From: nsekhar@ti•com (Sekhar Nori)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v2 07/14] arm: common: edma: API to request non default queue for a channel
Date: Fri, 11 Apr 2014 14:13:31 +0530 [thread overview]
Message-ID: <5347AB33.8000606@ti.com> (raw)
In-Reply-To: <1396357575-30585-8-git-send-email-peter.ujfalusi@ti.com>
On Tuesday 01 April 2014 06:36 PM, Peter Ujfalusi wrote:
> When using eDMA3 via dmaengine all dma channels will use the default queue.
> Since during request time we do not have means to change this it need to be done
> later, before the DMA has been started.
> With the added function it is possible to move the channel to a non default
> queue if it is possible, otherwise (when only one EQ/TC is available for the CC)
> the default queue is going to be used.
> For example: For optimal system performance the audio (cyclic) DMA should
> be placed to a separate queue which is different than what the rest of the
> system is using.
>
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti•com>
> ---
> arch/arm/common/edma.c | 27 +++++++++++++++++++++++++++
> include/linux/platform_data/edma.h | 2 ++
> 2 files changed, 29 insertions(+)
>
> diff --git a/arch/arm/common/edma.c b/arch/arm/common/edma.c
> index be267b2080be..eaf6dd19f082 100644
> --- a/arch/arm/common/edma.c
> +++ b/arch/arm/common/edma.c
> @@ -712,6 +712,33 @@ int edma_alloc_channel(int channel,
> }
> EXPORT_SYMBOL(edma_alloc_channel);
>
> +/**
> + * edma_request_non_default_queue - try to map the channel to non default queue
> + * @channel: dma channel returned from edma_alloc_channel()
> + *
> + * For certain type of applications like audio it is preferred to not use the
> + * default event queue/tc to avoid eDMA caused latency.
> + *
> + * This function will iterate through the event queues available for the CC and
> + * picks the first EQ/TC which is not set as the default for the CC
> + */
> +void edma_request_non_default_queue(int channel)
> +{
> + unsigned ctlr = EDMA_CTLR(channel);
> + enum dma_event_q eventq_no = EVENTQ_DEFAULT;
> + int i;
> +
> + for (i = 0; i < edma_cc[ctlr]->num_tc; i++) {
> + if (i != edma_cc[ctlr]->default_queue) {
> + eventq_no = i;
> + break;
> + }
> + }
> +
> + channel = EDMA_CHAN_SLOT(channel);
> + map_dmach_queue(ctlr, channel, eventq_no);
> +}
> +EXPORT_SYMBOL(edma_request_non_default_queue);
With this API, the caller cannot be sure of what the final affect on the
channel will be. It depends a lot on what the default queue setting is.
And that can change independent of this API.
I am not an expert in dmaengine, but it looks like we are trying to
workaround the fact that dmaengine does not support multiple transfer
priorities for a dma_chan. If yes, it will be better to add support for
doing this in dmaengine core itself. A generic priority space could be
supported which each DMA device can then map to its hardware support.
Thanks,
Sekhar
next prev parent reply other threads:[~2014-04-11 8:43 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-01 13:06 [PATCH v2 00/14] dma: edma: Fixes for cyclic (audio) operation Peter Ujfalusi
2014-04-01 13:06 ` [PATCH v2 01/14] platform_data: edma: Be precise with the paRAM struct Peter Ujfalusi
2014-04-01 13:06 ` [PATCH v2 02/14] dma: edma: Correct the handling of src/dst_maxburst == 0 Peter Ujfalusi
2014-04-01 13:06 ` [PATCH v2 03/14] dma: edma: Add support for DMA_PAUSE/RESUME operation Peter Ujfalusi
2014-04-11 16:43 ` Vinod Koul
2014-04-11 20:51 ` Joel Fernandes
2014-04-01 13:06 ` [PATCH v2 04/14] dma: edma: Set DMA_CYCLIC capability flag Peter Ujfalusi
2014-04-01 13:06 ` [PATCH v2 05/14] arm: common: edma: Select event queue 1 as default when booted with DT Peter Ujfalusi
2014-04-10 16:23 ` Joel Fernandes
2014-04-11 8:17 ` Sekhar Nori
2014-04-11 8:50 ` Peter Ujfalusi
2014-04-11 8:56 ` Sekhar Nori
2014-04-11 9:38 ` Peter Ujfalusi
2014-04-11 9:42 ` Vinod Koul
2014-04-11 10:19 ` Sekhar Nori
2014-04-11 11:32 ` Peter Ujfalusi
2014-04-11 11:31 ` Vinod Koul
2014-04-11 12:23 ` Peter Ujfalusi
2014-04-11 12:46 ` Vinod Koul
2014-04-14 11:56 ` Peter Ujfalusi
2014-04-14 12:12 ` Sekhar Nori
2014-04-14 12:41 ` Peter Ujfalusi
2014-04-14 14:32 ` Sekhar Nori
2014-04-16 12:59 ` Peter Ujfalusi
2014-04-16 16:05 ` Joel Fernandes
2014-04-24 9:07 ` Peter Ujfalusi
2014-04-11 20:16 ` Joel Fernandes
2014-04-01 13:06 ` [PATCH v2 06/14] arm: common: edma: Save the number of event queues/TCs Peter Ujfalusi
2014-04-01 13:06 ` [PATCH v2 07/14] arm: common: edma: API to request non default queue for a channel Peter Ujfalusi
2014-04-11 8:43 ` Sekhar Nori [this message]
2014-04-01 13:06 ` [PATCH v2 08/14] DMA: edma: Use different eventq for cyclic channels Peter Ujfalusi
2014-04-10 16:36 ` Joel Fernandes
2014-04-11 16:47 ` Vinod Koul
2014-04-11 20:56 ` Joel Fernandes
2014-04-01 13:06 ` [PATCH v2 09/14] dma: edma: Implement device_slave_caps callback Peter Ujfalusi
2014-04-01 13:06 ` [PATCH v2 10/14] dma: edma: Simplify direction configuration in edma_config_pset() Peter Ujfalusi
2014-04-10 22:40 ` Joel Fernandes
2014-04-11 6:39 ` Peter Ujfalusi
2014-04-11 19:57 ` Joel Fernandes
2014-04-01 13:06 ` [PATCH v2 11/14] dma: edma: Reduce debug print verbosity for non verbose debugging Peter Ujfalusi
2014-04-01 13:06 ` [PATCH v2 12/14] dma: edma: Prefix debug prints where the text were identical in prep callbacks Peter Ujfalusi
2014-04-01 13:06 ` [PATCH v2 13/14] dma: edma: Add channel number to debug prints Peter Ujfalusi
2014-04-01 13:06 ` [PATCH v2 14/14] dma: edma: Print the direction value as well when it is not supported Peter Ujfalusi
2014-04-10 22:52 ` [PATCH v2 00/14] dma: edma: Fixes for cyclic (audio) operation Joel Fernandes
2014-04-11 16:52 ` Vinod Koul
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