On 1/2/2018 12:12 PM, Keith Busch wrote: > On Tue, Jan 02, 2018 at 08:25:08AM -0500, Sinan Kaya wrote: >>> 2. A DPC event suppresses the error message required for the Linux >>> AER driver to run. How can AER and DPC run concurrently? >>> >> >> As we briefly discussed in previous email exchanges, I think you are >> looking at a use case with a switch that supports DPC functionality. > > No, I'm interested in DPC in a general. > >> Oza and I are looking at a root port functionality with DPC feature. >> >> As you already know, AER errors are logged to AER capability register >> independent of the DPC driver presence. > > The error is noted in the Uncorrectable Error Status Register if that's > what triggered the DPC event. This register has nothing to do with the > Root Error Status Register, which is required to have received an error > Message in order to have a status for the AER driver. > >> A root port is also allowed to share the MSI interrupts across DPC and >> AER. >> >> Therefore, when a DPC interrupt fires; both AER driver and DPC driver >> starts recovery work. This is the issue we are trying to deal with. > > If DPC is implemented correctly, the AER Root Status can't have an > uncorrectable status for the driver to deal with. The only thing the AER > driver could possibly see is a correctable error if DPC ERR_COR Enable > is set. > >> In the end, the driver needs to work for both root port and switches. >> I think you verified it against a switch. We are doing the same for a >> root port and submitting the plumbing code. > > I think we need to consider the possibility you are enabling a platform > that implemented DPC incorrectly. There's nothing in the specification > that says that DPC enabled root ports are not to discard the error message > if it came from downstream, or skip signalling the message for root port > detected errors. > I'll circle this with the HW team. The current code still doesn't handle outstanding transactions properly. We can probably split the patch into two and deal with this aspect later. -- Sinan Kaya Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
