From: Linus Walleij Date: Tue, 13 Mar 2012 12:27:23 +0000 (+0100) Subject: serial: PL011: clear pending interrupts X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=9b96fbacda34079dea0638ee1e92c56286f6114a;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git serial: PL011: clear pending interrupts 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 Reported-by: Chanho Min Suggested-by: Russell King Signed-off-by: Linus Walleij Reviewed-by: Jong-Sung Kim Cc: stable Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c index cc3ea066c43a..20d795d9b591 100644 --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -1396,6 +1396,10 @@ static int pl011_startup(struct uart_port *port) 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 */ @@ -1432,10 +1436,6 @@ static int pl011_startup(struct uart_port *port) 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 */ @@ -1450,6 +1450,9 @@ static int pl011_startup(struct uart_port *port) * 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; @@ -1942,6 +1945,10 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id) 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;