[PATCH v2 0/3] fix macb phy probe failure if phy-reset is not handled

[Andreas Schwab]

On Jan 13 2021, Palmer Dabbelt wrote:

> On Tue, 10 Nov 2020 07:22:09 PST (-0800), sagar.kadam at sifive.com wrote:
>> HiFive Unleashed is having VSC8541-01 ethernet phy device and requires a
>> specific reset sequence of 0-1-0-1 in order to use it in unmanaged mode.
>> This series addresses a corner case where phy reset is not handled by boot
>> stages prior to linux.
>> Somewhat similar unreliable phy probe failure was reported and discussed
>> here [1].
>> The macb driver fails to detect the ethernet phy device if the bootloader
>> doesn't provide a proper reset sequence to the phy device or the phy itself
>> is in some invalid state. Currently, the FSBL or u-boot-spl is resetting
>> the phy device, and so there is no issue observed in the linux network
>> setup.
>>
>> The series is based on linux-5.10-rc5.
>> Patch 1: Add the OUI to the phy dt node to fix issue of missing mdio device
>> Patch 2 and 3:
>> 	Resetting phy needs GPIO support so add to dt and defconfig.
>>
>> [1] https://lkml.org/lkml/2018/11/29/154
>>
>> To reproduce the issue:
>> Using FSBL:
>> 1. Comment out VSC8541 reset sequence in fsbl/main.c
>>    from within the freedom-u540-c000-bootloader.
>> 2. Build and flash fsbl.bin to micro sdcard.
>>
>> Using u-boot:
>> 1. Comment out VSC8541 reset sequence in board/sifive/fu540/spl.c
>>    from mainline u-boot source code.
>> 2. Build and flash u-boot binaries to micro sdcard.
>>
>> Boot the board and bootlog will show network setup failure messages as:
>>
>> [  1.069474] libphy: MACB_mii_bus: probed
>> [  1.073092] mdio_bus 10090000.ethernet-ffffffff: MDIO device at address 0
>> 	       is missing
>> .....
>> [  1.979252] macb 10090000.ethernet eth0: Could not attach PHY (-19)
>>
>> 3. Now apply the series build, and boot kernel.
>> 4. MACB and VSC8541 driver get successfully probed and the network is set
>>    without any failure.
>>
>>
>> So irrespective of whether the prior stages handle the phy reset sequence,
>> the probing is successful in both the cases of cold boot and warm boot.
>>
>> Change History:
>> ===============================
>> V2:
>> -Rebased v1 on linux kernel v5.10-rc3.
>>
>> V1:
>> -Ignore 4th patch as suggested and so removed it from the series.
>> -Verified this series on 5.7-rc5.
>>
>> V0: Base RFC patch. Verified on 5.7-rc2
>>
>> Sagar Shrikant Kadam (3):
>>   dts: phy: fix missing mdio device and probe failure of vsc8541-01
>>     device
>>   dts: phy: add GPIO number and active state used for phy reset
>>   riscv: defconfig: enable gpio support for HiFive Unleashed
>>
>>  arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts | 2 ++
>>  arch/riscv/configs/defconfig                        | 2 ++
>>  2 files changed, 4 insertions(+)
>
> David pointed out I missed these, they're on fixes.  Thanks!

This is now on 5.10.12, and breaks ethernet on the Hifive Unleashed:

[   12.777976] macb 10090000.ethernet: Registered clk switch 'sifive-gemgxl-mgmt'
[   12.784559] macb 10090000.ethernet: GEM doesn't support hardware ptp.
[   12.791629] libphy: MACB_mii_bus: probed
[   12.919728] MACsec IEEE 802.1AE
[   12.984676] macb 10090000.ethernet eth0: Cadence GEM rev 0x10070109 at 0x10090000 irq 16 (70:b3:d5:92:f1:07)
[   14.030319] Microsemi VSC8541 SyncE 10090000.ethernet-ffffffff:00: phy_poll_reset failed: -110
[   14.038986] macb 10090000.ethernet eth0: Could not attach PHY (-110)

Andreas.

-- 
Andreas Schwab, schwab at linux-m68k.org
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