[PATCH v2 2/2] drm/omap: partial workaround for DRA7xx DMM errata i878

[Tomi Valkeinen]

On 04/04/18 12:51, Laurent Pinchart wrote:
> Hi Tomi,
> 
> On Wednesday, 4 April 2018 10:37:05 EEST Tomi Valkeinen wrote:
>> On 04/04/18 00:11, Laurent Pinchart wrote:
>>> I assume access to DMM-mapped buffers to be way more frequent than access
>>> to the DMM registers. If that's the case, this partial workaround should
>>> only slightly lower the probability of system lock-up. Do you have plans
>>> to implement a workaround that will fix the problem completely ?
>>
>> CPU only accesses memory via DMM when using TILER 2D buffers, which are
>> not officially supported. For non-2D, the pages are mapped directly to
>> the CPU without DMM in between.
> 
> What is the DMM used for with non-2D then ? Does it need to be setup at all ?

It creates a contiguous view of memory for IPs without IOMMUs, like DSS.

 Tomi

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