brcm2708: update to latest patches from RPi foundation

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

1 files changed, 85 insertions, 0 deletions

diff --git a/target/linux/brcm2708/patches-4.19/950-0699-tty-amba-pl011-Make-TX-optimisation-conditional.patch b/target/linux/brcm2708/patches-4.19/950-0699-tty-amba-pl011-Make-TX-optimisation-conditional.patch
new file mode 100644
index 0000000000..ec6958949a
--- /dev/null
+++ b/target/linux/brcm2708/patches-4.19/950-0699-tty-amba-pl011-Make-TX-optimisation-conditional.patch
@@ -0,0 +1,85 @@
+From bad29ba77266dd37bdaf3bded68111c8a0a9de15 Mon Sep 17 00:00:00 2001
+From: Phil Elwell <phil@raspberrypi.org>
+Date: Thu, 11 Jul 2019 13:13:39 +0100
+Subject: [PATCH 699/773] tty: amba-pl011: Make TX optimisation conditional
+
+pl011_tx_chars takes a "from_irq" parameter to reduce the number of
+register accesses. When from_irq is true the function assumes that the
+FIFO is half empty and writes up to half a FIFO's worth of bytes
+without polling the FIFO status register, the reasoning being that
+the function is being called as a result of the TX interrupt being
+raised. This logic would work were it not for the fact that
+pl011_rx_chars, called from pl011_int before pl011_tx_chars, releases
+the spinlock before calling tty_flip_buffer_push.
+
+A user thread writing to the UART claims the spinlock and ultimately
+calls pl011_tx_chars with from_irq set to false. This reverts to the
+older logic that polls the FIFO status register before sending every
+byte. If this happen on an SMP system during the section of the IRQ
+handler where the spinlock has been released, then by the time the TX
+interrupt handler is called, the FIFO may already be full, and any
+further writes are likely to be lost.
+
+The fix involves adding a per-port flag that is true iff running from
+within the interrupt handler and the spinlock has not yet been released.
+This flag is then used as the value for the from_irq parameter of
+pl011_tx_chars, causing polling to be used in the unsafe case.
+
+Fixes: 1e84d22322ce ("serial/amba-pl011: Refactor and simplify TX FIFO handling")
+
+Signed-off-by: Phil Elwell <phil@raspberrypi.org>
+---
+ drivers/tty/serial/amba-pl011.c | 7 ++++++-
+ 1 file changed, 6 insertions(+), 1 deletion(-)
+
+--- a/drivers/tty/serial/amba-pl011.c
++++ b/drivers/tty/serial/amba-pl011.c
+@@ -270,6 +270,7 @@ struct uart_amba_port {
+ 	unsigned int		old_cr;		/* state during shutdown */
+ 	unsigned int		fixed_baud;	/* vendor-set fixed baud rate */
+ 	char			type[12];
++	bool			irq_locked;	/* in irq, unreleased lock */
+ #ifdef CONFIG_DMA_ENGINE
+ 	/* DMA stuff */
+ 	bool			using_tx_dma;
+@@ -814,6 +815,7 @@ __acquires(&uap->port.lock)
+ 		return;
+ 
+ 	/* Avoid deadlock with the DMA engine callback */
++	uap->irq_locked = 0;
+ 	spin_unlock(&uap->port.lock);
+ 	dmaengine_terminate_all(uap->dmatx.chan);
+ 	spin_lock(&uap->port.lock);
+@@ -941,6 +943,7 @@ static void pl011_dma_rx_chars(struct ua
+ 		fifotaken = pl011_fifo_to_tty(uap);
+ 	}
+ 
++	uap->irq_locked = 0;
+ 	spin_unlock(&uap->port.lock);
+ 	dev_vdbg(uap->port.dev,
+ 		 "Took %d chars from DMA buffer and %d chars from the FIFO\n",
+@@ -1349,6 +1352,7 @@ __acquires(&uap->port.lock)
+ {
+ 	pl011_fifo_to_tty(uap);
+ 
++	uap->irq_locked = 0;
+ 	spin_unlock(&uap->port.lock);
+ 	tty_flip_buffer_push(&uap->port.state->port);
+ 	/*
+@@ -1484,6 +1488,7 @@ static irqreturn_t pl011_int(int irq, vo
+ 	int handled = 0;
+ 
+ 	spin_lock_irqsave(&uap->port.lock, flags);
++	uap->irq_locked = 1;
+ 	status = pl011_read(uap, REG_RIS) & uap->im;
+ 	if (status) {
+ 		do {
+@@ -1503,7 +1508,7 @@ static irqreturn_t pl011_int(int irq, vo
+ 				      UART011_CTSMIS|UART011_RIMIS))
+ 				pl011_modem_status(uap);
+ 			if (status & UART011_TXIS)
+-				pl011_tx_chars(uap, true);
++				pl011_tx_chars(uap, uap->irq_locked);
+ 
+ 			if (pass_counter-- == 0)
+ 				break;