RE: [PATCH v2 1/3] mtd: rawnand: cadence: support deferred prob when DMA is not ready

[Rabara, Niravkumar L]

Hi Miquel,

> -----Original Message-----
> From: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
> Sent: Tuesday, 4 February, 2025 9:33 PM
> To: Rabara, Niravkumar L <niravkumar.l.rabara@xxxxxxxxx>
> Cc: Richard Weinberger <richard@xxxxxx>; Vignesh Raghavendra
> <vigneshr@xxxxxx>; linux@xxxxxxxxxxx; Shen Lichuan <shenlichuan@xxxxxxxx>;
> Jinjie Ruan <ruanjinjie@xxxxxxxxxx>; u.kleine-koenig@xxxxxxxxxxxx; linux-
> mtd@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v2 1/3] mtd: rawnand: cadence: support deferred prob when
> DMA is not ready
> 
> On 04/02/2025 at 10:43:20 GMT, "Rabara, Niravkumar L"
> <niravkumar.l.rabara@xxxxxxxxx> wrote:
> >> Hello,
> >>
> >> > My apologies for the confusion.
> >> > Slave DMA terminology used in cadence nand controller bindings and
> >> > driver is indeed confusing.
> >> >
> >> > To answer your question it is,
> >> > 1 - External DMA (Generic DMA controller).
> >> >
> >> > Nand controller IP do not have embedded DMA controller (2 -
> >> > peripheral
> >> DMA).
> >> >
> >> > FYR, how external DMA is used.
> >> > https://elixir.bootlin.com/linux/v6.13.1/source/drivers/mtd/nand/ra
> >> > w/c
> >> > adence-nand-controller.c#L1962
> >>
> >> In this case we should have a dmas property (and perhaps dma-names), no?
> >>
> > No, I believe.
> > Cadence NAND controller IP do not have dedicated handshake interface
> > to connect with DMA controller.
> > My understanding is dmas (and dma-names) are only used for the
> > dedicated handshake interface between peripheral and the DMA controller.
> 
> I don't see well how you can defer if there is no resource to grab. And if there is
> a resource to grab, why is it not described anywhere?
> 

Since NAND controller do not have handshake interface with DMA controller.
Driver is using external DMA for memory-to-memory copy. 

Your point is since the driver is using external DMA and it should be described in bindings? 

Thanks,
Nirav