[34-longterm 035/260] PCI: MSI: Remove unsafe and unnecessary hardware access

Paul Gortmaker
2011-01-02T07:21:55Z

From: Ben Hutchings <bhutchings@solarflare.com>

commit fcd097f31a6ee207cc0c3da9cccd2a86d4334785 upstream.

During suspend on an SMP system, {read,write}_msi_msg_desc() may be
called to mask and unmask interrupts on a device that is already in a
reduced power state. At this point memory-mapped registers including
MSI-X tables are not accessible, and config space may not be fully
functional either.

While a device is in a reduced power state its interrupts are
effectively masked and its MSI(-X) state will be restored when it is
brought back to D0. Therefore these functions can simply read and
write msi_desc::msg for devices not in D0.

Further, read_msi_msg_desc() should only ever be used to update a
previously written message, so it can always read msi_desc::msg
and never needs to touch the hardware.

Tested-by: "Michael Chan" <mchan@broadcom.com>
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
drivers/pci/msi.c | 34 +++++++++++-----------------------
1 files changed, 11 insertions(+), 23 deletions(-)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 77b68ea..03f04dc 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -196,30 +196,15 @@ void unmask_msi_irq(unsigned int irq)
void read_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg)
{
struct msi_desc *entry = get_irq_desc_msi(desc);
- if (entry->msi_attrib.is_msix) {
- void __iomem *base = entry->mask_base +
- entry->msi_attrib.entry_nr * PCI_MSIX_ENTRY_SIZE;

- msg->address_lo = readl(base + PCI_MSIX_ENTRY_LOWER_ADDR);
- msg->address_hi = readl(base + PCI_MSIX_ENTRY_UPPER_ADDR);
- msg->data = readl(base + PCI_MSIX_ENTRY_DATA);
- } else {
- struct pci_dev *dev = entry->dev;
- int pos = entry->msi_attrib.pos;
- u16 data;
+ /* We do not touch the hardware (which may not even be
+ * accessible at the moment) but return the last message
+ * written. Assert that this is valid, assuming that
+ * valid messages are not all-zeroes. */
+ BUG_ON(!(entry->msg.address_hi | entry->msg.address_lo |
+ entry->msg.data));

- pci_read_config_dword(dev, msi_lower_address_reg(pos),
- &msg->address_lo);
- if (entry->msi_attrib.is_64) {
- pci_read_config_dword(dev, msi_upper_address_reg(pos),
- &msg->address_hi);
- pci_read_config_word(dev, msi_data_reg(pos, 1), &data);
- } else {
- msg->address_hi = 0;
- pci_read_config_word(dev, msi_data_reg(pos, 0), &data);
- }
- msg->data = data;
- }
+ *msg = entry->msg;
}

void read_msi_msg(unsigned int irq, struct msi_msg *msg)
@@ -232,7 +217,10 @@ void read_msi_msg(unsigned int irq, struct msi_msg *msg)
void write_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg)
{
struct msi_desc *entry = get_irq_desc_msi(desc);
- if (entry->msi_attrib.is_msix) {
+
+ if (entry->dev->current_state != PCI_D0) {
+ /* Don't touch the hardware now */
+ } else if (entry->msi_attrib.is_msix) {
void __iomem *base;
base = entry->mask_base +
entry->msi_attrib.entry_nr * PCI_MSIX_ENTRY_SIZE;
--
1.7.3.3