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Message-ID: <d620c37f58b303260096f73e04dfff6bb65ed1ef.camel@gmail.com>
Subject: Re: [PATCH v9 09/38] dma: cirrus: Convert to DT for Cirrus EP93xx
From: Alexander Sverdlin <alexander.sverdlin@gmail.com>
To: Vinod Koul <vkoul@kernel.org>, nikita.shubin@maquefel.me
Cc: dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, Arnd Bergmann
	 <arnd@arndb.de>
Date: Thu, 28 Mar 2024 08:21:32 +0100
In-Reply-To: <ZgTytMtgvqcHlEsO@matsya>
References: <20240326-ep93xx-v9-0-156e2ae5dfc8@maquefel.me>
	 <20240326-ep93xx-v9-9-156e2ae5dfc8@maquefel.me> <ZgTytMtgvqcHlEsO@matsya>
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Hello Vinod!

On Thu, 2024-03-28 at 10:01 +0530, Vinod Koul wrote:
> On 26-03-24, 12:18, Nikita Shubin via B4 Relay wrote:
> > From: Nikita Shubin <nikita.shubin@maquefel.me>
> >=20
> > Convert Cirrus EP93xx DMA to device tree usage:
>=20
> Subsytem is dmaengine: pls fix that
>=20
> >=20
> > - add OF ID match table with data
> > - add of_probe for device tree
> > - add xlate for m2m/m2p
> > - drop subsys_initcall code
> > - drop platform probe
> > - drop platform structs usage
> >=20
> > > From now on it only supports device tree probing.
> >=20
> > Co-developed-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
> > Signed-off-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
> > Signed-off-by: Nikita Shubin <nikita.shubin@maquefel.me>
> > ---
> > =C2=A0 drivers/dma/ep93xx_dma.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 | 239 +++++++++++=
+++++++++++++-------
> > =C2=A0 include/linux/platform_data/dma-ep93xx.h |=C2=A0=C2=A0 6 +
> > =C2=A0 2 files changed, 191 insertions(+), 54 deletions(-)
> >=20
> > diff --git a/drivers/dma/ep93xx_dma.c b/drivers/dma/ep93xx_dma.c
> > index d6c60635e90d..17c8e2badee2 100644
> > --- a/drivers/dma/ep93xx_dma.c
> > +++ b/drivers/dma/ep93xx_dma.c

[...]

> > =C2=A0=20
> > @@ -104,6 +106,11 @@
> > =C2=A0 #define DMA_MAX_CHAN_BYTES		0xffff
> > =C2=A0 #define DMA_MAX_CHAN_DESCRIPTORS	32
> > =C2=A0=20
> > +enum ep93xx_dma_type {
> > +	M2P_DMA,
>=20
> Is this missing P2M?

Not really. It's not the most obvious one, but anyway a way to enumerate
two types of DMA engines:

"7.1.1 DMA Features List
DMA specific features are:
=E2=80=A2 Ten fully independent, programmable DMA controller internal M2P/P=
2M
channels (5 Tx and 5 Rx).
=E2=80=A2 Two dedicated channels for Memory-to-Memory (M2M) and
Memory-to-External Peripheral Transfers (external M2P/P2M)."

Now the confusing part is that this "M2M" engine is actually used
to transfer to and from *some* devices, like SPI and IDE.
So both engines are capable of M2P and P2M, maybe Cirrus has named
two engines in a sub-optimal way decades ago and this is now a bit
historical naming.

> > +	M2M_DMA,
> > +};

--=20
Alexander Sverdlin.