Subject: [PATCH 1/1] DMA: PL330: allow submitting 2 requests at a time

From: [email-masked] (dirac3000)
Date: Thu, 07 Feb 2013 14:46:37 +0100

On 02/07/2013 12:31 PM, Jassi Brar wrote:

> On Thu, Feb 7, 2013 at 4:08 PM, Alvaro Moran<[email-masked]>  wrote:
>> Due to the original driver design, only one request was processed at a
>> time by the driver, even if the low-level part of the driver was able to
>> handle 2 requests.
>> With this patch we are able to create 2 microcodes per thread and to
>> launch the second transfer on the interrupt handler of the first one,
>> instead of having to wait for the tasklet to generate the microcode.
>>
> The following seems more appropriate and complete. Does it fix your problem?
>
> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
> index 758122f..a821d71 100644
> --- a/drivers/dma/pl330.c
> +++ b/drivers/dma/pl330.c
> @@ -2292,13 +2292,12 @@ static inline void fill_queue(struct
> dma_pl330_chan *pch)
>
>   		/* If already submitted */
>   		if (desc->status == BUSY)
> -			break;
> +			continue;
>
>   		ret = pl330_submit_req(pch->pl330_chid,
>   						&desc->req);
>   		if (!ret) {
>   			desc->status = BUSY;
> -			break;
>   		} else if (ret == -EAGAIN) {
>   			/* QFull or DMAC Dying */
>   			break;

Actually that isn't good enough. With your patch it will keep on looping 
on the pch->work_list entries, but it will call pl330_submit_req the 
first time only. I want it to call the function twice, so it will 
generate 2 microcodes (one per available request) and it will be ready 
the moment we get into the interrupt handler.