[PULL][Zesty] Low-pin-count (LPC) controller support for arm64

Seth Forshee seth.forshee at canonical.com
Thu Mar 30 16:04:00 UTC 2017

On Wed, Mar 29, 2017 at 06:58:58PM -0600, dann frazier wrote:
> This is a port of the LIBIO infrastructure being prepared upstream to
> handle the low-pin-count (LPC) controller support needed for HiSilicon
> server SoCs, and which is also evolving into a generic PIO mapping
> system for the kernel. While the direction has upstream approval and
> some patches are acked, it is still evolving. I've therefore only
> enabled CONFIG_LIBIO on arm64, and also added a patch to revert to the
> existing PCI PIO mapping code when CONFIG_LIBIO is disabled.
> Tested on a HiSilicon D05 board. Regression tested on ppc64el by Manoj
> Iyer (for the OF change). Also regression tested on a Cavium ThunderX
> system. Built tested on all Ubuntu archs in ppa:dannf/test.
> Addresses: https://bugs.launchpad.net/bugs/1677319
> The following changes since commit 4bd7900ebaac4fd554f8b062954175a1de04686f:
>   UBUNTU: SAUCE: (no-up) net/mlx5: Avoid dereferencing uninitialized
> pointer (2017-03-29 06:19:51 -0600)
> are available in the git repository at:
>   git://git.launchpad.net/~dannf/ubuntu/+source/linux/+git/linux lpc
> for you to fetch changes up to 4354f8bbb202ae8374664b907d4a432e48cc057f:
>   UBUNTU: SAUCE: PCI: Restore codepath for !CONFIG_LIBIO (2017-03-29
> 15:33:44 -0600)

Some of this isn't exactly pretty. But it does look to keep nearly all
the changes in behavior isolated to arm64. Additionally, a good deal of
it is isolated to device-specific code. I think the OF changes look
safe, and testing seems to bear that out.

Given that we're very late in the zesty development cycle, the major
concern I have is the extent of regression testing on other arm64
platforms, with regard to the libio/pci changes in particular. I think
it would be better to try and get some broader testing, then SRU these a
bit later.

One curious thing I encountered while looking through the patches that I
hadn't noticed previously:

+static acpi_status
+acpi_build_libiores_template(struct acpi_device *adev,
+                       struct acpi_buffer *buffer)
+       acpi_handle handle = adev->handle;
+       struct acpi_resource *resource;
+       acpi_status status;
+       int res_cnt = 0;
+       status = acpi_walk_resources(handle, METHOD_NAME__CRS,
+                                    acpi_count_libiores, &res_cnt);
+       if (ACPI_FAILURE(status) || !res_cnt) {
+               dev_err(&adev->dev, "can't evaluate _CRS: %d\n", status);
+               return -EINVAL;
+       }
+       buffer->length = sizeof(struct acpi_resource) * (res_cnt + 1) + 1;
+       buffer->pointer = kzalloc(buffer->length - 1, GFP_KERNEL);

I don't understand allocating the buffer one byte less than
buffer->length. Can you confirm that this isn't a bug?


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