ar71xx: work around a PCI controller bug which causes reads to the PCI_COMMAND register to return bogus values - properly fixes ath9k module reload issues

SVN-Revision: 24236

package/mac80211/patches/520-ath9k_pci_error_fix.patch

@@ -1,13 +0,0 @@
---- a/drivers/net/wireless/ath/ath9k/pci.c
-+++ b/drivers/net/wireless/ath/ath9k/pci.c
-@@ -255,6 +255,10 @@ static void ath_pci_remove(struct pci_de
- 	struct ath_wiphy *aphy = hw->priv;
- 	struct ath_softc *sc = aphy->sc;
- 	void __iomem *mem = sc->mem;
-+	u16 val;
-+
-+	/* Do a config read to clear pre-existing pci error status */
-+	pci_read_config_word(pdev, PCI_COMMAND, &val);
- 
- 	ath9k_deinit_device(sc);
- 	free_irq(sc->irq, sc);

target/linux/ar71xx/files/arch/mips/pci/pci-ar71xx.c

@@ -136,6 +136,7 @@ static int ar71xx_pci_read_config(struct pci_bus *bus, unsigned int devfn,
 	static u32 mask[8] = {0, 0xff, 0xffff, 0, 0xffffffff, 0, 0, 0};
 	unsigned long flags;
 	u32 data;
+	int retry = 0;
 	int ret;
 
 	ret = PCIBIOS_SUCCESSFUL;
@@ -143,6 +144,7 @@ static int ar71xx_pci_read_config(struct pci_bus *bus, unsigned int devfn,
 	DBG("PCI: read config: %02x:%02x.%01x/%02x:%01d\n", bus->number,
 			PCI_SLOT(devfn), PCI_FUNC(devfn), where, size);
 
+retry:
 	spin_lock_irqsave(&ar71xx_pci_lock, flags);
 
 	if (bus->number == 0 && devfn == 0) {
@@ -176,6 +178,14 @@ static int ar71xx_pci_read_config(struct pci_bus *bus, unsigned int devfn,
 
 	*value = (data >> (8 * (where & 3))) & mask[size & 7];
 
+	/*
+	 * PCI controller bug: sometimes reads to the PCI_COMMAND register
+	 * return 0xffff, even though the PCI trace shows the correct value.
+	 * Work around this by retrying reads to this register
+	 */
+	if (where == PCI_COMMAND && (*value & 0xffff) == 0xffff && retry++ < 2)
+		goto retry;
+
 	return ret;
 }