You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
110 lines
3.7 KiB
110 lines
3.7 KiB
From d4601b298709e44a998df772ac1c85707603fde4 Mon Sep 17 00:00:00 2001
|
|
From: Phil Elwell <phil@raspberrypi.org>
|
|
Date: Fri, 18 May 2018 10:26:59 +0100
|
|
Subject: [PATCH 311/454] sc16is7xx: Fix for "Unexpected interrupt: 8"
|
|
|
|
The SC16IS752 has an Enhanced Feature Register which is aliased at the
|
|
same address as the Interrupt Identification Register; accessing it
|
|
requires that a magic value is written to the Line Configuration
|
|
Register. If an interrupt is raised while the EFR is mapped in then
|
|
the ISR won't be able to access the IIR, leading to the "Unexpected
|
|
interrupt" error messages.
|
|
|
|
Avoid the problem by claiming a mutex around accesses to the EFR
|
|
register, also claiming the mutex in the interrupt handler work
|
|
item (this is equivalent to disabling interrupts to interlock against
|
|
a non-threaded interrupt handler).
|
|
|
|
See: https://github.com/raspberrypi/linux/issues/2529
|
|
|
|
Signed-off-by: Phil Elwell <phil@raspberrypi.org>
|
|
---
|
|
drivers/tty/serial/sc16is7xx.c | 28 ++++++++++++++++++++++++++++
|
|
1 file changed, 28 insertions(+)
|
|
|
|
--- a/drivers/tty/serial/sc16is7xx.c
|
|
+++ b/drivers/tty/serial/sc16is7xx.c
|
|
@@ -333,6 +333,7 @@ struct sc16is7xx_port {
|
|
struct kthread_worker kworker;
|
|
struct task_struct *kworker_task;
|
|
struct kthread_work irq_work;
|
|
+ struct mutex efr_lock;
|
|
struct sc16is7xx_one p[0];
|
|
};
|
|
|
|
@@ -504,6 +505,21 @@ static int sc16is7xx_set_baud(struct uar
|
|
div /= 4;
|
|
}
|
|
|
|
+ /* In an amazing feat of design, the Enhanced Features Register shares
|
|
+ * the address of the Interrupt Identification Register, and is
|
|
+ * switched in by writing a magic value (0xbf) to the Line Control
|
|
+ * Register. Any interrupt firing during this time will see the EFR
|
|
+ * where it expects the IIR to be, leading to "Unexpected interrupt"
|
|
+ * messages.
|
|
+ *
|
|
+ * Prevent this possibility by claiming a mutex while accessing the
|
|
+ * EFR, and claiming the same mutex from within the interrupt handler.
|
|
+ * This is similar to disabling the interrupt, but that doesn't work
|
|
+ * because the bulk of the interrupt processing is run as a workqueue
|
|
+ * job in thread context.
|
|
+ */
|
|
+ mutex_lock(&s->efr_lock);
|
|
+
|
|
lcr = sc16is7xx_port_read(port, SC16IS7XX_LCR_REG);
|
|
|
|
/* Open the LCR divisors for configuration */
|
|
@@ -519,6 +535,8 @@ static int sc16is7xx_set_baud(struct uar
|
|
/* Put LCR back to the normal mode */
|
|
sc16is7xx_port_write(port, SC16IS7XX_LCR_REG, lcr);
|
|
|
|
+ mutex_unlock(&s->efr_lock);
|
|
+
|
|
sc16is7xx_port_update(port, SC16IS7XX_MCR_REG,
|
|
SC16IS7XX_MCR_CLKSEL_BIT,
|
|
prescaler);
|
|
@@ -701,6 +719,8 @@ static void sc16is7xx_ist(struct kthread
|
|
{
|
|
struct sc16is7xx_port *s = to_sc16is7xx_port(ws, irq_work);
|
|
|
|
+ mutex_lock(&s->efr_lock);
|
|
+
|
|
while (1) {
|
|
bool keep_polling = false;
|
|
int i;
|
|
@@ -710,6 +730,8 @@ static void sc16is7xx_ist(struct kthread
|
|
if (!keep_polling)
|
|
break;
|
|
}
|
|
+
|
|
+ mutex_unlock(&s->efr_lock);
|
|
}
|
|
|
|
static irqreturn_t sc16is7xx_irq(int irq, void *dev_id)
|
|
@@ -904,6 +926,9 @@ static void sc16is7xx_set_termios(struct
|
|
if (!(termios->c_cflag & CREAD))
|
|
port->ignore_status_mask |= SC16IS7XX_LSR_BRK_ERROR_MASK;
|
|
|
|
+ /* As above, claim the mutex while accessing the EFR. */
|
|
+ mutex_lock(&s->efr_lock);
|
|
+
|
|
sc16is7xx_port_write(port, SC16IS7XX_LCR_REG,
|
|
SC16IS7XX_LCR_CONF_MODE_B);
|
|
|
|
@@ -925,6 +950,8 @@ static void sc16is7xx_set_termios(struct
|
|
/* Update LCR register */
|
|
sc16is7xx_port_write(port, SC16IS7XX_LCR_REG, lcr);
|
|
|
|
+ mutex_unlock(&s->efr_lock);
|
|
+
|
|
/* Get baud rate generator configuration */
|
|
baud = uart_get_baud_rate(port, termios, old,
|
|
port->uartclk / 16 / 4 / 0xffff,
|
|
@@ -1187,6 +1214,7 @@ static int sc16is7xx_probe(struct device
|
|
s->regmap = regmap;
|
|
s->devtype = devtype;
|
|
dev_set_drvdata(dev, s);
|
|
+ mutex_init(&s->efr_lock);
|
|
|
|
kthread_init_worker(&s->kworker);
|
|
kthread_init_work(&s->irq_work, sc16is7xx_ist);
|
|
|