On Mon, Aug 28, 2017 at 7:23 AM, Lucas Stach [off-list ref] wrote:

Hi all,

this small series tries to fix/workaround a serious design flaw of the DWC PCIe
host controller: it is unable to work with both legacy and MSI IRQs enabled at
the same time. As soon as the first MSI is enabled in the DWC MSI controller,
the host stops forwarding legacy IRQs.

If the MSI controller is present, MSIs will be used for the PCIe port services
IRQs, leaving endpoint devices which don't support MSIs unable to raise IRQs.
It is only safe to enable the MSI controller if it is validated that all PCIe
devices and drivers in the system support working MSIs. As most devices
support falling back to using legacy PCIe IRQs if MSI support is missing it is
much safer to disable the MSI by default and only enable it on validated
systems.

Feedback welcome.

Regards,
Lucas

Lucas Stach (3):
  PCI: designware: only register MSI controller when MSI irq line is
    valid
  PCI: imx6: allow MSI irq to be absent
  ARM: dts: imx6qdl: remove MSI irq line

 .../devicetree/bindings/pci/fsl,imx6q-pcie.txt     |  8 ++++----
 arch/arm/boot/dts/imx6qdl.dtsi                     |  2 --
 drivers/pci/dwc/pci-imx6.c                         | 23 +++++++++++-----------
 drivers/pci/dwc/pcie-designware-host.c             |  4 ++--
 4 files changed, 17 insertions(+), 20 deletions(-)

Lucas,

Thank you for following up on this!

I tested it with and without the third patch that removes msi from the
dt thus with both an ath9k 802.11 device which only supports legacy
interrupts and a Marvell sky2 device which supports msi as well as
legacy interrupts and it works as expected:
 - without msi enabled in dts (default): both sky2 and ath9k work
 - with msi enabled in dt: sky2 works ath9k does not

Tested-by: Tim Harvey <tharvey@gateworks.com>

Regards,

Tim