[U-Boot] [PATCH 1/4 v2] spi: spi-mem: Use 2 SPI messages instead of a single full-duplex one

[Stefan Roese]

Hi Miquel,

On 09.08.2018 16:50, Miquel Raynal wrote:
> Stefan Roese <sr at denx.de> wrote on Thu, 9 Aug 2018 11:10:15 +0200:
> 
>> Hi Miquel,
>>
>> On 09.08.2018 10:13, Miquel Raynal wrote:
>>> Stefan Roese <sr at denx.de> wrote on Thu, 9 Aug 2018 07:24:14 +0200:
>>>>> Hi Miquel,
>>>>
>>>> On 08.08.2018 10:56, Miquel Raynal wrote:
>>>>> Boris Brezillon <boris.brezillon at bootlin.com> wrote on Tue, 7 Aug 2018
>>>>> 15:28:02 +0200:
>>>>>>> On Tue,  7 Aug 2018 14:16:52 +0200
>>>>>> Stefan Roese <sr at denx.de> wrote:
>>>>>>    >>>>> Some SPI controller do not support full-duplex SPI transfers. This patch
>>>>>>> changes the SPI transfer into 2 separate transfers - or 1, if no data is
>>>>>>> to transmitted.
>>>>>>>
>>>>>>> With this change, no buffers need to be allocated anymore. We use the
>>>>>>> TX and RX buffers that are passed to spi_mem_exec_op() directly.
>>>>>>>
>>>>>>> Signed-off-by: Stefan Roese <sr at denx.de>
>>>>>>> Suggested-by: Boris Brezillon <boris.brezillon at bootlin.com>
>>>>>>> Cc: Miquel Raynal <miquel.raynal at bootlin.com>
>>>>>>> Cc: Boris Brezillon <boris.brezillon at bootlin.com>
>>>>>>> Cc: Jagan Teki <jagan at openedev.com>
>>>>>>
>>>>>> Looks good overall, just a few comments (that you might chose to ignore
>>>>>> if you disagree).
>>>>>>
>>>>>> Reviewed-by: Boris Brezillon <boris.brezillon at bootlin.com>
>>>>>>
>>>>>> Sorry for being a bit late on the discussion, but while I do agree with
>>>>> the change, I'm not sure about its implementation : I think SPI
>>>>> controllers are supposed to be abstracted by the SPI layer.
>>>>> Addressing the controller's limitations in the SPI-mem layer would
>>>>> not be appropriate.
>>>>>> Would it be possible to adapt spi_xfer() to handle such case?
>>>>
>>>> No, I don't think so. Its impossible to guess in the SPI driver layer,
>>>> which parts of the message are TX data and which are RX data. So this
>>>> message can't be split up into a half-duplex one here. This can only
>>>> be done in the driver which constructs the SPI messages.
>>>>
>>>> Or did I miss something here?
>>>> Actually I'm fine with it as SPI-mem only uses half-duplex. It's not
>>> necessary to limit its use to SPI controllers (drivers) supporting
>>> full-duplex.
>>>> Stefan, shall I fold your changes in my series and resend? Or do I
>>> resend only my original patches and Jagan/Tom will apply yours on top
>>> of it?
>>
>> Do you need to re-send your original patches? If yes, then please do
>> with my patches folded in. If a re-send is not necessary, then Jagan
>> or Tom should be able to apply your latest patchset and mine on top
>> of it.
> 
> I suppose Jagan prefers formal patches than a Github branch so
> basically I have to pull Boris fixes, squash them, do the same with
> yours and resend.

I see. I was not aware, that the fixes from Boris have not been
squashed yet. Then re-sending this whole series is probably the
best solution.

> As we missed the merge window, maybe I'll also take the time to rework
> mtdparts. I plan to do that next week.

That would be great.

Thanks,
Stefan