+++ /dev/null
-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);
projects / openwrt / openwrt.git / commitdiff