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From: Dan Williams <dan.j.williams@intel.com>
To: Ben Widawsky <ben.widawsky@intel.com>
Cc: linux-cxl@vger.kernel.org, Linux PCI <linux-pci@vger.kernel.org>,
	Alison Schofield <alison.schofield@intel.com>,
	Ira Weiny <ira.weiny@intel.com>,
	Jonathan Cameron <Jonathan.Cameron@huawei.com>,
	Vishal Verma <vishal.l.verma@intel.com>
Subject: Re: [PATCH 05/23] cxl/pci: Don't poll doorbell for mailbox access
Date: Mon, 29 Nov 2021 11:37:34 -0800	[thread overview]
Message-ID: <CAPcyv4jT_5x7itJovgjRyfsRsjWqPghRYshxqvga=af8GJ6Nmw@mail.gmail.com> (raw)
In-Reply-To: <20211129193156.wtm7p7cdpn7iedqa@intel.com>

On Mon, Nov 29, 2021 at 11:32 AM Ben Widawsky <ben.widawsky@intel.com> wrote:
[..]
> >
> > Right, there's no harm in the check, it just seems overly paranoid to
> > me if it was already checked once. Until a doorbell timeout happens
> > it's an extra MMIO cycle that can saved for a "what happened?" check
> > after a timeout.
>
> Well I suspect we're just rearranging the deck chairs on the Titanic now, but...

Not so much, just trying to get this driver in line with other error
handling designs.

> I see doorbell timeouts as disconnected from whether or not the mailbox
> interface is ready. If they were the same, we wouldn't need both bits and we
> could just wait extra long for the doorbell when probing.
>
> In other words, I expect if the interface goes unready, doorbell timeout will
> occur, but I don't think we should assume if doorbell timeout occurs, the
> interface is no longer ready. I don't purport to know why a doorbell timeout
> might occur while the interface remains available (likely a firmware bug, I
> presume).
>
> It does seem interesting to check if the interface is no longer ready on timeout
> though.

So I'm just modeling this off of NVME error handling where there is a
Controller Fatal Status bit that could be checked every transaction,
but instead the driver waits until a command timeout to collect if the
device went fatal / not-ready.

  reply	other threads:[~2021-11-29 21:08 UTC|newest]

Thread overview: 133+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-20  0:02 [PATCH 00/23] Add drivers for CXL ports and mem devices Ben Widawsky
2021-11-20  0:02 ` [PATCH 01/23] cxl: Rename CXL_MEM to CXL_PCI Ben Widawsky
2021-11-22 14:47   ` Jonathan Cameron
2021-11-24  4:15   ` Dan Williams
2021-11-20  0:02 ` [PATCH 02/23] cxl: Flesh out register names Ben Widawsky
2021-11-22 14:49   ` Jonathan Cameron
2021-11-24  4:24   ` Dan Williams
2021-11-20  0:02 ` [PATCH 03/23] cxl/pci: Extract device status check Ben Widawsky
2021-11-22 15:03   ` Jonathan Cameron
2021-11-24 19:30   ` Dan Williams
2021-11-20  0:02 ` [PATCH 04/23] cxl/pci: Implement Interface Ready Timeout Ben Widawsky
2021-11-22 15:02   ` Jonathan Cameron
2021-11-22 17:17     ` Ben Widawsky
2021-11-22 17:53       ` Jonathan Cameron
2021-11-24 19:56         ` Dan Williams
2021-11-25  6:17           ` Ben Widawsky
2021-11-25  7:14             ` Dan Williams
2021-11-20  0:02 ` [PATCH 05/23] cxl/pci: Don't poll doorbell for mailbox access Ben Widawsky
2021-11-22 15:11   ` Jonathan Cameron
2021-11-22 17:24     ` Ben Widawsky
2021-11-24 21:55   ` Dan Williams
2021-11-29 18:33     ` Ben Widawsky
2021-11-29 19:02       ` Dan Williams
2021-11-29 19:11         ` Ben Widawsky
2021-11-29 19:18           ` Dan Williams
2021-11-29 19:31             ` Ben Widawsky
2021-11-29 19:37               ` Dan Williams [this message]
2021-11-29 19:50                 ` Ben Widawsky
2021-11-20  0:02 ` [PATCH 06/23] cxl/pci: Don't check media status for mbox access Ben Widawsky
2021-11-22 15:19   ` Jonathan Cameron
2021-11-24 21:58   ` Dan Williams
2021-11-20  0:02 ` [PATCH 07/23] cxl/pci: Add new DVSEC definitions Ben Widawsky
2021-11-22 15:22   ` Jonathan Cameron
2021-11-22 17:32     ` Ben Widawsky
2021-11-24 22:03       ` Dan Williams
2021-11-20  0:02 ` [PATCH 08/23] cxl/acpi: Map component registers for Root Ports Ben Widawsky
2021-11-22 15:51   ` Jonathan Cameron
2021-11-22 19:28     ` Ben Widawsky
2021-11-24 22:18   ` Dan Williams
2021-11-20  0:02 ` [PATCH 09/23] cxl: Introduce module_cxl_driver Ben Widawsky
2021-11-22 15:54   ` Jonathan Cameron
2021-11-24 22:22   ` Dan Williams
2021-11-20  0:02 ` [PATCH 10/23] cxl/core: Convert decoder range to resource Ben Widawsky
2021-11-22 16:08   ` Jonathan Cameron
2021-11-24 22:41   ` Dan Williams
2021-11-20  0:02 ` [PATCH 11/23] cxl/core: Document and tighten up decoder APIs Ben Widawsky
2021-11-22 16:13   ` Jonathan Cameron
2021-11-24 22:55   ` Dan Williams
2021-11-20  0:02 ` [PATCH 12/23] cxl: Introduce endpoint decoders Ben Widawsky
2021-11-22 16:20   ` Jonathan Cameron
2021-11-22 19:37     ` Ben Widawsky
2021-11-25  0:07       ` Dan Williams
2021-11-29 20:05         ` Ben Widawsky
2021-11-29 20:07           ` Dan Williams
2021-11-29 20:12             ` Ben Widawsky
2021-11-20  0:02 ` [PATCH 13/23] cxl/core: Move target population locking to caller Ben Widawsky
2021-11-22 16:33   ` Jonathan Cameron
2021-11-22 21:58     ` Ben Widawsky
2021-11-23 11:05       ` Jonathan Cameron
2021-11-25  0:34   ` Dan Williams
2021-11-20  0:02 ` [PATCH 14/23] cxl: Introduce topology host registration Ben Widawsky
2021-11-22 18:20   ` Jonathan Cameron
2021-11-22 22:30     ` Ben Widawsky
2021-11-25  1:09   ` Dan Williams
2021-11-29 21:23     ` Ben Widawsky
2021-11-20  0:02 ` [PATCH 15/23] cxl/core: Store global list of root ports Ben Widawsky
2021-11-22 18:22   ` Jonathan Cameron
2021-11-22 22:32     ` Ben Widawsky
2021-11-20  0:02 ` [PATCH 16/23] cxl/pci: Cache device DVSEC offset Ben Widawsky
2021-11-22 16:46   ` Jonathan Cameron
2021-11-22 22:34     ` Ben Widawsky
2021-11-20  0:02 ` [PATCH 17/23] cxl: Cache and pass DVSEC ranges Ben Widawsky
2021-11-20  4:29   ` kernel test robot
2021-11-20  4:29     ` kernel test robot
2021-11-22 17:00   ` Jonathan Cameron
2021-11-22 22:50     ` Ben Widawsky
2021-11-26 11:37   ` Jonathan Cameron
2021-11-20  0:02 ` [PATCH 18/23] cxl/pci: Implement wait for media active Ben Widawsky
2021-11-22 17:03   ` Jonathan Cameron
2021-11-22 22:57     ` Ben Widawsky
2021-11-23 11:09       ` Jonathan Cameron
2021-11-23 16:04         ` Ben Widawsky
2021-11-23 17:48           ` Bjorn Helgaas
2021-11-23 19:37             ` Ben Widawsky
2021-11-26 11:36     ` Jonathan Cameron
2021-11-20  0:02 ` [PATCH 19/23] cxl/pci: Store component register base in cxlds Ben Widawsky
2021-11-20  7:28   ` kernel test robot
2021-11-20  7:28     ` kernel test robot
2021-11-22 17:11   ` Jonathan Cameron
2021-11-22 23:01     ` Ben Widawsky
2021-11-20  0:02 ` [PATCH 20/23] cxl/port: Introduce a port driver Ben Widawsky
2021-11-20  3:14   ` kernel test robot
2021-11-20  3:14     ` kernel test robot
2021-11-20  5:38   ` kernel test robot
2021-11-20  5:38     ` kernel test robot
2021-11-22 17:41   ` Jonathan Cameron
2021-11-22 23:38     ` Ben Widawsky
2021-11-23 11:38       ` Jonathan Cameron
2021-11-23 16:14         ` Ben Widawsky
2021-11-23 18:21   ` Bjorn Helgaas
2021-11-23 22:03     ` Ben Widawsky
2021-11-23 22:36       ` Dan Williams
2021-11-23 23:38         ` Ben Widawsky
2021-11-23 23:55         ` Bjorn Helgaas
2021-11-24  0:40           ` Dan Williams
2021-11-24  6:33             ` Christoph Hellwig
2021-11-24  7:17               ` Dan Williams
2021-11-24  7:28                 ` Christoph Hellwig
2021-11-24  7:33                   ` Greg Kroah-Hartman
2021-11-24  7:54                     ` Dan Williams
2021-11-24  8:21                       ` Greg Kroah-Hartman
2021-11-24 18:24                         ` Dan Williams
2021-12-02 21:24                 ` Bjorn Helgaas
2021-12-03  1:38                   ` Dan Williams
2021-12-03 22:03                     ` Bjorn Helgaas
2021-12-04  1:24                       ` Dan Williams
2021-12-07  2:56                         ` Bjorn Helgaas
2021-12-07  4:48                           ` Dan Williams
2021-11-24 21:31       ` Bjorn Helgaas
2021-11-20  0:02 ` [PATCH 21/23] cxl: Unify port enumeration for decoders Ben Widawsky
2021-11-22 17:48   ` Jonathan Cameron
2021-11-22 23:44     ` Ben Widawsky
2021-11-20  0:02 ` [PATCH 22/23] cxl/mem: Introduce cxl_mem driver Ben Widawsky
2021-11-20  0:40   ` Randy Dunlap
2021-11-21  3:55     ` Ben Widawsky
2021-11-22 18:17   ` Jonathan Cameron
2021-11-23  0:05     ` Ben Widawsky
2021-11-20  0:02 ` [PATCH 23/23] cxl/mem: Disable switch hierarchies for now Ben Widawsky
2021-11-22 18:19   ` Jonathan Cameron
2021-11-22 19:17     ` Ben Widawsky
2021-11-25 21:53 [PATCH 14/23] cxl: Introduce topology host registration kernel test robot
2021-11-29 11:42 ` Dan Carpenter
2021-11-29 11:42 ` Dan Carpenter

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