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

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Date:	Mon, 12 Aug 2013 18:55:48 -0500
From:	Joel Fernandes <joelf@...com>
To:	Sekhar Nori <nsekhar@...com>
CC:	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

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?

Thanks,

-Joel

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