| From foo@baz Sun Nov 22 12:00:04 PM CET 2020 |
| From: Sven Van Asbroeck <thesven73@gmail.com> |
| Date: Thu, 12 Nov 2020 15:47:41 -0500 |
| Subject: lan743x: prevent entire kernel HANG on open, for some platforms |
| |
| From: Sven Van Asbroeck <thesven73@gmail.com> |
| |
| [ Upstream commit 796a2665ca3e91ebaba7222f76fd9a035714e2d8 ] |
| |
| 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 <thesven73@gmail.com> # arm imx6 lan7430 |
| Signed-off-by: Sven Van Asbroeck <thesven73@gmail.com> |
| Link: https://lore.kernel.org/r/20201112204741.12375-1-TheSven73@gmail.com |
| Signed-off-by: Jakub Kicinski <kuba@kernel.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| drivers/net/ethernet/microchip/lan743x_main.c | 3 ++- |
| 1 file changed, 2 insertions(+), 1 deletion(-) |
| |
| --- a/drivers/net/ethernet/microchip/lan743x_main.c |
| +++ b/drivers/net/ethernet/microchip/lan743x_main.c |
| @@ -145,7 +145,8 @@ static void lan743x_intr_software_isr(vo |
| |
| 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; |
| } |
| } |