Subject: Re: [PATCH v5 net-next 3/5] net: wwan: t7xx: PCIe reset rescan

From: Jakub Kicinski <[email-masked]>
Date: Tue, 24 Jan 2023 20:45:43 -0800

Hi Bjorn,

any objections to the kind of shenanigans this is playing?

On Sat, 21 Jan 2023 19:03:23 +0530 [email-masked] wrote:
> From: M Chetan Kumar <[email-masked]>
> 
> PCI rescan module implements "rescan work queue".
> In firmware flashing or coredump collection procedure
> WWAN device is programmed to boot in fastboot mode and
> a work item is scheduled for removal & detection.
> 
> The WWAN device is reset using APCI call as part driver
> removal flow. Work queue rescans pci bus at fixed interval
> for device detection, later when device is detect work queue
> exits.
> 
> Signed-off-by: Haijun Liu <[email-masked]>
> Co-developed-by: Madhusmita Sahu <[email-masked]>
> Signed-off-by: Madhusmita Sahu <[email-masked]>
> Signed-off-by: Ricardo Martinez <[email-masked]>
> Signed-off-by: M Chetan Kumar <[email-masked]>
> Signed-off-by: Devegowda Chandrashekar <[email-masked]>
> --
> v5:
>  * No Change.
> v4:
>  * Change "is still exist" to "still exists".
> v3:
>  * No Change.
> v2:
>  * Drop empty line inside critical sections.
>  * Correct log message.
>  * Correct logic inside t7xx_always_match().
>  * Drop hp_enable changes.
>  * Drop g_ prefix from t7xx_rescan_ctx.
>  * Use tab before comment in struct decl.
>  * Remove extra white space.
>  * Drop modem exception state check.
>  * Crit section newlines.
>  * Remove unnecessary header files inclusion.
>  * Drop spinlock around reset and rescan flow.
> ---
>  drivers/net/wwan/t7xx/Makefile          |  3 +-
>  drivers/net/wwan/t7xx/t7xx_modem_ops.c  |  3 +
>  drivers/net/wwan/t7xx/t7xx_pci.c        | 56 ++++++++++++++-
>  drivers/net/wwan/t7xx/t7xx_pci_rescan.c | 96 +++++++++++++++++++++++++
>  drivers/net/wwan/t7xx/t7xx_pci_rescan.h | 28 ++++++++
>  5 files changed, 184 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/net/wwan/t7xx/t7xx_pci_rescan.c
>  create mode 100644 drivers/net/wwan/t7xx/t7xx_pci_rescan.h
> 
> diff --git a/drivers/net/wwan/t7xx/Makefile b/drivers/net/wwan/t7xx/Makefile
> index 268ff9e87e5b..ba5c607404a4 100644
> --- a/drivers/net/wwan/t7xx/Makefile
> +++ b/drivers/net/wwan/t7xx/Makefile
> @@ -17,7 +17,8 @@ mtk_t7xx-y:=	t7xx_pci.o \
>  		t7xx_hif_dpmaif_tx.o \
>  		t7xx_hif_dpmaif_rx.o  \
>  		t7xx_dpmaif.o \
> -		t7xx_netdev.o
> +		t7xx_netdev.o \
> +		t7xx_pci_rescan.o
>  
>  mtk_t7xx-$(CONFIG_WWAN_DEBUGFS) += \
>  		t7xx_port_trace.o \
> diff --git a/drivers/net/wwan/t7xx/t7xx_modem_ops.c b/drivers/net/wwan/t7xx/t7xx_modem_ops.c
> index cbd65aa48721..2fcaea4694ba 100644
> --- a/drivers/net/wwan/t7xx/t7xx_modem_ops.c
> +++ b/drivers/net/wwan/t7xx/t7xx_modem_ops.c
> @@ -37,6 +37,7 @@
>  #include "t7xx_modem_ops.h"
>  #include "t7xx_netdev.h"
>  #include "t7xx_pci.h"
> +#include "t7xx_pci_rescan.h"
>  #include "t7xx_pcie_mac.h"
>  #include "t7xx_port.h"
>  #include "t7xx_port_proxy.h"
> @@ -194,6 +195,8 @@ static irqreturn_t t7xx_rgu_isr_thread(int irq, void *data)
>  
>  	msleep(RGU_RESET_DELAY_MS);
>  	t7xx_reset_device_via_pmic(t7xx_dev);
> +	t7xx_rescan_queue_work(t7xx_dev->pdev);
> +
>  	return IRQ_HANDLED;
>  }
>  
> diff --git a/drivers/net/wwan/t7xx/t7xx_pci.c b/drivers/net/wwan/t7xx/t7xx_pci.c
> index 871f2a27a398..3f5ebbc11b82 100644
> --- a/drivers/net/wwan/t7xx/t7xx_pci.c
> +++ b/drivers/net/wwan/t7xx/t7xx_pci.c
> @@ -38,6 +38,7 @@
>  #include "t7xx_mhccif.h"
>  #include "t7xx_modem_ops.h"
>  #include "t7xx_pci.h"
> +#include "t7xx_pci_rescan.h"
>  #include "t7xx_pcie_mac.h"
>  #include "t7xx_reg.h"
>  #include "t7xx_state_monitor.h"
> @@ -715,6 +716,7 @@ static int t7xx_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  		return ret;
>  	}
>  
> +	t7xx_rescan_done();
>  	t7xx_pcie_mac_set_int(t7xx_dev, MHCCIF_INT);
>  	t7xx_pcie_mac_interrupts_en(t7xx_dev);
>  
> @@ -754,7 +756,59 @@ static struct pci_driver t7xx_pci_driver = {
>  	.shutdown = t7xx_pci_shutdown,
>  };
>  
> -module_pci_driver(t7xx_pci_driver);
> +static int __init t7xx_pci_init(void)
> +{
> +	int ret;
> +
> +	t7xx_pci_dev_rescan();
> +	ret = t7xx_rescan_init();
> +	if (ret) {
> +		pr_err("Failed to init t7xx rescan work\n");
> +		return ret;
> +	}
> +
> +	return pci_register_driver(&t7xx_pci_driver);
> +}
> +module_init(t7xx_pci_init);
> +
> +static int t7xx_always_match(struct device *dev, const void *data)
> +{
> +	struct pci_dev *pdev = to_pci_dev(dev);
> +	const struct pci_device_id *id = data;
> +
> +	if (pci_match_id(id, pdev))
> +		return 1;
> +
> +	return 0;
> +}
> +
> +static void __exit t7xx_pci_cleanup(void)
> +{
> +	int remove_flag = 0;
> +	struct device *dev;
> +
> +	dev = driver_find_device(&t7xx_pci_driver.driver, NULL, &t7xx_pci_table[0],
> +				 t7xx_always_match);
> +	if (dev) {
> +		pr_debug("unregister t7xx PCIe driver while device still exists.\n");
> +		put_device(dev);
> +		remove_flag = 1;
> +	} else {
> +		pr_debug("no t7xx PCIe driver found.\n");
> +	}
> +
> +	pci_lock_rescan_remove();
> +	pci_unregister_driver(&t7xx_pci_driver);
> +	pci_unlock_rescan_remove();
> +
> +	t7xx_rescan_deinit();
> +	if (remove_flag) {
> +		pr_debug("remove t7xx PCI device\n");
> +		pci_stop_and_remove_bus_device_locked(to_pci_dev(dev));
> +	}
> +}
> +
> +module_exit(t7xx_pci_cleanup);
>  
>  MODULE_AUTHOR("MediaTek Inc");
>  MODULE_DESCRIPTION("MediaTek PCIe 5G WWAN modem T7xx driver");
> diff --git a/drivers/net/wwan/t7xx/t7xx_pci_rescan.c b/drivers/net/wwan/t7xx/t7xx_pci_rescan.c
> new file mode 100644
> index 000000000000..67f13c035846
> --- /dev/null
> +++ b/drivers/net/wwan/t7xx/t7xx_pci_rescan.c
> @@ -0,0 +1,96 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2021, MediaTek Inc.
> + * Copyright (c) 2021-2023, Intel Corporation.
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ":t7xx:%s: " fmt, __func__
> +#define dev_fmt(fmt) "t7xx: " fmt
> +
> +#include <linux/delay.h>
> +#include <linux/pci.h>
> +#include <linux/spinlock.h>
> +#include <linux/workqueue.h>
> +
> +#include "t7xx_pci.h"
> +#include "t7xx_pci_rescan.h"
> +
> +static struct remove_rescan_context t7xx_rescan_ctx;
> +
> +void t7xx_pci_dev_rescan(void)
> +{
> +	struct pci_bus *b = NULL;
> +
> +	pci_lock_rescan_remove();
> +	while ((b = pci_find_next_bus(b)))
> +		pci_rescan_bus(b);
> +	pci_unlock_rescan_remove();
> +}
> +
> +void t7xx_rescan_done(void)
> +{
> +	if (!atomic_read(&t7xx_rescan_ctx.rescan_done)) {
> +		atomic_set(&t7xx_rescan_ctx.rescan_done, 1);
> +		pr_debug("Rescan probe\n");
> +	} else {
> +		pr_debug("Init probe\n");
> +	}
> +}
> +
> +static void t7xx_remove_rescan(struct work_struct *work)
> +{
> +	int num_retries = RESCAN_RETRIES;
> +	struct pci_dev *pdev;
> +
> +	atomic_set(&t7xx_rescan_ctx.rescan_done, 0);
> +	pdev = t7xx_rescan_ctx.dev;
> +
> +	if (pdev) {
> +		pci_stop_and_remove_bus_device_locked(pdev);
> +		pr_debug("start remove and rescan flow\n");
> +	}
> +
> +	do {
> +		t7xx_pci_dev_rescan();
> +
> +		if (atomic_read(&t7xx_rescan_ctx.rescan_done))
> +			break;
> +
> +		msleep(DELAY_RESCAN_MTIME);
> +	} while (num_retries--);
> +}
> +
> +void t7xx_rescan_queue_work(struct pci_dev *pdev)
> +{
> +	if (!atomic_read(&t7xx_rescan_ctx.rescan_done)) {
> +		dev_err(&pdev->dev, "Rescan failed\n");
> +		return;
> +	}
> +
> +	t7xx_rescan_ctx.dev = pdev;
> +	queue_work(t7xx_rescan_ctx.pcie_rescan_wq, &t7xx_rescan_ctx.service_task);
> +}
> +
> +int t7xx_rescan_init(void)
> +{
> +	atomic_set(&t7xx_rescan_ctx.rescan_done, 1);
> +	t7xx_rescan_ctx.dev = NULL;
> +
> +	t7xx_rescan_ctx.pcie_rescan_wq = create_singlethread_workqueue(MTK_RESCAN_WQ);
> +	if (!t7xx_rescan_ctx.pcie_rescan_wq) {
> +		pr_err("Failed to create workqueue: %s\n", MTK_RESCAN_WQ);
> +		return -ENOMEM;
> +	}
> +
> +	INIT_WORK(&t7xx_rescan_ctx.service_task, t7xx_remove_rescan);
> +
> +	return 0;
> +}
> +
> +void t7xx_rescan_deinit(void)
> +{
> +	t7xx_rescan_ctx.dev = NULL;
> +	atomic_set(&t7xx_rescan_ctx.rescan_done, 0);
> +	cancel_work_sync(&t7xx_rescan_ctx.service_task);
> +	destroy_workqueue(t7xx_rescan_ctx.pcie_rescan_wq);
> +}
> diff --git a/drivers/net/wwan/t7xx/t7xx_pci_rescan.h b/drivers/net/wwan/t7xx/t7xx_pci_rescan.h
> new file mode 100644
> index 000000000000..80b25c44151c
> --- /dev/null
> +++ b/drivers/net/wwan/t7xx/t7xx_pci_rescan.h
> @@ -0,0 +1,28 @@
> +/* SPDX-License-Identifier: GPL-2.0-only
> + *
> + * Copyright (c) 2021, MediaTek Inc.
> + * Copyright (c) 2021-2023, Intel Corporation.
> + */
> +
> +#ifndef __T7XX_PCI_RESCAN_H__
> +#define __T7XX_PCI_RESCAN_H__
> +
> +#define MTK_RESCAN_WQ "mtk_rescan_wq"
> +
> +#define DELAY_RESCAN_MTIME 1000
> +#define RESCAN_RETRIES 35
> +
> +struct remove_rescan_context {
> +	struct work_struct service_task;
> +	struct workqueue_struct *pcie_rescan_wq;
> +	struct pci_dev *dev;
> +	atomic_t rescan_done;
> +};
> +
> +void t7xx_pci_dev_rescan(void);
> +void t7xx_rescan_queue_work(struct pci_dev *pdev);
> +int t7xx_rescan_init(void);
> +void t7xx_rescan_deinit(void);
> +void t7xx_rescan_done(void);
> +
> +#endif	/* __T7XX_PCI_RESCAN_H__ */