Re: 3.18 RT freezes on Raspberry Pi 2

[Mikhail Avkhimenia <mikhail.avkhimenia@emlid.com>]

Hello,

I think I found the solution. 
The problem is that new USB driver for Raspberry Pi uses FIQ in a manner that leads to lockups on SMP systems, while booting of the older non-FIQ driver was broken. 
The following patch fixes an error and allows to boot the non-FIQ driver:

---
 drivers/usb/host/dwc_otg/dwc_otg_hcd.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/host/dwc_otg/dwc_otg_hcd.c b/drivers/usb/host/dwc_otg/dwc_otg_hcd.c
index 68534d4..6a006c5 100644
--- a/drivers/usb/host/dwc_otg/dwc_otg_hcd.c
+++ b/drivers/usb/host/dwc_otg/dwc_otg_hcd.c
@@ -1414,8 +1414,12 @@ static void assign_and_init_hc(dwc_otg_hcd_t * hcd, dwc_otg_qh_t * qh)
 	dwc_otg_hc_init(hcd->core_if, hc);
 
 	local_irq_save(flags);
-	local_fiq_disable();
-	fiq_fsm_spin_lock(&hcd->fiq_state->lock);
+
+	if (fiq_enable) {
+		local_fiq_disable();
+		fiq_fsm_spin_lock(&hcd->fiq_state->lock);
+	}
+
 	/* Enable the top level host channel interrupt. */
 	intr_enable = (1 << hc->hc_num);
 	DWC_MODIFY_REG32(&hcd->core_if->host_if->host_global_regs->haintmsk, 0, intr_enable);
@@ -1423,8 +1427,12 @@ static void assign_and_init_hc(dwc_otg_hcd_t * hcd, dwc_otg_qh_t * qh)
 	/* Make sure host channel interrupts are enabled. */
 	gintmsk.b.hcintr = 1;
 	DWC_MODIFY_REG32(&hcd->core_if->core_global_regs->gintmsk, 0, gintmsk.d32);
-	fiq_fsm_spin_unlock(&hcd->fiq_state->lock);
-	local_fiq_enable();
+
+	if (fiq_enable) {
+		fiq_fsm_spin_unlock(&hcd->fiq_state->lock);
+		local_fiq_enable();
+	}
+	
 	local_irq_restore(flags);
 	hc->qh = qh;
 }
--


To boot the with the non-FIQ driver add this to the /boot/cmdline.txt:
dwc_otg.fiq_enable=0 dwc_otg.fiq_fsm_enable=0 dwc_otg.nak_holdoff=0
 

Best regards,
Mikhail Avkhimenia


09.03.2015, 17:13, "Sebastian Andrzej Siewior" <bigeasy@linutronix.de>:
> * Julien Ciesla | 2015-03-09 01:55:49 [+0000]:
>> Same issue on linux raspberrypi 3.18.9 with patch rt4.
>
> Then disable USB completely.
>
> Sebastian
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