From 6e36203bc14ce1470ad289ef050eb0fe542ee8b7 Mon Sep 17 00:00:00 2001 From: Marek Vasut Date: Sat, 12 Mar 2022 22:23:49 +0100 Subject: [PATCH] PCI: rcar: Use PCI_SET_ERROR_RESPONSE after read which triggered an exception MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit In case the controller is transitioning to L1 in rcar_pcie_config_access(), any read/write access to PCIECDR triggers asynchronous external abort. This is because the transition to L1 link state must be manually finished by the driver. The PCIe IP can transition back from L1 state to L0 on its own. The current asynchronous external abort hook implementation restarts the instruction which finally triggered the fault, which can be a different instruction than the read/write instruction which started the faulting access. Usually the instruction which finally triggers the fault is one which has some data dependency on the result of the read/write. In case of read, the read value after fixup is undefined, while a read value of faulting read should be PCI_ERROR_RESPONSE. It is possible to enforce the fault using 'isb' instruction placed right after the read/write instruction which started the faulting access. Add custom register accessors which perform the read/write followed immediately by 'isb'. This way, the fault always happens on the 'isb' and in case of read, which is located one instruction before the 'isb', it is now possible to fix up the return value of the read in the asynchronous external abort hook and make that read return PCI_ERROR_RESPONSE. Link: https://lore.kernel.org/r/20220312212349.781799-2-marek.vasut@gmail.com Tested-by: Geert Uytterhoeven Signed-off-by: Marek Vasut Signed-off-by: Lorenzo Pieralisi Reviewed-by: Arnd Bergmann Reviewed-by: Geert Uytterhoeven Cc: Arnd Bergmann Cc: Bjorn Helgaas Cc: Geert Uytterhoeven Cc: Krzysztof Wilczyński Cc: Lorenzo Pieralisi Cc: Wolfram Sang Cc: Yoshihiro Shimoda Cc: linux-renesas-soc@vger.kernel.org --- drivers/pci/controller/pcie-rcar-host.c | 56 ++++++++++++++++++++++++++++++--- 1 file changed, 52 insertions(+), 4 deletions(-) diff --git a/drivers/pci/controller/pcie-rcar-host.c b/drivers/pci/controller/pcie-rcar-host.c index 7d38a9c..712d374 100644 --- a/drivers/pci/controller/pcie-rcar-host.c +++ b/drivers/pci/controller/pcie-rcar-host.c @@ -114,6 +114,54 @@ static u32 rcar_read_conf(struct rcar_pcie *pcie, int where) return val >> shift; } +#ifdef CONFIG_ARM +#define __rcar_pci_rw_reg_workaround(instr) \ + " .arch armv7-a\n" \ + "1: " instr " %1, [%2]\n" \ + "2: isb\n" \ + "3: .pushsection .text.fixup,\"ax\"\n" \ + " .align 2\n" \ + "4: mov %0, #" __stringify(PCIBIOS_SET_FAILED) "\n" \ + " b 3b\n" \ + " .popsection\n" \ + " .pushsection __ex_table,\"a\"\n" \ + " .align 3\n" \ + " .long 1b, 4b\n" \ + " .long 2b, 4b\n" \ + " .popsection\n" +#endif + +static int rcar_pci_write_reg_workaround(struct rcar_pcie *pcie, u32 val, + unsigned int reg) +{ + int error = PCIBIOS_SUCCESSFUL; +#ifdef CONFIG_ARM + asm volatile( + __rcar_pci_rw_reg_workaround("str") + : "+r"(error):"r"(val), "r"(pcie->base + reg) : "memory"); +#else + rcar_pci_write_reg(pcie, val, reg); +#endif + return error; +} + +static int rcar_pci_read_reg_workaround(struct rcar_pcie *pcie, u32 *val, + unsigned int reg) +{ + int error = PCIBIOS_SUCCESSFUL; +#ifdef CONFIG_ARM + asm volatile( + __rcar_pci_rw_reg_workaround("ldr") + : "+r"(error), "=r"(*val) : "r"(pcie->base + reg) : "memory"); + + if (error != PCIBIOS_SUCCESSFUL) + PCI_SET_ERROR_RESPONSE(val); +#else + *val = rcar_pci_read_reg(pcie, reg); +#endif + return error; +} + /* Serialization is provided by 'pci_lock' in drivers/pci/access.c */ static int rcar_pcie_config_access(struct rcar_pcie_host *host, unsigned char access_type, struct pci_bus *bus, @@ -185,14 +233,14 @@ static int rcar_pcie_config_access(struct rcar_pcie_host *host, return PCIBIOS_DEVICE_NOT_FOUND; if (access_type == RCAR_PCI_ACCESS_READ) - *data = rcar_pci_read_reg(pcie, PCIECDR); + ret = rcar_pci_read_reg_workaround(pcie, data, PCIECDR); else - rcar_pci_write_reg(pcie, *data, PCIECDR); + ret = rcar_pci_write_reg_workaround(pcie, *data, PCIECDR); /* Disable the configuration access */ rcar_pci_write_reg(pcie, 0, PCIECCTLR); - return PCIBIOS_SUCCESSFUL; + return ret; } static int rcar_pcie_read_conf(struct pci_bus *bus, unsigned int devfn, @@ -1097,7 +1145,7 @@ static struct platform_driver rcar_pcie_driver = { static int rcar_pcie_aarch32_abort_handler(unsigned long addr, unsigned int fsr, struct pt_regs *regs) { - return !!rcar_pcie_wakeup(pcie_dev, pcie_base); + return !fixup_exception(regs); } static const struct of_device_id rcar_pcie_abort_handler_of_match[] __initconst = { -- 2.7.4