[PATCH 0/1] gpio: of: prepare for switching stmmac to GPIO descriptors

[PATCH 0/1] gpio: of: prepare for switching stmmac to GPIO descriptors

[Martin Blumenstingl]

This is a preparation patch which is needed before we can switch stmmac
to GPIO descriptors. stmmac has a custom "snps,reset-active-low"
property because it has ignored the GPIO flags including the polarity.

Add the parsing to gpiolib-of so we can port stmmac over to GPIO
descriptors.

This patch is split from my series at [0].

Linus W.: please create an immutable branch as discussed so I can send
the stmmac patches to the net-next tree (which will then have to pull
in your immutable branch).


[0] https://patchwork.kernel.org/cover/10983801/


Martin Blumenstingl (1):
  gpio: of: parse stmmac PHY reset line specific active-low property

 drivers/gpio/gpiolib-of.c | 6 ++++++
 1 file changed, 6 insertions(+)

-- 
2.22.0

[PATCH 1/1] gpio: of: parse stmmac PHY reset line specific active-low property

[Martin Blumenstingl]

The stmmac driver currently ignores the GPIO flags which are passed via
devicetree because it operates with legacy GPIO numbers instead of GPIO
descriptors. stmmac assumes that the GPIO is "active HIGH" by default.
This can be overwritten by setting "snps,reset-active-low" to make the
reset line "active LOW".

Recent Amlogic SoCs (G12A which includes S905X2 and S905D2 as well as
G12B which includes S922X) use GPIOZ_14 or GPIOZ_15 for the PHY reset
line. These GPIOs are special because they are marked as "3.3V input
tolerant open drain" pins which means they can only drive the pin output
LOW (to reset the PHY) or to switch to input mode (to take the PHY out
of reset).
The GPIO subsystem already supports this with the GPIO_OPEN_DRAIN and
GPIO_OPEN_SOURCE flags in the devicetree bindings.

Add the stmmac PHY reset line specific active low parsing to gpiolib-of
so stmmac can be ported to GPIO descriptors while being backwards
compatible with device trees which use the "old" way of specifying the
polarity.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/gpio/gpiolib-of.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index 00deb885409c..a8f02f551d6b 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -158,6 +158,12 @@ static void of_gpio_flags_quirks(struct device_node *np,
 			}
 		}
 	}
+
+	/* Legacy handling of stmmac's active-low PHY reset line */
+	if (IS_ENABLED(CONFIG_STMMAC_ETH) &&
+	    !strcmp(propname, "snps,reset-gpio") &&
+	    of_property_read_bool(np, "snps,reset-active-low"))
+		*flags |= OF_GPIO_ACTIVE_LOW;
 }
 
 /**
-- 
2.22.0

Re: [PATCH 0/1] gpio: of: prepare for switching stmmac to GPIO descriptors

[Linus Walleij]

On Mon, Jun 10, 2019 at 7:05 PM Martin Blumenstingl
<martin.blumenstingl@googlemail.com> wrote:

> This is a preparation patch which is needed before we can switch stmmac
> to GPIO descriptors. stmmac has a custom "snps,reset-active-low"
> property because it has ignored the GPIO flags including the polarity.
>
> Add the parsing to gpiolib-of so we can port stmmac over to GPIO
> descriptors.
>
> This patch is split from my series at [0].
>
> Linus W.: please create an immutable branch as discussed so I can send
> the stmmac patches to the net-next tree (which will then have to pull
> in your immutable branch).

Thanks Martin!
I have applied the patch and created an immutable branch:
git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio.git
ib-snps-reset-gpio

https://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio.git/log/?h=ib-snps-reset-gpio

Please refer to this so the network maintainer can pull it in.

It is based on v5.2-rc1

Yours,
Linus Walleij