When the UART is DMA receive mode (RDMAS set) and a character just
arrived, while another interrupt is handled, the RDRF (receiver data
register full flag) is set. But since the DMA will take care of it
there is no need to handle it by calling lpuart_prepare_rx. Handling
it leads in adding the RX timeout timer twice:
[ 43.528029] Kernel BUG at 8004ee7c [verbose debug info unavailable]
[ 43.534329] Internal error: Oops - BUG: 0 [#1] ARM
[ 43.539145] Modules linked in:
[ 43.542242] CPU: 0 PID: 0 Comm: swapper Not tainted 3.18.0-rc5-00014-ge956e1a-dirty #1293
[ 43.550448] task: 80795630 ti: 8078a000 task.ti: 8078a000
[ 43.555886] PC is at add_timer+0x24/0x28
[ 43.559833] LR is at lpuart_int+0x188/0x3b0
[ 43.564039] pc : [<8004ee7c>] lr : [<802cbd3c>] psr: a0000193
[ 43.564039] sp : 8078be18 ip : 8078be28 fp : 8078be24
[ 43.575560] r10: 8e80b840 r9 : 807d23ff r8 : 20000193
[ 43.580812] r7 : 00000020 r6 : 00000001 r5 : 000000a0 r4 : 8e994e10
[ 43.587368] r3 : ffff9bd1 r2 : 80815360 r1 : 8e994e10 r0 : 8e994f20
[ 43.593923] Flags: NzCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment kernel
[ 43.601352] Control: 10c5387d Table: 8c424059 DAC: 00000015
[ 43.607125] Process swapper (pid: 0, stack limit = 0x8078a238)
...
Signed-off-by: Stefan Agner <stefan@xxxxxxxx>
---
drivers/tty/serial/fsl_lpuart.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 629291d..be9ccdf 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -756,18 +756,18 @@ out:
static irqreturn_t lpuart_int(int irq, void *dev_id)
{
struct lpuart_port *sport = dev_id;
- unsigned char sts;
+ unsigned char sts, crdma;
sts = readb(sport->port.membase + UARTSR1);
+ crdma = readb(sport->port.membase + UARTCR5);
- if (sts & UARTSR1_RDRF) {
+ if (sts & UARTSR1_RDRF && !(crdma & UARTCR5_RDMAS)) {
if (sport->lpuart_dma_rx_use)
lpuart_prepare_rx(sport);
else
lpuart_rxint(irq, dev_id);
}
- if (sts & UARTSR1_TDRE &&
- !(readb(sport->port.membase + UARTCR5) & UARTCR5_TDMAS)) {
+ if (sts & UARTSR1_TDRE && !(crdma & UARTCR5_TDMAS)) {
if (sport->lpuart_dma_tx_use)
lpuart_pio_tx(sport);
else
--
2.1.3
--
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