linux-kernel - Re: [PATCH v3 01/12] dma: edma: Setup parameters to DMA MAX_NR

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Date:	Mon, 12 Aug 2013 19:19:58 -0500
From:	Joel Fernandes <joelf@...com>
To:	<joelf@...com>
CC:	Sekhar Nori <nsekhar@...com>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Sricharan R <r.sricharan@...com>,
	Rajendra Nayak <rnayak@...com>,
	Lokesh Vutla <lokeshvutla@...com>,
	Matt Porter <matt@...orter.com>,
	Vinod Koul <vinod.koul@...el.com>, Dan Williams <djbw@...com>,
	Russell King <linux@....linux.org.uk>,
	Linux OMAP List <linux-omap@...r.kernel.org>,
	Linux ARM Kernel List <linux-arm-kernel@...ts.infradead.org>,
	Linux DaVinci Kernel List 
	<davinci-linux-open-source@...ux.davincidsp.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 01/12] dma: edma: Setup parameters to DMA MAX_NR_SG
 at a time

On 08/12/2013 06:55 PM, Joel Fernandes wrote:
> Dropped quite a few from the CC list...
> 
> On 08/12/2013 02:15 AM, Sekhar Nori wrote:
>> On Monday 05 August 2013 09:44 PM, Joel Fernandes wrote:
>>> Changes are made here for configuring existing parameters to support
>>> DMA'ing them out in batches as needed.
>>>
>>> Also allocate as many as slots as needed by the SG list, but not more
>>> than MAX_NR_SG. Then these slots will be reused accordingly.
>>> For ex, if MAX_NR_SG=10, and number of SG entries is 40, still only
>>> 10 slots will be allocated to DMA the entire SG list of size 40.
>>>
>>> Signed-off-by: Joel Fernandes <joelf@...com>
>>> ---
>>>  drivers/dma/edma.c |   14 +++++++++++---
>>>  1 file changed, 11 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/dma/edma.c b/drivers/dma/edma.c
>>> index 5f3e532..7b0853c 100644
>>> --- a/drivers/dma/edma.c
>>> +++ b/drivers/dma/edma.c
>>> @@ -222,9 +222,9 @@ static struct dma_async_tx_descriptor *edma_prep_slave_sg(
>>>  	enum dma_slave_buswidth dev_width;
>>>  	u32 burst;
>>>  	struct scatterlist *sg;
>>> -	int i;
>>>  	int acnt, bcnt, ccnt, src, dst, cidx;
>>>  	int src_bidx, dst_bidx, src_cidx, dst_cidx;
>>> +	int i, num_slots_needed;
>>
>> 'nslots' is more to my liking. Better keep variable names short.
>>
>>>  
>>>  	if (unlikely(!echan || !sgl || !sg_len))
>>>  		return NULL;
>>> @@ -262,8 +262,11 @@ static struct dma_async_tx_descriptor *edma_prep_slave_sg(
>>>  
>>>  	edesc->pset_nr = sg_len;
>>>  
>>> -	for_each_sg(sgl, sg, sg_len, i) {
>>> -		/* Allocate a PaRAM slot, if needed */
>>> +	/* Allocate a PaRAM slot, if needed */
>>> +
>>> +	num_slots_needed = sg_len > MAX_NR_SG ? MAX_NR_SG : sg_len;
>>
>> nslots = min(MAX_NR_SG, sg_len);
> 
> I agree the original naming was quite long. I would rather using
> something more descriptive though than nslots. How does slots_needed sound?

Sorry for the noise, nslots is fine and I've changed it to the same.

-Joel

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