This is a note to let you know that I've just added the patch titled
serial: PL011: clear pending interrupts
to the 3.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
serial-pl011-clear-pending-interrupts.patch
and it can be found in the queue-3.3 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 9b96fbacda34079dea0638ee1e92c56286f6114a Mon Sep 17 00:00:00 2001
From: Linus Walleij <[email protected]>
Date: Tue, 13 Mar 2012 13:27:23 +0100
Subject: serial: PL011: clear pending interrupts
From: Linus Walleij <[email protected]>
commit 9b96fbacda34079dea0638ee1e92c56286f6114a upstream.
Chanho Min reported that when the boot loader transfers
control to the kernel, there may be pending interrupts
causing the UART to lock up in an eternal loop trying to
pick tokens from the FIFO (since the RX interrupt flag
indicates there are tokens) while in practice there are
no tokens - in fact there is only a pending IRQ flag.
This patch address the issue with a combination of two
patches suggested by Russell King that clears and mask
all interrupts at probe() and clears any pending error
and RX interrupts at port startup time.
We suspect the spurious interrupts are a side-effect of
switching the UART from FIFO to non-FIFO mode.
Cc: Shreshtha Kumar Sahu <[email protected]>
Reported-by: Chanho Min <[email protected]>
Suggested-by: Russell King <[email protected]>
Signed-off-by: Linus Walleij <[email protected]>
Reviewed-by: Jong-Sung Kim <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/tty/serial/amba-pl011.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -1381,6 +1381,10 @@ static int pl011_startup(struct uart_por
uap->port.uartclk = clk_get_rate(uap->clk);
+ /* Clear pending error and receive interrupts */
+ writew(UART011_OEIS | UART011_BEIS | UART011_PEIS | UART011_FEIS |
+ UART011_RTIS | UART011_RXIS, uap->port.membase + UART011_ICR);
+
/*
* Allocate the IRQ
*/
@@ -1417,10 +1421,6 @@ static int pl011_startup(struct uart_por
cr |= UART01x_CR_UARTEN | UART011_CR_RXE | UART011_CR_TXE;
writew(cr, uap->port.membase + UART011_CR);
- /* Clear pending error interrupts */
- writew(UART011_OEIS | UART011_BEIS | UART011_PEIS | UART011_FEIS,
- uap->port.membase + UART011_ICR);
-
/*
* initialise the old status of the modem signals
*/
@@ -1435,6 +1435,9 @@ static int pl011_startup(struct uart_por
* as well.
*/
spin_lock_irq(&uap->port.lock);
+ /* Clear out any spuriously appearing RX interrupts */
+ writew(UART011_RTIS | UART011_RXIS,
+ uap->port.membase + UART011_ICR);
uap->im = UART011_RTIM;
if (!pl011_dma_rx_running(uap))
uap->im |= UART011_RXIM;
@@ -1927,6 +1930,10 @@ static int pl011_probe(struct amba_devic
goto unmap;
}
+ /* Ensure interrupts from this UART are masked and cleared */
+ writew(0, uap->port.membase + UART011_IMSC);
+ writew(0xffff, uap->port.membase + UART011_ICR);
+
uap->vendor = vendor;
uap->lcrh_rx = vendor->lcrh_rx;
uap->lcrh_tx = vendor->lcrh_tx;
Patches currently in stable-queue which might be from [email protected]
are
queue-3.3/serial-pl011-clear-pending-interrupts.patch
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