On 10/06/2015 11:21 AM, Shawn Lin wrote:
Hi Vinod,
On 2015/10/5 23:37, Vinod Koul wrote:
On Mon, Sep 14, 2015 at 07:48:59AM +0800, Shawn Lin wrote:
Add dmaengine_get_quirks API for peripheral devices to query quirks if they need it to make special workaround due to broken dma controller design.
Signed-off-by: Shawn Lin shawn.lin@rock-chips.com
Changes in v5: None Changes in v4: None Changes in v3: None Changes in v2: None Changes in v1: None
include/linux/dmaengine.h | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h index e2f5eb4..5174ca4 100644 --- a/include/linux/dmaengine.h +++ b/include/linux/dmaengine.h @@ -704,6 +704,7 @@ struct dma_device {
int (*device_config)(struct dma_chan *chan, struct dma_slave_config *config);
- int (*device_get_quirks)(struct dma_chan *chan);
And why do we want to expose this to users? THis doesnt seem right!
Basically I agree not to expose dma's quirk to slave controllers...But, the fact I mentioned on cover letter explain the reasons why I have to let slave controllers know that they are working with a broken dma. It's a dilemma that if we don't want that to be exposed(let slave controllers' driver get the info via a API), we have t add broken quirk for all of them ,here and there, which seems to be a disaster:(
The problem with this API is that it transports values with device specific meanings over a generic API. Which is generally speaking not a good idea because the consumer witch is supposed to be generic suddenly needs to know which provider it is talking to.
A better solution in this case typically is either introduce a generic API with generic values or a custom API with custom values, but don't mix the two.
I would appreciate it if you could give me some suggestions at your earliest convenience. :)
In this case I think the best way to handle this is not quirks, but rather expose the actual maximum burst size using the DMA capabilities API. Since supporting only a certain burst depth is not really a quirk. All hardware has a limit for this and for some it might be larger or smaller than for others and it might be the same IP core but the maximum size depends on some IP core parameters. So this should be discoverable.
- Lars