Re: [PATCH 3/3] mtd: spi-nand: add devicetree binding

[Ezequiel Garcia <ezequiel.garcia@imgtec.com>]

On 01/08/2015 02:04 AM, Peter Pan 潘栋 (peterpandong) wrote:
>>> This commit adds the devicetree binding document that specifies the
>>> spi nand devices support.
>>>
>>> Signed-off-by: Peter Pan <peterpandong@micron.com>
>>> ---
>>>  Documentation/devicetree/bindings/mtd/spi-nand.txt | 22
>> ++++++++++++++++++++++
>>>  1 file changed, 22 insertions(+)
>>>  create mode 100644 Documentation/devicetree/bindings/mtd/spi-
>> nand.txt
>>>
>>> diff --git a/Documentation/devicetree/bindings/mtd/spi-nand.txt
>> b/Documentation/devicetree/bindings/mtd/spi-nand.txt
>>> new file mode 100644
>>> index 0000000..9dd3efd
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/mtd/spi-nand.txt
>>> @@ -0,0 +1,22 @@
>>> +* NAND driver for MT29F, GD5F and similar SPI NAND flash chips
>>> +
>>> +Required properties:
>>> +- #address-cells, #size-cells : Must be present if the device has
>> sub-nodes
>>> +  representing partitions.
>>> +- compatible : Should be the manufacturer and the name of the chip.
>> Bear in mind
>>>
>>
>> Unless I'm mistaken, we don't need the chip ID here, as SPI NAND allows
>> to autodetect the device. Any reason why we can't just use a generic
>> compatible "spi-nand" here?
>> --
>> Ezequiel
> 
> In fact, I don't know how to autodetect the SPI NAND device. Micron device and
> Gigadevice device have different read ID functions. The Chip ID here is used to
> determine which function to use.
> 

Isn't the difference between the Read ID very minor? One of the vendor
needs a 2-byte ID read, and the other one needs a 3-byte ID read.

So you can just try with 2-byte, and if that fails (no vendor ID is
found on the first byte), you can try with the 3-byte command.

It's not the most elegant solution, but it's not super awful either.
-- 
Ezequiel