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linux-next/drivers/pci/hotplug/pciehp_core.c
Lukas Wunner 32a8cef274 PCI: pciehp: Enable/disable exclusively from IRQ thread 
Besides the IRQ thread, there are several other places in the driver
which enable or disable the slot:

- pciehp_probe() enables the slot if it's occupied and the pciehp_force
  module parameter is used.

- pciehp_resume() enables or disables the slot after system sleep.

- pciehp_queue_pushbutton_work() enables or disables the slot after the
  5 second delay following an Attention Button press.

- pciehp_sysfs_enable_slot() and pciehp_sysfs_disable_slot() enable or
  disable the slot on sysfs write.

This requires locking and complicates pciehp's state machine.

A simplification can be achieved by enabling and disabling the slot
exclusively from the IRQ thread.

Amend the functions listed above to request slot enable/disablement from
the IRQ thread by either synthesizing a Presence Detect Changed event or,
in the case of a disable user request (via sysfs or an Attention Button
press), submitting a newly introduced force disable request.  The latter
is needed because the slot shall be forced off despite being occupied.
For this force disable request, avoid colliding with Slot Status register
bits by using a bit number greater than 16.

For synchronous execution of requests (on sysfs write), wait for the
request to finish and retrieve the result.  There can only ever be one
sysfs write in flight due to the locking in kernfs_fop_write(), hence
there is no risk of returning the result of a different sysfs request to
user space.

The POWERON_STATE and POWEROFF_STATE is now no longer entered by the
above-listed functions, but solely by the IRQ thread when it begins a
power transition.  Afterwards, it moves to STATIC_STATE.  The same
applies to canceling the Attention Button work, it likewise becomes an
IRQ thread only operation.

An immediate consequence is that the POWERON_STATE and POWEROFF_STATE is
never observed by the IRQ thread itself, only by functions called in a
different context, such as pciehp_sysfs_enable_slot().  So remove
handling of these states from pciehp_handle_button_press() and
pciehp_handle_link_change() which are exclusively called from the IRQ
thread.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
2018-07-23 17:04:15 -05:00

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// SPDX-License-Identifier: GPL-2.0+
/*
* PCI Express Hot Plug Controller Driver
*
* Copyright (C) 1995,2001 Compaq Computer Corporation
* Copyright (C) 2001 Greg Kroah-Hartman (greg@kroah.com)
* Copyright (C) 2001 IBM Corp.
* Copyright (C) 2003-2004 Intel Corporation
*
* All rights reserved.
*
* Send feedback to <greg@kroah.com>, <kristen.c.accardi@intel.com>
*
* Authors:
* Dan Zink <dan.zink@compaq.com>
* Greg Kroah-Hartman <greg@kroah.com>
* Dely Sy <dely.l.sy@intel.com>"
*/
#include <linux/moduleparam.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/pci.h>
#include "pciehp.h"
#include <linux/interrupt.h>
#include <linux/time.h>
/* Global variables */
bool pciehp_debug;
bool pciehp_poll_mode;
int pciehp_poll_time;
static bool pciehp_force;
/*
* not really modular, but the easiest way to keep compat with existing
* bootargs behaviour is to continue using module_param here.
*/
module_param(pciehp_debug, bool, 0644);
module_param(pciehp_poll_mode, bool, 0644);
module_param(pciehp_poll_time, int, 0644);
module_param(pciehp_force, bool, 0644);
MODULE_PARM_DESC(pciehp_debug, "Debugging mode enabled or not");
MODULE_PARM_DESC(pciehp_poll_mode, "Using polling mechanism for hot-plug events or not");
MODULE_PARM_DESC(pciehp_poll_time, "Polling mechanism frequency, in seconds");
MODULE_PARM_DESC(pciehp_force, "Force pciehp, even if OSHP is missing");
#define PCIE_MODULE_NAME "pciehp"
static int set_attention_status(struct hotplug_slot *slot, u8 value);
static int enable_slot(struct hotplug_slot *slot);
static int disable_slot(struct hotplug_slot *slot);
static int get_power_status(struct hotplug_slot *slot, u8 *value);
static int get_attention_status(struct hotplug_slot *slot, u8 *value);
static int get_latch_status(struct hotplug_slot *slot, u8 *value);
static int get_adapter_status(struct hotplug_slot *slot, u8 *value);
static int reset_slot(struct hotplug_slot *slot, int probe);
static int init_slot(struct controller *ctrl)
{
struct slot *slot = ctrl->slot;
struct hotplug_slot *hotplug = NULL;
struct hotplug_slot_info *info = NULL;
struct hotplug_slot_ops *ops = NULL;
char name[SLOT_NAME_SIZE];
int retval = -ENOMEM;
hotplug = kzalloc(sizeof(*hotplug), GFP_KERNEL);
if (!hotplug)
goto out;
info = kzalloc(sizeof(*info), GFP_KERNEL);
if (!info)
goto out;
/* Setup hotplug slot ops */
ops = kzalloc(sizeof(*ops), GFP_KERNEL);
if (!ops)
goto out;
ops->enable_slot = enable_slot;
ops->disable_slot = disable_slot;
ops->get_power_status = get_power_status;
ops->get_adapter_status = get_adapter_status;
ops->reset_slot = reset_slot;
if (MRL_SENS(ctrl))
ops->get_latch_status = get_latch_status;
if (ATTN_LED(ctrl)) {
ops->get_attention_status = get_attention_status;
ops->set_attention_status = set_attention_status;
} else if (ctrl->pcie->port->hotplug_user_indicators) {
ops->get_attention_status = pciehp_get_raw_indicator_status;
ops->set_attention_status = pciehp_set_raw_indicator_status;
}
/* register this slot with the hotplug pci core */
hotplug->info = info;
hotplug->private = slot;
hotplug->ops = ops;
slot->hotplug_slot = hotplug;
snprintf(name, SLOT_NAME_SIZE, "%u", PSN(ctrl));
retval = pci_hp_initialize(hotplug,
ctrl->pcie->port->subordinate, 0, name);
if (retval)
ctrl_err(ctrl, "pci_hp_initialize failed: error %d\n", retval);
out:
if (retval) {
kfree(ops);
kfree(info);
kfree(hotplug);
}
return retval;
}
static void cleanup_slot(struct controller *ctrl)
{
struct hotplug_slot *hotplug_slot = ctrl->slot->hotplug_slot;
pci_hp_destroy(hotplug_slot);
kfree(hotplug_slot->ops);
kfree(hotplug_slot->info);
kfree(hotplug_slot);
}
/*
* set_attention_status - Turns the Amber LED for a slot on, off or blink
*/
static int set_attention_status(struct hotplug_slot *hotplug_slot, u8 status)
{
struct slot *slot = hotplug_slot->private;
pciehp_set_attention_status(slot, status);
return 0;
}
static int enable_slot(struct hotplug_slot *hotplug_slot)
{
struct slot *slot = hotplug_slot->private;
return pciehp_sysfs_enable_slot(slot);
}
static int disable_slot(struct hotplug_slot *hotplug_slot)
{
struct slot *slot = hotplug_slot->private;
return pciehp_sysfs_disable_slot(slot);
}
static int get_power_status(struct hotplug_slot *hotplug_slot, u8 *value)
{
struct slot *slot = hotplug_slot->private;
pciehp_get_power_status(slot, value);
return 0;
}
static int get_attention_status(struct hotplug_slot *hotplug_slot, u8 *value)
{
struct slot *slot = hotplug_slot->private;
pciehp_get_attention_status(slot, value);
return 0;
}
static int get_latch_status(struct hotplug_slot *hotplug_slot, u8 *value)
{
struct slot *slot = hotplug_slot->private;
pciehp_get_latch_status(slot, value);
return 0;
}
static int get_adapter_status(struct hotplug_slot *hotplug_slot, u8 *value)
{
struct slot *slot = hotplug_slot->private;
pciehp_get_adapter_status(slot, value);
return 0;
}
static int reset_slot(struct hotplug_slot *hotplug_slot, int probe)
{
struct slot *slot = hotplug_slot->private;
return pciehp_reset_slot(slot, probe);
}
static int pciehp_probe(struct pcie_device *dev)
{
int rc;
struct controller *ctrl;
struct slot *slot;
u8 occupied, poweron;
/* If this is not a "hotplug" service, we have no business here. */
if (dev->service != PCIE_PORT_SERVICE_HP)
return -ENODEV;
if (!dev->port->subordinate) {
/* Can happen if we run out of bus numbers during probe */
dev_err(&dev->device,
"Hotplug bridge without secondary bus, ignoring\n");
return -ENODEV;
}
ctrl = pcie_init(dev);
if (!ctrl) {
dev_err(&dev->device, "Controller initialization failed\n");
return -ENODEV;
}
set_service_data(dev, ctrl);
/* Setup the slot information structures */
rc = init_slot(ctrl);
if (rc) {
if (rc == -EBUSY)
ctrl_warn(ctrl, "Slot already registered by another hotplug driver\n");
else
ctrl_err(ctrl, "Slot initialization failed (%d)\n", rc);
goto err_out_release_ctlr;
}
/* Enable events after we have setup the data structures */
rc = pcie_init_notification(ctrl);
if (rc) {
ctrl_err(ctrl, "Notification initialization failed (%d)\n", rc);
goto err_out_free_ctrl_slot;
}
/* Publish to user space */
slot = ctrl->slot;
rc = pci_hp_add(slot->hotplug_slot);
if (rc) {
ctrl_err(ctrl, "Publication to user space failed (%d)\n", rc);
goto err_out_shutdown_notification;
}
/* Check if slot is occupied */
mutex_lock(&slot->lock);
pciehp_get_adapter_status(slot, &occupied);
pciehp_get_power_status(slot, &poweron);
if (pciehp_force &&
((occupied && (slot->state == OFF_STATE ||
slot->state == BLINKINGON_STATE)) ||
(!occupied && (slot->state == ON_STATE ||
slot->state == BLINKINGOFF_STATE))))
pciehp_request(ctrl, PCI_EXP_SLTSTA_PDC);
/* If empty slot's power status is on, turn power off */
if (!occupied && poweron && POWER_CTRL(ctrl))
pciehp_power_off_slot(slot);
mutex_unlock(&slot->lock);
return 0;
err_out_shutdown_notification:
pcie_shutdown_notification(ctrl);
err_out_free_ctrl_slot:
cleanup_slot(ctrl);
err_out_release_ctlr:
pciehp_release_ctrl(ctrl);
return -ENODEV;
}
static void pciehp_remove(struct pcie_device *dev)
{
struct controller *ctrl = get_service_data(dev);
pci_hp_del(ctrl->slot->hotplug_slot);
pcie_shutdown_notification(ctrl);
cleanup_slot(ctrl);
pciehp_release_ctrl(ctrl);
}
#ifdef CONFIG_PM
static int pciehp_suspend(struct pcie_device *dev)
{
return 0;
}
static int pciehp_resume(struct pcie_device *dev)
{
struct controller *ctrl;
struct slot *slot;
u8 status;
ctrl = get_service_data(dev);
/* reinitialize the chipset's event detection logic */
pcie_reenable_notification(ctrl);
slot = ctrl->slot;
/* Check if slot is occupied */
pciehp_get_adapter_status(slot, &status);
mutex_lock(&slot->lock);
if ((status && (slot->state == OFF_STATE ||
slot->state == BLINKINGON_STATE)) ||
(!status && (slot->state == ON_STATE ||
slot->state == BLINKINGOFF_STATE)))
pciehp_request(ctrl, PCI_EXP_SLTSTA_PDC);
mutex_unlock(&slot->lock);
return 0;
}
#endif /* PM */
static struct pcie_port_service_driver hpdriver_portdrv = {
.name = PCIE_MODULE_NAME,
.port_type = PCIE_ANY_PORT,
.service = PCIE_PORT_SERVICE_HP,
.probe = pciehp_probe,
.remove = pciehp_remove,
#ifdef CONFIG_PM
.suspend = pciehp_suspend,
.resume = pciehp_resume,
#endif /* PM */
};
static int __init pcied_init(void)
{
int retval = 0;
retval = pcie_port_service_register(&hpdriver_portdrv);
dbg("pcie_port_service_register = %d\n", retval);
if (retval)
dbg("Failure to register service\n");
return retval;
}
device_initcall(pcied_init);
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