Add a fault handler which handles reads in Thumb-2 mode. Install the appropriate handler depending on which mode the kernel has been built. This avoids an "Unhandled fault: external abort on non-linefetch (0x1008) at 0xf0a80000" during boot on a device with a PCIe switch connected. Link: https://lore.kernel.org/linux-pci/20181126161645.8177-1-stefan@xxxxxxxx/ Signed-off-by: Stefan Agner <stefan@xxxxxxxx> --- FWIW, I found this manual helpful to write the code below: http://hermes.wings.cs.wisc.edu/files/Thumb-2SupplementReferenceManual.pdf#page=43&zoom=100,0,66 -- Stefan drivers/pci/controller/dwc/pci-imx6.c | 37 ++++++++++++++++++++++++++- 1 file changed, 36 insertions(+), 1 deletion(-) diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c index 69f86234f7c0..683deb74d69f 100644 --- a/drivers/pci/controller/dwc/pci-imx6.c +++ b/drivers/pci/controller/dwc/pci-imx6.c @@ -29,6 +29,7 @@ #include <linux/reset.h> #include <linux/pm_domain.h> #include <linux/pm_runtime.h> +#include <asm/opcodes.h> #include "pcie-designware.h" @@ -299,6 +300,37 @@ static int imx6q_pcie_abort_handler(unsigned long addr, return 1; } +static int imx6q_pcie_abort_handler_thumb2(unsigned long addr, + unsigned int fsr, struct pt_regs *regs) +{ + unsigned long pc = instruction_pointer(regs); + unsigned long instr = *(unsigned long *)pc; + unsigned long thumb2_instr = __mem_to_opcode_thumb16(instr); + int reg = thumb2_instr & 7; + + if (!__opcode_is_thumb16(instr & 0x0000ffffUL)) + return 1; + + /* Load word/byte and halfword immediate offset */ + if (((thumb2_instr & 0xe800) == 0x6800) || + ((thumb2_instr & 0xf800) == 0x8800)) { + unsigned long val; + + if (thumb2_instr & 0x1000) + val = 0xff; + else if (thumb2_instr & 0x8000) + val = 0xffff; + else + val = 0xffffffffUL; + + regs->uregs[reg] = val; + regs->ARM_pc += 2; + return 0; + } + + return 1; +} + static int imx6_pcie_attach_pd(struct device *dev) { struct imx6_pcie *imx6_pcie = dev_get_drvdata(dev); @@ -1069,6 +1101,8 @@ static struct platform_driver imx6_pcie_driver = { static int __init imx6_pcie_init(void) { + bool thumb2 = IS_ENABLED(CONFIG_THUMB2_KERNEL); + /* * Since probe() can be deferred we need to make sure that * hook_fault_code is not called after __init memory is freed @@ -1076,7 +1110,8 @@ static int __init imx6_pcie_init(void) * we can install the handler here without risking it * accessing some uninitialized driver state. */ - hook_fault_code(8, imx6q_pcie_abort_handler, SIGBUS, 0, + hook_fault_code(8, thumb2 ? imx6q_pcie_abort_handler_thumb2 : + imx6q_pcie_abort_handler, SIGBUS, 0, "external abort on non-linefetch"); return platform_driver_register(&imx6_pcie_driver); -- 2.19.1
