Re: [PATCH v5 1/2] dt-bindings: dma: Add bindings for intel LGM SOC

[Reddy, MallikarjunaX]

Hi Vinod,
Thanks for the review, please see my comments inline.

On 8/31/2020 7:00 PM, Vinod Koul wrote:
> On 31-08-20, 16:06, Reddy, MallikarjunaX wrote:
> > Hi Vinod,
> >
> > Thanks for the review. Please see my comment inline.
> >
> > On 8/28/2020 6:45 PM, Vinod Koul wrote:
> > > On 27-08-20, 17:54, Reddy, MallikarjunaX wrote:
> > > > Hi Vinod,
> > > > Thanks for the review comments.
> > > >
> > > > On 8/25/2020 7:21 PM, Vinod Koul wrote:
> > > > > On 18-08-20, 15:00, Reddy, MallikarjunaX wrote:
> > > > >
> > > > > > > > +
> > > > > > > > +            intel,chans:
> > > > > > > > +              $ref: /schemas/types.yaml#/definitions/uint32-array
> > > > > > > > +              description:
> > > > > > > > +                 The channels included on this port. Format is channel start
> > > > > > > > +                 number and how many channels on this port.
> > > > > > > Why does this need to be in DT? This all seems like it can be in the dma
> > > > > > > cells for each client.
> > > > > > (*ABC)
> > > > > > Yes. We need this.
> > > > > > for dma0(lgm-cdma) old SOC supports 16 channels and the new SOC supports 22
> > > > > > channels. and the logical channel mapping for the peripherals also differ
> > > > > > b/w old and new SOCs.
> > > > > >
> > > > > > Because of this hardware limitation we are trying to configure the total
> > > > > > channels and port-channel mapping dynamically from device tree.
> > > > > >
> > > > > > based on port name we are trying to configure the default values for
> > > > > > different peripherals(ports).
> > > > > > Example: burst length is not same for all ports, so using port name to do
> > > > > > default configurations.
> > > > > Sorry that does not make sense to me, why not specify the values to be
> > > > > used here instead of defining your own name scheme!
> > > > OK. Agreed. I will remove port name from DT and only use intel,chans
> > > what is intel,chans, why not use dma-channels?
> >   The intel,chans says about the channels included on the correspondng port.
> What do you mean by a port here?
Here Port is nothing but Peripheral(SPI, HSNAND...)
> > Format is channel start number and how many channels on this port.
> It is perfectly reasonable to have 16 channels but linux not use use all, lets
> say from 5th channel channel onwards
>
> So you need to use standard dma-channels also with dma-channel-mask to
> specify which channels linux can use
Ok, let me verify and use the standard dma-channels also dma-channel-mask.
> >   The reasong behind using this attribute instead of standrad dma-channels
> > is...
> >
> >
> > DMA_VER22 HW supports 22 channels. But there is a hole in HW, total it can
> > use only 16.
> >
> > Old soc supports 4ports and 16 channels.
> > New soc supports 6ports and 22 channels.
> > (old and new soc carry the same version VER22)
> >
> > port channel mapping for the old and new soc also not the same.
> > old soc: logical channels:(Rx, Tx)
> > 0, 1 - SPI0
> > 2, 3 - SPI1
> > 4, 5 - HSNAND
> > 12, 14, 13, 15 - Memcopy
> >
> > New soc: Logical channels(Rx, Tx)
> > 0, 1 - SPI0
> > 2, 3 - SPI1
> > 4, 5 - SPI2
> > 6, 7 - SPI3
> > 8, 9 - HSNAND
> > 10 to 21 - Mcopy
> Mapping is different, client can set that channel required in dmas
> property and use a specific required channel.
OK.
> > Because of these reasons we are trying to use "intel,chans" attribute, and
> > reading then number of channels from the dt.
> > Advantaage:
> > 1. we can map the channels correspondign to port
> > 2. Dynamically configure the channels (due to hw limitation)
> >
> > If this is not ok, please suggest us the better way to handle this.