From: Marek Vasut marek.vasut+renesas@gmail.com
[ Upstream commit a115b1bd3af0c2963e72f6e47143724c59251be6 ]
When the link is in L1, hardware should return it to L0 automatically whenever a transaction targets a component on the other end of the link (PCIe r5.0, sec 5.2).
The R-Car PCIe controller doesn't handle this transition correctly. If the link is not in L0, an MMIO transaction targeting a downstream device fails, and the controller reports an ARM imprecise external abort.
Work around this by hooking the abort handler so the driver can detect this situation and help the hardware complete the link state transition.
When the R-Car controller receives a PM_ENTER_L1 DLLP from the downstream component, it sets PMEL1RX bit in PMSR register, but then the controller enters some sort of in-between state. A subsequent MMIO transaction will fail, resulting in the external abort. The abort handler detects this condition and completes the link state transition by setting the L1IATN bit in PMCTLR and waiting for the link state transition to complete.
Link: https://lore.kernel.org/r/20210815181650.132579-1-marek.vasut@gmail.com Signed-off-by: Marek Vasut marek.vasut+renesas@gmail.com Signed-off-by: Lorenzo Pieralisi lorenzo.pieralisi@arm.com Cc: Bjorn Helgaas bhelgaas@google.com Cc: Geert Uytterhoeven geert+renesas@glider.be Cc: Lorenzo Pieralisi lorenzo.pieralisi@arm.com Cc: Wolfram Sang wsa@the-dreams.de Cc: Yoshihiro Shimoda yoshihiro.shimoda.uh@renesas.com Cc: linux-renesas-soc@vger.kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/pci/controller/pcie-rcar-host.c | 86 +++++++++++++++++++++++++ drivers/pci/controller/pcie-rcar.h | 7 ++ 2 files changed, 93 insertions(+)
diff --git a/drivers/pci/controller/pcie-rcar-host.c b/drivers/pci/controller/pcie-rcar-host.c index 765cf2b45e24..11fcaa54c169 100644 --- a/drivers/pci/controller/pcie-rcar-host.c +++ b/drivers/pci/controller/pcie-rcar-host.c @@ -13,12 +13,14 @@
#include <linux/bitops.h> #include <linux/clk.h> +#include <linux/clk-provider.h> #include <linux/delay.h> #include <linux/interrupt.h> #include <linux/irq.h> #include <linux/irqdomain.h> #include <linux/kernel.h> #include <linux/init.h> +#include <linux/iopoll.h> #include <linux/msi.h> #include <linux/of_address.h> #include <linux/of_irq.h> @@ -41,6 +43,21 @@ struct rcar_msi { int irq2; };
+#ifdef CONFIG_ARM +/* + * Here we keep a static copy of the remapped PCIe controller address. + * This is only used on aarch32 systems, all of which have one single + * PCIe controller, to provide quick access to the PCIe controller in + * the L1 link state fixup function, called from the ARM fault handler. + */ +static void __iomem *pcie_base; +/* + * Static copy of bus clock pointer, so we can check whether the clock + * is enabled or not. + */ +static struct clk *pcie_bus_clk; +#endif + /* Structure representing the PCIe interface */ struct rcar_pcie_host { struct rcar_pcie pcie; @@ -776,6 +793,12 @@ static int rcar_pcie_get_resources(struct rcar_pcie_host *host) } host->msi.irq2 = i;
+#ifdef CONFIG_ARM + /* Cache static copy for L1 link state fixup hook on aarch32 */ + pcie_base = pcie->base; + pcie_bus_clk = host->bus_clk; +#endif + return 0;
err_irq2: @@ -1031,4 +1054,67 @@ static struct platform_driver rcar_pcie_driver = { }, .probe = rcar_pcie_probe, }; + +#ifdef CONFIG_ARM +static DEFINE_SPINLOCK(pmsr_lock); +static int rcar_pcie_aarch32_abort_handler(unsigned long addr, + unsigned int fsr, struct pt_regs *regs) +{ + unsigned long flags; + u32 pmsr, val; + int ret = 0; + + spin_lock_irqsave(&pmsr_lock, flags); + + if (!pcie_base || !__clk_is_enabled(pcie_bus_clk)) { + ret = 1; + goto unlock_exit; + } + + pmsr = readl(pcie_base + PMSR); + + /* + * Test if the PCIe controller received PM_ENTER_L1 DLLP and + * the PCIe controller is not in L1 link state. If true, apply + * fix, which will put the controller into L1 link state, from + * which it can return to L0s/L0 on its own. + */ + if ((pmsr & PMEL1RX) && ((pmsr & PMSTATE) != PMSTATE_L1)) { + writel(L1IATN, pcie_base + PMCTLR); + ret = readl_poll_timeout_atomic(pcie_base + PMSR, val, + val & L1FAEG, 10, 1000); + WARN(ret, "Timeout waiting for L1 link state, ret=%d\n", ret); + writel(L1FAEG | PMEL1RX, pcie_base + PMSR); + } + +unlock_exit: + spin_unlock_irqrestore(&pmsr_lock, flags); + return ret; +} + +static const struct of_device_id rcar_pcie_abort_handler_of_match[] __initconst = { + { .compatible = "renesas,pcie-r8a7779" }, + { .compatible = "renesas,pcie-r8a7790" }, + { .compatible = "renesas,pcie-r8a7791" }, + { .compatible = "renesas,pcie-rcar-gen2" }, + {}, +}; + +static int __init rcar_pcie_init(void) +{ + if (of_find_matching_node(NULL, rcar_pcie_abort_handler_of_match)) { +#ifdef CONFIG_ARM_LPAE + hook_fault_code(17, rcar_pcie_aarch32_abort_handler, SIGBUS, 0, + "asynchronous external abort"); +#else + hook_fault_code(22, rcar_pcie_aarch32_abort_handler, SIGBUS, 0, + "imprecise external abort"); +#endif + } + + return platform_driver_register(&rcar_pcie_driver); +} +device_initcall(rcar_pcie_init); +#else builtin_platform_driver(rcar_pcie_driver); +#endif diff --git a/drivers/pci/controller/pcie-rcar.h b/drivers/pci/controller/pcie-rcar.h index d4c698b5f821..9bb125db85c6 100644 --- a/drivers/pci/controller/pcie-rcar.h +++ b/drivers/pci/controller/pcie-rcar.h @@ -85,6 +85,13 @@ #define LTSMDIS BIT(31) #define MACCTLR_INIT_VAL (LTSMDIS | MACCTLR_NFTS_MASK) #define PMSR 0x01105c +#define L1FAEG BIT(31) +#define PMEL1RX BIT(23) +#define PMSTATE GENMASK(18, 16) +#define PMSTATE_L1 (3 << 16) +#define PMCTLR 0x011060 +#define L1IATN BIT(31) + #define MACS2R 0x011078 #define MACCGSPSETR 0x011084 #define SPCNGRSN BIT(31)