brcm2708: add linux 4.19 support

Boot tested on Raspberry Pi B+ (BCM2708) and Raspberry Pi 2 (BCM2709)

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>

1 files changed, 110 insertions, 0 deletions

diff --git a/target/linux/brcm2708/patches-4.19/950-0298-sc16is7xx-Fix-for-Unexpected-interrupt-8.patch b/target/linux/brcm2708/patches-4.19/950-0298-sc16is7xx-Fix-for-Unexpected-interrupt-8.patch
new file mode 100644
index 0000000000..8c980ce43c
--- /dev/null
+++ b/target/linux/brcm2708/patches-4.19/950-0298-sc16is7xx-Fix-for-Unexpected-interrupt-8.patch
@@ -0,0 +1,110 @@
+From 2328af8468b09a20258488b2126449aa8539ee5a Mon Sep 17 00:00:00 2001
+From: Phil Elwell <phil@raspberrypi.org>
+Date: Fri, 18 May 2018 10:26:59 +0100
+Subject: [PATCH 298/703] 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
+@@ -328,6 +328,7 @@ 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];
+ };
+ 
+@@ -499,6 +500,21 @@ 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 */
+@@ -514,6 +530,8 @@ 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);
+@@ -698,6 +716,8 @@ 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;
+@@ -707,6 +727,8 @@ 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)
+@@ -901,6 +923,9 @@ 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);
+ 
+@@ -922,6 +947,8 @@ 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);