[PATCH net v2] net: stmmac: platform: guarantee uniqueness of bus_id

[PATCH net v2] net: stmmac: platform: guarantee uniqueness of bus_id

[Quentin Schulz]

From: Quentin Schulz <quentin.schulz@cherry.de>

bus_id is currently derived from the ethernetX alias. If one is missing
for the device, 0 is used. If ethernet0 points to another stmmac device
or if there are 2+ stmmac devices without an ethernet alias, then bus_id
will be 0 for all of those.

This is an issue because the bus_id is used to generate the mdio bus id
(new_bus->id in drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
stmmac_mdio_register) and this needs to be unique.

This allows to avoid needing to define ethernet aliases for devices with
multiple stmmac controllers (such as the Rockchip RK3588) for multiple
stmmac devices to probe properly.

Obviously, the bus_id isn't guaranteed to be stable across reboots if no
alias is set for the device but that is easily fixed by simply adding an
alias if this is desired.

Fixes: 25c83b5c2e82 ("dt:net:stmmac: Add support to dwmac version 3.610 and 3.710")
Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
---
Unsure if I should cc stable since people who encountered that issue for
sure had to add an ethernet alias to make things work with their DT so
shouldn't be too much of an actual issue?

Based on Paolo's feedback, have a Fixes tag regardless of the answer to
the above question.
---
Changes in v2:
- added Fixes tag,
- Link to v1: https://lore.kernel.org/r/20250521-stmmac-mdio-bus_id-v1-1-918a3c11bf2c@cherry.de
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
index c73eff6a56b87a3783c91b2ffbf5807a27df303f..15205a47cafc276442c3759a36d115d8da1fe51d 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
@@ -430,6 +430,7 @@ stmmac_probe_config_dt(struct platform_device *pdev, u8 *mac)
 	struct device_node *np = pdev->dev.of_node;
 	struct plat_stmmacenet_data *plat;
 	struct stmmac_dma_cfg *dma_cfg;
+	static int bus_id = -ENODEV;
 	int phy_mode;
 	void *ret;
 	int rc;
@@ -465,8 +466,14 @@ stmmac_probe_config_dt(struct platform_device *pdev, u8 *mac)
 	of_property_read_u32(np, "max-speed", &plat->max_speed);
 
 	plat->bus_id = of_alias_get_id(np, "ethernet");
-	if (plat->bus_id < 0)
-		plat->bus_id = 0;
+	if (plat->bus_id < 0) {
+		if (bus_id < 0)
+			bus_id = of_alias_get_highest_id("ethernet");
+		/* No ethernet alias found, init at -1 so first bus_id is 0 */
+		if (bus_id < 0)
+			bus_id = -1;
+		plat->bus_id = ++bus_id;
+	}
 
 	/* Default to phy auto-detection */
 	plat->phy_addr = -1;

---
base-commit: 4a95bc121ccdaee04c4d72f84dbfa6b880a514b6
change-id: 20250521-stmmac-mdio-bus_id-313b74c77933

Best regards,
-- 
Quentin Schulz <quentin.schulz@cherry.de>

Re: [PATCH net v2] net: stmmac: platform: guarantee uniqueness of bus_id

[Maxime Chevallier]

Hello Quentin,

On Tue, 27 May 2025 13:56:23 +0200
Quentin Schulz <foss+kernel@0leil.net> wrote:

> From: Quentin Schulz <quentin.schulz@cherry.de>
> 
> bus_id is currently derived from the ethernetX alias. If one is missing
> for the device, 0 is used. If ethernet0 points to another stmmac device
> or if there are 2+ stmmac devices without an ethernet alias, then bus_id
> will be 0 for all of those.
> 
> This is an issue because the bus_id is used to generate the mdio bus id
> (new_bus->id in drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
> stmmac_mdio_register) and this needs to be unique.
> 
> This allows to avoid needing to define ethernet aliases for devices with
> multiple stmmac controllers (such as the Rockchip RK3588) for multiple
> stmmac devices to probe properly.
> 
> Obviously, the bus_id isn't guaranteed to be stable across reboots if no
> alias is set for the device but that is easily fixed by simply adding an
> alias if this is desired.
> 
> Fixes: 25c83b5c2e82 ("dt:net:stmmac: Add support to dwmac version 3.610 and 3.710")
> Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>

This looks correct, thanks !

Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>

Maxime

Re: [PATCH net v2] net: stmmac: platform: guarantee uniqueness of bus_id

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Paolo Abeni <pabeni@redhat.com>:

On Tue, 27 May 2025 13:56:23 +0200 you wrote:
> From: Quentin Schulz <quentin.schulz@cherry.de>
> 
> bus_id is currently derived from the ethernetX alias. If one is missing
> for the device, 0 is used. If ethernet0 points to another stmmac device
> or if there are 2+ stmmac devices without an ethernet alias, then bus_id
> will be 0 for all of those.
> 
> [...]

Here is the summary with links:
  - [net,v2] net: stmmac: platform: guarantee uniqueness of bus_id
    https://git.kernel.org/netdev/net/c/eb7fd7aa35bf

You are awesome, thank you!
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