Re: DMA support for FlexSPI driver

[Frieder Schrempf <frieder.schrempf@xxxxxxxxxx>]

On 19.12.22 21:21, Michael Walle wrote:
> [+ Frieder and Boris]
> 
> Hi,
> 
> Am 2022-12-19 21:09, schrieb Han Xu:
>> On 22/12/19 02:08PM, Fabio Estevam wrote:
>>> Hi,
>>>
>>> Currently, there is no DMA support for the drivers/spi/spi-nxp-fspi.c
>>> driver.
>>>
>>> Is there a technical reason that prevents DMA to be used on this
>>> driver with the i.MX8MM?
>>>
>>> Also checked the NXP vendor driver, but DMA support is also missing.
>>>
>>> Does anyone know more about the reason for this?
> 
> flexspi is a copy of the spi-fsl-qspi driver and I'd say the
> latter just got the basic operations polled IO or the memory
> mapped access and nobody cared :)

The QSPI SPI MEM driver was derived from the original QSPI SPI NOR
driver and IIRC this didn't have DMA support either. And FSPI was
basically copied from QSPI as Michael already pointed out.

So yes, I guess the reason is nobody cared so far. I don't know of any
technical reasons for not having DMA support.

> 
>> We are working on that, both flexspi driver and sdma driver need to be
>> updated,
>> and will upstream all once done.
> 
> Are you also working on the DMA support for the layerscape
> architecture which is using eDMA?
> 
> -michael