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lan743x: prevent entire kernel HANG on open, for some platforms 

[ Upstream commit 796a2665ca ]

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: 23f0703c12 ("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>
5.4-rM2-2.2.x-imx-squashed
Sven Van Asbroeck 2020-11-12 15:47:41 -05:00 committed by Greg Kroah-Hartman
parent 5c7a00aa05
commit c35a7de217
1 changed files with 2 additions and 1 deletions
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3
drivers/net/ethernet/microchip/lan743x_main.c
View File

@ -145,7 +145,8 @@ 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;
}
}