[PATCH v1 0/3] fix macb phy probe failure if phy-reset is not handled

[PATCH v1 0/3] fix macb phy probe failure if phy-reset is not handled

[Sagar Shrikant Kadam]

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 is resetting the phy device,
and so there is no issue observed in the linux network setup.

The series is based on linux-5.7-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: 
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.

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:
===============================
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(+)

-- 
2.7.4

[PATCH v1 1/3] dts: phy: fix missing mdio device and probe failure of vsc8541-01 device

[Sagar Shrikant Kadam]

HiFive unleashed A00 board has VSC8541-01 ethernet phy, this device is
identified as a Revision B device as described in device identification
registers. In order to use this phy in the unmanaged mode, it requires
a specific reset sequence of logical 0-1-0-1 transition on the NRESET pin
as documented here [1].

Currently, the bootloader (fsbl) takes care of the phy reset. If due to
some reason the phy device hasn't received the reset by the prior stages
before the linux macb driver comes into the picture, the MACB mii bus gets
probed but the mdio scan fails and is not even able to read the phy ID
registers. It gives an error message:

"libphy: MACB_mii_bus: probed
mdio_bus 10090000.ethernet-ffffffff: MDIO device at address 0 is missing."

Thus adding the device OUI (Organizationally Unique Identifier) to the phy
device node helps to probe the phy device.

[1]: VSC8541-01 datasheet:
https://www.mouser.com/ds/2/523/Microsemi_VSC8541-01_Datasheet_10496_V40-1148034.pdf

Signed-off-by: Sagar Shrikant Kadam <sagar.kadam@sifive.com>
---
 arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts b/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts
index 4a2729f..60846e8 100644
--- a/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts
+++ b/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts
@@ -88,6 +88,7 @@
 	phy-mode = "gmii";
 	phy-handle = <&phy0>;
 	phy0: ethernet-phy@0 {
+		compatible = "ethernet-phy-id0007.0771";
 		reg = <0>;
 	};
 };
-- 
2.7.4

[PATCH v1 2/3] dts: phy: add GPIO number and active state used for phy reset

[Sagar Shrikant Kadam]

The GEMGXL_RST line on HiFive Unleashed is pulled low and is
using GPIO number 12. Add these reset-gpio details to dt-node
using which the linux phylib can reset the phy.

Signed-off-by: Sagar Shrikant Kadam <sagar.kadam@sifive.com>
---
 arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts b/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts
index 60846e8..24d75a1 100644
--- a/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts
+++ b/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts
@@ -90,6 +90,7 @@
 	phy0: ethernet-phy@0 {
 		compatible = "ethernet-phy-id0007.0771";
 		reg = <0>;
+		reset-gpios = <&gpio 12 GPIO_ACTIVE_LOW>;
 	};
 };
 
-- 
2.7.4

[PATCH v1 3/3] riscv: defconfig: enable gpio support for HiFive Unleashed

[Sagar Shrikant Kadam]

Ethernet phy VSC8541-01 on HiFive Unleashed has its reset line
connected to a gpio, so enable GPIO driver's required to reset
the phy.

Signed-off-by: Sagar Shrikant Kadam <sagar.kadam@sifive.com>
---
 arch/riscv/configs/defconfig | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/riscv/configs/defconfig b/arch/riscv/configs/defconfig
index 4da4886..20c38b59 100644
--- a/arch/riscv/configs/defconfig
+++ b/arch/riscv/configs/defconfig
@@ -63,6 +63,8 @@ CONFIG_HW_RANDOM=y
 CONFIG_HW_RANDOM_VIRTIO=y
 CONFIG_SPI=y
 CONFIG_SPI_SIFIVE=y
+CONFIG_GPIOLIB=y
+CONFIG_GPIO_SIFIVE=y
 # CONFIG_PTP_1588_CLOCK is not set
 CONFIG_POWER_RESET=y
 CONFIG_DRM=y
-- 
2.7.4

RE: [PATCH v1 0/3] fix macb phy probe failure if phy-reset is not handled

[Sagar Kadam]

Hello,

A gentle reminder. Any suggestions here?

BR,
Sagar

> -----Original Message-----
> From: Sagar Kadam <sagar.kadam@sifive.com>
> Sent: Wednesday, May 13, 2020 7:27 PM
> To: linux-kernel@vger.kernel.org; linux-riscv@lists.infradead.org;
> devicetree@vger.kernel.org; robh+dt@kernel.org
> Cc: palmer@dabbelt.com; Paul Walmsley <paul.walmsley@sifive.com>;
> atish.patra@wdc.com; Sagar Kadam <sagar.kadam@sifive.com>
> Subject: [PATCH v1 0/3] fix macb phy probe failure if phy-reset is not
> handled
> 
> 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 is resetting the phy device, and
> so there is no issue observed in the linux network setup.
> 
> The series is based on linux-5.7-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:
> 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.
> 
> 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:
> ===============================
> 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(+)
> 
> --
> 2.7.4