Re: [RFC PATCH v2 19/27] PCI: dwc: ep: Cache MSI outbound iATU mapping

[Niklas Cassel <cassel@kernel.org>]

On Wed, Dec 03, 2025 at 05:40:45PM +0900, Koichiro Den wrote:
> > 
> > If we want to improve the dw-edma driver, so that an EPF driver can have
> > multiple outstanding transfers, I think the best way forward would be to create
> > a new _prep_slave_memcpy() or similar, that does take a direction, and thus
> > does not require dmaengine_slave_config() to be called before every
> > _prep_slave_memcpy() call.
> 
> Would dmaengine_prep_slave_single_config(), which Frank tolds us in this
> thread, be sufficient?

I think that Frank is suggesting a new dmaengine API,
dmaengine_prep_slave_single_config(), which is like
dmaengine_prep_slave_single(), but also takes a struct dma_slave_config *
as a parameter.


I really like the idea.
I think it would allow us to remove the mutex in nvmet_pci_epf_dma_transfer():
https://github.com/torvalds/linux/blob/v6.18/drivers/nvme/target/pci-epf.c#L389-L429

Frank you wrote: "Thanks, we also consider ..."
Does that mean that you have any plans to work on this?
I would definitely be interested.


Kind regards,
Niklas