The following series of patches adds support for active-low gpio pins
as well as for systems with separate MDI and MDO pins to the mdio-gpio
driver.
A board using those features is based on a COM Express CPU board.
The COM Express standard supports GPIO pins on its connector,
with one caveat: The pins on the connector have fixed direction
and are hard configured either as input or output pins.
The COM Express Design Guide [1] provides additional details.
The hardware uses three of the GPO/GPI pins from the COM Express board
to drive an MDIO bus. Connectivity between GPI/GPO pins and the MDIO bus
is as follows.
GPI2 --------------------+------------ MDIO
|
+--------+ |
GPO2 ---+---G | |
| | | |
4.7k | 2N7002 D---+
| | |
+---S |
| +--------+
GND
GPO1 --------------------------------- MDC
To support this hardware, two extensions to the driver were necessary.
- Due to the FET in the MDO path (GPO2), the MDO signal is inverted.
The driver therefore has to support active-low GPIO pins.
- The MDIO signal must be separated into MDI and MDO.
Those changes are implemented in patch 2/3 and 3/3.
Patch 1/3 simplifies the error path and thus the subsequent
patches.
[1] http://www.picmg.org/pdf/picmg_comdg_100.pdf
----------------------------------------------------------------
Guenter Roeck (3):
net: mdio-gpio: Use devm_ functions where possible
net: mdio-gpio: Add support for active low gpio pins
net: mdio-gpio: Add support for separate MDI and MDO gpio pins
drivers/net/phy/mdio-gpio.c | 68 ++++++++++++++++++++++++++++++-------------
include/linux/mdio-gpio.h | 5 ++++
2 files changed, 52 insertions(+), 21 deletions(-)
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