[PATCH v3 1/3] serial: samsung: Use right device for DMA-mapping calls

[PATCH v3 1/3] serial: samsung: Use right device for DMA-mapping calls

[Marek Szyprowski]

Driver should provide its own struct device for all DMA-mapping calls instead
of extracting device pointer from DMA engine channel. Although this is harmless
from the driver operation perspective on ARM architecture, it is always good
to use the DMA mapping API in a proper way. This patch fixes following DMA API
debug warning:

WARNING: CPU: 0 PID: 0 at lib/dma-debug.c:1241 check_sync+0x520/0x9f4
samsung-uart 12c20000.serial: DMA-API: device driver tries to sync DMA memory it has not allocated [device address=0x000000006df0f580] [size=64 bytes]
Modules linked in:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.11.0-rc1-00137-g07ca963 #51
Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[<c011aaa4>] (unwind_backtrace) from [<c01127c0>] (show_stack+0x20/0x24)
[<c01127c0>] (show_stack) from [<c06ba5d8>] (dump_stack+0x84/0xa0)
[<c06ba5d8>] (dump_stack) from [<c0139528>] (__warn+0x14c/0x180)
[<c0139528>] (__warn) from [<c01395a4>] (warn_slowpath_fmt+0x48/0x50)
[<c01395a4>] (warn_slowpath_fmt) from [<c0729058>] (check_sync+0x520/0x9f4)
[<c0729058>] (check_sync) from [<c072967c>] (debug_dma_sync_single_for_device+0x88/0xc8)
[<c072967c>] (debug_dma_sync_single_for_device) from [<c0803c10>] (s3c24xx_serial_start_tx_dma+0x100/0x2f8)
[<c0803c10>] (s3c24xx_serial_start_tx_dma) from [<c0804338>] (s3c24xx_serial_tx_chars+0x198/0x33c)

Reported-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Fixes: 62c37eedb74c8 ("serial: samsung: add dma reqest/release functions")
CC: stable@vger.kernel.org # v4.0+
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
---
v3:
- extended commit message

v2:
- fixed commit id in 'fixes' tag, added 'reviewed-by' tag
---
 drivers/tty/serial/samsung.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
index 7a17aedbf902..9f3759bdb44f 100644
--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -901,14 +901,13 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
 		return -ENOMEM;
 	}
 
-	dma->rx_addr = dma_map_single(dma->rx_chan->device->dev, dma->rx_buf,
+	dma->rx_addr = dma_map_single(p->port.dev, dma->rx_buf,
 				dma->rx_size, DMA_FROM_DEVICE);
 
 	spin_lock_irqsave(&p->port.lock, flags);
 
 	/* TX buffer */
-	dma->tx_addr = dma_map_single(dma->tx_chan->device->dev,
-				p->port.state->xmit.buf,
+	dma->tx_addr = dma_map_single(p->port.dev, p->port.state->xmit.buf,
 				UART_XMIT_SIZE, DMA_TO_DEVICE);
 
 	spin_unlock_irqrestore(&p->port.lock, flags);
@@ -922,7 +921,7 @@ static void s3c24xx_serial_release_dma(struct s3c24xx_uart_port *p)
 
 	if (dma->rx_chan) {
 		dmaengine_terminate_all(dma->rx_chan);
-		dma_unmap_single(dma->rx_chan->device->dev, dma->rx_addr,
+		dma_unmap_single(p->port.dev, dma->rx_addr,
 				dma->rx_size, DMA_FROM_DEVICE);
 		kfree(dma->rx_buf);
 		dma_release_channel(dma->rx_chan);
@@ -931,7 +930,7 @@ static void s3c24xx_serial_release_dma(struct s3c24xx_uart_port *p)
 
 	if (dma->tx_chan) {
 		dmaengine_terminate_all(dma->tx_chan);
-		dma_unmap_single(dma->tx_chan->device->dev, dma->tx_addr,
+		dma_unmap_single(p->port.dev, dma->tx_addr,
 				UART_XMIT_SIZE, DMA_TO_DEVICE);
 		dma_release_channel(dma->tx_chan);
 		dma->tx_chan = NULL;
-- 
1.9.1

[PATCH v3 2/3] serial: samsung: Add missing checks for dma_map_single failure

[Marek Szyprowski]

This patch adds missing checks for dma_map_single() failure and proper error
reporting. Although this issue was harmless on ARM architecture, it is always
good to use the DMA mapping API in a proper way. This patch fixes the following
DMA API debug warning:

WARNING: CPU: 1 PID: 3785 at lib/dma-debug.c:1171 check_unmap+0x8a0/0xf28
dma-pl330 121a0000.pdma: DMA-API: device driver failed to check map error[device address=0x000000006e0f9000] [size=4096 bytes] [mapped as single]
Modules linked in:
CPU: 1 PID: 3785 Comm: (agetty) Tainted: G        W       4.11.0-rc1-00137-g07ca963-dirty #59
Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[<c011aaa4>] (unwind_backtrace) from [<c01127c0>] (show_stack+0x20/0x24)
[<c01127c0>] (show_stack) from [<c06ba5d8>] (dump_stack+0x84/0xa0)
[<c06ba5d8>] (dump_stack) from [<c0139528>] (__warn+0x14c/0x180)
[<c0139528>] (__warn) from [<c01395a4>] (warn_slowpath_fmt+0x48/0x50)
[<c01395a4>] (warn_slowpath_fmt) from [<c072a114>] (check_unmap+0x8a0/0xf28)
[<c072a114>] (check_unmap) from [<c072a834>] (debug_dma_unmap_page+0x98/0xc8)
[<c072a834>] (debug_dma_unmap_page) from [<c0803874>] (s3c24xx_serial_shutdown+0x314/0x52c)
[<c0803874>] (s3c24xx_serial_shutdown) from [<c07f5124>] (uart_port_shutdown+0x54/0x88)
[<c07f5124>] (uart_port_shutdown) from [<c07f522c>] (uart_shutdown+0xd4/0x110)
[<c07f522c>] (uart_shutdown) from [<c07f6a8c>] (uart_hangup+0x9c/0x208)
[<c07f6a8c>] (uart_hangup) from [<c07c426c>] (__tty_hangup+0x49c/0x634)
[<c07c426c>] (__tty_hangup) from [<c07c78ac>] (tty_ioctl+0xc88/0x16e4)
[<c07c78ac>] (tty_ioctl) from [<c03b5f2c>] (do_vfs_ioctl+0xc4/0xd10)
[<c03b5f2c>] (do_vfs_ioctl) from [<c03b6bf4>] (SyS_ioctl+0x7c/0x8c)
[<c03b6bf4>] (SyS_ioctl) from [<c010b4a0>] (ret_fast_syscall+0x0/0x3c)

Reported-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Fixes: 62c37eedb74c8 ("serial: samsung: add dma reqest/release functions")
CC: stable@vger.kernel.org # v4.10+
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
---
This issue was there since adding DMA support, but this patch applies cleanly
only to v4.10+ kernels due to other changes in the surrounding code.

v3:
- moved spinlock removal to separate patch, extended commit message

v2:
- fixed commit id in 'fixes' tag, added 'reviewed-by' tag
---
 drivers/tty/serial/samsung.c | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
index 9f3759bdb44f..ca0bcd7fd61f 100644
--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -859,7 +859,7 @@ static void s3c24xx_serial_break_ctl(struct uart_port *port, int break_state)
 static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
 {
 	struct s3c24xx_uart_dma	*dma = p->dma;
-	unsigned long flags;
+	int ret;
 
 	/* Default slave configuration parameters */
 	dma->rx_conf.direction		= DMA_DEV_TO_MEM;
@@ -884,8 +884,8 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
 
 	dma->tx_chan = dma_request_chan(p->port.dev, "tx");
 	if (IS_ERR(dma->tx_chan)) {
-		dma_release_channel(dma->rx_chan);
-		return PTR_ERR(dma->tx_chan);
+		ret = PTR_ERR(dma->tx_chan);
+		goto err_release_rx;
 	}
 
 	dmaengine_slave_config(dma->tx_chan, &dma->tx_conf);
@@ -894,15 +894,17 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
 	dma->rx_size = PAGE_SIZE;
 
 	dma->rx_buf = kmalloc(dma->rx_size, GFP_KERNEL);
-
 	if (!dma->rx_buf) {
-		dma_release_channel(dma->rx_chan);
-		dma_release_channel(dma->tx_chan);
-		return -ENOMEM;
+		ret = -ENOMEM;
+		goto err_release_tx;
 	}
 
 	dma->rx_addr = dma_map_single(p->port.dev, dma->rx_buf,
 				dma->rx_size, DMA_FROM_DEVICE);
+	if (dma_mapping_error(p->port.dev, dma->rx_addr)) {
+		ret = -EIO;
+		goto err_free_rx;
+	}
 
 	spin_lock_irqsave(&p->port.lock, flags);
 
@@ -911,8 +913,23 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
 				UART_XMIT_SIZE, DMA_TO_DEVICE);
 
 	spin_unlock_irqrestore(&p->port.lock, flags);
+	if (dma_mapping_error(p->port.dev, dma->tx_addr)) {
+		ret = -EIO;
+		goto err_unmap_rx;
+	}
 
 	return 0;
+
+err_unmap_rx:
+	dma_unmap_single(p->port.dev, dma->rx_addr, dma->rx_size,
+			 DMA_FROM_DEVICE);
+err_free_rx:
+	kfree(dma->rx_buf);
+err_release_tx:
+	dma_release_channel(dma->tx_chan);
+err_release_rx:
+	dma_release_channel(dma->rx_chan);
+	return ret;
 }
 
 static void s3c24xx_serial_release_dma(struct s3c24xx_uart_port *p)
-- 
1.9.1

Re: [PATCH v3 2/3] serial: samsung: Add missing checks for dma_map_single failure

[Shuah Khan]

Hi Marek,

On Mon, Apr 3, 2017 at 12:21 AM, Marek Szyprowski
<m.szyprowski@samsung.com> wrote:
> This patch adds missing checks for dma_map_single() failure and proper error
> reporting. Although this issue was harmless on ARM architecture, it is always
> good to use the DMA mapping API in a proper way. This patch fixes the following
> DMA API debug warning:
>
> WARNING: CPU: 1 PID: 3785 at lib/dma-debug.c:1171 check_unmap+0x8a0/0xf28
> dma-pl330 121a0000.pdma: DMA-API: device driver failed to check map error[device address=0x000000006e0f9000] [size=4096 bytes] [mapped as single]
> Modules linked in:
> CPU: 1 PID: 3785 Comm: (agetty) Tainted: G        W       4.11.0-rc1-00137-g07ca963-dirty #59
> Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
> [<c011aaa4>] (unwind_backtrace) from [<c01127c0>] (show_stack+0x20/0x24)
> [<c01127c0>] (show_stack) from [<c06ba5d8>] (dump_stack+0x84/0xa0)
> [<c06ba5d8>] (dump_stack) from [<c0139528>] (__warn+0x14c/0x180)
> [<c0139528>] (__warn) from [<c01395a4>] (warn_slowpath_fmt+0x48/0x50)
> [<c01395a4>] (warn_slowpath_fmt) from [<c072a114>] (check_unmap+0x8a0/0xf28)
> [<c072a114>] (check_unmap) from [<c072a834>] (debug_dma_unmap_page+0x98/0xc8)
> [<c072a834>] (debug_dma_unmap_page) from [<c0803874>] (s3c24xx_serial_shutdown+0x314/0x52c)
> [<c0803874>] (s3c24xx_serial_shutdown) from [<c07f5124>] (uart_port_shutdown+0x54/0x88)
> [<c07f5124>] (uart_port_shutdown) from [<c07f522c>] (uart_shutdown+0xd4/0x110)
> [<c07f522c>] (uart_shutdown) from [<c07f6a8c>] (uart_hangup+0x9c/0x208)
> [<c07f6a8c>] (uart_hangup) from [<c07c426c>] (__tty_hangup+0x49c/0x634)
> [<c07c426c>] (__tty_hangup) from [<c07c78ac>] (tty_ioctl+0xc88/0x16e4)
> [<c07c78ac>] (tty_ioctl) from [<c03b5f2c>] (do_vfs_ioctl+0xc4/0xd10)
> [<c03b5f2c>] (do_vfs_ioctl) from [<c03b6bf4>] (SyS_ioctl+0x7c/0x8c)
> [<c03b6bf4>] (SyS_ioctl) from [<c010b4a0>] (ret_fast_syscall+0x0/0x3c)
>
> Reported-by: Seung-Woo Kim <sw0312.kim@samsung.com>
> Fixes: 62c37eedb74c8 ("serial: samsung: add dma reqest/release functions")
> CC: stable@vger.kernel.org # v4.10+
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Reviewed-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
> ---

Looks good.

Reviewed-by: shuahkh@osg.samsung.com

thanks,
-- Shuah

> This issue was there since adding DMA support, but this patch applies cleanly
> only to v4.10+ kernels due to other changes in the surrounding code.
>
> v3:
> - moved spinlock removal to separate patch, extended commit message
>
> v2:
> - fixed commit id in 'fixes' tag, added 'reviewed-by' tag
> ---
>  drivers/tty/serial/samsung.c | 31 ++++++++++++++++++++++++-------
>  1 file changed, 24 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
> index 9f3759bdb44f..ca0bcd7fd61f 100644
> --- a/drivers/tty/serial/samsung.c
> +++ b/drivers/tty/serial/samsung.c
> @@ -859,7 +859,7 @@ static void s3c24xx_serial_break_ctl(struct uart_port *port, int break_state)
>  static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
>  {
>         struct s3c24xx_uart_dma *dma = p->dma;
> -       unsigned long flags;
> +       int ret;
>
>         /* Default slave configuration parameters */
>         dma->rx_conf.direction          = DMA_DEV_TO_MEM;
> @@ -884,8 +884,8 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
>
>         dma->tx_chan = dma_request_chan(p->port.dev, "tx");
>         if (IS_ERR(dma->tx_chan)) {
> -               dma_release_channel(dma->rx_chan);
> -               return PTR_ERR(dma->tx_chan);
> +               ret = PTR_ERR(dma->tx_chan);
> +               goto err_release_rx;
>         }
>
>         dmaengine_slave_config(dma->tx_chan, &dma->tx_conf);
> @@ -894,15 +894,17 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
>         dma->rx_size = PAGE_SIZE;
>
>         dma->rx_buf = kmalloc(dma->rx_size, GFP_KERNEL);
> -
>         if (!dma->rx_buf) {
> -               dma_release_channel(dma->rx_chan);
> -               dma_release_channel(dma->tx_chan);
> -               return -ENOMEM;
> +               ret = -ENOMEM;
> +               goto err_release_tx;
>         }
>
>         dma->rx_addr = dma_map_single(p->port.dev, dma->rx_buf,
>                                 dma->rx_size, DMA_FROM_DEVICE);
> +       if (dma_mapping_error(p->port.dev, dma->rx_addr)) {
> +               ret = -EIO;
> +               goto err_free_rx;
> +       }
>
>         spin_lock_irqsave(&p->port.lock, flags);
>
> @@ -911,8 +913,23 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
>                                 UART_XMIT_SIZE, DMA_TO_DEVICE);
>
>         spin_unlock_irqrestore(&p->port.lock, flags);
> +       if (dma_mapping_error(p->port.dev, dma->tx_addr)) {
> +               ret = -EIO;
> +               goto err_unmap_rx;
> +       }
>
>         return 0;
> +
> +err_unmap_rx:
> +       dma_unmap_single(p->port.dev, dma->rx_addr, dma->rx_size,
> +                        DMA_FROM_DEVICE);
> +err_free_rx:
> +       kfree(dma->rx_buf);
> +err_release_tx:
> +       dma_release_channel(dma->tx_chan);
> +err_release_rx:
> +       dma_release_channel(dma->rx_chan);
> +       return ret;
>  }
>
>  static void s3c24xx_serial_release_dma(struct s3c24xx_uart_port *p)
> --
> 1.9.1
>

Re: [PATCH v3 2/3] serial: samsung: Add missing checks for dma_map_single failure

[Krzysztof Kozlowski]

On Mon, Apr 03, 2017 at 08:21:00AM +0200, Marek Szyprowski wrote:
> This patch adds missing checks for dma_map_single() failure and proper error
> reporting. Although this issue was harmless on ARM architecture, it is always
> good to use the DMA mapping API in a proper way. This patch fixes the following
> DMA API debug warning:
> 
> WARNING: CPU: 1 PID: 3785 at lib/dma-debug.c:1171 check_unmap+0x8a0/0xf28
> dma-pl330 121a0000.pdma: DMA-API: device driver failed to check map error[device address=0x000000006e0f9000] [size=4096 bytes] [mapped as single]
> Modules linked in:
> CPU: 1 PID: 3785 Comm: (agetty) Tainted: G        W       4.11.0-rc1-00137-g07ca963-dirty #59
> Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
> [<c011aaa4>] (unwind_backtrace) from [<c01127c0>] (show_stack+0x20/0x24)
> [<c01127c0>] (show_stack) from [<c06ba5d8>] (dump_stack+0x84/0xa0)
> [<c06ba5d8>] (dump_stack) from [<c0139528>] (__warn+0x14c/0x180)
> [<c0139528>] (__warn) from [<c01395a4>] (warn_slowpath_fmt+0x48/0x50)
> [<c01395a4>] (warn_slowpath_fmt) from [<c072a114>] (check_unmap+0x8a0/0xf28)
> [<c072a114>] (check_unmap) from [<c072a834>] (debug_dma_unmap_page+0x98/0xc8)
> [<c072a834>] (debug_dma_unmap_page) from [<c0803874>] (s3c24xx_serial_shutdown+0x314/0x52c)
> [<c0803874>] (s3c24xx_serial_shutdown) from [<c07f5124>] (uart_port_shutdown+0x54/0x88)
> [<c07f5124>] (uart_port_shutdown) from [<c07f522c>] (uart_shutdown+0xd4/0x110)
> [<c07f522c>] (uart_shutdown) from [<c07f6a8c>] (uart_hangup+0x9c/0x208)
> [<c07f6a8c>] (uart_hangup) from [<c07c426c>] (__tty_hangup+0x49c/0x634)
> [<c07c426c>] (__tty_hangup) from [<c07c78ac>] (tty_ioctl+0xc88/0x16e4)
> [<c07c78ac>] (tty_ioctl) from [<c03b5f2c>] (do_vfs_ioctl+0xc4/0xd10)
> [<c03b5f2c>] (do_vfs_ioctl) from [<c03b6bf4>] (SyS_ioctl+0x7c/0x8c)
> [<c03b6bf4>] (SyS_ioctl) from [<c010b4a0>] (ret_fast_syscall+0x0/0x3c)
> 
> Reported-by: Seung-Woo Kim <sw0312.kim@samsung.com>
> Fixes: 62c37eedb74c8 ("serial: samsung: add dma reqest/release functions")
> CC: stable@vger.kernel.org # v4.10+
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Reviewed-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
> ---
> This issue was there since adding DMA support, but this patch applies cleanly
> only to v4.10+ kernels due to other changes in the surrounding code.
> 
> v3:
> - moved spinlock removal to separate patch, extended commit message

Thanks for the changes, looks fine.
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>

Best regards,
Krzysztof

[PATCH v3 3/3] serial: samsung: Remove useless spinlock

[Marek Szyprowski]

Spinlock taken only for dma_map_single() for TX buffer is completely
useless and doesn't protect anything, so remove it to simplify the code.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
 drivers/tty/serial/samsung.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
index ca0bcd7fd61f..8aca18c4cdea 100644
--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -906,13 +906,9 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
 		goto err_free_rx;
 	}
 
-	spin_lock_irqsave(&p->port.lock, flags);
-
 	/* TX buffer */
 	dma->tx_addr = dma_map_single(p->port.dev, p->port.state->xmit.buf,
 				UART_XMIT_SIZE, DMA_TO_DEVICE);
-
-	spin_unlock_irqrestore(&p->port.lock, flags);
 	if (dma_mapping_error(p->port.dev, dma->tx_addr)) {
 		ret = -EIO;
 		goto err_unmap_rx;
-- 
1.9.1

Re: [PATCH v3 3/3] serial: samsung: Remove useless spinlock

[Krzysztof Kozlowski]

On Mon, Apr 03, 2017 at 08:21:01AM +0200, Marek Szyprowski wrote:
> Spinlock taken only for dma_map_single() for TX buffer is completely
> useless and doesn't protect anything, so remove it to simplify the code.
> 
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
>  drivers/tty/serial/samsung.c | 4 ----
>  1 file changed, 4 deletions(-)
> 

Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>

Best regards,
Krzysztof

Re: [PATCH v3 1/3] serial: samsung: Use right device for DMA-mapping calls

[Shuah Khan]

On Mon, Apr 3, 2017 at 12:20 AM, Marek Szyprowski
<m.szyprowski@samsung.com> wrote:
> Driver should provide its own struct device for all DMA-mapping calls instead
> of extracting device pointer from DMA engine channel. Although this is harmless
> from the driver operation perspective on ARM architecture, it is always good
> to use the DMA mapping API in a proper way. This patch fixes following DMA API
> debug warning:
>
> WARNING: CPU: 0 PID: 0 at lib/dma-debug.c:1241 check_sync+0x520/0x9f4
> samsung-uart 12c20000.serial: DMA-API: device driver tries to sync DMA memory it has not allocated [device address=0x000000006df0f580] [size=64 bytes]
> Modules linked in:
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.11.0-rc1-00137-g07ca963 #51
> Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
> [<c011aaa4>] (unwind_backtrace) from [<c01127c0>] (show_stack+0x20/0x24)
> [<c01127c0>] (show_stack) from [<c06ba5d8>] (dump_stack+0x84/0xa0)
> [<c06ba5d8>] (dump_stack) from [<c0139528>] (__warn+0x14c/0x180)
> [<c0139528>] (__warn) from [<c01395a4>] (warn_slowpath_fmt+0x48/0x50)
> [<c01395a4>] (warn_slowpath_fmt) from [<c0729058>] (check_sync+0x520/0x9f4)
> [<c0729058>] (check_sync) from [<c072967c>] (debug_dma_sync_single_for_device+0x88/0xc8)
> [<c072967c>] (debug_dma_sync_single_for_device) from [<c0803c10>] (s3c24xx_serial_start_tx_dma+0x100/0x2f8)
> [<c0803c10>] (s3c24xx_serial_start_tx_dma) from [<c0804338>] (s3c24xx_serial_tx_chars+0x198/0x33c)
>
> Reported-by: Seung-Woo Kim <sw0312.kim@samsung.com>
> Fixes: 62c37eedb74c8 ("serial: samsung: add dma reqest/release functions")
> CC: stable@vger.kernel.org # v4.0+
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Reviewed-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
> Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>

The change looks good.

Reviewed-by: Shuah Khan <shuahkh@osg.samsung.com>

-- Shuah

> ---
> v3:
> - extended commit message
>
> v2:
> - fixed commit id in 'fixes' tag, added 'reviewed-by' tag
> ---
>  drivers/tty/serial/samsung.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
> index 7a17aedbf902..9f3759bdb44f 100644
> --- a/drivers/tty/serial/samsung.c
> +++ b/drivers/tty/serial/samsung.c
> @@ -901,14 +901,13 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
>                 return -ENOMEM;
>         }
>
> -       dma->rx_addr = dma_map_single(dma->rx_chan->device->dev, dma->rx_buf,
> +       dma->rx_addr = dma_map_single(p->port.dev, dma->rx_buf,
>                                 dma->rx_size, DMA_FROM_DEVICE);
>
>         spin_lock_irqsave(&p->port.lock, flags);
>
>         /* TX buffer */
> -       dma->tx_addr = dma_map_single(dma->tx_chan->device->dev,
> -                               p->port.state->xmit.buf,
> +       dma->tx_addr = dma_map_single(p->port.dev, p->port.state->xmit.buf,
>                                 UART_XMIT_SIZE, DMA_TO_DEVICE);
>
>         spin_unlock_irqrestore(&p->port.lock, flags);
> @@ -922,7 +921,7 @@ static void s3c24xx_serial_release_dma(struct s3c24xx_uart_port *p)
>
>         if (dma->rx_chan) {
>                 dmaengine_terminate_all(dma->rx_chan);
> -               dma_unmap_single(dma->rx_chan->device->dev, dma->rx_addr,
> +               dma_unmap_single(p->port.dev, dma->rx_addr,
>                                 dma->rx_size, DMA_FROM_DEVICE);
>                 kfree(dma->rx_buf);
>                 dma_release_channel(dma->rx_chan);
> @@ -931,7 +930,7 @@ static void s3c24xx_serial_release_dma(struct s3c24xx_uart_port *p)
>
>         if (dma->tx_chan) {
>                 dmaengine_terminate_all(dma->tx_chan);
> -               dma_unmap_single(dma->tx_chan->device->dev, dma->tx_addr,
> +               dma_unmap_single(p->port.dev, dma->tx_addr,
>                                 UART_XMIT_SIZE, DMA_TO_DEVICE);
>                 dma_release_channel(dma->tx_chan);
>                 dma->tx_chan = NULL;
> --
> 1.9.1
>