linux-kernel - Re: Re: [PATCH 2/2] dma: pl330: Use the generic of_dma_xlate_by_chan

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Message-id: <26789240.182151364893959039.JavaMail.weblogic@epv6ml02>
Date:	Tue, 02 Apr 2013 09:12:41 +0000 (GMT)
From:	PADMAVATHI VENNA <padma.v@...sung.com>
To:	Lars-Peter Clausen <lars@...afoo.de>
Cc:	Vinod Koul <vinod.koul@...el.com>, Dan Williams <djbw@...com>,
	Jon Hunter <jon-hunter@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Re: [PATCH 2/2] dma: pl330: Use the generic of_dma_xlate_by_chan_id

Hi Lars,

------- Original Message -------
Sender : Lars-Peter Clausen<lars@...afoo.de>
Date : Apr 02, 2013 16:33 (GMT+09:00)
Title : Re: [PATCH 2/2] dma: pl330: Use the generic of_dma_xlate_by_chan_id

On 04/02/2013 08:27 AM, PADMAVATHI VENNA wrote:
> 
> Hi,
> ------- Original Message -------
> Sender : Lars-Peter Clausen
> Date : Mar 25, 2013 22:16 (GMT+09:00)
> Title : [PATCH 2/2] dma: pl330: Use the generic of_dma_xlate_by_chan_id
> 
> Use the generic of_dma_xlate_by_chan_id xlate callback instead of a custom
> implementation.
> 
> There is one minor difference between the generic of_dma_xlate_by_chan_id
> function and the pl330 specific one. of_dma_xlate_by_chan_id only sets the
> DMA_SLAVE capability for the channel capability mask, while the pl330 driver
> additionally sets the DMA_CYCLIC capability. But since all pl330 channels which
> have the DMA_SLAVE capability set also have DMA_CYCLIC capability set both
> functions will have the same result.
> 
> I am not clear about the dma capabilities. Is it mentioned some where that if we set DMA_SLAVE capability
> will that also set DMA_CYCLIC capability?
> 

Well DMA_SLAVE won't automatically set DMA_CYCLIC. But the driver sets both.

I tested your patches, it's woking for audio. But I need some clarification related to capabilities.
As per my understanding, controller driver registers the available capabilities in the probe and 
client drivers requests for a particular capability. In both the cases, in the dmaengine it checks
if the requested capability is satisfied.
If we don't set the DMA_CYCLIC, how __dma_device_satisfies_mask works?

 Please correct me if I am wrong.

Thanks
Padma
- Lars

> Signed-off-by: Lars-Peter Clausen 
> ---
> drivers/dma/pl330.c | 41 +----------------------------------------
> 1 file changed, 1 insertion(+), 40 deletions(-)
> 
> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
> index 345e2a1..ea48de7 100644
> --- a/drivers/dma/pl330.c
> +++ b/drivers/dma/pl330.c
> @@ -608,11 +608,6 @@ struct dma_pl330_desc {
> struct dma_pl330_chan *pchan;
> };
> 
> -struct dma_pl330_filter_args {
> - struct dma_pl330_dmac *pdmac;
> - unsigned int chan_id;
> -};
> -
> static inline void _callback(struct pl330_req *r, enum pl330_op_err err)
> {
> if (r && r->xfer_cb)
> @@ -2358,16 +2353,6 @@ static void dma_pl330_rqcb(void *token, enum pl330_op_err err)
> tasklet_schedule(&pch->task);
> }
> 
> -static bool pl330_dt_filter(struct dma_chan *chan, void *param)
> -{
> - struct dma_pl330_filter_args *fargs = param;
> -
> - if (chan->device != &fargs->pdmac->ddma)
> - return false;
> -
> - return (chan->chan_id == fargs->chan_id);
> -}
> -
> bool pl330_filter(struct dma_chan *chan, void *param)
> {
> u8 *peri_id;
> @@ -2380,30 +2365,6 @@ bool pl330_filter(struct dma_chan *chan, void *param)
> }
> EXPORT_SYMBOL(pl330_filter);
> 
> -static struct dma_chan *of_dma_pl330_xlate(struct of_phandle_args *dma_spec,
> - struct of_dma *ofdma)
> -{
> - int count = dma_spec->args_count;
> - struct dma_pl330_dmac *pdmac = ofdma->of_dma_data;
> - struct dma_pl330_filter_args fargs;
> - dma_cap_mask_t cap;
> -
> - if (!pdmac)
> - return NULL;
> -
> - if (count != 1)
> - return NULL;
> -
> - fargs.pdmac = pdmac;
> - fargs.chan_id = dma_spec->args[0];
> -
> - dma_cap_zero(cap);
> - dma_cap_set(DMA_SLAVE, cap);
> - dma_cap_set(DMA_CYCLIC, cap);
> -
> - return dma_request_channel(cap, pl330_dt_filter, &fargs);
> -}
> -
> static int pl330_alloc_chan_resources(struct dma_chan *chan)
> {
> struct dma_pl330_chan *pch = to_pchan(chan);
> @@ -2996,7 +2957,7 @@ pl330_probe(struct amba_device *adev, const struct amba_id *id)
> pi->pcfg.num_peri, pi->pcfg.num_events);
> 
> ret = of_dma_controller_register(adev->dev.of_node,
> - of_dma_pl330_xlate, pdmac);
> + of_dma_xlate_by_chan_id, pd);
> if (ret) {
> dev_err(&adev->dev,
> "unable to register DMA to the generic DT DMA helpers\n");