Linux host behavior when CSTS.CFS bit is set to 1

[Ken Chen (kchena)]

Hi All,

>From a recent message exchange in this mail list, I saw the following statement:

"In the nvme Linux driver in function nvme_kthread() the CSTS register is read once a second to check for controller status failure." 

If this statement is true, is Linux supposed to initiate a reset to the drive if CSTS.CFS bit is set to 1?

I am working on a SSD firmware. When certain hardware exceptions occur in the drive, the firmware sets CSTS.CFS bit to 1, expecting a reset by the host.  I am using Centos 7 with kernel 4.2.2-1.el7.elrepo.x86_64. In my tests, when firmware sets CFS bit, the host does not seem to reset the drive. That is, there is no transition of CC.EN bit from 1 to 0, there is no setting CC.SHN bit to 1, and there is no writing "NVMe" to NSSR register, etc. Is there anything else that firmware needs to do to trigger a reset from the host? Or is there any configuration (such as PCIe AER) that needs to be enabled in order for Linux to support this functionality?

Any advice will be appreciated.

Thanks,

Ken