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Andrew Halaney 6d01d9f66a net: stmmac: don't create a MDIO bus if unnecessary 
[ Upstream commit f3c2caacee ]

Currently a MDIO bus is created if the devicetree description is either:

    1. Not fixed-link
    2. fixed-link but contains a MDIO bus as well

The "1" case above isn't always accurate. If there's a phy-handle,
it could be referencing a phy on another MDIO controller's bus[1]. In
this case, where the MDIO bus is not described at all, currently
stmmac will make a MDIO bus and scan its address space to discover
phys (of which there are none). This process takes time scanning a bus
that is known to be empty, delaying time to complete probe.

There are also a lot of upstream devicetrees[2] that expect a MDIO bus
to be created, scanned for phys, and the first one found connected
to the MAC. This case can be inferred from the platform description by
not having a phy-handle && not being fixed-link. This hits case "1" in
the current driver's logic, and must be handled in any logic change here
since it is a valid legacy dt-binding.

Let's improve the logic to create a MDIO bus if either:

    - Devicetree contains a MDIO bus
    - !fixed-link && !phy-handle (legacy handling)

This way the case where no MDIO bus should be made is handled, as well
as retaining backwards compatibility with the valid cases.

Below devicetree snippets can be found that explain some of
the cases above more concretely.

Here's[0] a devicetree example where the MAC is both fixed-link and
driving a switch on MDIO (case "2" above). This needs a MDIO bus to
be created:

    &fec1 {
            phy-mode = "rmii";

            fixed-link {
                    speed = <100>;
                    full-duplex;
            };

            mdio1: mdio {
                    switch0: switch0@0 {
                            compatible = "marvell,mv88e6190";
                            pinctrl-0 = <&pinctrl_gpio_switch0>;
                    };
            };
    };

Here's[1] an example where there is no MDIO bus or fixed-link for
the ethernet1 MAC, so no MDIO bus should be created since ethernet0
is the MDIO master for ethernet1's phy:

    &ethernet0 {
            phy-mode = "sgmii";
            phy-handle = <&sgmii_phy0>;

            mdio {
                    compatible = "snps,dwmac-mdio";
                    sgmii_phy0: phy@8 {
                            compatible = "ethernet-phy-id0141.0dd4";
                            reg = <0x8>;
                            device_type = "ethernet-phy";
                    };

                    sgmii_phy1: phy@a {
                            compatible = "ethernet-phy-id0141.0dd4";
                            reg = <0xa>;
                            device_type = "ethernet-phy";
                    };
            };
    };

    &ethernet1 {
            phy-mode = "sgmii";
            phy-handle = <&sgmii_phy1>;
    };

Finally there's descriptions like this[2] which don't describe the
MDIO bus but expect it to be created and the whole address space
scanned for a phy since there's no phy-handle or fixed-link described:

    &gmac {
            phy-supply = <&vcc_lan>;
            phy-mode = "rmii";
            snps,reset-gpio = <&gpio3 RK_PB4 GPIO_ACTIVE_HIGH>;
            snps,reset-active-low;
            snps,reset-delays-us = <0 10000 1000000>;
    };

[0] https://elixir.bootlin.com/linux/v6.5-rc5/source/arch/arm/boot/dts/nxp/vf/vf610-zii-ssmb-dtu.dts
[1] https://elixir.bootlin.com/linux/v6.6-rc5/source/arch/arm64/boot/dts/qcom/sa8775p-ride.dts
[2] https://elixir.bootlin.com/linux/v6.6-rc5/source/arch/arm64/boot/dts/rockchip/rk3368-r88.dts#L164

Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
Co-developed-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: 2b6ffcd787 ("net: stmmac: restructure the error path of stmmac_probe_config_dt()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-01-09 13:31:59 +01:00
arch powerpc: Remove initialisation of readpos 2025-01-09 13:31:55 +01:00
block block: avoid to reuse hctx not removed from cpuhp callback list 2025-01-02 10:32:11 +01:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto crypto: ecc - Prevent ecc_digits_from_bytes from reading too many bytes 2025-01-09 13:31:52 +01:00
Documentation ACPI/IORT: Add PMCG platform information for HiSilicon HIP09A 2025-01-09 13:31:51 +01:00
drivers net: stmmac: don't create a MDIO bus if unnecessary 2025-01-09 13:31:59 +01:00
fs ceph: give up on paths longer than PATH_MAX 2025-01-09 13:31:54 +01:00
include RDMA/mlx5: Enforce same type port association for multiport RoCE 2025-01-09 13:31:56 +01:00
init Compiler Attributes: disable __counted_by for clang < 19.1.3 2024-12-09 10:32:46 +01:00
io_uring io_uring/sqpoll: fix sqpoll error handling races 2025-01-02 10:32:10 +01:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-09 10:32:54 +01:00
kernel tracing: Check "%s" dereference via the field and not the TP_printk format 2025-01-09 13:31:55 +01:00
lib seq_buf: Introduce DECLARE_SEQ_BUF and seq_buf_str() 2025-01-09 13:31:55 +01:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm memblock: allow zero threshold in validate_numa_converage() 2025-01-09 13:31:40 +01:00
net net: mctp: handle skb cleanup on sock_queue failures 2025-01-09 13:31:54 +01:00
rust rust: macros: fix documentation of the paste! macro 2024-12-09 10:32:25 +01:00
samples samples/bpf: Fix a resource leak 2024-12-14 20:00:03 +01:00
scripts setlocalversion: work around "git describe" performance 2024-12-14 20:00:17 +01:00
security selinux: ignore unknown extended permissions 2025-01-09 13:31:54 +01:00
sound ALSA: ump: Shut up truncated string warning 2025-01-09 13:31:53 +01:00
tools stddef: make __struct_group() UAPI C++-friendly 2025-01-02 10:32:03 +01:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt KVM: Use dedicated mutex to protect kvm_usage_count to avoid deadlock 2024-10-04 16:29:47 +02:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Remove *.orig pattern from .gitignore 2024-10-04 16:29:44 +02:00
.mailmap 20 hotfixes. 12 are cc:stable and the remainder address post-6.5 issues 2023-10-24 09:52:16 -10:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS membarrier: riscv: Add full memory barrier in switch_mm() 2024-09-12 11:11:45 +02:00
Makefile Linux 6.6.69 2025-01-02 10:32:11 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.