Date: Fri, 18 Aug 2017 21:00:21 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 221616] incorrect nvme driver init sequence Message-ID: <bug-221616-8@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=221616 Bug ID: 221616 Summary: incorrect nvme driver init sequence Product: Base System Version: 10.3-STABLE Hardware: amd64 OS: Any Status: New Severity: Affects Some People Priority: --- Component: kern Assignee: freebsd-bugs@FreeBSD.org Reporter: kinjal.patel@taec.toshiba.com Created attachment 185557 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=185557&action=edit patch to correct the NVMe driver init sequence At present, the NVMe driver init sequence is, 1) Enable controller (CC.EN=1) 2) Wait for controller ready (CSTS.RDY=1) 3) Set PCI bus master enable (BME=1) As per NVMe spec, when NVMe controller becomes ready it has to process command. "Enable (EN): When set to '1', then the controller shall process commands based on Submission Queue Tail doorbell writes" And per PCI Express spec when BME is not set, the PCI Express Function is not allowed to issue any Memory or I/O requests. "Bus Master Enable - Controls the ability of a PCI Express Endpoint to issue Memory95 and I/O Read/Write Requests, and the ability of a Root or Switch Port to forward Memory and I/O Read/Write Requests in the Upstream direction" Enabling controller before setting BME=1 is violation of spec, as controller has to accept commands but BME is prerequisite for that. The FreeBSD NVMe driver sequence should be changed to set BME=1 before attempting to enable controller. The Linux device driver init sequence also does the same. That is, 1) Set PCI bus master enable (BME=1) 2) Enable Controller (CC.EN=1) 3) Wait for controller ready (CSTS.RDY=1) Please find attached patch to correct the NVMe driver init sequence. The patch is based on "FreeBSD 10.3-STABLE amd64" source. Thanks, Kinjal Patel -- You are receiving this mail because: You are the assignee for the bug.help
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