Re: [PATCH v5 2/2] Add Intel LGM soc DMA support.

[Reddy, MallikarjunaX]

On 8/28/2020 7:17 PM, Peter Ujfalusi wrote:
> Hi,
>
> On 27/08/2020 17.41, Reddy, MallikarjunaX wrote:
> > > > > > +
> > > > > > +    dma_dev->device_alloc_chan_resources =
> > > > > > +        d->inst->ops->device_alloc_chan_resources;
> > > > > > +    dma_dev->device_free_chan_resources =
> > > > > > +        d->inst->ops->device_free_chan_resources;
> > > > > > +    dma_dev->device_terminate_all =
> > > > > > d->inst->ops->device_terminate_all;
> > > > > > +    dma_dev->device_issue_pending =
> > > > > > d->inst->ops->device_issue_pending;
> > > > > > +    dma_dev->device_tx_status = d->inst->ops->device_tx_status;
> > > > > > +    dma_dev->device_resume = d->inst->ops->device_resume;
> > > > > > +    dma_dev->device_pause = d->inst->ops->device_pause;
> > > > > > +    dma_dev->device_config = d->inst->ops->device_config;
> > > > > > +    dma_dev->device_prep_slave_sg =
> > > > > > d->inst->ops->device_prep_slave_sg;
> > > > > > +    dma_dev->device_synchronize = d->inst->ops->device_synchronize;
> > > > > > +
> > > > > > +    if (d->ver == DMA_VER22) {
> > > > > > +        dma_dev->src_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
> > > > > > +        dma_dev->dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
> > > > > > +        dma_dev->directions = BIT(DMA_MEM_TO_DEV) |
> > > > > > +                      BIT(DMA_DEV_TO_MEM);
> > > > > > +        dma_dev->residue_granularity =
> > > > > > +                    DMA_RESIDUE_GRANULARITY_DESCRIPTOR;
> > > > > > +    }
> > > > > So, if version is != DMA_VER22, then you don't support any direction?
> > > > > Why register the DMA device if it can not do any transfer?
> > > > Only dma0 instance (intel,lgm-cdma) is used as a general purpose slave
> > > > DMA. we set both control and datapath here.
> > > > Other instances we set only control path. data path is taken care by dma
> > > > client(GSWIP).
> > > How the client (GSWIP) can request a channel from intel,lgm-* ? Don't
> > > you need some capabilities for the DMA device so core can sort out the
> > > request?
> > client request channel by name, dma_request_slave_channel(dev, name);
> clients should use dma_request_chan(dev, name);
>
> If the channel can be requested via DT or ACPI then we don't check the
> capabilities at all, so yes, that could work.
>
> > > > Only thing needs to do is get the channel, set the descriptor and just
> > > > on the channel.
> > > How do you 'on' the channel?
> > we on the channel in issue_pending.
> Right.
> Basically you only prep_slave_sg/single for the DMA_VER22? Or do you
> that for the others w/o direction support?
Yes. prep_slave_sg/single only for the DMA_VER22.
> For the intel,lgm-* DMAs you only call issue_pending() and probably
> terminate_all?
Yes, correct.
> Interesting setup ;)
>
> - Péter
>
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki