diff options
Diffstat (limited to 'target/linux/brcm2708/patches-4.14/950-0311-sc16is7xx-Fix-for-Unexpected-interrupt-8.patch')
| -rw-r--r-- | target/linux/brcm2708/patches-4.14/950-0311-sc16is7xx-Fix-for-Unexpected-interrupt-8.patch | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/target/linux/brcm2708/patches-4.14/950-0311-sc16is7xx-Fix-for-Unexpected-interrupt-8.patch b/target/linux/brcm2708/patches-4.14/950-0311-sc16is7xx-Fix-for-Unexpected-interrupt-8.patch new file mode 100644 index 0000000000..b01e523a1e --- /dev/null +++ b/target/linux/brcm2708/patches-4.14/950-0311-sc16is7xx-Fix-for-Unexpected-interrupt-8.patch @@ -0,0 +1,110 @@ +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); |