From 0da408b4d5a9eefc81ce099d34c25e7d602887aa Mon Sep 17 00:00:00 2001 From: Huacai Chen Date: Thu, 14 Jul 2022 20:42:13 +0800 Subject: [PATCH] PCI: loongson: Don't access non-existent devices 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 Signed-off-by: Bjorn Helgaas --- drivers/pci/controller/pci-loongson.c | 29 +++++++++++++++++++++------ 1 file changed, 23 insertions(+), 6 deletions(-) diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c index cd29800974e70..6ed125c7d86a3 100644 --- a/drivers/pci/controller/pci-loongson.c +++ b/drivers/pci/controller/pci-loongson.c @@ -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); -- 2.39.5