From: Sven Van Asbroeck <[email protected]>
On arm imx6, when opening the chip's netdev, the whole Linux
kernel intermittently hangs/freezes.
This is caused by a bug in the driver code which tests if pcie
interrupts are working correctly, using the software interrupt:
1. open: enable the software interrupt
2. open: tell the chip to assert the software interrupt
3. open: wait for flag
4. ISR: acknowledge s/w interrupt, set flag
5. open: notice flag, disable the s/w interrupt, continue
Unfortunately the ISR only acknowledges the s/w interrupt, but
does not disable it. This will re-trigger the ISR in a tight
loop.
On some (lucky) platforms, open proceeds to disable the s/w
interrupt even while the ISR is 'spinning'. On arm imx6,
the spinning ISR does not allow open to proceed, resulting
in a hung Linux kernel.
Fix minimally by disabling the s/w interrupt in the ISR, which
will prevent it from spinning. This won't break anything because
the s/w interrupt is used as a one-shot interrupt.
Note that this is a minimal fix, overlooking many possible
cleanups, e.g.:
- lan743x_intr_software_isr() is completely redundant and reads
INT_STS twice for no apparent reason
- disabling the s/w interrupt in lan743x_intr_test_isr() is now
redundant, but harmless
- waiting on software_isr_flag can be converted from a sleeping
poll loop to wait_event_timeout()
Fixes: 23f0703c125b ("lan743x: Add main source files for new lan743x driver")
Tested-by: Sven Van Asbroeck <[email protected]> # arm imx6 lan7430
Signed-off-by: Sven Van Asbroeck <[email protected]>
---
Tree: git://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git # edbc21113bde
To: Jakub Kicinski <[email protected]>
To: Bryan Whitehead <[email protected]>
To: "David S. Miller" <[email protected]>
Cc: Microchip Linux Driver Support <[email protected]>
Cc: Andrew Lunn <[email protected]>
Cc: [email protected]
Cc: [email protected]
drivers/net/ethernet/microchip/lan743x_main.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/microchip/lan743x_main.c b/drivers/net/ethernet/microchip/lan743x_main.c
index 065e10bc98f2..f4a09e0f3ec5 100644
--- a/drivers/net/ethernet/microchip/lan743x_main.c
+++ b/drivers/net/ethernet/microchip/lan743x_main.c
@@ -148,7 +148,8 @@ static void lan743x_intr_software_isr(void *context)
int_sts = lan743x_csr_read(adapter, INT_STS);
if (int_sts & INT_BIT_SW_GP_) {
- lan743x_csr_write(adapter, INT_STS, INT_BIT_SW_GP_);
+ /* disable the interrupt to prevent repeated re-triggering */
+ lan743x_csr_write(adapter, INT_EN_CLR, INT_BIT_SW_GP_);
intr->software_isr_flag = 1;
}
}
--
2.17.1
On Thu, 12 Nov 2020 15:47:41 -0500 Sven Van Asbroeck wrote:
> From: Sven Van Asbroeck <[email protected]>
>
> On arm imx6, when opening the chip's netdev, the whole Linux
> kernel intermittently hangs/freezes.
>
> This is caused by a bug in the driver code which tests if pcie
> interrupts are working correctly, using the software interrupt:
>
> 1. open: enable the software interrupt
> 2. open: tell the chip to assert the software interrupt
> 3. open: wait for flag
> 4. ISR: acknowledge s/w interrupt, set flag
> 5. open: notice flag, disable the s/w interrupt, continue
>
> Unfortunately the ISR only acknowledges the s/w interrupt, but
> does not disable it. This will re-trigger the ISR in a tight
> loop.
>
> On some (lucky) platforms, open proceeds to disable the s/w
> interrupt even while the ISR is 'spinning'. On arm imx6,
> the spinning ISR does not allow open to proceed, resulting
> in a hung Linux kernel.
>
> Fix minimally by disabling the s/w interrupt in the ISR, which
> will prevent it from spinning. This won't break anything because
> the s/w interrupt is used as a one-shot interrupt.
>
> Note that this is a minimal fix, overlooking many possible
> cleanups, e.g.:
> - lan743x_intr_software_isr() is completely redundant and reads
> INT_STS twice for no apparent reason
> - disabling the s/w interrupt in lan743x_intr_test_isr() is now
> redundant, but harmless
> - waiting on software_isr_flag can be converted from a sleeping
> poll loop to wait_event_timeout()
>
> Fixes: 23f0703c125b ("lan743x: Add main source files for new lan743x driver")
> Tested-by: Sven Van Asbroeck <[email protected]> # arm imx6 lan7430
> Signed-off-by: Sven Van Asbroeck <[email protected]>
Applied, thank you!