kernel-packages team mailing list archive

[dann frazier <dann.frazier@xxxxxxxxxxxxx>]

On Thu, Nov 27, 2014 at 8:17 PM, Ming Lei <1386490@xxxxxxxxxxxxxxxxxx> wrote:
> >From ARM64 maintainer's viewpoint:
>
>          http://marc.info/?l=linux-arm-kernel&m=141708838404470&w=2
>
>          Either way, I don't think it's a problem for the kernel. We just need to
>          change the default DMA ops to coherent when booting with ACPI (using
>          non-coherent ops for a coherent device is not safe as the CPU can
>          corrupt cache lines written by the device).
>
> So I suggest to revert c7a4a7658d689f6 for utopic since utopic ships APM's
> non-upstreamed PCI implementation, and APM's ARM64 Soc is coherent
> arch.
>
> Dann, what do you think about it?

Ming,
 Thanks for looking into this.
I'm not sure I follow the relevancy of a couple things:

 - The upstream discussion seems to have gotten rerouted to solving
the problem for ACPI, but this issue is regarding device-tree (as was
your patch), since that is what Ubuntu/m400 uses. I'm having trouble
seeing how the ACPI solution helps us.

 - I'm confident I reproduced this problem with all upstream bits
after PCI was merged. Therefore my assumption was that this issue is
independent of PCI stack choice. Do you believe that the solution for
the upstream PCI stack is different than the solution for the APM PCI
stack?

In general I'm OK with a revert of c7a4a7658d689f6 for utopic, as long
as we have a plan for an upstream answer for vivid and beyond (>=
3.19). I don't think the kernel team would support a plan that
involves carrying this revert indefinitely (if that's what you're
suggesting, I'm not sure it is).

  -dann

> Thanks,
>
> ** Changed in: linux (Ubuntu Utopic)
>      Assignee: (unassigned) => Ming Lei (tom-leiming)
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1386490
>
> Title:
>   HP ProLiant m400 nic doesn't work after trusty
>
> To manage notifications about this bug go to:
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https://bugs.launchpad.net/bugs/1386490

Title:
  HP ProLiant m400 nic doesn't work after trusty

Status in linux package in Ubuntu:
  Confirmed
Status in linux source package in Utopic:
  Confirmed
Status in linux source package in Vivid:
  Confirmed

Bug description:
  Starting in 3.15, arm64 began defaulting to non-coherent dma_ops:

  commit c7a4a7658d689f664050c45493d79adf053f226e
  Author: Ritesh Harjani <ritesh.harjani@xxxxxxxxx>
  Date:   Wed Apr 23 06:29:46 2014 +0100

      arm64: Make default dma_ops to be noncoherent

  Firmware (dtb in the case of the m400) is responsible for telling the
  kernel when a device requires coherent dma_ops. However, as of utopic,
  this property is not being inherited by downstream devices.
  Specifically, the xgene-pcie device is marked as coherent, but the
  devices behind it (mellanox card) still get initialized with non-
  coherent ops.

  This results in the mlx4 driver bailing out with the following messages:
  [   18.703635] mlx4_core 0000:01:00.0: command 0x23 timed out (go bit not cleared)
  [   18.710911] mlx4_core 0000:01:00.0: Failed to initialize queue pair table, aborting

  
  There's an upstream discussion on the topic here:
    http://www.spinics.net/lists/arm-kernel/msg362320.html

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