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

[Marek Vasut]

On 12/05/2016 11:46 AM, Phil Edworthy wrote:
> Hi Jagan,
> 
> 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:
>>> HI Jagan,
>>>
>>> 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:
>>>>> Hi Jagan,
>>>>>
>>>>> 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.
>>>>>>>
>>>>>>> Signed-off-by: Phil Edworthy <phil.edworthy at renesas.com>
>>>>>>> ---
>>>>>>>  v3:
>>>>>>>   - Patch split so this one only has code related to the subject.
>>>>>>>   - Commit message updated.
>>>>>>>  v2:
>>>>>>>   - Change name of DT prop and provide details of what it does.
>>>>>>>     Whilst at it, move the code to read the "sram-size" property
>>>>>>>     into the other code that reads properties from the node, rather
>>>>>>>     than the SF subnode.
>>>>>>>
>>>>>>>     Also change the code to use a bool for the bypass arg.
>>>>>>> ---
>>>>>>>  doc/device-tree-bindings/spi/spi-cadence.txt |  2 ++
>>>>>>>  drivers/spi/cadence_qspi.c                   | 10 +++++++---
>>>>>>>  drivers/spi/cadence_qspi.h                   |  3 ++-
>>>>>>>  drivers/spi/cadence_qspi_apb.c               |  8 +++++++-
>>>>>>>  4 files changed, 18 insertions(+), 5 deletions(-)
>>>>>>>
>>>>>>> diff --git a/doc/device-tree-bindings/spi/spi-cadence.txt b/doc/device-
>> tree-
>>>>>> bindings/spi/spi-cadence.txt
>>>>>>> index c1e2233..94c800b 100644
>>>>>>> --- a/doc/device-tree-bindings/spi/spi-cadence.txt
>>>>>>> +++ b/doc/device-tree-bindings/spi/spi-cadence.txt
>>>>>>> @@ -26,3 +26,5 @@ connected flash properties
>>>>>>>                           select (n_ss_out).
>>>>>>>  - tslch-ns             : Delay in master reference clocks between setting
>>>>>>>                           n_ss_out low and first bit transfer
>>>>>>> +- sample-edge-rising   : Data outputs from flash memory will be sampled
>> on
>>>>>> the
>>>>>>> +                         rising edge. Default is falling edge.
>>>>>>
>>>>>> 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

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.

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.

-- 
Best regards,
Marek Vasut