[PATCH] PCI: Move test of INTx masking to pci_setup_device
From: Piotr Gregor
Date: Thu May 25 2017 - 14:16:32 EST
The test for INTx masking via config space command performed
in pci_intx_mask_supported should be performed before PCI device
can be used. This is to avoid reading/writing of PCI_COMMAND_INTX_DISABLE
register which may collide with MSI/MSI-X interrupts.
This patch simplifies test performed in pci_intx_mask_supported
and introduces intx_mask_support field in struct pci_dev to store
the result. The test itself is moved to pci_setup_device.
The result can be queried at any time later from the pci_dev with
static inline bool pci_is_intx_mask_supported(struct pci_dev *pdev)
{
/*
* INTx masking is supported if device passed INTx test
* and it's INTx masking feature works properly.
*/
return (pdev->intx_mask_support && !pdev->broken_intx_masking);
}
Signed-off-by: Piotr Gregor <piotrgregor@xxxxxxxxxxx>
---
drivers/pci/pci.c | 42 +++++++++++++++++++++++-------------------
drivers/pci/probe.c | 3 +++
drivers/uio/uio_pci_generic.c | 2 +-
drivers/vfio/pci/vfio_pci.c | 2 +-
include/linux/pci.h | 10 ++++++++++
5 files changed, 38 insertions(+), 21 deletions(-)
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b01bd5b..bcaab9b 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3709,42 +3709,46 @@ void pci_intx(struct pci_dev *pdev, int enable)
EXPORT_SYMBOL_GPL(pci_intx);
/**
- * pci_intx_mask_supported - probe for INTx masking support
+ * pci_intx_mask_supported - probe for INTx masking support in pci_setup_device
* @dev: the PCI device to operate on
*
- * Check if the device dev support INTx masking via the config space
- * command word.
+ * Check if the device dev supports INTx masking via the config space
+ * command word. Executed when PCI device is setup. Result is saved
+ * in intx_mask_support field of pci_dev and should be checked
+ * with pci_is_intx_mask_supported() after PCI device has been setup
+ * to avoid reading/writing of PCI_COMMAND_INTX_DISABLE register.
*/
bool pci_intx_mask_supported(struct pci_dev *dev)
{
- bool mask_supported = false;
- u16 orig, new;
+ u16 orig, toggle, new;
+ /*
+ * If device doesn't support this feature though it could pass the test.
+ */
if (dev->broken_intx_masking)
return false;
pci_cfg_access_lock(dev);
+ /*
+ * Perform the test.
+ */
pci_read_config_word(dev, PCI_COMMAND, &orig);
- pci_write_config_word(dev, PCI_COMMAND,
- orig ^ PCI_COMMAND_INTX_DISABLE);
+ toggle = orig ^ PCI_COMMAND_INTX_DISABLE;
+ pci_write_config_word(dev, PCI_COMMAND, toggle);
pci_read_config_word(dev, PCI_COMMAND, &new);
/*
- * There's no way to protect against hardware bugs or detect them
- * reliably, but as long as we know what the value should be, let's
- * go ahead and check it.
+ * Restore initial state.
*/
- if ((new ^ orig) & ~PCI_COMMAND_INTX_DISABLE) {
- dev_err(&dev->dev, "Command register changed from 0x%x to 0x%x: driver or hardware bug?\n",
- orig, new);
- } else if ((new ^ orig) & PCI_COMMAND_INTX_DISABLE) {
- mask_supported = true;
- pci_write_config_word(dev, PCI_COMMAND, orig);
- }
+ pci_write_config_word(dev, PCI_COMMAND, orig);
pci_cfg_access_unlock(dev);
- return mask_supported;
+
+ if (new == toggle)
+ return true;
+
+ return false;
}
EXPORT_SYMBOL_GPL(pci_intx_mask_supported);
@@ -3798,7 +3802,7 @@ static bool pci_check_and_set_intx_mask(struct pci_dev *dev, bool mask)
* @dev: the PCI device to operate on
*
* Check if the device dev has its INTx line asserted, mask it and
- * return true in that case. False is returned if not interrupt was
+ * return true in that case. False is returned if no interrupt was
* pending.
*/
bool pci_check_and_mask_intx(struct pci_dev *dev)
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 19c8950..16c60ce 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1399,6 +1399,9 @@ int pci_setup_device(struct pci_dev *dev)
}
}
+ if (pci_intx_mask_supported(dev))
+ dev->intx_mask_support = 1;
+
switch (dev->hdr_type) { /* header type */
case PCI_HEADER_TYPE_NORMAL: /* standard header */
if (class == PCI_CLASS_BRIDGE_PCI)
diff --git a/drivers/uio/uio_pci_generic.c b/drivers/uio/uio_pci_generic.c
index d0b508b..8cd443c 100644
--- a/drivers/uio/uio_pci_generic.c
+++ b/drivers/uio/uio_pci_generic.c
@@ -73,7 +73,7 @@ static int probe(struct pci_dev *pdev,
return -ENODEV;
}
- if (!pci_intx_mask_supported(pdev)) {
+ if (!pci_is_intx_mask_supported(pdev)) {
err = -ENODEV;
goto err_verify;
}
diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 324c52e..933456e 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -239,7 +239,7 @@ static int vfio_pci_enable(struct vfio_pci_device *vdev)
vdev->nointx = true;
pci_intx(pdev, 0);
} else
- vdev->pci_2_3 = pci_intx_mask_supported(pdev);
+ vdev->pci_2_3 = pci_is_intx_mask_supported(pdev);
}
pci_read_config_word(pdev, PCI_COMMAND, &cmd);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 33c2b0b..0fbd278 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -367,6 +367,7 @@ struct pci_dev {
unsigned int __aer_firmware_first_valid:1;
unsigned int __aer_firmware_first:1;
unsigned int broken_intx_masking:1;
+ unsigned int intx_mask_support:1; /* INTx masking is supported */
unsigned int io_window_1k:1; /* Intel P2P bridge 1K I/O windows */
unsigned int irq_managed:1;
unsigned int has_secondary_link:1;
@@ -1003,6 +1004,15 @@ int __must_check pci_reenable_device(struct pci_dev *);
int __must_check pcim_enable_device(struct pci_dev *pdev);
void pcim_pin_device(struct pci_dev *pdev);
+static inline bool pci_is_intx_mask_supported(struct pci_dev *pdev)
+{
+ /*
+ * INTx masking is supported if device passed INTx test and it's INTx
+ * masking feature works properly.
+ */
+ return (pdev->intx_mask_support && !pdev->broken_intx_masking);
+}
+
static inline int pci_is_enabled(struct pci_dev *pdev)
{
return (atomic_read(&pdev->enable_cnt) > 0);
--
2.1.4