[PATCH AUTOSEL 5.9 120/147] PCI: dwc: Add link up check in dw_child_pcie_ops.map_bus()

Sasha Levin
2020-10-27T00:32:11Z

From: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>

[ Upstream commit 15b23906347c0af8778d1d4edeea415290342d35 ]

NXP Layerscape (ls1028a, ls2088a), dra7xxx and imx6 platforms are either
programmed or statically configured to forward the error triggered by a
link-down state (eg no connected endpoint device) on the system bus for
PCI configuration transactions; these errors are reported as an SError
at system level, which is fatal.

Enumerating a PCI tree when the PCIe link is down is not sensible
either, so even if the link-up check is racy (link can go down after
map_bus() is called) add a link-up check in map_bus() to prevent issuing
configuration transactions when the link is down.

SError report:

SError Interrupt on CPU2, code 0xbf000002 -- SError
CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.9.0-rc5-next-20200914-00001-gf965d3ec86fa #67
Hardware name: LS1046A RDB Board (DT)
pstate: 20000085 (nzCv daIf -PAN -UAO BTYPE=--)
pc : pci_generic_config_read+0x3c/0xe0
lr : pci_generic_config_read+0x24/0xe0
sp : ffff80001003b7b0
x29: ffff80001003b7b0 x28: ffff80001003ba74
x27: ffff000971d96800 x26: ffff00096e77e0a8
x25: ffff80001003b874 x24: ffff80001003b924
x23: 0000000000000004 x22: 0000000000000000
x21: 0000000000000000 x20: ffff80001003b874
x19: 0000000000000004 x18: ffffffffffffffff
x17: 00000000000000c0 x16: fffffe0025981840
x15: ffffb94c75b69948 x14: 62203a383634203a
x13: 666e6f635f726568 x12: 202c31203d207265
x11: 626d756e3e2d7375 x10: 656877202c307830
x9 : 203d206e66766564 x8 : 0000000000000908
x7 : 0000000000000908 x6 : ffff800010900000
x5 : ffff00096e77e080 x4 : 0000000000000000
x3 : 0000000000000003 x2 : 84fa3440ff7e7000
x1 : 0000000000000000 x0 : ffff800010034000
Kernel panic - not syncing: Asynchronous SError Interrupt
CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.9.0-rc5-next-20200914-00001-gf965d3ec86fa #67
Hardware name: LS1046A RDB Board (DT)
Call trace:
dump_backtrace+0x0/0x1c0
show_stack+0x18/0x28
dump_stack+0xd8/0x134
panic+0x180/0x398
add_taint+0x0/0xb0
arm64_serror_panic+0x78/0x88
do_serror+0x68/0x180
el1_error+0x84/0x100
pci_generic_config_read+0x3c/0xe0
dw_pcie_rd_other_conf+0x78/0x110
pci_bus_read_config_dword+0x88/0xe8
pci_bus_generic_read_dev_vendor_id+0x30/0x1b0
pci_bus_read_dev_vendor_id+0x4c/0x78
pci_scan_single_device+0x80/0x100

Link: https://lore.kernel.org/r/20200916054130.8685-1-Zhiqiang.Hou@nxp.com
Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
[lorenzo.pieralisi@arm.com: rewrote the commit log, remove Fixes tag]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/pci/controller/dwc/pcie-designware-host.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index 9dafecba347f0..bbffaa98729fb 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -515,6 +515,17 @@ static int dw_pcie_access_other_conf(struct pcie_port *pp, struct pci_bus *bus,
void __iomem *va_cfg_base;
struct dw_pcie *pci = to_dw_pcie_from_pp(pp);

+ /*
+ * Checking whether the link is up here is a last line of defense
+ * against platforms that forward errors on the system bus as
+ * SError upon PCI configuration transactions issued when the link
+ * is down. This check is racy by definition and does not stop
+ * the system from triggering an SError if the link goes down
+ * after this check is performed.
+ */
+ if (!dw_pcie_link_up(pci))
+ return NULL;
+
busdev = PCIE_ATU_BUS(bus->number) | PCIE_ATU_DEV(PCI_SLOT(devfn)) |
PCIE_ATU_FUNC(PCI_FUNC(devfn));

--
2.25.1