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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,
	Chet Douglas <chet.r.douglas@intel.com>,
	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: [RFC PATCH v2 11/28] cxl/acpi: Rescan bus at probe completion
Date: Sun, 31 Oct 2021 12:25:32 -0700	[thread overview]
Message-ID: <CAPcyv4jm3Hp_XYkQiNYvwhF-S6-3k4qvs-a=4zS1YKukne1dnQ@mail.gmail.com> (raw)
In-Reply-To: <20211022183709.1199701-12-ben.widawsky@intel.com>

On Fri, Oct 22, 2021 at 11:37 AM Ben Widawsky <ben.widawsky@intel.com> wrote:
>
> Ensure that devices being probed before cxl_acpi has completed will get
> a second chance.

I think this is at the wrong level... more below.
>
> CXL drivers are brought up through two enumerable, asynchronous
> mechanism. The leaf nodes in the CXL topology, endpoints, are enumerated
> via PCI headers. The root node's enumeration is platform specific. The
> current defacto mechanism for enumerating the root node is through the
> presence of an ACPI device, ACPI0017.
>
> The primary job of a cxl_mem driver is to determine if CXL.mem traffic
> can be routed to/from the PCIe device that it is being probed. A
> prerequisite in this determination is that all CXL components in the
> path from root to leaf are capable of routing CXL.mem traffic. If the
> cxl_mem driver is probed before cxl_acpi is complete the driver will be
> unable to make this determination. To address this, cxl_acpi (or in the
> future, another platform specific driver) will rescan all devices to
> make sure the ordering is correct.
>
> Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
> ---
>  drivers/cxl/acpi.c | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index 625c5d95b83f..1cc3a74c16bd 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -451,6 +451,14 @@ static u32 cedt_instance(struct platform_device *pdev)
>         return U32_MAX;
>  }
>
> +static void bus_rescan(struct work_struct *work)
> +{
> +       if (bus_rescan_devices(&cxl_bus_type))
> +               pr_err("Failed to rescan CXL bus\n");
> +}
> +
> +static DECLARE_WORK(deferred_bus_rescan, bus_rescan);
> +
>  static int cxl_acpi_probe(struct platform_device *pdev)
>  {
>         int rc;
> @@ -484,9 +492,19 @@ static int cxl_acpi_probe(struct platform_device *pdev)
>         if (rc)
>                 goto out;
>
> -       if (IS_ENABLED(CONFIG_CXL_PMEM))
> +       if (IS_ENABLED(CONFIG_CXL_PMEM)) {
>                 rc = device_for_each_child(&root_port->dev, root_port,
>                                            add_root_nvdimm_bridge);
> +               if (rc)
> +                       goto out;
> +       }
> +
> +       /*
> +        * While ACPI is scanning hostbridge ports, switches and memory devices
> +        * may have been probed. Those devices will need to know whether the
> +        * hostbridge is CXL capable.
> +        */
> +       schedule_work(&deferred_bus_rescan);

I think this belongs in port driver similar to the one in
drivers/cxl/pmem.c, because any port online event might mean that a
downstream port can now attach to the port driver. I prefer a local
ordered workqueue via queue_work() rather than the global unordered
workqueue primarily because it can be flushed without getting
entangled with other random work in the system, but also because the
ordered property is useful for comprehended hierarchical topology
events.

In any event this is missing flushing to prevent races between .text
removal at module_exit() and pending work.

  reply	other threads:[~2021-10-31 19:25 UTC|newest]

Thread overview: 112+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-22 18:36 [RFC PATCH v2 00/28] CXL Region Creation / HDM decoder programming Ben Widawsky
2021-10-22 18:36 ` [RFC PATCH v2 01/28] cxl: Rename CXL_MEM to CXL_PCI Ben Widawsky
2021-10-29 20:15   ` Dan Williams
2021-10-29 21:20     ` Ben Widawsky
2021-10-29 21:39       ` Dan Williams
2021-10-22 18:36 ` [RFC PATCH v2 02/28] cxl: Move register block enumeration to core Ben Widawsky
2021-10-29 20:23   ` Dan Williams
2021-10-29 21:23     ` Ben Widawsky
2021-10-22 18:36 ` [RFC PATCH v2 03/28] cxl/acpi: Map component registers for Root Ports Ben Widawsky
2021-10-29 20:28   ` Dan Williams
2021-10-22 18:36 ` [RFC PATCH v2 04/28] cxl: Add helper for new drivers Ben Widawsky
2021-10-29 20:30   ` Dan Williams
2021-10-22 18:36 ` [RFC PATCH v2 05/28] cxl/core: Convert decoder range to resource Ben Widawsky
2021-10-29 20:50   ` Dan Williams
2021-10-29 21:26     ` Ben Widawsky
2021-10-29 22:22       ` Dan Williams
2021-10-29 22:37         ` Ben Widawsky
2021-11-01 14:33           ` Ben Widawsky
2021-10-22 18:36 ` [RFC PATCH v2 06/28] cxl: Introduce endpoint decoders Ben Widawsky
2021-10-29 21:00   ` Dan Williams
2021-10-29 22:02     ` Ben Widawsky
2021-10-29 22:25       ` Dan Williams
2021-10-22 18:36 ` [RFC PATCH v2 07/28] cxl/core: Move target population locking to caller Ben Widawsky
2021-10-29 23:03   ` Dan Williams
2021-10-22 18:36 ` [RFC PATCH v2 08/28] cxl/port: Introduce a port driver Ben Widawsky
2021-10-30  1:37   ` Dan Williams
2021-10-31 17:53     ` Dan Williams
2021-10-31 18:10       ` Dan Williams
2021-11-01 17:36         ` Ben Widawsky
2021-11-01 17:53     ` Ben Widawsky
2021-11-01 17:54       ` Ben Widawsky
2021-11-02  3:31       ` Dan Williams
2021-11-02 16:27         ` Ben Widawsky
2021-11-02 17:21           ` Dan Williams
2021-11-02 16:58         ` Ben Widawsky
2021-11-04 19:10           ` Dan Williams
2021-11-04 19:49             ` Ben Widawsky
2021-11-04 20:04               ` Dan Williams
2021-11-04 21:25                 ` Ben Widawsky
2021-11-04 16:37     ` Ben Widawsky
2021-11-04 19:17       ` Dan Williams
2021-11-04 19:46         ` Ben Widawsky
2021-11-04 20:00           ` Dan Williams
2021-11-04 21:26             ` Ben Widawsky
2021-11-03 15:18   ` Jonathan Cameron
2021-10-22 18:36 ` [RFC PATCH v2 09/28] cxl/acpi: Map single port host bridge component registers Ben Widawsky
2021-10-31 18:03   ` Dan Williams
2021-11-01 17:07     ` Ben Widawsky
2021-11-02  2:15       ` Dan Williams
2021-11-02 16:31         ` Ben Widawsky
2021-11-02 17:46           ` Dan Williams
2021-11-02 17:57             ` Ben Widawsky
2021-11-02 18:10               ` Dan Williams
2021-11-02 18:27                 ` Ben Widawsky
2021-11-02 18:49                   ` Dan Williams
2021-11-02 21:15                     ` Ben Widawsky
2021-11-02 21:34                       ` Dan Williams
2021-11-02 21:47                         ` Ben Widawsky
2021-10-22 18:36 ` [RFC PATCH v2 10/28] cxl/core: Store global list of root ports Ben Widawsky
2021-10-31 18:32   ` Dan Williams
2021-11-01 18:43     ` Ben Widawsky
2021-11-02  2:04       ` Dan Williams
2021-10-22 18:36 ` [RFC PATCH v2 11/28] cxl/acpi: Rescan bus at probe completion Ben Widawsky
2021-10-31 19:25   ` Dan Williams [this message]
2021-11-01 18:56     ` Ben Widawsky
2021-11-01 21:45       ` Ben Widawsky
2021-11-02  1:56         ` Dan Williams
2021-10-22 18:36 ` [RFC PATCH v2 12/28] cxl/core: Store component register base for memdevs Ben Widawsky
2021-10-31 20:13   ` Dan Williams
2021-11-01 21:50     ` Ben Widawsky
2021-10-22 18:36 ` [RFC PATCH v2 13/28] cxl: Flesh out register names Ben Widawsky
2021-10-31 20:18   ` Dan Williams
2021-11-01 22:00     ` Ben Widawsky
2021-11-02  1:53       ` Dan Williams
2021-11-03 15:53   ` Jonathan Cameron
2021-11-03 16:03     ` Ben Widawsky
2021-11-03 16:42       ` Jonathan Cameron
2021-11-03 17:05         ` Ben Widawsky
2021-10-22 18:36 ` [RFC PATCH v2 14/28] cxl: Hide devm host for ports Ben Widawsky
2021-10-31 21:14   ` Dan Williams
2021-10-22 18:36 ` [RFC PATCH v2 15/28] cxl/core: Introduce API to scan switch ports Ben Widawsky
2021-11-01  5:39   ` Dan Williams
2021-11-01 22:56     ` Ben Widawsky
2021-11-02  1:45       ` Dan Williams
2021-11-02 16:39         ` Ben Widawsky
2021-11-02 20:00           ` Dan Williams
2021-11-16 16:50         ` Ben Widawsky
2021-11-16 17:51           ` Dan Williams
2021-11-16 18:02             ` Ben Widawsky
2021-11-03 16:08   ` Jonathan Cameron
2021-11-10 17:49     ` Ben Widawsky
2021-11-10 18:10       ` Jonathan Cameron
2021-11-10 21:03         ` Dan Williams
2021-10-22 18:36 ` [RFC PATCH v2 16/28] cxl: Introduce cxl_mem driver Ben Widawsky
2021-10-22 18:36 ` [RFC PATCH v2 17/28] cxl: Disable switch hierarchies for now Ben Widawsky
2021-10-22 18:36 ` [RFC PATCH v2 18/28] cxl/region: Add region creation ABI Ben Widawsky
2021-10-22 18:37 ` [RFC PATCH v2 19/28] cxl/region: Introduce concept of region configuration Ben Widawsky
2021-12-15 17:47   ` Jonathan Cameron
2021-10-22 18:37 ` [RFC PATCH v2 20/28] cxl/region: Introduce a cxl_region driver Ben Widawsky
2021-10-22 18:37 ` [RFC PATCH v2 21/28] cxl/acpi: Handle address space allocation Ben Widawsky
2021-10-22 18:37 ` [RFC PATCH v2 22/28] cxl/region: Address " Ben Widawsky
2021-10-22 18:37 ` [RFC PATCH v2 23/28] cxl/region: Implement XHB verification Ben Widawsky
2022-01-06 16:55   ` Jonathan Cameron
2022-01-06 16:58     ` Ben Widawsky
2022-01-06 17:33       ` Jonathan Cameron
2022-01-06 18:10         ` Jonathan Cameron
2022-01-06 18:34           ` Ben Widawsky
2021-10-22 18:37 ` [RFC PATCH v2 24/28] cxl/region: HB port config verification Ben Widawsky
2021-10-22 18:37 ` [RFC PATCH v2 25/28] cxl/region: Record host bridge target list Ben Widawsky
2021-10-22 18:37 ` [RFC PATCH v2 26/28] cxl/mem: Store the endpoint's uport Ben Widawsky
2021-10-22 18:37 ` [RFC PATCH v2 27/28] cxl/region: Gather HDM decoder resources Ben Widawsky
2021-10-22 18:37 ` [RFC PATCH v2 28/28] cxl: Program decoders for regions Ben Widawsky

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