During an online device reset it may be useful to disable bus-mastering.
pci_disable_device() does that, and far more besides, so is not suitable
for an online reset.
Add pci_clear_master() which does just this.
Signed-off-by: Ben Hutchings <bhutchings@xxxxxxxxxxxxxx>
---
Now with added documentation!
Ben.
Documentation/PCI/pci.txt | 3 ++-
drivers/pci/pci.c | 39 ++++++++++++++++++++++++++++-----------
include/linux/pci.h | 1 +
3 files changed, 31 insertions(+), 12 deletions(-)
diff --git a/Documentation/PCI/pci.txt b/Documentation/PCI/pci.txt
index fd4907a..7f6de6e 100644
--- a/Documentation/PCI/pci.txt
+++ b/Documentation/PCI/pci.txt
@@ -294,7 +294,8 @@ NOTE: pci_enable_device() can fail! Check the return value.
pci_set_master() will enable DMA by setting the bus master bit
in the PCI_COMMAND register. It also fixes the latency timer value if
-it's set to something bogus by the BIOS.
+it's set to something bogus by the BIOS. pci_clear_master() will
+disable DMA by clearing the bus master bit.
If the PCI device can use the PCI Memory-Write-Invalidate transaction,
call pci_set_mwi(). This enables the PCI_COMMAND bit for Mem-Wr-Inval
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 1b80733..bb68128 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1644,6 +1644,22 @@ int pci_request_regions_exclusive(struct pci_dev *pdev, const char *res_name)
((1 << 6) - 1), res_name);
}
+static void __pci_set_master(struct pci_dev *dev, bool enable)
+{
+ u16 old_cmd, cmd;
+
+ pci_read_config_word(dev, PCI_COMMAND, &old_cmd);
+ if (enable)
+ cmd = old_cmd | PCI_COMMAND_MASTER;
+ else
+ cmd = old_cmd & ~PCI_COMMAND_MASTER;
+ if (cmd != old_cmd) {
+ dev_dbg(&dev->dev, "%s bus mastering\n",
+ enable ? "enabling" : "disabling");
+ pci_write_config_word(dev, PCI_COMMAND, cmd);
+ }
+ dev->is_busmaster = enable;
+}
/**
* pci_set_master - enables bus-mastering for device dev
@@ -1652,21 +1668,21 @@ int pci_request_regions_exclusive(struct pci_dev *pdev, const char *res_name)
* Enables bus-mastering on the device and calls pcibios_set_master()
* to do the needed arch specific settings.
*/
-void
-pci_set_master(struct pci_dev *dev)
+void pci_set_master(struct pci_dev *dev)
{
- u16 cmd;
-
- pci_read_config_word(dev, PCI_COMMAND, &cmd);
- if (! (cmd & PCI_COMMAND_MASTER)) {
- dev_dbg(&dev->dev, "enabling bus mastering\n");
- cmd |= PCI_COMMAND_MASTER;
- pci_write_config_word(dev, PCI_COMMAND, cmd);
- }
- dev->is_busmaster = 1;
+ __pci_set_master(dev, true);
pcibios_set_master(dev);
}
+/**
+ * pci_clear_master - disables bus-mastering for device dev
+ * @dev: the PCI device to disable
+ */
+void pci_clear_master(struct pci_dev *dev)
+{
+ __pci_set_master(dev, false);
+}
+
#ifdef PCI_DISABLE_MWI
int pci_set_mwi(struct pci_dev *dev)
{
@@ -2323,6 +2339,7 @@ EXPORT_SYMBOL(pci_release_selected_regions);
EXPORT_SYMBOL(pci_request_selected_regions);
EXPORT_SYMBOL(pci_request_selected_regions_exclusive);
EXPORT_SYMBOL(pci_set_master);
+EXPORT_SYMBOL(pci_clear_master);
EXPORT_SYMBOL(pci_set_mwi);
EXPORT_SYMBOL(pci_try_set_mwi);
EXPORT_SYMBOL(pci_clear_mwi);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 43ec6aa..b57e4c1 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -636,6 +636,7 @@ static inline int pci_is_managed(struct pci_dev *pdev)
void pci_disable_device(struct pci_dev *dev);
void pci_set_master(struct pci_dev *dev);
+void pci_clear_master(struct pci_dev *dev);
int pci_set_pcie_reset_state(struct pci_dev *dev, enum pcie_reset_state state);
#define HAVE_PCI_SET_MWI
int __must_check pci_set_mwi(struct pci_dev *dev);
--
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.
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