* [PATCH] Allow to use DMA_CTRL_REUSE flag for all channel types
@ 2017-04-28 13:37 Eugeniy Paltsev
2017-05-01 5:51 ` Vinod Koul
0 siblings, 1 reply; 4+ messages in thread
From: Eugeniy Paltsev @ 2017-04-28 13:37 UTC (permalink / raw)
To: dmaengine
Cc: linux-kernel, linux-snps-arc, Dan Williams, Vinod Koul,
Andy Shevchenko, Alexey Brodkin, Eugeniy Paltsev
In the current implementation dma_get_slave_caps is used to check
state of descriptor_reuse option. But dma_get_slave_caps includes
check if the channel supports slave transactions.
So DMA_CTRL_REUSE flag can be set (even for MEM-TO-MEM tranfers)
only if channel supports slave transactions.
Now we can use DMA_CTRL_REUSE flag for all channel types.
Also it allows to test reusing mechanism with simply mem-to-mem dma
test.
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
---
include/linux/dmaengine.h | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 5336808..92cf8b0 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -1376,11 +1376,7 @@ static inline int dma_get_slave_caps(struct dma_chan *chan,
static inline int dmaengine_desc_set_reuse(struct dma_async_tx_descriptor *tx)
{
- struct dma_slave_caps caps;
-
- dma_get_slave_caps(tx->chan, &caps);
-
- if (caps.descriptor_reuse) {
+ if (tx->chan->device->descriptor_reuse) {
tx->flags |= DMA_CTRL_REUSE;
return 0;
} else {
--
2.9.3
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] Allow to use DMA_CTRL_REUSE flag for all channel types
2017-04-28 13:37 [PATCH] Allow to use DMA_CTRL_REUSE flag for all channel types Eugeniy Paltsev
@ 2017-05-01 5:51 ` Vinod Koul
2017-05-02 15:16 ` Eugeniy Paltsev
0 siblings, 1 reply; 4+ messages in thread
From: Vinod Koul @ 2017-05-01 5:51 UTC (permalink / raw)
To: Eugeniy Paltsev
Cc: dmaengine, linux-kernel, linux-snps-arc, Dan Williams,
Andy Shevchenko, Alexey Brodkin
On Fri, Apr 28, 2017 at 04:37:46PM +0300, Eugeniy Paltsev wrote:
> In the current implementation dma_get_slave_caps is used to check
> state of descriptor_reuse option. But dma_get_slave_caps includes
> check if the channel supports slave transactions.
> So DMA_CTRL_REUSE flag can be set (even for MEM-TO-MEM tranfers)
> only if channel supports slave transactions.
>
> Now we can use DMA_CTRL_REUSE flag for all channel types.
> Also it allows to test reusing mechanism with simply mem-to-mem dma
> test.
We do not want to allow that actually. Slave is always treated as a special
case, so resue was allowed.
With memcpy the assumptions are different and clients can do reuse.
>
> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
> ---
> include/linux/dmaengine.h | 6 +-----
> 1 file changed, 1 insertion(+), 5 deletions(-)
>
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index 5336808..92cf8b0 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -1376,11 +1376,7 @@ static inline int dma_get_slave_caps(struct dma_chan *chan,
>
> static inline int dmaengine_desc_set_reuse(struct dma_async_tx_descriptor *tx)
> {
> - struct dma_slave_caps caps;
> -
> - dma_get_slave_caps(tx->chan, &caps);
> -
> - if (caps.descriptor_reuse) {
> + if (tx->chan->device->descriptor_reuse) {
> tx->flags |= DMA_CTRL_REUSE;
> return 0;
> } else {
> --
> 2.9.3
>
> --
> To unsubscribe from this list: send the line "unsubscribe dmaengine" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
~Vinod
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] Allow to use DMA_CTRL_REUSE flag for all channel types
2017-05-01 5:51 ` Vinod Koul
@ 2017-05-02 15:16 ` Eugeniy Paltsev
2017-05-10 3:55 ` Vinod Koul
0 siblings, 1 reply; 4+ messages in thread
From: Eugeniy Paltsev @ 2017-05-02 15:16 UTC (permalink / raw)
To: vinod.koul
Cc: dmaengine, linux-kernel, andriy.shevchenko, dan.j.williams,
Alexey.Brodkin, Eugeniy.Paltsev, linux-snps-arc
Hi Vinod,
On Mon, 2017-05-01 at 11:21 +0530, Vinod Koul wrote:
> On Fri, Apr 28, 2017 at 04:37:46PM +0300, Eugeniy Paltsev wrote:
> > In the current implementation dma_get_slave_caps is used to check
> > state of descriptor_reuse option. But dma_get_slave_caps includes
> > check if the channel supports slave transactions.
> > So DMA_CTRL_REUSE flag can be set (even for MEM-TO-MEM tranfers)
> > only if channel supports slave transactions.
> >
> > Now we can use DMA_CTRL_REUSE flag for all channel types.
> > Also it allows to test reusing mechanism with simply mem-to-mem dma
> > test.
>
> We do not want to allow that actually. Slave is always treated as a
> special
> case, so resue was allowed.
>
> With memcpy the assumptions are different and clients can do reuse.
Could you please clarify why don't we want to allow use DMA_CTRL_REUSE
for mem-to-mem transfers?
Reusing of mem-to-mem (MEMCPY and DMA_SG) descriptors will work fine on
virt-dma based drivers.
Anyway the current implementation behaviour is quite strange:
If channel supports *slave* transfers DMA_CTRL_REUSE can be set to
slave and *mem-to-mem* transfers.
And, of course, we can pass DMA_CTRL_REUSE flag to device_prep_dma_sg
or device_prep_dma_memcpy directly without checks.
> >
> > Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
> > ---
> > include/linux/dmaengine.h | 6 +-----
> > 1 file changed, 1 insertion(+), 5 deletions(-)
> >
> > diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> > index 5336808..92cf8b0 100644
> > --- a/include/linux/dmaengine.h
> > +++ b/include/linux/dmaengine.h
> > @@ -1376,11 +1376,7 @@ static inline int dma_get_slave_caps(struct
> > dma_chan *chan,
> >
> > static inline int dmaengine_desc_set_reuse(struct
> > dma_async_tx_descriptor *tx)
> > {
> > - struct dma_slave_caps caps;
> > -
> > - dma_get_slave_caps(tx->chan, &caps);
> > -
> > - if (caps.descriptor_reuse) {
> > + if (tx->chan->device->descriptor_reuse) {
> > tx->flags |= DMA_CTRL_REUSE;
> > return 0;
> > } else {
> > --
> > 2.9.3
> >
> > --
--
Eugeniy Paltsev
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] Allow to use DMA_CTRL_REUSE flag for all channel types
2017-05-02 15:16 ` Eugeniy Paltsev
@ 2017-05-10 3:55 ` Vinod Koul
0 siblings, 0 replies; 4+ messages in thread
From: Vinod Koul @ 2017-05-10 3:55 UTC (permalink / raw)
To: Eugeniy Paltsev
Cc: dmaengine, linux-kernel, andriy.shevchenko, dan.j.williams,
Alexey.Brodkin, linux-snps-arc
On Tue, May 02, 2017 at 03:16:18PM +0000, Eugeniy Paltsev wrote:
> Hi Vinod,
>
> On Mon, 2017-05-01 at 11:21 +0530, Vinod Koul wrote:
> > On Fri, Apr 28, 2017 at 04:37:46PM +0300, Eugeniy Paltsev wrote:
> > > In the current implementation dma_get_slave_caps is used to check
> > > state of descriptor_reuse option. But dma_get_slave_caps includes
> > > check if the channel supports slave transactions.
> > > So DMA_CTRL_REUSE flag can be set (even for MEM-TO-MEM tranfers)
> > > only if channel supports slave transactions.
> > >
> > > Now we can use DMA_CTRL_REUSE flag for all channel types.
> > > Also it allows to test reusing mechanism with simply mem-to-mem dma
> > > test.
> >
> > We do not want to allow that actually. Slave is always treated as a
> > special
> > case, so resue was allowed.
> >
> > With memcpy the assumptions are different and clients can do reuse.
>
> Could you please clarify why don't we want to allow use DMA_CTRL_REUSE
> for mem-to-mem transfers?
>
> Reusing of mem-to-mem (MEMCPY and DMA_SG) descriptors will work fine on
> virt-dma based drivers.
Precisely, the client does not know if you have a virt-dma or some other
kind if implementation
For them they see a channel and use it!
> Anyway the current implementation behaviour is quite strange:
> If channel supports *slave* transfers DMA_CTRL_REUSE can be set to
> slave and *mem-to-mem* transfers.
>
> And, of course, we can pass DMA_CTRL_REUSE flag to device_prep_dma_sg
> or device_prep_dma_memcpy directly without checks.
Yeah thats bad, do send a patch to forbid that..
--
~Vinod
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2017-05-10 3:53 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-04-28 13:37 [PATCH] Allow to use DMA_CTRL_REUSE flag for all channel types Eugeniy Paltsev
2017-05-01 5:51 ` Vinod Koul
2017-05-02 15:16 ` Eugeniy Paltsev
2017-05-10 3:55 ` Vinod Koul
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).