Re: [PATCH v2 3/3] ARM: OMAP2+: Add GPMC DT support for Ethernet child nodes

[Jon Hunter <jon-hunter@ti.com>]

On 03/14/2013 04:08 PM, Javier Martinez Canillas wrote:
> 
> 
> Javier
> 
> Hi Jon,
> 
> On 14/03/2013, at 21:43, Jon Hunter <jon-hunter@ti.com> wrote:
> 
>>
>> On 03/14/2013 03:33 PM, Javier Martinez Canillas wrote:
>>> Besides being used to interface with external memory devices,
>>> the General-Purpose Memory Controller can be used to connect
>>> Pseudo-SRAM devices such as ethernet controllers to OMAP2+
>>> processors using the TI GPMC as a data bus.
>>>
>>> This patch allows an ethernet chip to be defined as an GPMC
>>> child device node.
>>>
>>> Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
>>> ---
>>>
>>> Changes since v1:
>>>  - Improve the DT binding documentation explaining that even when the GPMC
>>>    maximum bus address width is 16-bit, it supports devices with 32-bit
>>>    registers address width and the device property especifying this has to
>>>    be set accordingly; suggested by Jon Hunter.
>>>
>>>
>>> Documentation/devicetree/bindings/net/gpmc-eth.txt |  101 ++++++++++++++++++++
>>> arch/arm/mach-omap2/gpmc.c                         |    8 ++
>>> 2 files changed, 109 insertions(+), 0 deletions(-)
>>> create mode 100644 Documentation/devicetree/bindings/net/gpmc-eth.txt
>>>
>>> diff --git a/Documentation/devicetree/bindings/net/gpmc-eth.txt b/Documentation/devicetree/bindings/net/gpmc-eth.txt
>>> new file mode 100644
>>> index 0000000..8c8be58
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/net/gpmc-eth.txt
>>> @@ -0,0 +1,101 @@
>>> +Device tree bindings for Ethernet chip connected to TI GPMC
>>> +
>>> +Besides being used to interface with external memory devices, the
>>> +General-Purpose Memory Controller can be used to connect Pseudo-SRAM devices
>>> +such as ethernet controllers to processors using the TI GPMC as a data bus.
>>> +
>>> +Ethernet controllers connected to TI GPMC are represented as child nodes of
>>> +the GPMC controller with an "ethernet" name.
>>> +
>>> +All timing relevant properties as well as generic GPMC child properties are
>>> +explained in a separate documents. Please refer to
>>> +Documentation/devicetree/bindings/bus/ti-gpmc.txt
>>> +
>>> +For the properties relevant to the ethernet controller connected to the GPMC
>>> +refer to the binding documentation of the device. For example, the documentation
>>> +for the SMSC 911x is Documentation/devicetree/bindings/net/smsc911x.txt
>>> +
>>> +Child nodes need to specify the GPMC bus address width using the "bank-width"
>>> +property but is possible that an ethernet controller also has a property to
>>> +specify the I/O registers address width. Even when the GPMC has a maximum 16-bit
>>> +address width, it supports devices with 32-bit word registers.
>>> +For example with an SMSC LAN911x/912x controller connected to the TI GPMC on an
>>> +OMAP2+ board, "bank-width = <2>;" and "reg-io-width = <4>;".
>>> +
>>> +Required properties:
>>> +- bank-width:        Address width of the device in bytes. GPMC supports 8-bit
>>> +            and 16-bit devices and so must be either 1 or 2 bytes.
>>> +- compatible:        Compatible string property for the ethernet child device.
>>> +- gpmc,cs-on:        Chip-select assertion time
>>> +- gpmc,cs-rd-off:    Chip-select de-assertion time for reads
>>> +- gpmc,cs-wr-off:    Chip-select de-assertion time for writes
>>> +- gpmc,oe-on:        Output-enable assertion time
>>> +- gpmc,oe-off        Output-enable de-assertion time
>>> +- gpmc,we-on:        Write-enable assertion time
>>> +- gpmc,we-off:        Write-enable de-assertion time
>>> +- gpmc,access:        Start cycle to first data capture (read access)
>>> +- gpmc,rd-cycle:    Total read cycle time
>>> +- gpmc,wr-cycle:    Total write cycle time
>>> +- reg:            Chip-select, base address (relative to chip-select)
>>> +            and size of the memory mapped for the device.
>>> +            Note that base address will be typically 0 as this
>>> +            is the start of the chip-select.
>>> +
>>> +Optional properties:
>>> +- gpmc,XXX        Additional GPMC timings and settings parameters. See
>>> +            Documentation/devicetree/bindings/bus/ti-gpmc.txt
>>
>> Should we add "reg-io-width" here and say can be 2 or 4 and to refer to
>> the above description?
>>
> 
> I'm not sure about that, this property is not used (neither relevant) to the GPMC driver but is used by the smsc911x driver.
> 
> Other Ethernet chips could not need that (e.g: supports only 32 bit word accesses) or can have a different property. Uses should check the documentation binding for the connected device.

Good point. Let's not bother adding that.

>>> +
>>> +Optional properties for partiton table parsing:
>>> +- #address-cells: should be set to 1
>>> +- #size-cells: should be set to 1
>>
>> Sorry should have caught this earlier. The above is not relevant for
>> ethernet.
>>
> 
> I should have catch that before sending the first version!
> 
> I took the properties from your gpmc-nor.txt documentation and this is a left over. Will send a v3 removing that.
> 
> Sorry for being so carelessly...

No problem. Thanks for getting this done. Now just to figure out how to
handle the darn gpio interrupt ;-)

Jon