From: Marc Zyngier <marc.zyngier@xxxxxxx> There is a lot of broken firmware out there that don't really expose the information the kernel requires when it comes with dealing with GICv2: (1) Firmware that only describes the first 4kB of GICv2 (2) Firmware that describe 128kB of CPU interface, while the usable portion of the address space is between 60 and 68kB So far, we only deal with (2). But we have platforms exhibiting behaviour (1), resulting in two sub-cases: (a) The GIC is occupying 8kB, as required by the GICv2 architecture (b) It is actually spread 128kB, and this is likely to be a version of (2) This patch tries to work around both (a) and (b) by poking at the outside of the described memory region, and try to work out what is actually there. This is of course unsafe, and should only be enabled if there is no way to otherwise fix the DT provided by the firmware (we provide a "irqchip.gicv2_force_probe" option to that effect). Note that for the time being, we restrict ourselves to GICv2 implementations provided by ARM, since there I have no knowledge of an alternative implementations. This could be relaxed if such an implementation comes to light on a broken platform. Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx> Signed-off-by: Christoffer Dall <cdall@xxxxxxxxxx> --- Documentation/admin-guide/kernel-parameters.txt | 7 +++ drivers/irqchip/irq-gic.c | 71 +++++++++++++++++++++---- 2 files changed, 69 insertions(+), 9 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 0549662..3daa0a5 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1713,6 +1713,13 @@ irqaffinity= [SMP] Set the default irq affinity mask The argument is a cpu list, as described above. + irqchip.gicv2_force_probe= + [ARM, ARM64] + Format: <bool> + Force the kernel to look for the second 4kB page + of a GICv2 controller even if the memory range + exposed by the device tree is too small. + irqfixup [HW] When an interrupt is not handled search all handlers for it. Intended to get systems with badly broken diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c index 651d726..f641e8e 100644 --- a/drivers/irqchip/irq-gic.c +++ b/drivers/irqchip/irq-gic.c @@ -1256,6 +1256,19 @@ static void gic_teardown(struct gic_chip_data *gic) #ifdef CONFIG_OF static int gic_cnt __initdata; +static bool gicv2_force_probe; + +static int __init gicv2_force_probe_cfg(char *buf) +{ + return strtobool(buf, &gicv2_force_probe); +} +early_param("irqchip.gicv2_force_probe", gicv2_force_probe_cfg); + +static bool gic_check_gicv2(void __iomem *base) +{ + u32 val = readl_relaxed(base + GIC_CPU_IDENT); + return (val & 0xff0fff) == 0x02043B; +} static bool gic_check_eoimode(struct device_node *node, void __iomem **base) { @@ -1265,20 +1278,60 @@ static bool gic_check_eoimode(struct device_node *node, void __iomem **base) if (!is_hyp_mode_available()) return false; - if (resource_size(&cpuif_res) < SZ_8K) - return false; - if (resource_size(&cpuif_res) == SZ_128K) { - u32 val_low, val_high; + if (resource_size(&cpuif_res) < SZ_8K) { + void __iomem *alt; + /* + * Check for a stupid firmware that only exposes the + * first page of a GICv2. + */ + if (!gic_check_gicv2(*base)) + return false; + if (!gicv2_force_probe) { + pr_warn("GIC: GICv2 detected, but range too small and irqchip.gicv2_force_probe not set\n"); + return false; + } + + alt = ioremap(cpuif_res.start, SZ_8K); + if (!alt) + return false; + if (!gic_check_gicv2(alt + SZ_4K)) { + /* + * The first page was that of a GICv2, and + * the second was *something*. Let's trust it + * to be a GICv2, and update the mapping. + */ + pr_warn("GIC: GICv2 at %pa, but range is too small (broken DT?), assuming 8kB\n", + &cpuif_res.start); + iounmap(*base); + *base = alt; + return true; + } + + /* + * We detected *two* initial GICv2 pages in a + * row. Could be a GICv2 aliased over two 64kB + * pages. Update the resource, map the iospace, and + * pray. + */ + iounmap(alt); + alt = ioremap(cpuif_res.start, SZ_128K); + if (!alt) + return false; + pr_warn("GIC: Aliased GICv2 at %pa, trying to find the canonical range over 128kB\n", + &cpuif_res.start); + cpuif_res.end = cpuif_res.start + SZ_128K -1; + iounmap(*base); + *base = alt; + } + if (resource_size(&cpuif_res) == SZ_128K) { /* - * Verify that we have the first 4kB of a GIC400 + * Verify that we have the first 4kB of a GICv2 * aliased over the first 64kB by checking the * GICC_IIDR register on both ends. */ - val_low = readl_relaxed(*base + GIC_CPU_IDENT); - val_high = readl_relaxed(*base + GIC_CPU_IDENT + 0xf000); - if ((val_low & 0xffff0fff) != 0x0202043B || - val_low != val_high) + if (!gic_check_gicv2(*base) || + !gic_check_gicv2(*base + 0xf000)) return false; /* -- 2.9.0