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PCI: add support for function level reset

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Sometimes, it's necessary to enable software's ability to quiesce and
reset endpoint hardware with function-level granularity, so provide
support for it.

The patch implement Function Level Reset(FLR) feature following PCI-e
spec. And this is the first step. We would add more generic method, like
D0/D3, to allow more devices support this function.

The patch contains two functions. pcie_reset_function() is the new
driver API, and, contains some action to quiesce a device.  The other
function is a helper:  pcie_execute_reset_function() just executes the
reset for a particular device function.

Current the usage model is in KVM. Function reset is necessary for
assigning device to a guest, or moving it between partitions.

For Function Level Reset(FLR), please refer to PCI Express spec chapter
6.6.2.

Signed-off-by: Sheng Yang <[email protected]>
Signed-off-by: Matthew Wilcox <[email protected]>
Signed-off-by: Jesse Barnes <[email protected]>
This commit is contained in:
Sheng Yang 2008-10-21 17:38:25 +08:00 • committed by Jesse Barnes
commit 8dd7f8036c
3 changed files with 102 additions and 0 deletions
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98
drivers/pci/pci.c
View file

@ -18,6 +18,7 @@
#include <linux/log2.h>
#include <linux/pci-aspm.h>
#include <linux/pm_wakeup.h>
#include <linux/interrupt.h>
#include <asm/dma.h> /* isa_dma_bridge_buggy */
#include "pci.h"
@ -1745,6 +1746,103 @@ int pci_set_dma_seg_boundary(struct pci_dev *dev, unsigned long mask)
EXPORT_SYMBOL(pci_set_dma_seg_boundary);
#endif
/**
* pci_execute_reset_function() - Reset a PCI device function
* @dev: Device function to reset
*
* Some devices allow an individual function to be reset without affecting
* other functions in the same device. The PCI device must be responsive
* to PCI config space in order to use this function.
*
* The device function is presumed to be unused when this function is called.
* Resetting the device will make the contents of PCI configuration space
* random, so any caller of this must be prepared to reinitialise the
* device including MSI, bus mastering, BARs, decoding IO and memory spaces,
* etc.
*
* Returns 0 if the device function was successfully reset or -ENOTTY if the
* device doesn't support resetting a single function.
*/
int pci_execute_reset_function(struct pci_dev *dev)
{
u16 status;
u32 cap;
int exppos = pci_find_capability(dev, PCI_CAP_ID_EXP);
if (!exppos)
return -ENOTTY;
pci_read_config_dword(dev, exppos + PCI_EXP_DEVCAP, &cap);
if (!(cap & PCI_EXP_DEVCAP_FLR))
return -ENOTTY;
pci_block_user_cfg_access(dev);
/* Wait for Transaction Pending bit clean */
msleep(100);
pci_read_config_word(dev, exppos + PCI_EXP_DEVSTA, &status);
if (status & PCI_EXP_DEVSTA_TRPND) {
dev_info(&dev->dev, "Busy after 100ms while trying to reset; "
"sleeping for 1 second\n");
ssleep(1);
pci_read_config_word(dev, exppos + PCI_EXP_DEVSTA, &status);
if (status & PCI_EXP_DEVSTA_TRPND)
dev_info(&dev->dev, "Still busy after 1s; "
"proceeding with reset anyway\n");
}
pci_write_config_word(dev, exppos + PCI_EXP_DEVCTL,
PCI_EXP_DEVCTL_BCR_FLR);
mdelay(100);
pci_unblock_user_cfg_access(dev);
return 0;
}
EXPORT_SYMBOL_GPL(pci_execute_reset_function);
/**
* pci_reset_function() - quiesce and reset a PCI device function
* @dev: Device function to reset
*
* Some devices allow an individual function to be reset without affecting
* other functions in the same device. The PCI device must be responsive
* to PCI config space in order to use this function.
*
* This function does not just reset the PCI portion of a device, but
* clears all the state associated with the device. This function differs
* from pci_execute_reset_function in that it saves and restores device state
* over the reset.
*
* Returns 0 if the device function was successfully reset or -ENOTTY if the
* device doesn't support resetting a single function.
*/
int pci_reset_function(struct pci_dev *dev)
{
u32 cap;
int exppos = pci_find_capability(dev, PCI_CAP_ID_EXP);
int r;
if (!exppos)
return -ENOTTY;
pci_read_config_dword(dev, exppos + PCI_EXP_DEVCAP, &cap);
if (!(cap & PCI_EXP_DEVCAP_FLR))
return -ENOTTY;
if (!dev->msi_enabled && !dev->msix_enabled)
disable_irq(dev->irq);
pci_save_state(dev);
pci_write_config_word(dev, PCI_COMMAND, PCI_COMMAND_INTX_DISABLE);
r = pci_execute_reset_function(dev);
pci_restore_state(dev);
if (!dev->msi_enabled && !dev->msix_enabled)
enable_irq(dev->irq);
return r;
}
EXPORT_SYMBOL_GPL(pci_reset_function);
/**
* pcix_get_max_mmrbc - get PCI-X maximum designed memory read byte count
* @dev: PCI device to query