Re: [PATCH v2 0/3] iommu: Enable non-strict DMA on QCom SD/MMC

From: Robin Murphy
Date: Tue Jul 13 2021 - 14:07:14 EST


On 2021-07-08 15:36, Doug Anderson wrote:
[...]
Or document for the users that want performance how to
change the setting, so that they can decide.

Pushing this to the users can make sense for a Linux distribution but
probably less sense for an embedded platform. So I'm happy to make
some way for a user to override this (like via kernel command line),
but I also strongly believe there should be a default that users don't
have to futz with that we think is correct.

FYI I did make progress on the "punt it to userspace" approach. I'm not posting it even as an RFC yet because I still need to set up a machine to try actually testing any of it (it's almost certainly broken somewhere), but in the end it comes out looking surprisingly not too bad overall. If you're curious to take a look in the meantime I put it here:

https://gitlab.arm.com/linux-arm/linux-rm/-/commits/iommu/fq

Cheers,
Robin.