Hi Tim, Am Dienstag, den 11.04.2017, 09:05 -0700 schrieb Tim Harvey: > On Wed, Apr 5, 2017 at 5:16 AM, Lucas Stach <l.stach@xxxxxxxxxxxxxx> wrote: > > Am Mittwoch, den 05.04.2017, 13:07 +0100 schrieb Joao Pinto: > > [...] > >> >>> Lucas, > >> >>> > >> >>> I feel a bit dumb here for forgetting about this issue and letting it > >> >>> drop, but I've just spent a day debugging an issue with the ath9k > >> >>> wireless driver only to realize it was that the ath9k card and/or > >> >>> driver doesn't support MSI interrupts and thus no longer work on > >> >>> mainline kernels that have MSI enabled. To be honest I'm not sure how > >> >>> many PCIe devices out there can't support MSI because of hardware > >> >>> limitations vs drivers that simply have not implemented it. > >> >>> > >> >>> To make matters worse 3ee803641e76bea76ec730c80dcc64739a9919ff makes > >> >>> it such that you can't disable MSI on the IMX6. > >> >>> > >> >>> Is there some fix you can think of to make the IMX6 PCIe host > >> >>> controller raise an interrupt for cards/drivers that use legacy irq's? > >> >>> If not, then we need to allow MSI to be disabled for IMX6 and default > >> >>> it to disabled for compatibility. > >> >>> > >> >> > >> >> Joao / Jingoo, > >> >> > >> >> (Adding linux-pci to the list to pick up maintainers of other DWC PCIe > >> >> core drivers) > >> >> > >> >> Is Luca's statement that 'legacy IRQs and MSIs can't be used together' > >> >> true in general for the DW PCIe core? If any of the host controllers > >> >> using this core can't support both legacy and MSI irqs together I > >> >> still believe we shouldn't enable/require MSI as it breaks any > >> >> card/driver that only supports legacy interrupts (such as ath9k). > >> > > >> > If there are 2 DW PCIe controllers, one controller can be used for legacy > >> > and another controller can be used for MSI. > >> > > >> > But, I am not sure that one DW PCIe controller can support both MSI device > >> > and legacy interrupt device at the same time. > >> > > >> > To Joao Pinto, > >> > Will you confirm this? > >> > > >> > >> Hi Jingoo, > >> I confirm that if a RC has MSI enable, it won't support legacy interrupts. > > > > Okay, so the only way to solve this in a generic way, that I can see at > > the moment is to defer MSI enable until the downstream device actually > > requests an MSI irq. > > > > Also we need to disable the MSI capability if any bridge device turns up > > during the bus topology scan, as we can have devices with conflicting > > requirements connected to the RC in that case. > > > > I'll cook up some patches to implement this. > > > > Lucas, > > Any thoughts yet? I'll likely want to backport this to stable although > the restructuring to drivers/pci/dwc and subsequent changes since 4.10 > will likely require a re-written patch. I have a fix for this, that I'm currently testing on different setups. I'll probably send it out in a few hours. Regards, Lucas
