[PATCH] msi: fix up the msi enable/disable logic

enable/disable_msi_mode have several side effects which keeps them from being
generally useful.  So this patch replaces them with with two much more
targeted functions: msi_set_enable and msix_set_enable.

This patch makes pci_dev->msi_enabled and pci_dev->msix_enabled the definitive
way to test if linux has enabled the msi capability, and has the appropriate
msi data structures set up.

This patch ensures that while writing the msi messages in save/restore and
during device initialization we have the msi capability disabled so we don't
get into races.  The pci spec requires that we do not have the msi capability
enabled and the msi messages unmasked while we write the messages.  Completely
disabling the capability is overkill but it is easy :)

Care has been taken so we never have both a msi capability and intx enabled
simultaneously.  We haven't run into a problem yet but better safe then sorry.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Michael Ellerman <michael@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/pci/msi.c

@@ -38,6 +38,36 @@ static int msi_cache_init(void)
 	return 0;
 }
 
+static void msi_set_enable(struct pci_dev *dev, int enable)
+{
+	int pos;
+	u16 control;
+
+	pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
+	if (pos) {
+		pci_read_config_word(dev, pos + PCI_MSI_FLAGS, &control);
+		control &= ~PCI_MSI_FLAGS_ENABLE;
+		if (enable)
+			control |= PCI_MSI_FLAGS_ENABLE;
+		pci_write_config_word(dev, pos + PCI_MSI_FLAGS, control);
+	}
+}
+
+static void msix_set_enable(struct pci_dev *dev, int enable)
+{
+	int pos;
+	u16 control;
+
+	pos = pci_find_capability(dev, PCI_CAP_ID_MSIX);
+	if (pos) {
+		pci_read_config_word(dev, pos + PCI_MSIX_FLAGS, &control);
+		control &= ~PCI_MSIX_FLAGS_ENABLE;
+		if (enable)
+			control |= PCI_MSIX_FLAGS_ENABLE;
+		pci_write_config_word(dev, pos + PCI_MSIX_FLAGS, control);
+	}
+}
+
 static void msi_set_mask_bit(unsigned int irq, int flag)
 {
 	struct msi_desc *entry;
@@ -192,44 +222,6 @@ static struct msi_desc* alloc_msi_entry(void)
 	return entry;
 }
 
-static void enable_msi_mode(struct pci_dev *dev, int pos, int type)
-{
-	u16 control;
-
-	pci_read_config_word(dev, msi_control_reg(pos), &control);
-	if (type == PCI_CAP_ID_MSI) {
-		/* Set enabled bits to single MSI & enable MSI_enable bit */
-		msi_enable(control, 1);
-		pci_write_config_word(dev, msi_control_reg(pos), control);
-		dev->msi_enabled = 1;
-	} else {
-		msix_enable(control);
-		pci_write_config_word(dev, msi_control_reg(pos), control);
-		dev->msix_enabled = 1;
-	}
-
-	pci_intx(dev, 0);  /* disable intx */
-}
-
-static void disable_msi_mode(struct pci_dev *dev, int pos, int type)
-{
-	u16 control;
-
-	pci_read_config_word(dev, msi_control_reg(pos), &control);
-	if (type == PCI_CAP_ID_MSI) {
-		/* Set enabled bits to single MSI & enable MSI_enable bit */
-		msi_disable(control);
-		pci_write_config_word(dev, msi_control_reg(pos), control);
-		dev->msi_enabled = 0;
-	} else {
-		msix_disable(control);
-		pci_write_config_word(dev, msi_control_reg(pos), control);
-		dev->msix_enabled = 0;
-	}
-
-	pci_intx(dev, 1);  /* enable intx */
-}
-
 #ifdef CONFIG_PM
 static int __pci_save_msi_state(struct pci_dev *dev)
 {
@@ -238,12 +230,11 @@ static int __pci_save_msi_state(struct pci_dev *dev)
 	struct pci_cap_saved_state *save_state;
 	u32 *cap;
 
-	pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
-	if (pos <= 0 || dev->no_msi)
+	if (!dev->msi_enabled)
 		return 0;
 
-	pci_read_config_word(dev, msi_control_reg(pos), &control);
-	if (!(control & PCI_MSI_FLAGS_ENABLE))
+	pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
+	if (pos <= 0)
 		return 0;
 
 	save_state = kzalloc(sizeof(struct pci_cap_saved_state) + sizeof(u32) * 5,
@@ -276,13 +267,18 @@ static void __pci_restore_msi_state(struct pci_dev *dev)
 	struct pci_cap_saved_state *save_state;
 	u32 *cap;
 
+	if (!dev->msi_enabled)
+		return;
+
 	save_state = pci_find_saved_cap(dev, PCI_CAP_ID_MSI);
 	pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
 	if (!save_state || pos <= 0)
 		return;
 	cap = &save_state->data[0];
 
+	pci_intx(dev, 0);		/* disable intx */
 	control = cap[i++] >> 16;
+	msi_set_enable(dev, 0);
 	pci_write_config_dword(dev, pos + PCI_MSI_ADDRESS_LO, cap[i++]);
 	if (control & PCI_MSI_FLAGS_64BIT) {
 		pci_write_config_dword(dev, pos + PCI_MSI_ADDRESS_HI, cap[i++]);
@@ -292,7 +288,6 @@ static void __pci_restore_msi_state(struct pci_dev *dev)
 	if (control & PCI_MSI_FLAGS_MASKBIT)
 		pci_write_config_dword(dev, pos + PCI_MSI_MASK_BIT, cap[i++]);
 	pci_write_config_word(dev, pos + PCI_MSI_FLAGS, control);
-	enable_msi_mode(dev, pos, PCI_CAP_ID_MSI);
 	pci_remove_saved_cap(save_state);
 	kfree(save_state);
 }
@@ -308,13 +303,11 @@ static int __pci_save_msix_state(struct pci_dev *dev)
 		return 0;
 
 	pos = pci_find_capability(dev, PCI_CAP_ID_MSIX);
-	if (pos <= 0 || dev->no_msi)
+	if (pos <= 0)
 		return 0;
 
 	/* save the capability */
 	pci_read_config_word(dev, msi_control_reg(pos), &control);
-	if (!(control & PCI_MSIX_FLAGS_ENABLE))
-		return 0;
 	save_state = kzalloc(sizeof(struct pci_cap_saved_state) + sizeof(u16),
 		GFP_KERNEL);
 	if (!save_state) {
@@ -376,6 +369,8 @@ static void __pci_restore_msix_state(struct pci_dev *dev)
 		return;
 
 	/* route the table */
+	pci_intx(dev, 0);		/* disable intx */
+	msix_set_enable(dev, 0);
 	irq = head = dev->first_msi_irq;
 	while (head != tail) {
 		entry = get_irq_msi(irq);
@@ -386,7 +381,6 @@ static void __pci_restore_msix_state(struct pci_dev *dev)
 	}
 
 	pci_write_config_word(dev, msi_control_reg(pos), save);
-	enable_msi_mode(dev, pos, PCI_CAP_ID_MSIX);
 }
 
 void pci_restore_msi_state(struct pci_dev *dev)
@@ -411,6 +405,8 @@ static int msi_capability_init(struct pci_dev *dev)
 	int pos, irq;
 	u16 control;
 
+	msi_set_enable(dev, 0);	/* Ensure msi is disabled as I set it up */
+
    	pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
 	pci_read_config_word(dev, msi_control_reg(pos), &control);
 	/* MSI Entry Initialization */
@@ -454,7 +450,9 @@ static int msi_capability_init(struct pci_dev *dev)
 	set_irq_msi(irq, entry);
 
 	/* Set MSI enabled bits	 */
-	enable_msi_mode(dev, pos, PCI_CAP_ID_MSI);
+	pci_intx(dev, 0);		/* disable intx */
+	msi_set_enable(dev, 1);
+	dev->msi_enabled = 1;
 
 	dev->irq = irq;
 	return 0;
@@ -481,6 +479,8 @@ static int msix_capability_init(struct pci_dev *dev,
 	u8 bir;
 	void __iomem *base;
 
+	msix_set_enable(dev, 0);/* Ensure msix is disabled as I set it up */
+
    	pos = pci_find_capability(dev, PCI_CAP_ID_MSIX);
 	/* Request & Map MSI-X table region */
  	pci_read_config_word(dev, msi_control_reg(pos), &control);
@@ -549,7 +549,9 @@ static int msix_capability_init(struct pci_dev *dev,
 	}
 	dev->first_msi_irq = entries[0].vector;
 	/* Set MSI-X enabled bits */
-	enable_msi_mode(dev, pos, PCI_CAP_ID_MSIX);
+	pci_intx(dev, 0);		/* disable intx */
+	msix_set_enable(dev, 1);
+	dev->msix_enabled = 1;
 
 	return 0;
 }
@@ -611,12 +613,11 @@ int pci_enable_msi(struct pci_dev* dev)
 	WARN_ON(!!dev->msi_enabled);
 
 	/* Check whether driver already requested for MSI-X irqs */
-	pos = pci_find_capability(dev, PCI_CAP_ID_MSIX);
-	if (pos > 0 && dev->msix_enabled) {
-			printk(KERN_INFO "PCI: %s: Can't enable MSI.  "
-			       "Device already has MSI-X enabled\n",
-			       pci_name(dev));
-			return -EINVAL;
+	if (dev->msix_enabled) {
+		printk(KERN_INFO "PCI: %s: Can't enable MSI.  "
+			"Device already has MSI-X enabled\n",
+			pci_name(dev));
+		return -EINVAL;
 	}
 	status = msi_capability_init(dev);
 	return status;
@@ -625,8 +626,7 @@ int pci_enable_msi(struct pci_dev* dev)
 void pci_disable_msi(struct pci_dev* dev)
 {
 	struct msi_desc *entry;
-	int pos, default_irq;
-	u16 control;
+	int default_irq;
 
 	if (!pci_msi_enable)
 		return;
@@ -636,16 +636,9 @@ void pci_disable_msi(struct pci_dev* dev)
 	if (!dev->msi_enabled)
 		return;
 
-	pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
-	if (!pos)
-		return;
-
-	pci_read_config_word(dev, msi_control_reg(pos), &control);
-	if (!(control & PCI_MSI_FLAGS_ENABLE))
-		return;
-
-
-	disable_msi_mode(dev, pos, PCI_CAP_ID_MSI);
+	msi_set_enable(dev, 0);
+	pci_intx(dev, 1);		/* enable intx */
+	dev->msi_enabled = 0;
 
 	entry = get_irq_msi(dev->first_msi_irq);
 	if (!entry || !entry->dev || entry->msi_attrib.type != PCI_CAP_ID_MSI) {
@@ -746,8 +739,7 @@ int pci_enable_msix(struct pci_dev* dev, struct msix_entry *entries, int nvec)
 	WARN_ON(!!dev->msix_enabled);
 
 	/* Check whether driver already requested for MSI irq */
-   	if (pci_find_capability(dev, PCI_CAP_ID_MSI) > 0 &&
-		dev->msi_enabled) {
+   	if (dev->msi_enabled) {
 		printk(KERN_INFO "PCI: %s: Can't enable MSI-X.  "
 		       "Device already has an MSI irq assigned\n",
 		       pci_name(dev));
@@ -760,8 +752,6 @@ int pci_enable_msix(struct pci_dev* dev, struct msix_entry *entries, int nvec)
 void pci_disable_msix(struct pci_dev* dev)
 {
 	int irq, head, tail = 0, warning = 0;
-	int pos;
-	u16 control;
 
 	if (!pci_msi_enable)
 		return;
@@ -771,15 +761,9 @@ void pci_disable_msix(struct pci_dev* dev)
 	if (!dev->msix_enabled)
 		return;
 
-	pos = pci_find_capability(dev, PCI_CAP_ID_MSIX);
-	if (!pos)
-		return;
-
-	pci_read_config_word(dev, msi_control_reg(pos), &control);
-	if (!(control & PCI_MSIX_FLAGS_ENABLE))
-		return;
-
-	disable_msi_mode(dev, pos, PCI_CAP_ID_MSIX);
+	msix_set_enable(dev, 0);
+	pci_intx(dev, 1);		/* enable intx */
+	dev->msix_enabled = 0;
 
 	irq = head = dev->first_msi_irq;
 	while (head != tail) {