On 6/3/25 3:19 PM, Smita Koralahalli wrote:
> Introduce a waitqueue mechanism to coordinate initialization between the
> cxl_pci and cxl_mem drivers.
>
> Launch a background worker from cxl_acpi_probe() that waits for both
> drivers to complete initialization before invoking wait_for_device_probe().
> Without this, the probe completion wait could begin prematurely, before
> the drivers are present, leading to missed updates.
>
> Co-developed-by: Nathan Fontenot <Nathan.Fontenot@xxxxxxx>
> Signed-off-by: Nathan Fontenot <Nathan.Fontenot@xxxxxxx>
> Co-developed-by: Terry Bowman <terry.bowman@xxxxxxx>
> Signed-off-by: Terry Bowman <terry.bowman@xxxxxxx>
> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@xxxxxxx>
> ---
> 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);
> +
> 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))
I'm trying to understand why cxl_pci_loaded() is needed. cxl_mem_active() goes above 0 when a cxl_mem_probe() instance succeeds. cxl_mem_probe() being triggered implies that an instance of cxl_pci_probe() has been called since cxl_mem_probe() is triggered from devm_cxl_add_memdev() with memdev being added and cxl_mem driver also have been loaded. So does cxl_mem_active() not imply cxl_pci_loaded() and makes it unnecessary?
DJ
> + pr_debug("Timeout waiting for cxl_pci or cxl_mem probing\n");
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_wait_for_pci_mem, "CXL");
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index a9ab46eb0610..1ba7d39c2991 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -902,6 +902,8 @@ void cxl_coordinates_combine(struct access_coordinate *out,
>
> bool cxl_endpoint_decoder_reset_detected(struct cxl_port *port);
>
> +void cxl_wait_for_pci_mem(void);
> +
> /*
> * Unit test builds overrides this to __weak, find the 'strong' version
> * of these symbols in tools/testing/cxl/.
