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PCI: loongson: Don't access non-existent devices

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On LS2K/LS7A, config reads to some non-existent devices don't return
0xffffffff (they are hidden devices for debug, and accessing the config
space may cause machine hang). This is a hardware flaw but we can only
avoid it by software now.

Link: https://lore.kernel.org/r/20220714124216.1489304-5-chenhuacai@loongson.cn
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
This commit is contained in:
Huacai Chen 2022-07-14 20:42:13 +08:00 committed by Bjorn Helgaas
parent cd89edda40
commit 2410e3301f
1 changed files with 23 additions and 6 deletions
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29
drivers/pci/controller/pci-loongson.c
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@ -26,6 +26,7 @@
#define FLAG_CFG0 BIT(0)
#define FLAG_CFG1 BIT(1)
#define FLAG_DEV_FIX BIT(2)
#define FLAG_DEV_HIDDEN BIT(3)
struct loongson_pci_data {
u32 flags;
@ -138,18 +139,34 @@ static void __iomem *cfg1_map(struct loongson_pci *priv, struct pci_bus *bus,
return priv->cfg1_base + addroff;
}
static bool pdev_may_exist(struct pci_bus *bus, unsigned int device,
unsigned int function)
{
return !(pci_is_root_bus(bus) &&
(device >= 9 && device <= 20) && (function > 0));
}
static void __iomem *pci_loongson_map_bus(struct pci_bus *bus,
unsigned int devfn, int where)
{
unsigned int device = PCI_SLOT(devfn);
unsigned int function = PCI_FUNC(devfn);
struct loongson_pci *priv = pci_bus_to_loongson_pci(bus);
/*
* Do not read more than one device on the bus other than
* the host bus.
*/
if (priv->data->flags & FLAG_DEV_FIX &&
!pci_is_root_bus(bus) && PCI_SLOT(devfn) > 0)
return NULL;
if ((priv->data->flags & FLAG_DEV_FIX) && bus->self) {
if (!pci_is_root_bus(bus) && (device > 0))
return NULL;
}
/* Don't access non-existent devices */
if (priv->data->flags & FLAG_DEV_HIDDEN) {
if (!pdev_may_exist(bus, device, function))
return NULL;
}
/* CFG0 can only access standard space */
if (where < PCI_CFG_SPACE_SIZE && priv->cfg0_base)
@ -197,12 +214,12 @@ static struct pci_ops loongson_pci_ops32 = {
};
static const struct loongson_pci_data ls2k_pci_data = {
.flags = FLAG_CFG1 | FLAG_DEV_FIX,
.flags = FLAG_CFG1 | FLAG_DEV_FIX | FLAG_DEV_HIDDEN,
.ops = &loongson_pci_ops,
};
static const struct loongson_pci_data ls7a_pci_data = {
.flags = FLAG_CFG1 | FLAG_DEV_FIX,
.flags = FLAG_CFG1 | FLAG_DEV_FIX | FLAG_DEV_HIDDEN,
.ops = &loongson_pci_ops,
};
@ -297,7 +314,7 @@ static int loongson_pci_ecam_init(struct pci_config_window *cfg)
return -ENOMEM;
cfg->priv = priv;
data->flags = FLAG_CFG1;
data->flags = FLAG_CFG1 | FLAG_DEV_HIDDEN;
priv->data = data;
priv->cfg1_base = cfg->win - (cfg->busr.start << 16);