lkml.org 
[lkml]   [2019]   [Jan]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 3/4] dma-buf: add support for mapping with dma mapping attributes
From
Date
On 1/18/19 1:32 PM, Liam Mark wrote:
> On Fri, 18 Jan 2019, Laura Abbott wrote:
>
>> On 1/18/19 10:37 AM, Liam Mark wrote:
>>> Add support for configuring dma mapping attributes when mapping
>>> and unmapping memory through dma_buf_map_attachment and
>>> dma_buf_unmap_attachment.
>>>
>>> Signed-off-by: Liam Mark <lmark@codeaurora.org>
>>> ---
>>> include/linux/dma-buf.h | 3 +++
>>> 1 file changed, 3 insertions(+)
>>>
>>> diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
>>> index 58725f890b5b..59bf33e09e2d 100644
>>> --- a/include/linux/dma-buf.h
>>> +++ b/include/linux/dma-buf.h
>>> @@ -308,6 +308,8 @@ struct dma_buf {
>>> * @dev: device attached to the buffer.
>>> * @node: list of dma_buf_attachment.
>>> * @priv: exporter specific attachment data.
>>> + * @dma_map_attrs: DMA mapping attributes to be used in
>>> + * dma_buf_map_attachment() and dma_buf_unmap_attachment().
>>> *
>>> * This structure holds the attachment information between the dma_buf
>>> buffer
>>> * and its user device(s). The list contains one attachment struct per
>>> device
>>> @@ -323,6 +325,7 @@ struct dma_buf_attachment {
>>> struct device *dev;
>>> struct list_head node;
>>> void *priv;
>>> + unsigned long dma_map_attrs;
>>> };
>>> /**
>>>
>>
>> Did you miss part of this patch? This only adds it to the structure but
>> doesn't
>> add it to any API. The same commment applies to the follow up patch,
>> I don't quite see how it's being used.
>>
>
> Were you asking for a cleaner DMA-buf API to set this field or were you
> asking for a change to an upstream client to make use of this field?
>
> I have clients set the dma_map_attrs field directly on their
> dma_buf_attachment struct before calling dma_buf_map_attachment (if they
> need this functionality).
> Of course this is all being used in Android for out of tree drivers, but
> I assume it is just as useful to everyone else who has cached ION buffers
> which aren't always accessed by the CPU.
>
> My understanding is that AOSP Android on Hikey 960 also is currently
> suffering from too many CMOs due to dma_map_attachemnt always applying
> CMOs, so this support should help them avoid it.
>

Ahhhh I see how you intend this to be used now! I was missing
that clients would do attachment->dma_map_attrs = blah
and that was how it would be stored as opposed to passing
it in at the top level for dma_buf_map. I'll give this some
more thought but I think it could work if Sumit is okay
with the approach.

Thanks,
Laura

\
 
 \ /
  Last update: 2019-01-18 23:46    [W:0.136 / U:0.648 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site