[RFC PATCH 0/4] fix macb phy probe failure if phy-reset is not handled

[RFC PATCH 0/4] 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-rc2.
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.
Patch 4: Add dt binding for OUI introduced in patch 1.

[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 add 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.

Sagar Shrikant Kadam (4):
  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
  dt-bindings: net: phy: extend dt binding for VSC8541 ethernet-phy

 Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt | 3 +++
 arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts        | 2 ++
 arch/riscv/configs/defconfig                               | 2 ++
 3 files changed, 7 insertions(+)

-- 
2.7.4

[RFC PATCH 1/4] 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

[RFC PATCH 2/4] 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

[RFC PATCH 3/4] 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

[RFC PATCH 4/4] dt-bindings: net: phy: extend dt binding for VSC8541 ethernet-phy

[Sagar Shrikant Kadam]

Adding a OUI (Organizationally Unique Identifier) for VSC8541-01
device to dt node requires a corresponding dt-binding entry as well
so that checkpatch doesn't complain with a warning:

DT compatible string "ethernet-phy-id0007.0771" appears un-documented

Here extend the existing dt binding of VSC8531 device to include
VSC8541 device example.

Signed-off-by: Sagar Shrikant Kadam <sagar.kadam@sifive.com>
---
 Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt b/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
index 5ff37c6..774448a 100644
--- a/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
+++ b/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
@@ -68,3 +68,6 @@ Example:
                 vsc8531,led-0-mode	= <LINK_1000_ACTIVITY>;
                 vsc8531,led-1-mode	= <LINK_100_ACTIVITY>;
         };
+        vsc8541_0: ethernet-phy@0 {
+                compatible = "ethernet-phy-id0007.0771";
+	};
-- 
2.7.4

Re: [RFC PATCH 4/4] dt-bindings: net: phy: extend dt binding for VSC8541 ethernet-phy

[Rob Herring]

On Tue, Apr 28, 2020 at 04:16:48AM -0700, Sagar Shrikant Kadam wrote:
> Adding a OUI (Organizationally Unique Identifier) for VSC8541-01
> device to dt node requires a corresponding dt-binding entry as well
> so that checkpatch doesn't complain with a warning:
> 
> DT compatible string "ethernet-phy-id0007.0771" appears un-documented
> 
> Here extend the existing dt binding of VSC8531 device to include
> VSC8541 device example.

Checkpatch.pl is just dumb here and can be ignored. We have the regex 
that documents this compatible. We don't need every VID/PID listed.

> 
> Signed-off-by: Sagar Shrikant Kadam <sagar.kadam@sifive.com>
> ---
>  Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt b/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
> index 5ff37c6..774448a 100644
> --- a/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
> +++ b/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
> @@ -68,3 +68,6 @@ Example:
>                  vsc8531,led-0-mode	= <LINK_1000_ACTIVITY>;
>                  vsc8531,led-1-mode	= <LINK_100_ACTIVITY>;
>          };
> +        vsc8541_0: ethernet-phy@0 {
> +                compatible = "ethernet-phy-id0007.0771";
> +	};
> -- 
> 2.7.4
> 

RE: [RFC PATCH 4/4] dt-bindings: net: phy: extend dt binding for VSC8541 ethernet-phy

[Sagar Kadam]

Hello Rob,

> -----Original Message-----
> From: Rob Herring <robh@kernel.org>
> Sent: Tuesday, May 12, 2020 7:42 AM
> To: Sagar Kadam <sagar.kadam@sifive.com>
> Cc: linux-kernel@vger.kernel.org; linux-riscv@lists.infradead.org;
> palmer@dabbelt.com; Paul Walmsley <paul.walmsley@sifive.com>;
> atish.patra@wdc.com; devicetree@vger.kernel.org
> Subject: Re: [RFC PATCH 4/4] dt-bindings: net: phy: extend dt binding for
> VSC8541 ethernet-phy
> 
> [External Email] Do not click links or attachments unless you recognize the
> sender and know the content is safe
> 
> On Tue, Apr 28, 2020 at 04:16:48AM -0700, Sagar Shrikant Kadam wrote:
> > Adding a OUI (Organizationally Unique Identifier) for VSC8541-01
> > device to dt node requires a corresponding dt-binding entry as well
> > so that checkpatch doesn't complain with a warning:
> >
> > DT compatible string "ethernet-phy-id0007.0771" appears un-documented
> >
> > Here extend the existing dt binding of VSC8531 device to include
> > VSC8541 device example.
> 
> Checkpatch.pl is just dumb here and can be ignored. We have the regex
> that documents this compatible. We don't need every VID/PID listed.
>
Thank you for the information. 
We can then drop this patch to handle un-documented warning.

BR,
Sagar Kadam
 
> >
> > Signed-off-by: Sagar Shrikant Kadam <sagar.kadam@sifive.com>
> > ---
> >  Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
> b/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
> > index 5ff37c6..774448a 100644
> > --- a/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
> > +++ b/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
> > @@ -68,3 +68,6 @@ Example:
> >                  vsc8531,led-0-mode   = <LINK_1000_ACTIVITY>;
> >                  vsc8531,led-1-mode   = <LINK_100_ACTIVITY>;
> >          };
> > +        vsc8541_0: ethernet-phy@0 {
> > +                compatible = "ethernet-phy-id0007.0771";
> > +     };
> > --
> > 2.7.4
> >