[PATCH net-next v1] net: stmmac: initialize the reset delay array

[PATCH net-next v1] net: stmmac: initialize the reset delay array

[Martin Blumenstingl]

Commit ce4ab73ab0c27c ("net: stmmac: drop the reset delays from struct
stmmac_mdio_bus_data") moved the reset delay array from struct
stmmac_mdio_bus_data to a stack variable.
The values from the array inside struct stmmac_mdio_bus_data were
previously initialized to 0 because the struct was allocated using
devm_kzalloc(). The array on the stack has to be initialized
explicitly, else we might be reading garbage values.

Initialize all reset delays to 0 to ensure that the values are 0 if the
"snps,reset-delays-us" property is not defined.
This fixes booting at least two boards (MIPS pistachio marduk and ARM
sun8i H2+ Orange Pi Zero). These are hanging during boot when
initializing the stmmac Ethernet controller (as found by Kernel CI).
Both have in common that they don't define the "snps,reset-delays-us"
property.

Fixes: ce4ab73ab0c27c ("net: stmmac: drop the reset delays from struct stmmac_mdio_bus_data")
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
---
On my Amlogic boards the delay values are 0 even without this patch.
I may have been lucky with my kernel build that I'm not triggering
the same fault as Kernel CI found on the two boards mentioned here: [0]

Please feel free to squash this into net-next commit ce4ab73ab0c27c.

[0] https://lore.kernel.org/netdev/7hr27qdedo.fsf@baylibre.com/T/#u


 drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
index da310de06bf6..18cadf0b0d66 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
@@ -241,7 +241,7 @@ int stmmac_mdio_reset(struct mii_bus *bus)
 #ifdef CONFIG_OF
 	if (priv->device->of_node) {
 		struct gpio_desc *reset_gpio;
-		u32 delays[3];
+		u32 delays[3] = { 0, 0, 0 };
 
 		reset_gpio = devm_gpiod_get_optional(priv->device,
 						     "snps,reset",
-- 
2.22.0

Re: [PATCH net-next v1] net: stmmac: initialize the reset delay array

[Martin Blumenstingl]

On Tue, Jun 18, 2019 at 10:39 PM Martin Blumenstingl
<martin.blumenstingl@googlemail.com> wrote:
>
> Commit ce4ab73ab0c27c ("net: stmmac: drop the reset delays from struct
> stmmac_mdio_bus_data") moved the reset delay array from struct
> stmmac_mdio_bus_data to a stack variable.
> The values from the array inside struct stmmac_mdio_bus_data were
> previously initialized to 0 because the struct was allocated using
> devm_kzalloc(). The array on the stack has to be initialized
> explicitly, else we might be reading garbage values.
>
> Initialize all reset delays to 0 to ensure that the values are 0 if the
> "snps,reset-delays-us" property is not defined.
> This fixes booting at least two boards (MIPS pistachio marduk and ARM
> sun8i H2+ Orange Pi Zero). These are hanging during boot when
> initializing the stmmac Ethernet controller (as found by Kernel CI).
> Both have in common that they don't define the "snps,reset-delays-us"
> property.
>
> Fixes: ce4ab73ab0c27c ("net: stmmac: drop the reset delays from struct stmmac_mdio_bus_data")
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
to complete what I already wrote as part of the patch description this
issue was:
Reported-by: "kernelci.org bot" <bot@kernelci.org>

Re: [PATCH net-next v1] net: stmmac: initialize the reset delay array

[David Miller]

From: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Date: Tue, 18 Jun 2019 22:39:27 +0200

> Commit ce4ab73ab0c27c ("net: stmmac: drop the reset delays from struct
> stmmac_mdio_bus_data") moved the reset delay array from struct
> stmmac_mdio_bus_data to a stack variable.
> The values from the array inside struct stmmac_mdio_bus_data were
> previously initialized to 0 because the struct was allocated using
> devm_kzalloc(). The array on the stack has to be initialized
> explicitly, else we might be reading garbage values.
> 
> Initialize all reset delays to 0 to ensure that the values are 0 if the
> "snps,reset-delays-us" property is not defined.
> This fixes booting at least two boards (MIPS pistachio marduk and ARM
> sun8i H2+ Orange Pi Zero). These are hanging during boot when
> initializing the stmmac Ethernet controller (as found by Kernel CI).
> Both have in common that they don't define the "snps,reset-delays-us"
> property.
> 
> Fixes: ce4ab73ab0c27c ("net: stmmac: drop the reset delays from struct stmmac_mdio_bus_data")
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>

Applied, thanks.

> Please feel free to squash this into net-next commit ce4ab73ab0c27c.

We do not "squash" things into existing net-next commits, as commits in
my tree(s) are permanent and immutable.

Re: [PATCH net-next v1] net: stmmac: initialize the reset delay array

[Martin Blumenstingl]

On Wed, Jun 19, 2019 at 11:41 PM David Miller <davem@davemloft.net> wrote:
>
> From: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
> Date: Tue, 18 Jun 2019 22:39:27 +0200
>
> > Commit ce4ab73ab0c27c ("net: stmmac: drop the reset delays from struct
> > stmmac_mdio_bus_data") moved the reset delay array from struct
> > stmmac_mdio_bus_data to a stack variable.
> > The values from the array inside struct stmmac_mdio_bus_data were
> > previously initialized to 0 because the struct was allocated using
> > devm_kzalloc(). The array on the stack has to be initialized
> > explicitly, else we might be reading garbage values.
> >
> > Initialize all reset delays to 0 to ensure that the values are 0 if the
> > "snps,reset-delays-us" property is not defined.
> > This fixes booting at least two boards (MIPS pistachio marduk and ARM
> > sun8i H2+ Orange Pi Zero). These are hanging during boot when
> > initializing the stmmac Ethernet controller (as found by Kernel CI).
> > Both have in common that they don't define the "snps,reset-delays-us"
> > property.
> >
> > Fixes: ce4ab73ab0c27c ("net: stmmac: drop the reset delays from struct stmmac_mdio_bus_data")
> > Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
>
> Applied, thanks.
thank you!

> > Please feel free to squash this into net-next commit ce4ab73ab0c27c.
>
> We do not "squash" things into existing net-next commits, as commits in
> my tree(s) are permanent and immutable.
understood. other maintainers do it so I thought I would mention it
I'm happy either way


Martin