[ 017/108] MIPS: pci-ar724x: avoid data bus error due to a missing PCIe module

From: Greg Kroah-Hartman
Date: Wed Sep 12 2012 - 20:44:07 EST

From: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>

3.5-stable review patch. If anyone has any objections, please let me know.


From: Gabor Juhos <juhosg@xxxxxxxxxxx>

commit a1dca315ce3f78347bca8ce8befe3cc71ae63b7e upstream.

If the controller has no PCIe module attached, accessing of the device
configuration space causes a data bus error. Avoid this by checking the
status of the PCIe link in advance, and indicate an error if the link
is down.

Signed-off-by: Gabor Juhos <juhosg@xxxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Patchwork: https://patchwork.linux-mips.org/patch/4293/
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

arch/mips/pci/pci-ar724x.c | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)

--- a/arch/mips/pci/pci-ar724x.c
+++ b/arch/mips/pci/pci-ar724x.c
@@ -23,9 +23,12 @@
#define AR724X_PCI_MEM_BASE 0x10000000
#define AR724X_PCI_MEM_SIZE 0x08000000

+#define AR724X_PCI_REG_RESET 0x18
#define AR724X_PCI_REG_INT_STATUS 0x4c
#define AR724X_PCI_REG_INT_MASK 0x50

+#define AR724X_PCI_RESET_LINK_UP BIT(0)
#define AR724X_PCI_INT_DEV0 BIT(14)

#define AR724X_PCI_IRQ_COUNT 1
@@ -38,6 +41,15 @@ static void __iomem *ar724x_pci_ctrl_bas

static u32 ar724x_pci_bar0_value;
static bool ar724x_pci_bar0_is_cached;
+static bool ar724x_pci_link_up;
+static inline bool ar724x_pci_check_link(void)
+ u32 reset;
+ reset = __raw_readl(ar724x_pci_ctrl_base + AR724X_PCI_REG_RESET);
+ return reset & AR724X_PCI_RESET_LINK_UP;

static int ar724x_pci_read(struct pci_bus *bus, unsigned int devfn, int where,
int size, uint32_t *value)
@@ -46,6 +58,9 @@ static int ar724x_pci_read(struct pci_bu
void __iomem *base;
u32 data;

+ if (!ar724x_pci_link_up)
if (devfn)

@@ -96,6 +111,9 @@ static int ar724x_pci_write(struct pci_b
u32 data;
int s;

+ if (!ar724x_pci_link_up)
if (devfn)

@@ -280,6 +298,10 @@ int __init ar724x_pcibios_init(int irq)
if (ar724x_pci_ctrl_base == NULL)
goto err_unmap_devcfg;

+ ar724x_pci_link_up = ar724x_pci_check_link();
+ if (!ar724x_pci_link_up)
+ pr_warn("ar724x: PCIe link is down\n");

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