[PATCH 5/6] PCI MSI: Refactor interrupt masking code

Matthew Wilcox
2009-02-23T17:52:23Z

From: Matthew Wilcox <willy@linux.intel.com>

Since most of the callers already know whether they have an MSI or
an MSI-X capability, split msi_set_mask_bits() into msi_mask_irq()
and msix_mask_irq(). The only callers which don't (mask_msi_irq()
and unmask_msi_irq()) can share code in msi_set_mask_bit(). This then
becomes the only caller of msix_flush_writes(), so we can inline it.
The flushing read can be to any address that belongs to the device,
so we can eliminate the calculation too.

We can also get rid of maskbits_mask from struct msi_desc and simply
recalculate it on the rare occasion that we need it. The single-bit
'masked' element is replaced by a copy of the 32-bit 'masked' register,
so this patch does not affect the size of msi_desc.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
---
drivers/pci/msi.c | 157 +++++++++++++++++++++++++--------------------------
include/linux/msi.h | 5 +-
2 files changed, 79 insertions(+), 83 deletions(-)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index fcde04d..41f18cb 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -105,17 +105,14 @@ static inline __attribute_const__ u32 msi_mask(unsigned x)
return (1 << (1 << x)) - 1;
}

-static void msix_flush_writes(struct irq_desc *desc)
+static inline __attribute_const__ u32 msi_capable_mask(u16 control)
{
- struct msi_desc *entry;
+ return msi_mask((control >> 1) & 7);
+}

- entry = get_irq_desc_msi(desc);
- BUG_ON(!entry);
- if (entry->msi_attrib.is_msix) {
- int offset = entry->msi_attrib.entry_nr * PCI_MSIX_ENTRY_SIZE +
- PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET;
- readl(entry->mask_base + offset);
- }
+static inline __attribute_const__ u32 msi_enabled_mask(u16 control)
+{
+ return msi_mask((control >> 4) & 7);
}

/*
@@ -127,34 +124,62 @@ static void msix_flush_writes(struct irq_desc *desc)
* Returns 1 if it succeeded in masking the interrupt and 0 if the device
* doesn't support MSI masking.
*/
-static int msi_set_mask_bits(struct irq_desc *desc, u32 mask, u32 flag)
+static int msi_mask_irq(struct msi_desc *desc, u32 mask, u32 flag)
{
- struct msi_desc *entry;
+ u32 mask_bits = desc->masked;

- entry = get_irq_desc_msi(desc);
- BUG_ON(!entry);
- if (entry->msi_attrib.is_msix) {
- int offset = entry->msi_attrib.entry_nr * PCI_MSIX_ENTRY_SIZE +
- PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET;
- writel(flag, entry->mask_base + offset);
- readl(entry->mask_base + offset);
- } else {
- int pos;
- u32 mask_bits;
+ if (!desc->msi_attrib.maskbit)
+ return 0;

- if (!entry->msi_attrib.maskbit)
- return 0;
+ mask_bits &= ~mask;
+ mask_bits |= flag;
+ pci_write_config_dword(desc->dev, desc->mask_pos, mask_bits);
+ desc->masked = mask_bits;

- pos = entry->mask_pos;
- pci_read_config_dword(entry->dev, pos, &mask_bits);
- mask_bits &= ~mask;
- mask_bits |= flag & mask;
- pci_write_config_dword(entry->dev, pos, mask_bits);
- }
- entry->msi_attrib.masked = !!flag;
return 1;
}

+/*
+ * This internal function does not flush PCI writes to the device.
+ * All users must ensure that they read from the device before either
+ * assuming that the device state is up to date, or returning out of this
+ * file. This saves a few milliseconds when initialising devices with lots
+ * of MSI-X interrupts.
+ */
+static void msix_mask_irq(struct msi_desc *desc, u32 flag)
+{
+ u32 mask_bits = desc->masked;
+ unsigned offset = desc->msi_attrib.entry_nr * PCI_MSIX_ENTRY_SIZE +
+ PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET;
+ mask_bits &= ~1;
+ mask_bits |= flag;
+ writel(mask_bits, desc->mask_base + offset);
+ desc->masked = mask_bits;
+}
+
+static int msi_set_mask_bit(unsigned irq, u32 flag)
+{
+ struct msi_desc *desc = get_irq_msi(irq);
+
+ if (desc->msi_attrib.is_msix) {
+ msix_mask_irq(desc, flag);
+ readl(desc->mask_base); /* Flush write to device */
+ return 1;
+ } else {
+ return msi_mask_irq(desc, 1, flag);
+ }
+}
+
+void mask_msi_irq(unsigned int irq)
+{
+ msi_set_mask_bit(irq, 1);
+}
+
+void unmask_msi_irq(unsigned int irq)
+{
+ msi_set_mask_bit(irq, 0);
+}
+
void read_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg)
{
struct msi_desc *entry = get_irq_desc_msi(desc);
@@ -230,22 +255,6 @@ void write_msi_msg(unsigned int irq, struct msi_msg *msg)
write_msi_msg_desc(desc, msg);
}

-void mask_msi_irq(unsigned int irq)
-{
- struct irq_desc *desc = irq_to_desc(irq);
-
- msi_set_mask_bits(desc, 1, 1);
- msix_flush_writes(desc);
-}
-
-void unmask_msi_irq(unsigned int irq)
-{
- struct irq_desc *desc = irq_to_desc(irq);
-
- msi_set_mask_bits(desc, 1, 0);
- msix_flush_writes(desc);
-}
-
static int msi_free_irqs(struct pci_dev* dev);

static struct msi_desc *alloc_msi_entry(struct pci_dev *dev)
@@ -281,13 +290,9 @@ static void __pci_restore_msi_state(struct pci_dev *dev)
pci_intx_for_msi(dev, 0);
msi_set_enable(dev, 0);
write_msi_msg(dev->irq, &entry->msg);
- if (entry->msi_attrib.maskbit) {
- struct irq_desc *desc = irq_to_desc(dev->irq);
- msi_set_mask_bits(desc, entry->msi_attrib.maskbits_mask,
- entry->msi_attrib.masked);
- }

pci_read_config_word(dev, pos + PCI_MSI_FLAGS, &control);
+ msi_mask_irq(entry, msi_capable_mask(control), entry->masked);
control &= ~PCI_MSI_FLAGS_QSIZE;
control |= PCI_MSI_FLAGS_ENABLE;
pci_write_config_word(dev, pos + PCI_MSI_FLAGS, control);
@@ -307,9 +312,8 @@ static void __pci_restore_msix_state(struct pci_dev *dev)
msix_set_enable(dev, 0);

list_for_each_entry(entry, &dev->msi_list, list) {
- struct irq_desc *desc = irq_to_desc(entry->irq);
write_msi_msg(entry->irq, &entry->msg);
- msi_set_mask_bits(desc, 1, entry->msi_attrib.masked);
+ msix_mask_irq(entry, entry->masked);
}

BUG_ON(list_empty(&dev->msi_list));
@@ -342,6 +346,7 @@ static int msi_capability_init(struct pci_dev *dev)
struct msi_desc *entry;
int pos, ret;
u16 control;
+ unsigned mask;

msi_set_enable(dev, 0); /* Ensure msi is disabled as I set it up */

@@ -356,21 +361,15 @@ static int msi_capability_init(struct pci_dev *dev)
entry->msi_attrib.is_64 = is_64bit_address(control);
entry->msi_attrib.entry_nr = 0;
entry->msi_attrib.maskbit = is_mask_bit_support(control);
- entry->msi_attrib.masked = 1;
entry->msi_attrib.default_irq = dev->irq; /* Save IOAPIC IRQ */
entry->msi_attrib.pos = pos;
- if (entry->msi_attrib.maskbit) {
- unsigned int base, maskbits, temp;
-
- base = msi_mask_bits_reg(pos, entry->msi_attrib.is_64);
- entry->mask_pos = base;
- /* All MSIs are unmasked by default, Mask them all */
- pci_read_config_dword(dev, base, &maskbits);
- temp = msi_mask((control & PCI_MSI_FLAGS_QMASK) >> 1);
- maskbits |= temp;
- pci_write_config_dword(dev, base, maskbits);
- entry->msi_attrib.maskbits_mask = temp;
- }
+
+ entry->mask_pos = msi_mask_bits_reg(pos, entry->msi_attrib.is_64);
+ /* All MSIs are unmasked by default, Mask them all */
+ pci_read_config_dword(dev, entry->mask_pos, &entry->masked);
+ mask = msi_capable_mask(control);
+ msi_mask_irq(entry, mask, mask);
+
list_add_tail(&entry->list, &dev->msi_list);

/* Configure MSI capability structure */
@@ -435,11 +434,12 @@ static int msix_capability_init(struct pci_dev *dev,
entry->msi_attrib.is_msix = 1;
entry->msi_attrib.is_64 = 1;
entry->msi_attrib.entry_nr = j;
- entry->msi_attrib.maskbit = 1;
- entry->msi_attrib.masked = 1;
entry->msi_attrib.default_irq = dev->irq;
entry->msi_attrib.pos = pos;
entry->mask_base = base;
+ entry->masked = readl(base + j * PCI_MSIX_ENTRY_SIZE +
+ PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET);
+ msix_mask_irq(entry, 1);

list_add_tail(&entry->list, &dev->msi_list);
}
@@ -556,9 +556,11 @@ int pci_enable_msi(struct pci_dev* dev)
}
EXPORT_SYMBOL(pci_enable_msi);

-void pci_msi_shutdown(struct pci_dev* dev)
+void pci_msi_shutdown(struct pci_dev *dev)
{
- struct msi_desc *entry;
+ struct msi_desc *desc;
+ u32 mask;
+ u16 ctrl;

if (!pci_msi_enable || !dev || !dev->msi_enabled)
return;
@@ -568,18 +570,13 @@ void pci_msi_shutdown(struct pci_dev* dev)
dev->msi_enabled = 0;

BUG_ON(list_empty(&dev->msi_list));
- entry = list_entry(dev->msi_list.next, struct msi_desc, list);
- /* Return the the pci reset with msi irqs unmasked */
- if (entry->msi_attrib.maskbit) {
- u32 mask = entry->msi_attrib.maskbits_mask;
- struct irq_desc *desc = irq_to_desc(dev->irq);
- msi_set_mask_bits(desc, mask, ~mask);
- }
- if (entry->msi_attrib.is_msix)
- return;
+ desc = list_first_entry(&dev->msi_list, struct msi_desc, list);
+ pci_read_config_word(dev, desc->msi_attrib.pos + PCI_MSI_FLAGS, &ctrl);
+ mask = msi_capable_mask(ctrl);
+ msi_mask_irq(desc, mask, ~mask);

/* Restore dev->irq to its default pin-assertion irq */
- dev->irq = entry->msi_attrib.default_irq;
+ dev->irq = desc->msi_attrib.default_irq;
}

void pci_disable_msi(struct pci_dev* dev)
diff --git a/include/linux/msi.h b/include/linux/msi.h
index 5025ca4..37c1bbe 100644
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -22,14 +22,13 @@ struct msi_desc {
struct {
__u8 is_msix : 1;
__u8 maskbit : 1; /* mask-pending bit supported ? */
- __u8 masked : 1;
__u8 is_64 : 1; /* Address size: 0=32bit 1=64bit */
__u8 pos; /* Location of the msi capability */
__u16 entry_nr; /* specific enabled entry */
- __u32 maskbits_mask; /* mask bits mask */
unsigned default_irq; /* default pre-assigned irq */
- }msi_attrib;
+ } msi_attrib;

+ u32 masked; /* mask bits */
unsigned int irq;
struct list_head list;

--
1.5.6.5