rust version kernel
configuration.

Signed-off-by: FUJITA Tomonori <[e-mail]>
Reviewed-by: Trevor Gross <[e-mail]>
Reviewed-by: Benno Lossin <[e-mail]>
Reviewed-by: Andrew Lunn <[e-mail]>
Reviewed-by: Alice Ryhl <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

MAINTAINERS

···
 F:	Documentation/devicetree/bindings/net/asix,ax88796c.yaml
 F:	drivers/net/ethernet/asix/ax88796c_*
 
+ASIX PHY DRIVER [RUST]
+M:	FUJITA Tomonori <[e-mail]>
+R:	Trevor Gross <[e-mail]>
+L:	[e-mail]
+L:	[e-mail]
+S:	Maintained
+F:	drivers/net/phy/ax88796b_rust.rs
+
 ASPEED CRYPTO DRIVER
 M:	Neal Liu <[e-mail]>
 L:	[e-mail] (moderated for non-subscribers)

drivers/net/phy/Kconfig

···
 	  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

drivers/net/phy/Makefile

···
 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

drivers/net/phy/ax88796b_rust.rs

···
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2023 FUJITA Tomonori <[e-mail]>
+
+//! 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 <[e-mail]>",
+    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)
+    }
+}

rust/uapi/uapi_helper.h

···
  */
 
 #include <uapi/asm-generic/ioctl.h>
+#include <uapi/linux/mii.h>
+#include <uapi/linux/ethtool.h>