Message-ID: <534856E0.1040806@ti.com>
Date: Fri, 11 Apr 2014 15:56:00 -0500
From: Joel Fernandes <joelf@ti.com>
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To: Vinod Koul <vinod.koul@intel.com>
CC: Peter Ujfalusi <peter.ujfalusi@ti.com>, <dan.j.williams@intel.com>,
        <nsekhar@ti.com>, <dmaengine@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <linux-arm-kernel@lists.infradead.org>,
        <linux-omap@vger.kernel.org>,
        <davinci-linux-open-source@linux.davincidsp.com>, <mporter@linaro.org>
Subject: Re: [PATCH v2 08/14] DMA: edma: Use different eventq for cyclic channels
References: <1396357575-30585-1-git-send-email-peter.ujfalusi@ti.com> <1396357575-30585-9-git-send-email-peter.ujfalusi@ti.com> <5346C88E.8010504@ti.com> <20140411164755.GE32284@intel.com>
In-Reply-To: <20140411164755.GE32284@intel.com>
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On 04/11/2014 11:47 AM, Vinod Koul wrote:
> On Thu, Apr 10, 2014 at 11:36:30AM -0500, Joel Fernandes wrote:
>> On 04/01/2014 08:06 AM, Peter Ujfalusi wrote:
>>> To improve latency with cyclic DMA operation it is preferred to
>>> use different eventq/tc than the default which is used by all
>>> other drivers (mmc, spi, i2c, etc).
>>> When preparing the cyclic dma ask for non default queue for the
>>> channel which is going to be used with cyclic mode.
>>>
>>> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
>>> ---
>>>  drivers/dma/edma.c | 3 +++
>>>  1 file changed, 3 insertions(+)
>>>
>>> diff --git a/drivers/dma/edma.c b/drivers/dma/edma.c
>>> index 1dd9e8806975..10048b40fac8 100644
>>> --- a/drivers/dma/edma.c
>>> +++ b/drivers/dma/edma.c
>>> @@ -628,6 +628,9 @@ static struct dma_async_tx_descriptor *edma_prep_dma_cyclic(
>>>  		edesc->pset[i].opt |= TCINTEN;
>>>  	}
>>>  
>>> +	/* Use different eventq/tc for cyclic DMA to reduce latency */
>>> +	edma_request_non_default_queue(echan->ch_num);
>>> +
>>>  	return vchan_tx_prep(&echan->vchan, &edesc->vdesc, tx_flags);
>>>  }
>>>  
>>>
>>
>> Is there any way to guarantee that the non-default queue is of the
>> highest priority, or in other words default queue is of lowest priority.
> well as we are discussing in other thread, it would make sense to pass the
> required priority (i am using audio so pls give me highest one)
> 

Yes, I'm aware of that part of the discussion ;) I also replied there.
This post was sent much earlier on.

thanks,

-Joel
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