From fcd097f31a6ee207cc0c3da9cccd2a86d4334785 Mon Sep 17 00:00:00 2001

From: Ben Hutchings <bhutchings@solarflare.com>

Date: Thu, 17 Jun 2010 20:16:36 +0100

Subject: PCI: MSI: Remove unsafe and unnecessary hardware access

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: Greg Kroah-Hartman <gregkh@suse.de>

---

 drivers/pci/msi.c |   36 ++++++++++++------------------------

 1 file changed, 12 insertions(+), 24 deletions(-)

--- a/drivers/pci/msi.c

+++ b/drivers/pci/msi.c

@@ -195,30 +195,15 @@ 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;

-

-		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;

-	}

+	/* 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));

+

+	*msg = entry->msg;

 }

 void read_msi_msg(unsigned int irq, struct msi_msg *msg)

@@ -231,7 +216,10 @@ void read_msi_msg(unsigned int irq, stru

 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;