linux-kernel - Re: [PATCH v4 4/7] cxl/acpi: Add background worker to wait for cxl_pci and cxl

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Message-ID: <860121d7-4f40-4da5-b49a-cfeea5bc14c5@fujitsu.com>
Date: Wed, 4 Jun 2025 09:40:26 +0000
From: "Zhijian Li (Fujitsu)" <lizhijian@...itsu.com>
To: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>,
	"linux-cxl@...r.kernel.org" <linux-cxl@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"nvdimm@...ts.linux.dev" <nvdimm@...ts.linux.dev>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
CC: Davidlohr Bueso <dave@...olabs.net>, Jonathan Cameron
	<jonathan.cameron@...wei.com>, Dave Jiang <dave.jiang@...el.com>, Alison
 Schofield <alison.schofield@...el.com>, Vishal Verma
	<vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>, Dan Williams
	<dan.j.williams@...el.com>, Matthew Wilcox <willy@...radead.org>, Jan Kara
	<jack@...e.cz>, "Rafael J . Wysocki" <rafael@...nel.org>, Len Brown
	<len.brown@...el.com>, Pavel Machek <pavel@...nel.org>, Li Ming
	<ming.li@...omail.com>, Jeff Johnson <jeff.johnson@....qualcomm.com>, Ying
 Huang <huang.ying.caritas@...il.com>, "Xingtao Yao (Fujitsu)"
	<yaoxt.fnst@...itsu.com>, Peter Zijlstra <peterz@...radead.org>, Greg KH
	<gregkh@...uxfoundation.org>, Nathan Fontenot <nathan.fontenot@....com>,
	Terry Bowman <terry.bowman@....com>, Robert Richter <rrichter@....com>,
	Benjamin Cheatham <benjamin.cheatham@....com>, PradeepVineshReddy Kodamati
	<PradeepVineshReddy.Kodamati@....com>
Subject: Re: [PATCH v4 4/7] cxl/acpi: Add background worker to wait for
 cxl_pci and cxl_mem probe



On 04/06/2025 06:19, Smita Koralahalli wrote:
>   drivers/cxl/acpi.c         | 23 +++++++++++++++++++++++
>   drivers/cxl/core/suspend.c | 21 +++++++++++++++++++++
>   drivers/cxl/cxl.h          |  2 ++
>   3 files changed, 46 insertions(+)
> 
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index cb14829bb9be..978f63b32b41 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -813,6 +813,24 @@ static int pair_cxl_resource(struct device *dev, void *data)
>   	return 0;
>   }
>   
> +static void cxl_softreserv_mem_work_fn(struct work_struct *work)
> +{
> +	/* Wait for cxl_pci and cxl_mem drivers to load */
> +	cxl_wait_for_pci_mem();
> +
> +	/*
> +	 * Wait for the driver probe routines to complete after cxl_pci
> +	 * and cxl_mem drivers are loaded.
> +	 */
> +	wait_for_device_probe();
> +}
> +static DECLARE_WORK(cxl_sr_work, cxl_softreserv_mem_work_fn);
> +
> +static void cxl_softreserv_mem_update(void)
> +{
> +	schedule_work(&cxl_sr_work);
> +}
> +
>   static int cxl_acpi_probe(struct platform_device *pdev)
>   {
>   	int rc;
> @@ -887,6 +905,10 @@ static int cxl_acpi_probe(struct platform_device *pdev)
>   
>   	/* In case PCI is scanned before ACPI re-trigger memdev attach */
>   	cxl_bus_rescan();
> +
> +	/* Update SOFT RESERVE resources that intersect with CXL regions */
> +	cxl_softreserv_mem_update();
> +
>   	return 0;
>   }
>   
> @@ -918,6 +940,7 @@ static int __init cxl_acpi_init(void)
>   
>   static void __exit cxl_acpi_exit(void)
>   {
> +	cancel_work_sync(&cxl_sr_work);
>   	platform_driver_unregister(&cxl_acpi_driver);
>   	cxl_bus_drain();
>   }
> diff --git a/drivers/cxl/core/suspend.c b/drivers/cxl/core/suspend.c
> index 72818a2c8ec8..c0d8f70aed56 100644
> --- a/drivers/cxl/core/suspend.c
> +++ b/drivers/cxl/core/suspend.c
> @@ -2,12 +2,15 @@
>   /* Copyright(c) 2022 Intel Corporation. All rights reserved. */
>   #include <linux/atomic.h>
>   #include <linux/export.h>
> +#include <linux/wait.h>
>   #include "cxlmem.h"
>   #include "cxlpci.h"
>   
>   static atomic_t mem_active;
>   static atomic_t pci_loaded;
>   
> +static DECLARE_WAIT_QUEUE_HEAD(cxl_wait_queue);

Given that this file (suspend.c) focuses on power management functions,
it might be more appropriate to move the wait queue declaration and its
related changes to acpi.c in where the its caller is.


Thanks
Zhijian

> +
>   bool cxl_mem_active(void)
>   {
>   	if (IS_ENABLED(CONFIG_CXL_MEM))
> @@ -19,6 +22,7 @@ bool cxl_mem_active(void)
>   void cxl_mem_active_inc(void)
>   {
>   	atomic_inc(&mem_active);
> +	wake_up(&cxl_wait_queue);
>   }
>   EXPORT_SYMBOL_NS_GPL(cxl_mem_active_inc, "CXL");
>   
> @@ -28,8 +32,25 @@ void cxl_mem_active_dec(void)
>   }
>   EXPORT_SYMBOL_NS_GPL(cxl_mem_active_dec, "CXL");
>   
> +static bool cxl_pci_loaded(void)
> +{
> +	if (IS_ENABLED(CONFIG_CXL_PCI))
> +		return atomic_read(&pci_loaded) != 0;
> +
> +	return false;
> +}
> +
>   void mark_cxl_pci_loaded(void)
>   {
>   	atomic_inc(&pci_loaded);
> +	wake_up(&cxl_wait_queue);
>   }
>   EXPORT_SYMBOL_NS_GPL(mark_cxl_pci_loaded, "CXL");
> +
> +void cxl_wait_for_pci_mem(void)
> +{
> +	if (!wait_event_timeout(cxl_wait_queue, cxl_pci_loaded() &&
> +				cxl_mem_active(), 30 * HZ))
> +		pr_debug("Timeout waiting for cxl_pci or cxl_mem probing\n");
> +}