[U-Boot] [PATCH v3 11/11] spi: cadence_qspi: Support specifying the sample edge used

[Jagan Teki]

On Tue, Dec 6, 2016 at 6:00 PM, Phil Edworthy <phil.edworthy at renesas.com> wrote:
> Hi Jagan, Marek,
>
> On 06 December 2016 12:39 Marek Vasut wrote:
>> On 12/06/2016 11:25 AM, Phil Edworthy wrote:
>> > On 05 December 2016 13:31, Marek Vasut wrote:
>> >> On 12/05/2016 11:46 AM, Phil Edworthy wrote:
>> >>> On 05 December 2016 10:42, Jagan Teki wrote:
>> >>>> On Mon, Dec 5, 2016 at 11:31 AM, Phil Edworthy
>> >>>> <phil.edworthy at renesas.com> wrote:
>> >>>>> On 05 December 2016 10:26, Jagan Teki wrote:
>> >>>>>> On Mon, Dec 5, 2016 at 11:09 AM, Phil Edworthy
>> >>>>>> <phil.edworthy at renesas.com> wrote:
>> >>>>>>> On 02 December 2016 14:23, Jagan Teki wrote:
>> >>>>>>>> On Tue, Nov 29, 2016 at 6:28 PM, Phil Edworthy
>> >>>>>>>> <phil.edworthy at renesas.com> wrote:
>> >>>>>>>>> Introduce a new DT property to specify whether the QSPI Controller
>> >>>>>>>>> samples the data on a rising edge. The default is falling edge.
>> >>>>>>>>> Some versions of the QSPI Controller do not implement this bit, in
>> >>>>>>>>> which case the property should be omitted.
> <snip>
>
>> >>>>>>>> Code look reasonable, but how Linux handling this with the same dt
>> >>>>>>>> property, any idea? I couldn't find it either.
>> >>>>>>> The Linux driver does not yet have this property. Is there a policy to add
>> >> new
>> >>>>>>> props to Linux first?
>> >>>>>>
>> >>>>>> If the same/equal code used in Linux better to have the same property
>> >>>>>> instead of another name used in U-boot?
>> >>>>> Of course, but I cannot see this in Linux:
>> >>>>> https://git.kernel.org/cgit/linux/kernel/git/next/linux-
>> >>>> next.git/tree/Documentation/devicetree/bindings/spi/spi-cadence.txt
>> >>>>
>> >>>> Yeah, I saw this. Do you have any idea how Linux handling this sample
>> edge?
>> >>> The same way U-Boot currently handles it, i.e. it does nothing with this.
>> >> Intel/Altera
>> >>> (Chin Liang) said that they do not have this bit in their version of the Cadence
>> >> QSPI
>> >>> Controller.
>> >>>
>> >>> We are using a later version that has had this bit added.
>> >>
>> >> You were looking at the wrong bindings:
>> >> https://git.kernel.org/cgit/linux/kernel/git/next/linux-
>> >> next.git/tree/Documentation/devicetree/bindings/mtd/cadence-quadspi.txt
>> > Thanks for pointing that out!
>> >
>> >> but yes, Linux does not do support the data edge toggling. I think there
>> >> was another QSPI patch in Linux which tried adding such property, so
>> >> check linux-mtd for it. Generic one would be great.
>> > I had a search around, but couldn't find anything.
>>
>> Look for negative_edge here:
>> http://www.spinics.net/lists/devicetree/msg153582.html
>>
>> >> And no, there is no policy for pushing new props to linux first. New DT
>> >> props should ideally get approved via devicetree at vger though, but that's
>> >> about it. Also, while I tried backporting the Linux CQSPI driver to
>> >> U-Boot, but unfortunately, it turned out to be extremely difficult due
>> >> significant differences between the Linux and U-Boot SPI NOR  framework.
>> > OK, thanks for the information.
>
> Since it will take a bit more time to get a generic prop for the sample edge to
> be ack'd by devicetree at vger, would it make sense to drop it from this series,
> so we can get the rest in?

I can drop 10 and 11 from the series, is that OK?

thanks!
-- 
Jagan Teki
Free Software Engineer | www.openedev.com
U-Boot, Linux | Upstream Maintainer
Hyderabad, India.