Re: [PATCH V8 1/2] mtd: spi-nor: Bindings for Cadence Quad SPI Flash Controller driver.

[vikas <vikas.manocha@st.com>]

Hi,

On 08/27/2015 11:12 AM, Marek Vasut wrote:
> On Thursday, August 27, 2015 at 07:44:34 PM, vikas wrote:
>> Hi,
>>
>> On 08/21/2015 02:20 AM, Marek Vasut wrote:
>>> From: Graham Moore <grmoore@opensource.altera.com>
>>>
>>> Add binding document for the Cadence QSPI controller.
>>>
>>> Signed-off-by: Graham Moore <grmoore@opensource.altera.com>
>>> Signed-off-by: Marek Vasut <marex@denx.de>
>>> Cc: Alan Tull <atull@opensource.altera.com>
>>> Cc: Brian Norris <computersforpeace@gmail.com>
>>> Cc: David Woodhouse <dwmw2@infradead.org>
>>> Cc: Dinh Nguyen <dinguyen@opensource.altera.com>
>>> Cc: Graham Moore <grmoore@opensource.altera.com>
>>> Cc: Vikas MANOCHA <vikas.manocha@st.com>
>>> Cc: Yves Vandervennet <yvanderv@opensource.altera.com>
>>> Cc: devicetree@vger.kernel.org
>>> ---
>>>
>>>  .../devicetree/bindings/mtd/cadence-quadspi.txt    | 56
>>>  ++++++++++++++++++++++ 1 file changed, 56 insertions(+)
>>>  create mode 100644
>>>  Documentation/devicetree/bindings/mtd/cadence-quadspi.txt
>>>
>>> V2: Add cdns prefix to driver-specific bindings.
>>> V3: Use existing property "is-decoded-cs" instead of creating a
>>>
>>>     duplicate, "ext-decoder". Timing parameters are in nanoseconds,
>>>     not master reference clocks. Remove bus-num completely.
>>>
>>> V4: Add new properties fifo-width and trigger-address
>>> V7: - Prefix all of the Cadence-specific properties with cdns prefix,
>>>
>>>       those are in particular "cdns,is-decoded-cs", "cdns,fifo-depth",
>>>       "cdns,fifo-width", "cdns,trigger-address".
>>>     
>>>     - Drop bogus properties which were not used and were incorrect.
>>>
>>> V8: Align lines to 80 chars.
>>>
>>> diff --git a/Documentation/devicetree/bindings/mtd/cadence-quadspi.txt
>>> b/Documentation/devicetree/bindings/mtd/cadence-quadspi.txt new file
>>> mode 100644
>>> index 0000000..f248056
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/mtd/cadence-quadspi.txt
>>> @@ -0,0 +1,56 @@
>>> +* Cadence Quad SPI controller
>>> +
>>> +Required properties:
>>> +- compatible : Should be "cdns,qspi-nor".
>>> +- reg : Contains two entries, each of which is a tuple consisting of a
>>> +	physical address and length. The first entry is the address and
>>> +	length of the controller register set. The second entry is the
>>> +	address and length of the QSPI Controller data area.
>>
>> still hooked up with  "Controller data area", it is ambiguous.
>> Use something which is more clear: Nor Flash memory mapped address.
> 
> I have to disagree, I will call it whatever it is called in the datasheet
> and it is called "controller data area".

It is preferable to use terminology which readers understand & that is the purpose
of explaining it here otherwise we could have just pasted the doc link.
I have to stop here for this point.

> 
>>> +- interrupts : Unit interrupt specifier for the controller interrupt.
>>> +- clocks : phandle to the Quad SPI clock.
>>> +- cdns,fifo-depth : Size of the data FIFO in words.
>>> +- cdns,fifo-width : Bus width of the data FIFO in bytes.
>>> +- cdns,trigger-address : 32-bit indirect AHB trigger address.
>>> +
>>
>>> +Optional properties:
>> again, is it optional ? can the driver be used without these properties ?
> 
> Why wouldn't it be possible to use the driver with no SPI NOR attached to
> it? It's a cornercase, but still a valid one.

that's not right, this controller is only spi flash controller.

> 
>>> +- cdns,is-decoded-cs : Flag to indicate whether decoder is used or not.
>>
>> again, add info what the decoder is for ?
> 
> This is something Graham has to clarify. Based on the code (I'm sure you did
> check the code), it's a 4:16 demuxer.

Please clarify if possible & add the info for others benefit. This part is not common in other spi/nor controllers.

> 
>>> +
>>> +Optional subnodes:
>>> +Subnodes of the Cadence Quad SPI controller are spi slave nodes with
>>> additional +custom properties:
>>> +- cdns,read-delay : Delay for read capture logic, in clock cycles
>>> +- cdns,tshsl-ns : Delay in nanoseconds for the length that the master
>>> +                  mode chip select outputs are de-asserted between
>>> +		  transactions.
>>> +- cdns,tsd2d-ns : Delay in nanoseconds between one chip select being
>>> +                  de-activated and the activation of another.
>>> +- cdns,tchsh-ns : Delay in nanoseconds between last bit of current
>>> +                  transaction and deasserting the device chip select
>>> +		  (qspi_n_ss_out).
>>> +- cdns,tslch-ns : Delay in nanoseconds between setting qspi_n_ss_out low
>>> +                  and first bit transfer.
>>> +
>>> +Example:
>>> +
>>> +	qspi: spi@ff705000 {
>>> +		compatible = "cdns,qspi-nor";
>>> +		#address-cells = <1>;
>>> +		#size-cells = <0>;
>>> +		reg = <0xff705000 0x1000>,
>>> +		      <0xffa00000 0x1000>;
>>> +		interrupts = <0 151 4>;
>>> +		clocks = <&qspi_clk>;
>>> +		cdns,is-decoded-cs;
>>
>> flag value ?
> 
> Sorry, I don't quite understand the question. If you mean why there is no
> value, it's because this is a boolean OF node, which just does't need to
> have a value ; it's either present or not.

you are right, thanks.

Cheers,
Vikas

> 
> Best regards,
> Marek Vasut
> .
>