OpenWrt – Rev 1
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From efdde709efccc4f95c7641eea8960dbc31fc58b5 Mon Sep 17 00:00:00 2001
From: P33M <p33m@github.com>
Date: Thu, 15 Feb 2018 11:22:44 +0000
Subject: [PATCH 207/454] dwc_otg: add smp_mb() to prevent driver state
corruption on boot
Occasional crashes have been seen where the FIQ code dereferences
invalid/random pointers immediately after being set up, leading to
panic on boot.
The crash occurs as the FIQ code races against hcd_init_fiq() and
the hcd_init_fiq() code races against the outstanding memory stores
from dwc_otg_hcd_init(). Use explicit barriers after touching
driver state.
---
drivers/usb/host/dwc_otg/dwc_otg_hcd_linux.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
--- a/drivers/usb/host/dwc_otg/dwc_otg_hcd_linux.c
+++ b/drivers/usb/host/dwc_otg/dwc_otg_hcd_linux.c
@@ -519,6 +519,11 @@ static void hcd_init_fiq(void *cookie)
DWC_ERROR("Can't get FIQ irq");
return;
}
+ /*
+ * We could take an interrupt immediately after enabling the FIQ.
+ * Ensure coherency of hcd->fiq_state.
+ */
+ smp_mb();
enable_fiq(irq);
local_fiq_enable();
#endif
@@ -598,7 +603,11 @@ int hcd_init(dwc_bus_dev_t *_dev)
if (fiq_enable) {
if (num_online_cpus() > 1) {
- /* bcm2709: can run the FIQ on a separate core to IRQs */
+ /*
+ * bcm2709: can run the FIQ on a separate core to IRQs.
+ * Ensure driver state is visible to other cores before setting up the FIQ.
+ */
+ smp_mb();
smp_call_function_single(1, hcd_init_fiq, otg_dev, 1);
} else {
smp_call_function_single(0, hcd_init_fiq, otg_dev, 1);