Move dma_request_chan() out of the atomic context. First this call
should not be in the atomic context at all and second the
dev_info_once() may cause a hang because because the console takes this
spinlock, too.
Fixes: 159381df1442f ("tty: serial: fsl_lpuart: fix DMA operation when using IOMMU")
Reported-by: Leonard Crestez <[email protected]>
Signed-off-by: Michael Walle <[email protected]>
---
changes since v1:
- instead of just moving the dev_info_once() out of the spinlock protected
section, move the whole dma_request_chan(). Thanks Andy!
I've tested this on my board. Andy, Leonard, can you double check it? For
all which are not aware, this deadlock happens only if you have the kernel
console output on the lpuart, so if someone wants to test it, make sure you
have something like console=ttyLP0,115200.
drivers/tty/serial/fsl_lpuart.c | 36 +++++++++++++++++++++------------
1 file changed, 23 insertions(+), 13 deletions(-)
diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 9c6a018b1390..131018979b77 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1510,20 +1510,33 @@ static void rx_dma_timer_init(struct lpuart_port *sport)
add_timer(&sport->lpuart_timer);
}
-static void lpuart_tx_dma_startup(struct lpuart_port *sport)
+static void lpuart_request_dma(struct lpuart_port *sport)
{
- u32 uartbaud;
- int ret;
-
sport->dma_tx_chan = dma_request_chan(sport->port.dev, "tx");
if (IS_ERR(sport->dma_tx_chan)) {
dev_info_once(sport->port.dev,
"DMA tx channel request failed, operating without tx DMA (%ld)\n",
PTR_ERR(sport->dma_tx_chan));
sport->dma_tx_chan = NULL;
- goto err;
}
+ sport->dma_rx_chan = dma_request_chan(sport->port.dev, "rx");
+ if (IS_ERR(sport->dma_rx_chan)) {
+ dev_info_once(sport->port.dev,
+ "DMA rx channel request failed, operating without rx DMA (%ld)\n",
+ PTR_ERR(sport->dma_rx_chan));
+ sport->dma_rx_chan = NULL;
+ }
+}
+
+static void lpuart_tx_dma_startup(struct lpuart_port *sport)
+{
+ u32 uartbaud;
+ int ret;
+
+ if (!sport->dma_tx_chan)
+ goto err;
+
ret = lpuart_dma_tx_request(&sport->port);
if (!ret)
goto err;
@@ -1549,14 +1562,8 @@ static void lpuart_rx_dma_startup(struct lpuart_port *sport)
{
int ret;
- sport->dma_rx_chan = dma_request_chan(sport->port.dev, "rx");
- if (IS_ERR(sport->dma_rx_chan)) {
- dev_info_once(sport->port.dev,
- "DMA rx channel request failed, operating without rx DMA (%ld)\n",
- PTR_ERR(sport->dma_rx_chan));
- sport->dma_rx_chan = NULL;
+ if (!sport->dma_rx_chan)
goto err;
- }
ret = lpuart_start_rx_dma(sport);
if (ret)
@@ -1592,6 +1599,8 @@ static int lpuart_startup(struct uart_port *port)
sport->rxfifo_size = UARTFIFO_DEPTH((temp >> UARTPFIFO_RXSIZE_OFF) &
UARTPFIFO_FIFOSIZE_MASK);
+ lpuart_request_dma(sport);
+
spin_lock_irqsave(&sport->port.lock, flags);
lpuart_setup_watermark_enable(sport);
@@ -1649,11 +1658,12 @@ static int lpuart32_startup(struct uart_port *port)
sport->port.fifosize = sport->txfifo_size;
}
+ lpuart_request_dma(sport);
+
spin_lock_irqsave(&sport->port.lock, flags);
lpuart32_setup_watermark_enable(sport);
-
lpuart_rx_dma_startup(sport);
lpuart_tx_dma_startup(sport);
--
2.20.1
From: Michael Walle <[email protected]> Sent: Wednesday, March 25, 2020 5:07 PM
> Move dma_request_chan() out of the atomic context. First this call should not
> be in the atomic context at all and second the
> dev_info_once() may cause a hang because because the console takes this
> spinlock, too.
>
> Fixes: 159381df1442f ("tty: serial: fsl_lpuart: fix DMA operation when using
> IOMMU")
> Reported-by: Leonard Crestez <[email protected]>
> Signed-off-by: Michael Walle <[email protected]>
Reviewed-by: Fugang Duan <[email protected]>
> ---
> changes since v1:
> - instead of just moving the dev_info_once() out of the spinlock protected
> section, move the whole dma_request_chan(). Thanks Andy!
>
> I've tested this on my board. Andy, Leonard, can you double check it? For all
> which are not aware, this deadlock happens only if you have the kernel
> console output on the lpuart, so if someone wants to test it, make sure you
> have something like console=ttyLP0,115200.
>
> drivers/tty/serial/fsl_lpuart.c | 36 +++++++++++++++++++++------------
> 1 file changed, 23 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c index
> 9c6a018b1390..131018979b77 100644
> --- a/drivers/tty/serial/fsl_lpuart.c
> +++ b/drivers/tty/serial/fsl_lpuart.c
> @@ -1510,20 +1510,33 @@ static void rx_dma_timer_init(struct lpuart_port
> *sport)
> add_timer(&sport->lpuart_timer); }
>
> -static void lpuart_tx_dma_startup(struct lpuart_port *sport)
> +static void lpuart_request_dma(struct lpuart_port *sport)
> {
> - u32 uartbaud;
> - int ret;
> -
> sport->dma_tx_chan = dma_request_chan(sport->port.dev, "tx");
> if (IS_ERR(sport->dma_tx_chan)) {
> dev_info_once(sport->port.dev,
> "DMA tx channel request failed,
> operating without tx DMA (%ld)\n",
> PTR_ERR(sport->dma_tx_chan));
> sport->dma_tx_chan = NULL;
> - goto err;
> }
>
> + sport->dma_rx_chan = dma_request_chan(sport->port.dev, "rx");
> + if (IS_ERR(sport->dma_rx_chan)) {
> + dev_info_once(sport->port.dev,
> + "DMA rx channel request failed,
> operating without rx DMA (%ld)\n",
> + PTR_ERR(sport->dma_rx_chan));
> + sport->dma_rx_chan = NULL;
> + }
> +}
> +
> +static void lpuart_tx_dma_startup(struct lpuart_port *sport) {
> + u32 uartbaud;
> + int ret;
> +
> + if (!sport->dma_tx_chan)
> + goto err;
> +
> ret = lpuart_dma_tx_request(&sport->port);
> if (!ret)
> goto err;
> @@ -1549,14 +1562,8 @@ static void lpuart_rx_dma_startup(struct
> lpuart_port *sport) {
> int ret;
>
> - sport->dma_rx_chan = dma_request_chan(sport->port.dev, "rx");
> - if (IS_ERR(sport->dma_rx_chan)) {
> - dev_info_once(sport->port.dev,
> - "DMA rx channel request failed,
> operating without rx DMA (%ld)\n",
> - PTR_ERR(sport->dma_rx_chan));
> - sport->dma_rx_chan = NULL;
> + if (!sport->dma_rx_chan)
> goto err;
> - }
>
> ret = lpuart_start_rx_dma(sport);
> if (ret)
> @@ -1592,6 +1599,8 @@ static int lpuart_startup(struct uart_port *port)
> sport->rxfifo_size = UARTFIFO_DEPTH((temp >>
> UARTPFIFO_RXSIZE_OFF) &
>
> UARTPFIFO_FIFOSIZE_MASK);
>
> + lpuart_request_dma(sport);
> +
> spin_lock_irqsave(&sport->port.lock, flags);
>
> lpuart_setup_watermark_enable(sport);
> @@ -1649,11 +1658,12 @@ static int lpuart32_startup(struct uart_port
> *port)
> sport->port.fifosize = sport->txfifo_size;
> }
>
> + lpuart_request_dma(sport);
> +
> spin_lock_irqsave(&sport->port.lock, flags);
>
> lpuart32_setup_watermark_enable(sport);
>
> -
> lpuart_rx_dma_startup(sport);
> lpuart_tx_dma_startup(sport);
>
> --
> 2.20.1
On 2020-03-25 11:07 AM, Michael Walle wrote:
> Move dma_request_chan() out of the atomic context. First this call
> should not be in the atomic context at all and second the
> dev_info_once() may cause a hang because because the console takes this
> spinlock, too.
>
> Fixes: 159381df1442f ("tty: serial: fsl_lpuart: fix DMA operation when using IOMMU")
> Reported-by: Leonard Crestez <[email protected]>
> Signed-off-by: Michael Walle <[email protected]>
> ---
> changes since v1:
> - instead of just moving the dev_info_once() out of the spinlock protected
> section, move the whole dma_request_chan(). Thanks Andy!
>
> I've tested this on my board. Andy, Leonard, can you double check it? For
> all which are not aware, this deadlock happens only if you have the kernel
> console output on the lpuart, so if someone wants to test it, make sure you
> have something like console=ttyLP0,115200.
>
> drivers/tty/serial/fsl_lpuart.c | 36 +++++++++++++++++++++------------
> 1 file changed, 23 insertions(+), 13 deletions(-)
Tested-by: Leonard Crestez <[email protected]>
Since the original commit only made it into next it might make sense to
squash the commits in the tty tree.
This way future bisections won't get stuck on a boot failure.
>
> diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
> index 9c6a018b1390..131018979b77 100644
> --- a/drivers/tty/serial/fsl_lpuart.c
> +++ b/drivers/tty/serial/fsl_lpuart.c
> @@ -1510,20 +1510,33 @@ static void rx_dma_timer_init(struct lpuart_port *sport)
> add_timer(&sport->lpuart_timer);
> }
>
> -static void lpuart_tx_dma_startup(struct lpuart_port *sport)
> +static void lpuart_request_dma(struct lpuart_port *sport)
> {
> - u32 uartbaud;
> - int ret;
> -
> sport->dma_tx_chan = dma_request_chan(sport->port.dev, "tx");
> if (IS_ERR(sport->dma_tx_chan)) {
> dev_info_once(sport->port.dev,
> "DMA tx channel request failed, operating without tx DMA (%ld)\n",
> PTR_ERR(sport->dma_tx_chan));
> sport->dma_tx_chan = NULL;
> - goto err;
> }
>
> + sport->dma_rx_chan = dma_request_chan(sport->port.dev, "rx");
> + if (IS_ERR(sport->dma_rx_chan)) {
> + dev_info_once(sport->port.dev,
> + "DMA rx channel request failed, operating without rx DMA (%ld)\n",
> + PTR_ERR(sport->dma_rx_chan));
> + sport->dma_rx_chan = NULL;
> + }
> +}
> +
> +static void lpuart_tx_dma_startup(struct lpuart_port *sport)
> +{
> + u32 uartbaud;
> + int ret;
> +
> + if (!sport->dma_tx_chan)
> + goto err;
> +
> ret = lpuart_dma_tx_request(&sport->port);
> if (!ret)
> goto err;
> @@ -1549,14 +1562,8 @@ static void lpuart_rx_dma_startup(struct lpuart_port *sport)
> {
> int ret;
>
> - sport->dma_rx_chan = dma_request_chan(sport->port.dev, "rx");
> - if (IS_ERR(sport->dma_rx_chan)) {
> - dev_info_once(sport->port.dev,
> - "DMA rx channel request failed, operating without rx DMA (%ld)\n",
> - PTR_ERR(sport->dma_rx_chan));
> - sport->dma_rx_chan = NULL;
> + if (!sport->dma_rx_chan)
> goto err;
> - }
>
> ret = lpuart_start_rx_dma(sport);
> if (ret)
> @@ -1592,6 +1599,8 @@ static int lpuart_startup(struct uart_port *port)
> sport->rxfifo_size = UARTFIFO_DEPTH((temp >> UARTPFIFO_RXSIZE_OFF) &
> UARTPFIFO_FIFOSIZE_MASK);
>
> + lpuart_request_dma(sport);
> +
> spin_lock_irqsave(&sport->port.lock, flags);
>
> lpuart_setup_watermark_enable(sport);
> @@ -1649,11 +1658,12 @@ static int lpuart32_startup(struct uart_port *port)
> sport->port.fifosize = sport->txfifo_size;
> }
>
> + lpuart_request_dma(sport);
> +
> spin_lock_irqsave(&sport->port.lock, flags);
>
> lpuart32_setup_watermark_enable(sport);
>
> -
> lpuart_rx_dma_startup(sport);
> lpuart_tx_dma_startup(sport);
>
>
On Wed, Mar 25, 2020 at 06:05:16PM +0000, Leonard Crestez wrote:
> On 2020-03-25 11:07 AM, Michael Walle wrote:
> > Move dma_request_chan() out of the atomic context. First this call
> > should not be in the atomic context at all and second the
> > dev_info_once() may cause a hang because because the console takes this
> > spinlock, too.
> >
> > Fixes: 159381df1442f ("tty: serial: fsl_lpuart: fix DMA operation when using IOMMU")
> > Reported-by: Leonard Crestez <[email protected]>
> > Signed-off-by: Michael Walle <[email protected]>
> > ---
> > changes since v1:
> > - instead of just moving the dev_info_once() out of the spinlock protected
> > section, move the whole dma_request_chan(). Thanks Andy!
> >
> > I've tested this on my board. Andy, Leonard, can you double check it? For
> > all which are not aware, this deadlock happens only if you have the kernel
> > console output on the lpuart, so if someone wants to test it, make sure you
> > have something like console=ttyLP0,115200.
> >
> > drivers/tty/serial/fsl_lpuart.c | 36 +++++++++++++++++++++------------
> > 1 file changed, 23 insertions(+), 13 deletions(-)
>
> Tested-by: Leonard Crestez <[email protected]>
>
> Since the original commit only made it into next it might make sense to
> squash the commits in the tty tree.
>
> This way future bisections won't get stuck on a boot failure.
My tree does not rebase, sorry. And neither should any other public git
tree without really really good reasons.
thanks,
greg k-h