Subject: [PATCH] dmaengine: pl330: Set residue in tx_status callback

From: [email-masked] (Lars-Peter Clausen)
Date: Tue, 02 Dec 2014 18:25:49 +0100

On 12/02/2014 06:38 AM, Padma Venkat wrote:
> Hi Vinod/Lars,
>
> On 11/26/14, Padmavathi Venna <[email-masked]> wrote:
>> Fill txstate.residue with the amount of bytes remaining in the current
>> transfer if the transfer is not complete.  This will be of particular
>> use to i2s DMA transfers, providing more accurate hw_ptr values to ASoC.
>>
>> I had taken the code from Dylan Reid <[email-masked]> patch from the
>> below link and modified according to the current dmaengine framework.
>> http://comments.gmane.org/gmane.linux.kernel.samsung-soc/23007
>>
>> Cc: Dylan Reid <[email-masked]>
>> Signed-off-by: Padmavathi Venna <[email-masked]>
>> ---
>>
>> This patch has been tested for audio playback on exynos5420 peach-pit.
>>
>>   drivers/dma/pl330.c |   67
>> +++++++++++++++++++++++++++++++++++++++++++++++++-
>>   1 files changed, 65 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
>> index b7493d2..db880ae 100644
>> --- a/drivers/dma/pl330.c
>> +++ b/drivers/dma/pl330.c
>> @@ -2182,11 +2182,74 @@ static void pl330_free_chan_resources(struct
>> dma_chan *chan)
>>   	pm_runtime_put_autosuspend(pch->dmac->ddma.dev);
>>   }
>>
>> +static inline int
>> +pl330_src_addr_in_desc(struct dma_pl330_desc *desc, unsigned int sar)
>> +{
>> +	return ((desc->px.src_addr <= sar) &&
>> +		(sar <= (desc->px.src_addr + desc->px.bytes)));
>> +}
>> +
>> +static inline int
>> +pl330_dst_addr_in_desc(struct dma_pl330_desc *desc, unsigned int dar)
>> +{
>> +	return ((desc->px.dst_addr <= dar) &&
>> +		(dar <= (desc->px.dst_addr + desc->px.bytes)));
>> +}
>> +
>>   static enum dma_status
>>   pl330_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
>>   		 struct dma_tx_state *txstate)
>>   {
>> -	return dma_cookie_status(chan, cookie, txstate);
>> +	dma_addr_t sar, dar;
>> +	struct dma_pl330_chan *pch = to_pchan(chan);
>> +	void __iomem *regs = pch->dmac->base;
>> +	struct pl330_thread *thrd = pch->thread;
>> +	struct dma_pl330_desc *desc;
>> +	unsigned int residue = 0;
>> +	unsigned long flags;
>> +	bool first = true;
>> +	dma_cookie_t first_c, current_c;
>> +	dma_cookie_t used;
>> +	enum dma_status ret;
>> +
>> +	ret = dma_cookie_status(chan, cookie, txstate);
>> +	if (ret == DMA_COMPLETE || !txstate)
>> +		return ret;
>> +
>> +	used = txstate->used;
>> +
>> +	spin_lock_irqsave(&pch->lock, flags);
>> +	sar = readl(regs + SA(thrd->id));
>> +	dar = readl(regs + DA(thrd->id));
>> +
>> +	list_for_each_entry(desc, &pch->work_list, node) {
>> +		if (desc->status == BUSY) {
>> +			current_c = desc->txd.cookie;
>> +			if (first) {
>> +				first_c = desc->txd.cookie;
>> +				first = false;
>> +			}
>> +
>> +			if (first_c < current_c)
>> +				residue += desc->px.bytes;
>> +			else {
>> +				if (desc->rqcfg.src_inc && pl330_src_addr_in_desc(desc, sar)) {
>> +					residue += desc->px.bytes;
>> +					residue -= sar - desc->px.src_addr;
>> +				} else if (desc->rqcfg.dst_inc && pl330_dst_addr_in_desc(desc, dar)) {
>> +					residue += desc->px.bytes;
>> +					residue -= dar - desc->px.dst_addr;
>> +				}
>> +			}
>> +		} else if (desc->status == PREP)
>> +			residue += desc->px.bytes;
>> +
>> +		if (desc->txd.cookie == used)
>> +			break;
>> +	}
>> +	spin_unlock_irqrestore(&pch->lock, flags);
>> +	dma_set_residue(txstate, residue);
>> +	return ret;
>>   }
>>
>>   static void pl330_issue_pending(struct dma_chan *chan)
>> @@ -2631,7 +2694,7 @@ static int pl330_dma_device_slave_caps(struct dma_chan
>> *dchan,
>>   	caps->directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
>>   	caps->cmd_pause = false;
>>   	caps->cmd_terminate = true;
>> -	caps->residue_granularity = DMA_RESIDUE_GRANULARITY_DESCRIPTOR;
>> +	caps->residue_granularity = DMA_RESIDUE_GRANULARITY_SEGMENT;
>>
>>   	return 0;
>>   }
>
> Any comment on this patch?

Well it doesn't break audio, but I don't think it has the correct haviour 
for all cases yet.

Again, the semantics are that it should return the progress of the transfer 
for which the allocation function returned the cookie that is passe to this 
function. You have to consider that there might be multiple different 
descriptors submitted and in the work list, not just the one we want to know 
the status of. The big problem with the pl330 driver is that the current 
structure of the driver makes it not so easy to implement the residue 
reporting correctly.

- Lars