@@ -61,6 +61,7 @@
| SHORTCUT1_MASK | SHORTCUT2_MASK)
#define REG_FIQ_CONTROL 0x0c
+#define FIQ_CONTROL_ENABLE BIT(7)
#define NR_BANKS 3
#define IRQS_PER_BANK 32
@@ -135,6 +136,7 @@ static int __init armctrl_of_init(struct device_node *node,
{
void __iomem *base;
int irq, b, i;
+ u32 reg;
base = of_iomap(node, 0);
if (!base)
@@ -157,6 +159,19 @@ static int __init armctrl_of_init(struct device_node *node,
handle_level_irq);
irq_set_probe(irq);
}
+
+ reg = readl_relaxed(intc.enable[b]);
+ if (reg) {
+ writel_relaxed(reg, intc.disable[b]);
+ pr_err(FW_BUG "Bootloader left irq enabled: "
+ "bank %d irq %*pbl\n", b, IRQS_PER_BANK, ®);
+ }
+ }
+
+ reg = readl_relaxed(base + REG_FIQ_CONTROL);
+ if (reg & FIQ_CONTROL_ENABLE) {
+ writel_relaxed(0, base + REG_FIQ_CONTROL);
+ pr_err(FW_BUG "Bootloader left fiq enabled\n");
}
if (is_2836) {
Per the spec, the BCM2835's IRQs are all disabled when coming out of power-on reset. Its IRQ driver assumes that's still the case when the kernel boots and does not perform any initialization of the registers. However the Raspberry Pi Foundation's bootloader leaves the USB interrupt enabled when handing over control to the kernel. Quiesce IRQs and the FIQ if they were left enabled and log a message to let users know that they should update the bootloader once a fixed version is released. If the USB interrupt is not quiesced and the USB driver later on claims the FIQ (as it does on the Raspberry Pi Foundation's downstream kernel), interrupt latency for all other peripherals increases and occasional lockups occur. That's because both the FIQ and the normal USB interrupt fire simultaneously: On a multicore Raspberry Pi, if normal interrupts are routed to CPU 0 and the FIQ to CPU 1 (hardcoded in the Foundation's kernel), then a USB interrupt causes CPU 0 to spin in bcm2836_chained_handle_irq() until the FIQ on CPU 1 has cleared it. Other peripherals' interrupts are starved as long. I've seen CPU 0 blocked for up to 2.9 msec. eMMC throughput on a Compute Module 3 irregularly dips to 23.0 MB/s without this commit but remains relatively constant at 23.5 MB/s with this commit. The lockups occur when CPU 0 receives a USB interrupt while holding a lock which CPU 1 is trying to acquire while the FIQ is temporarily disabled on CPU 1. At best users get RCU CPU stall warnings, but most of the time the system just freezes. Fixes: 89214f009c1d ("ARM: bcm2835: add interrupt controller driver") Signed-off-by: Lukas Wunner <lukas@wunner.de> Reviewed-by: Florian Fainelli <f.fainelli@gmail.com> Reviewed-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de> Cc: stable@vger.kernel.org # v3.7+ Cc: Serge Schneider <serge@raspberrypi.org> Cc: Kristina Brooks <notstina@gmail.com> Cc: Stefan Wahren <wahrenst@gmx.net> --- v4: * Add missing REG_FIQ_ENABLE macro, rename to FIQ_CONTROL_ENABLE (Stefan) v3: (submitted as inline patch) * Shorten commit message (Florian, Marc) v2: * Use "relaxed" MMIO accessors to avoid memory barriers (Marc) * Use u32 instead of int for register access (Marc) * Quiesce FIQ as well (Marc) * Quiesce IRQs after mapping them for better readability * Drop alternative approach from commit message (Marc) drivers/irqchip/irq-bcm2835.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)