From: Andy Shevchenko andriy.shevchenko@linux.intel.com
commit 7febbcbc48fc92e3f33863b32ed715ba4aff18c4 upstream.
The commit 54e53b2e8081 ("tty: serial: 8250: pass IRQ shared flag to UART ports") nicely explained the problem:
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On some systems IRQ lines between multiple UARTs might be shared. If so, the irqflags have to be configured accordingly. The reason is: The 8250 port startup code performs IRQ tests *before* the IRQ handler for that particular port is registered. This is performed in serial8250_do_startup(). This function checks whether IRQF_SHARED is configured and only then disables the IRQ line while testing.
This test is performed upon each open() of the UART device. Imagine two UARTs share the same IRQ line: On is already opened and the IRQ is active. When the second UART is opened, the IRQ line has to be disabled while performing IRQ tests. Otherwise an IRQ might handler might be invoked, but the IRQ itself cannot be handled, because the corresponding handler isn't registered, yet. That's because the 8250 code uses a chain-handler and invokes the corresponding port's IRQ handling routines himself.
Unfortunately this IRQF_SHARED flag isn't configured for UARTs probed via device tree even if the IRQs are shared. This way, the actual and shared IRQ line isn't disabled while performing tests and the kernel correctly detects a spurious IRQ. So, adding this flag to the DT probe solves the issue.
Note: The UPF_SHARE_IRQ flag is configured unconditionally. Therefore, the IRQF_SHARED flag can be set unconditionally as well.
Example stack trace by performing `echo 1 > /dev/ttyS2` on a non-patched system:
|irq 85: nobody cared (try booting with the "irqpoll" option) | [...] |handlers: |[<ffff0000080fc628>] irq_default_primary_handler threaded [<ffff00000855fbb8>] serial8250_interrupt |Disabling IRQ #85
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But unfortunately didn't fix the root cause. Let's try again here by moving IRQ flag assignment from serial_link_irq_chain() to serial8250_do_startup().
This should fix the similar issue reported for 8250_pnp case.
Since this change we don't need to have custom solutions in 8250_aspeed_vuart and 8250_of drivers, thus, drop them.
Fixes: 1c2f04937b3e ("serial: 8250: add IRQ trigger support") Reported-by: Li RongQing lirongqing@baidu.com Cc: Kurt Kanzenbach kurt@linutronix.de Cc: Vikram Pandita vikram.pandita@ti.com Signed-off-by: Andy Shevchenko andriy.shevchenko@linux.intel.com Cc: stable stable@vger.kernel.org Acked-by: Kurt Kanzenbach kurt@linutronix.de Link: https://lore.kernel.org/r/20200211135559.85960-1-andriy.shevchenko@linux.int... [Kurt: Backport to v4.9] Signed-off-by: Kurt Kanzenbach kurt@linutronix.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/tty/serial/8250/8250_core.c | 5 ++--- drivers/tty/serial/8250/8250_port.c | 4 ++++ 2 files changed, 6 insertions(+), 3 deletions(-)
--- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -181,7 +181,7 @@ static int serial_link_irq_chain(struct struct hlist_head *h; struct hlist_node *n; struct irq_info *i; - int ret, irq_flags = up->port.flags & UPF_SHARE_IRQ ? IRQF_SHARED : 0; + int ret;
mutex_lock(&hash_mutex);
@@ -216,9 +216,8 @@ static int serial_link_irq_chain(struct INIT_LIST_HEAD(&up->list); i->head = &up->list; spin_unlock_irq(&i->lock); - irq_flags |= up->port.irqflags; ret = request_irq(up->port.irq, serial8250_interrupt, - irq_flags, "serial", i); + up->port.irqflags, "serial", i); if (ret < 0) serial_do_unlink(i, up); } --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -2199,6 +2199,10 @@ int serial8250_do_startup(struct uart_po } }
+ /* Check if we need to have shared IRQs */ + if (port->irq && (up->port.flags & UPF_SHARE_IRQ)) + up->port.irqflags |= IRQF_SHARED; + if (port->irq) { unsigned char iir1; /*