From bae94d02371c402408a4edfb95e71e88dbd3e973 Mon Sep 17 00:00:00 2001 From: Inaky Perez-Gonzalez Date: Wed, 22 Nov 2006 12:40:31 -0800 Subject: [PATCH] PCI: switch pci_{enable,disable}_device() to be nestable Changes the pci_{enable,disable}_device() functions to work in a nested basis, so that eg, three calls to enable_device() require three calls to disable_device(). The reason for this is to simplify PCI drivers for multi-interface/capability devices. These are devices that cram more than one interface in a single function. A relevant example of that is the Wireless [USB] Host Controller Interface (similar to EHCI) [see http://www.intel.com/technology/comms/wusb/whci.htm]. In these kind of devices, multiple interfaces are accessed through a single bar and IRQ line. For that, the drivers map only the smallest area of the bar to access their register banks and use shared IRQ handlers. However, because the order at which those drivers load cannot be known ahead of time, the sequence in which the calls to pci_enable_device() and pci_disable_device() cannot be predicted. Thus: 1. driverA starts pci_enable_device() 2. driverB starts pci_enable_device() 3. driverA shutdown pci_disable_device() 4. driverB shutdown pci_disable_device() between steps 3 and 4, driver B would loose access to it's device, even if it didn't intend to. By using this modification, the device won't be disabled until all the callers to enable() have called disable(). This is implemented by replacing 'struct pci_dev->is_enabled' from a bitfield to an atomic use count. Each caller to enable increments it, each caller to disable decrements it. When the count increments from 0 to 1, __pci_enable_device() is called to actually enable the device. When it drops to zero, pci_disable_device() actually does the disabling. We keep the backend __pci_enable_device() for pci_default_resume() to use and also change the sysfs method implementation, so that userspace enabling/disabling the device doesn't disable it one time too much. Signed-off-by: Inaky Perez-Gonzalez Signed-off-by: Greg Kroah-Hartman --- drivers/pci/pci-driver.c | 4 ++-- drivers/pci/pci-sysfs.c | 33 +++++++++++++++++++++------------ drivers/pci/pci.c | 40 +++++++++++++++++++++++++++++++++------- drivers/pci/pci.h | 1 + include/linux/pci.h | 3 ++- 5 files changed, 59 insertions(+), 22 deletions(-) diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c index 84ec9c8f6703..e5ae3a0c13bb 100644 --- a/drivers/pci/pci-driver.c +++ b/drivers/pci/pci-driver.c @@ -329,8 +329,8 @@ static int pci_default_resume(struct pci_dev *pci_dev) /* restore the PCI config space */ pci_restore_state(pci_dev); /* if the device was enabled before suspend, reenable */ - if (pci_dev->is_enabled) - retval = pci_enable_device(pci_dev); + if (atomic_read(&pci_dev->enable_cnt)) + retval = __pci_enable_device(pci_dev); /* if the device was busmaster before the suspend, make it busmaster again */ if (pci_dev->is_busmaster) pci_set_master(pci_dev); diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index f952bfea48a6..7a94076752d0 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -42,7 +42,6 @@ pci_config_attr(subsystem_vendor, "0x%04x\n"); pci_config_attr(subsystem_device, "0x%04x\n"); pci_config_attr(class, "0x%06x\n"); pci_config_attr(irq, "%u\n"); -pci_config_attr(is_enabled, "%u\n"); static ssize_t broken_parity_status_show(struct device *dev, struct device_attribute *attr, @@ -112,26 +111,36 @@ static ssize_t modalias_show(struct device *dev, struct device_attribute *attr, (u8)(pci_dev->class >> 16), (u8)(pci_dev->class >> 8), (u8)(pci_dev->class)); } -static ssize_t -is_enabled_store(struct device *dev, struct device_attribute *attr, - const char *buf, size_t count) + +static ssize_t is_enabled_store(struct device *dev, + struct device_attribute *attr, const char *buf, + size_t count) { + ssize_t result = -EINVAL; struct pci_dev *pdev = to_pci_dev(dev); - int retval = 0; /* this can crash the machine when done on the "wrong" device */ if (!capable(CAP_SYS_ADMIN)) return count; - if (*buf == '0') - pci_disable_device(pdev); + if (*buf == '0') { + if (atomic_read(&pdev->enable_cnt) != 0) + pci_disable_device(pdev); + else + result = -EIO; + } else if (*buf == '1') + result = pci_enable_device(pdev); + + return result < 0 ? result : count; +} - if (*buf == '1') - retval = pci_enable_device(pdev); +static ssize_t is_enabled_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct pci_dev *pdev; - if (retval) - return retval; - return count; + pdev = to_pci_dev (dev); + return sprintf (buf, "%u\n", atomic_read(&pdev->enable_cnt)); } static ssize_t diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 427991741cf3..5a14b73cf3a1 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -612,29 +612,50 @@ pci_enable_device_bars(struct pci_dev *dev, int bars) } /** - * pci_enable_device - Initialize device before it's used by a driver. + * __pci_enable_device - Initialize device before it's used by a driver. * @dev: PCI device to be initialized * * Initialize device before it's used by a driver. Ask low-level code * to enable I/O and memory. Wake up the device if it was suspended. * Beware, this function can fail. + * + * Note this function is a backend and is not supposed to be called by + * normal code, use pci_enable_device() instead. */ int -pci_enable_device(struct pci_dev *dev) +__pci_enable_device(struct pci_dev *dev) { int err; - if (dev->is_enabled) - return 0; - err = pci_enable_device_bars(dev, (1 << PCI_NUM_RESOURCES) - 1); if (err) return err; pci_fixup_device(pci_fixup_enable, dev); - dev->is_enabled = 1; return 0; } +/** + * pci_enable_device - Initialize device before it's used by a driver. + * @dev: PCI device to be initialized + * + * Initialize device before it's used by a driver. Ask low-level code + * to enable I/O and memory. Wake up the device if it was suspended. + * Beware, this function can fail. + * + * Note we don't actually enable the device many times if we call + * this function repeatedly (we just increment the count). + */ +int pci_enable_device(struct pci_dev *dev) +{ + int result; + if (atomic_add_return(1, &dev->enable_cnt) > 1) + return 0; /* already enabled */ + result = __pci_enable_device(dev); + if (result < 0) + atomic_dec(&dev->enable_cnt); + return result; +} + /** * pcibios_disable_device - disable arch specific PCI resources for device dev * @dev: the PCI device to disable @@ -651,12 +672,18 @@ void __attribute__ ((weak)) pcibios_disable_device (struct pci_dev *dev) {} * * Signal to the system that the PCI device is not in use by the system * anymore. This only involves disabling PCI bus-mastering, if active. + * + * Note we don't actually disable the device until all callers of + * pci_device_enable() have called pci_device_disable(). */ void pci_disable_device(struct pci_dev *dev) { u16 pci_command; + if (atomic_sub_return(1, &dev->enable_cnt) != 0) + return; + if (dev->msi_enabled) disable_msi_mode(dev, pci_find_capability(dev, PCI_CAP_ID_MSI), PCI_CAP_ID_MSI); @@ -672,7 +699,6 @@ pci_disable_device(struct pci_dev *dev) dev->is_busmaster = 0; pcibios_disable_device(dev); - dev->is_enabled = 0; } /** diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index 6bf327db5c5e..398852f526a6 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -1,5 +1,6 @@ /* Functions internal to the PCI core code */ +extern int __must_check __pci_enable_device(struct pci_dev *); extern int pci_uevent(struct device *dev, char **envp, int num_envp, char *buffer, int buffer_size); extern int pci_create_sysfs_dev_files(struct pci_dev *pdev); diff --git a/include/linux/pci.h b/include/linux/pci.h index 09be0f81b27b..01c707261f9c 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -51,6 +51,7 @@ #include #include #include +#include #include /* File state for mmap()s on /proc/bus/pci/X/Y */ @@ -159,7 +160,6 @@ struct pci_dev { unsigned int transparent:1; /* Transparent PCI bridge */ unsigned int multifunction:1;/* Part of multi-function device */ /* keep track of device state */ - unsigned int is_enabled:1; /* pci_enable_device has been called */ unsigned int is_busmaster:1; /* device is busmaster */ unsigned int no_msi:1; /* device may not use msi */ unsigned int no_d1d2:1; /* only allow d0 or d3 */ @@ -167,6 +167,7 @@ struct pci_dev { unsigned int broken_parity_status:1; /* Device generates false positive parity */ unsigned int msi_enabled:1; unsigned int msix_enabled:1; + atomic_t enable_cnt; /* pci_enable_device has been called */ u32 saved_config_space[16]; /* config space saved at suspend time */ struct hlist_head saved_cap_space; -- 2.20.1