[patch RFC 30/38] PCI/MSI: Allow to disable arch fallbacks

Thomas Gleixner
2020-08-21T02:18:26Z

[-- Attachment #1: PCI-MSI--Allow-to-disable-arch-fallbacks.patch --]
[-- Type: text/plain, Size: 2901 bytes --]

If an architecture does not require the MSI setup/teardown fallback
functions, then allow them to be replaced by stub functions which emit a
warning.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci@vger.kernel.org
---
drivers/pci/Kconfig | 3 +++
drivers/pci/msi.c | 3 ++-
include/linux/msi.h | 31 ++++++++++++++++++++++++++-----
3 files changed, 31 insertions(+), 6 deletions(-)

--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -56,6 +56,9 @@ config PCI_MSI_IRQ_DOMAIN
depends on PCI_MSI
select GENERIC_MSI_IRQ_DOMAIN

+config PCI_MSI_DISABLE_ARCH_FALLBACKS
+ bool
+
config PCI_QUIRKS
default y
bool "Enable PCI quirk workarounds" if EXPERT
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -58,8 +58,8 @@ static void pci_msi_teardown_msi_irqs(st
#define pci_msi_teardown_msi_irqs arch_teardown_msi_irqs
#endif

+#ifndef CONFIG_PCI_MSI_DISABLE_ARCH_FALLBACKS
/* Arch hooks */
-
int __weak arch_setup_msi_irq(struct pci_dev *dev, struct msi_desc *desc)
{
struct msi_controller *chip = dev->bus->msi;
@@ -132,6 +132,7 @@ void __weak arch_teardown_msi_irqs(struc
{
return default_teardown_msi_irqs(dev);
}
+#endif /* !CONFIG_PCI_MSI_DISABLE_ARCH_FALLBACKS */

static void default_restore_msi_irq(struct pci_dev *dev, int irq)
{
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -193,17 +193,38 @@ void pci_msi_mask_irq(struct irq_data *d
void pci_msi_unmask_irq(struct irq_data *data);

/*
- * The arch hooks to setup up msi irqs. Those functions are
- * implemented as weak symbols so that they /can/ be overriden by
- * architecture specific code if needed.
+ * The arch hooks to setup up msi irqs. Default functions are implemented
+ * as weak symbols so that they /can/ be overriden by architecture specific
+ * code if needed.
+ *
+ * They can be replaced by stubs with warnings via
+ * CONFIG_PCI_MSI_DISABLE_ARCH_FALLBACKS when the architecture fully
+ * utilizes direct irqdomain based setup.
*/
+#ifndef CONFIG_PCI_MSI_DISABLE_ARCH_FALLBACKS
int arch_setup_msi_irq(struct pci_dev *dev, struct msi_desc *desc);
void arch_teardown_msi_irq(unsigned int irq);
int arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type);
void arch_teardown_msi_irqs(struct pci_dev *dev);
-void arch_restore_msi_irqs(struct pci_dev *dev);
-
void default_teardown_msi_irqs(struct pci_dev *dev);
+#else
+static inline int arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
+{
+ WARN_ON_ONCE(1);
+ return -ENODEV;
+}
+
+static inline void arch_teardown_msi_irqs(struct pci_dev *dev)
+{
+ WARN_ON_ONCE(1);
+}
+#endif
+
+/*
+ * The restore hooks are still available as they are useful even
+ * for fully irq domain based setups. Courtesy to XEN/X86.
+ */
+void arch_restore_msi_irqs(struct pci_dev *dev);
void default_restore_msi_irqs(struct pci_dev *dev);

struct msi_controller {