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

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Date:	Tue, 02 Apr 2013 12:44:36 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	padma.v@...sung.com
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: [PATCH 2/2] dma: pl330: Use the generic of_dma_xlate_by_chan_id

On 04/02/2013 11:12 AM, PADMAVATHI VENNA wrote:
> 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

Hi,

Well, DMA_SLAVE | DMA_CYCLIC is a more restrictive mask than DMA_SLAVE. So
any channel that matches DMA_SLAVE | DMA_CYCLIC will also match DMA_SLAVE.

- Lars

> - 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");

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