[RFC 0/2] iommu: arm-smmu: Add support for early direct mappings

Laurentiu Tudor laurentiu.tudor at nxp.com
Wed May 27 09:06:51 UTC 2020


On 5/26/2020 11:34 PM, John Stultz wrote:
> On Thu, May 14, 2020 at 12:34 PM <bjorn.andersson at linaro.org> wrote:
>>
>> On Thu 27 Feb 18:57 PST 2020, Bjorn Andersson wrote:
>>
>> Rob, Will, we're reaching the point where upstream has enough
>> functionality that this is becoming a critical issue for us.
>>
>> E.g. Lenovo Yoga C630 is lacking this and a single dts patch to boot
>> mainline with display, GPU, WiFi and audio working and the story is
>> similar on several devboards.
>>
>> As previously described, the only thing I want is the stream mapping
>> related to the display controller in place, either with the CB with
>> translation disabled or possibly with a way to specify the framebuffer
>> region (although this turns out to mess things up in the display
>> driver...)
>>
>> I did pick this up again recently and concluded that by omitting the
>> streams for the USB controllers causes an instability issue seen on one
>> of the controller to disappear. So I would prefer if we somehow could
>> have a mechanism to only pick the display streams and the context
>> allocation for this.
>>
>>
>> Can you please share some pointers/insights/wishes for how we can
>> conclude on this subject?
> 
> Ping? I just wanted to follow up on this discussion as this small
> series is crucial for booting mainline on the Dragonboard 845c
> devboard. It would be really valuable to be able to get some solution
> upstream so we can test mainline w/o adding additional patches.

+1

There are also some NXP chips that depend on this. Also, I've submitted
a v2 [1] a while back that tries to address the feedback on the initial
implementation.

[1] https://patchwork.ozlabs.org/project/linux-tegra/list/?series=164853

---
Best Regards, Laurentiu


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