| Message ID | 1396357575-30585-8-git-send-email-peter.ujfalusi@ti.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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
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); /** * edma_free_channel - deallocate DMA channel diff --git a/include/linux/platform_data/edma.h b/include/linux/platform_data/edma.h index 923f8a3e4ce0..5d0a1b98f205 100644 --- a/include/linux/platform_data/edma.h +++ b/include/linux/platform_data/edma.h @@ -117,6 +117,8 @@ int edma_alloc_channel(int channel, void *data, enum dma_event_q); void edma_free_channel(unsigned channel); +void edma_request_non_default_queue(int channel); + /* alloc/free parameter RAM slots */ int edma_alloc_slot(unsigned ctlr, int slot); void edma_free_slot(unsigned slot);
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(+)