[PATCH v6 0/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

[PATCH v6 0/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

[Matwey V. Kornilov]

DMA cocherency slows the transfer down on systems without hardware coherent
DMA. In order to demontrate this we introduce performance measurement
facilities in patch 1 and fix the performance issue in patch 2 in order to
obtain 3.3 times speedup.

Changes since v5:
 * add dma_sync_single_for_device() as required by Laurent Pinchart

Changes since v4:
 * fix fields order in trace events 
 * minor style fixes

Changes since v3:
 * fix scripts/checkpatch.pl errors
 * use __string to store name in trace events

Changes since v2:
 * use dma_sync_single_for_cpu() to achive better performance
 * remeasured performance

Changes since v1:
 * trace_pwc_handler_exit() call moved to proper place
 * detailed description added for commit 1
 * additional output added to trace to track separate frames

Matwey V. Kornilov (2):
  media: usb: pwc: Introduce TRACE_EVENTs for pwc_isoc_handler()
  media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

 drivers/media/usb/pwc/pwc-if.c | 69 ++++++++++++++++++++++++++++++++++--------
 include/trace/events/pwc.h     | 65 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 121 insertions(+), 13 deletions(-)
 create mode 100644 include/trace/events/pwc.h

-- 
2.16.4

[PATCH v6 1/2] media: usb: pwc: Introduce TRACE_EVENTs for pwc_isoc_handler()

[Matwey V. Kornilov]

There were reports that PWC-based webcams don't work at some
embedded ARM platforms. [1] Isochronous transfer handler seems to
work too long leading to the issues in MUSB USB host subsystem.
Also note, that urb->giveback() handlers are still called with
disabled interrupts. In order to be able to measure performance of
PWC driver, traces are introduced in URB handler section.

[1] https://www.spinics.net/lists/linux-usb/msg165735.html

Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>
---
 drivers/media/usb/pwc/pwc-if.c |  7 +++++
 include/trace/events/pwc.h     | 65 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 72 insertions(+)
 create mode 100644 include/trace/events/pwc.h

diff --git a/drivers/media/usb/pwc/pwc-if.c b/drivers/media/usb/pwc/pwc-if.c
index 72704f4d5330..53c111bd5a22 100644
--- a/drivers/media/usb/pwc/pwc-if.c
+++ b/drivers/media/usb/pwc/pwc-if.c
@@ -76,6 +76,9 @@
 #include "pwc-dec23.h"
 #include "pwc-dec1.h"
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/pwc.h>
+
 /* Function prototypes and driver templates */
 
 /* hotplug device table support */
@@ -260,6 +263,8 @@ static void pwc_isoc_handler(struct urb *urb)
 	int i, fst, flen;
 	unsigned char *iso_buf = NULL;
 
+	trace_pwc_handler_enter(urb, pdev);
+
 	if (urb->status == -ENOENT || urb->status == -ECONNRESET ||
 	    urb->status == -ESHUTDOWN) {
 		PWC_DEBUG_OPEN("URB (%p) unlinked %ssynchronously.\n",
@@ -348,6 +353,8 @@ static void pwc_isoc_handler(struct urb *urb)
 	}
 
 handler_end:
+	trace_pwc_handler_exit(urb, pdev);
+
 	i = usb_submit_urb(urb, GFP_ATOMIC);
 	if (i != 0)
 		PWC_ERROR("Error (%d) re-submitting urb in pwc_isoc_handler.\n", i);
diff --git a/include/trace/events/pwc.h b/include/trace/events/pwc.h
new file mode 100644
index 000000000000..a2da764a3b41
--- /dev/null
+++ b/include/trace/events/pwc.h
@@ -0,0 +1,65 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#if !defined(_TRACE_PWC_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_PWC_H
+
+#include <linux/usb.h>
+#include <linux/tracepoint.h>
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM pwc
+
+TRACE_EVENT(pwc_handler_enter,
+	TP_PROTO(struct urb *urb, struct pwc_device *pdev),
+	TP_ARGS(urb, pdev),
+	TP_STRUCT__entry(
+		__field(struct urb*, urb)
+		__field(struct pwc_frame_buf*, fbuf)
+		__field(int, urb__status)
+		__field(u32, urb__actual_length)
+		__field(int, fbuf__filled)
+		__string(name, pdev->v4l2_dev.name)
+	),
+	TP_fast_assign(
+		__entry->urb = urb;
+		__entry->fbuf = pdev->fill_buf;
+		__entry->urb__status = urb->status;
+		__entry->urb__actual_length = urb->actual_length;
+		__entry->fbuf__filled = (pdev->fill_buf
+					 ? pdev->fill_buf->filled : 0);
+		__assign_str(name, pdev->v4l2_dev.name);
+	),
+	TP_printk("dev=%s (fbuf=%p filled=%d) urb=%p (status=%d actual_length=%u)",
+		__get_str(name),
+		__entry->fbuf,
+		__entry->fbuf__filled,
+		__entry->urb,
+		__entry->urb__status,
+		__entry->urb__actual_length)
+);
+
+TRACE_EVENT(pwc_handler_exit,
+	TP_PROTO(struct urb *urb, struct pwc_device *pdev),
+	TP_ARGS(urb, pdev),
+	TP_STRUCT__entry(
+		__field(struct urb*, urb)
+		__field(struct pwc_frame_buf*, fbuf)
+		__field(int, fbuf__filled)
+		__string(name, pdev->v4l2_dev.name)
+	),
+	TP_fast_assign(
+		__entry->urb = urb;
+		__entry->fbuf = pdev->fill_buf;
+		__entry->fbuf__filled = pdev->fill_buf->filled;
+		__assign_str(name, pdev->v4l2_dev.name);
+	),
+	TP_printk(" dev=%s (fbuf=%p filled=%d) urb=%p",
+		__get_str(name),
+		__entry->fbuf,
+		__entry->fbuf__filled,
+		__entry->urb)
+);
+
+#endif /* _TRACE_PWC_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
-- 
2.16.4

[PATCH v6 2/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

[Matwey V. Kornilov]

DMA cocherency slows the transfer down on systems without hardware
coherent DMA.
Instead we use noncocherent DMA memory and explicit sync at data receive
handler.

Based on previous commit the following performance benchmarks have been
carried out. Average memcpy() data transfer rate (rate) and handler
completion time (time) have been measured when running video stream at
640x480 resolution at 10fps.

x86_64 based system (Intel Core i5-3470). This platform has hardware
coherent DMA support and proposed change doesn't make big difference here.

 * kmalloc:            rate = (2.0 +- 0.4) GBps
                       time = (5.0 +- 3.0) usec
 * usb_alloc_coherent: rate = (3.4 +- 1.2) GBps
                       time = (3.5 +- 3.0) usec

We see that the measurements agree within error ranges in this case.
So theoretically predicted performance downgrade cannot be reliably
measured here.

armv7l based system (TI AM335x BeagleBone Black @ 300MHz). This platform
has no hardware coherent DMA support. DMA coherence is implemented via
disabled page caching that slows down memcpy() due to memory controller
behaviour.

 * kmalloc:            rate =  ( 94 +- 4) MBps
                       time =  (101 +- 4) usec
 * usb_alloc_coherent: rate = (28.1 +- 0.1) MBps
                       time =  (341 +- 2) usec

Note, that quantative difference leads (this commit leads to 3.3 times
acceleration) to qualitative behavior change in this case. As it was
stated before, the video stream cannot be successfully received at AM335x
platforms with MUSB based USB host controller due to performance issues
[1].

[1] https://www.spinics.net/lists/linux-usb/msg165735.html

Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>
---
 drivers/media/usb/pwc/pwc-if.c | 62 +++++++++++++++++++++++++++++++++---------
 1 file changed, 49 insertions(+), 13 deletions(-)

diff --git a/drivers/media/usb/pwc/pwc-if.c b/drivers/media/usb/pwc/pwc-if.c
index 53c111bd5a22..a81fb319b339 100644
--- a/drivers/media/usb/pwc/pwc-if.c
+++ b/drivers/media/usb/pwc/pwc-if.c
@@ -159,6 +159,32 @@ static const struct video_device pwc_template = {
 /***************************************************************************/
 /* Private functions */
 
+static void *pwc_alloc_urb_buffer(struct device *dev,
+				  size_t size, dma_addr_t *dma_handle)
+{
+	void *buffer = kmalloc(size, GFP_KERNEL);
+
+	if (!buffer)
+		return NULL;
+
+	*dma_handle = dma_map_single(dev, buffer, size, DMA_FROM_DEVICE);
+	if (dma_mapping_error(dev, *dma_handle)) {
+		kfree(buffer);
+		return NULL;
+	}
+
+	return buffer;
+}
+
+static void pwc_free_urb_buffer(struct device *dev,
+				size_t size,
+				void *buffer,
+				dma_addr_t dma_handle)
+{
+	dma_unmap_single(dev, dma_handle, size, DMA_FROM_DEVICE);
+	kfree(buffer);
+}
+
 static struct pwc_frame_buf *pwc_get_next_fill_buf(struct pwc_device *pdev)
 {
 	unsigned long flags = 0;
@@ -306,6 +332,11 @@ static void pwc_isoc_handler(struct urb *urb)
 	/* Reset ISOC error counter. We did get here, after all. */
 	pdev->visoc_errors = 0;
 
+	dma_sync_single_for_cpu(&urb->dev->dev,
+				urb->transfer_dma,
+				urb->transfer_buffer_length,
+				DMA_FROM_DEVICE);
+
 	/* vsync: 0 = don't copy data
 		  1 = sync-hunt
 		  2 = synched
@@ -352,6 +383,11 @@ static void pwc_isoc_handler(struct urb *urb)
 		pdev->vlast_packet_size = flen;
 	}
 
+	dma_sync_single_for_device(&urb->dev->dev,
+				   urb->transfer_dma,
+				   urb->transfer_buffer_length,
+				   DMA_FROM_DEVICE);
+
 handler_end:
 	trace_pwc_handler_exit(urb, pdev);
 
@@ -428,16 +464,15 @@ static int pwc_isoc_init(struct pwc_device *pdev)
 		urb->dev = udev;
 		urb->pipe = usb_rcvisocpipe(udev, pdev->vendpoint);
 		urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
-		urb->transfer_buffer = usb_alloc_coherent(udev,
-							  ISO_BUFFER_SIZE,
-							  GFP_KERNEL,
-							  &urb->transfer_dma);
+		urb->transfer_buffer_length = ISO_BUFFER_SIZE;
+		urb->transfer_buffer = pwc_alloc_urb_buffer(&udev->dev,
+							    urb->transfer_buffer_length,
+							    &urb->transfer_dma);
 		if (urb->transfer_buffer == NULL) {
 			PWC_ERROR("Failed to allocate urb buffer %d\n", i);
 			pwc_isoc_cleanup(pdev);
 			return -ENOMEM;
 		}
-		urb->transfer_buffer_length = ISO_BUFFER_SIZE;
 		urb->complete = pwc_isoc_handler;
 		urb->context = pdev;
 		urb->start_frame = 0;
@@ -488,15 +523,16 @@ static void pwc_iso_free(struct pwc_device *pdev)
 
 	/* Freeing ISOC buffers one by one */
 	for (i = 0; i < MAX_ISO_BUFS; i++) {
-		if (pdev->urbs[i]) {
+		struct urb *urb = pdev->urbs[i];
+
+		if (urb) {
 			PWC_DEBUG_MEMORY("Freeing URB\n");
-			if (pdev->urbs[i]->transfer_buffer) {
-				usb_free_coherent(pdev->udev,
-					pdev->urbs[i]->transfer_buffer_length,
-					pdev->urbs[i]->transfer_buffer,
-					pdev->urbs[i]->transfer_dma);
-			}
-			usb_free_urb(pdev->urbs[i]);
+			if (urb->transfer_buffer)
+				pwc_free_urb_buffer(&urb->dev->dev,
+						    urb->transfer_buffer_length,
+						    urb->transfer_buffer,
+						    urb->transfer_dma);
+			usb_free_urb(urb);
 			pdev->urbs[i] = NULL;
 		}
 	}
-- 
2.16.4

Re: [PATCH v6 1/2] media: usb: pwc: Introduce TRACE_EVENTs for pwc_isoc_handler()

[Steven Rostedt]

On Fri,  9 Nov 2018 22:03:26 +0300
"Matwey V. Kornilov" <matwey@sai.msu.ru> wrote:

> There were reports that PWC-based webcams don't work at some
> embedded ARM platforms. [1] Isochronous transfer handler seems to
> work too long leading to the issues in MUSB USB host subsystem.
> Also note, that urb->giveback() handlers are still called with
> disabled interrupts. In order to be able to measure performance of
> PWC driver, traces are introduced in URB handler section.
> 
> [1] https://www.spinics.net/lists/linux-usb/msg165735.html

From a tracing perspective, I don't see anything wrong with this patch.

Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

-- Steve

> 
> Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>
> ---
>  drivers/media/usb/pwc/pwc-if.c |  7 +++++
>  include/trace/events/pwc.h     | 65 ++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 72 insertions(+)
>  create mode 100644 include/trace/events/pwc.h
> 
> diff --git a/drivers/media/usb/pwc/pwc-if.c b/drivers/media/usb/pwc/pwc-if.c
> index 72704f4d5330..53c111bd5a22 100644
> --- a/drivers/media/usb/pwc/pwc-if.c
> +++ b/drivers/media/usb/pwc/pwc-if.c
> @@ -76,6 +76,9 @@
>  #include "pwc-dec23.h"
>  #include "pwc-dec1.h"
>  
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/pwc.h>
> +
>  /* Function prototypes and driver templates */
>  
>  /* hotplug device table support */
> @@ -260,6 +263,8 @@ static void pwc_isoc_handler(struct urb *urb)
>  	int i, fst, flen;
>  	unsigned char *iso_buf = NULL;
>  
> +	trace_pwc_handler_enter(urb, pdev);
> +
>  	if (urb->status == -ENOENT || urb->status == -ECONNRESET ||
>  	    urb->status == -ESHUTDOWN) {
>  		PWC_DEBUG_OPEN("URB (%p) unlinked %ssynchronously.\n",
> @@ -348,6 +353,8 @@ static void pwc_isoc_handler(struct urb *urb)
>  	}
>  
>  handler_end:
> +	trace_pwc_handler_exit(urb, pdev);
> +
>  	i = usb_submit_urb(urb, GFP_ATOMIC);
>  	if (i != 0)
>  		PWC_ERROR("Error (%d) re-submitting urb in pwc_isoc_handler.\n", i);
> diff --git a/include/trace/events/pwc.h b/include/trace/events/pwc.h
> new file mode 100644
> index 000000000000..a2da764a3b41
> --- /dev/null
> +++ b/include/trace/events/pwc.h
> @@ -0,0 +1,65 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#if !defined(_TRACE_PWC_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_PWC_H
> +
> +#include <linux/usb.h>
> +#include <linux/tracepoint.h>
> +
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM pwc
> +
> +TRACE_EVENT(pwc_handler_enter,
> +	TP_PROTO(struct urb *urb, struct pwc_device *pdev),
> +	TP_ARGS(urb, pdev),
> +	TP_STRUCT__entry(
> +		__field(struct urb*, urb)
> +		__field(struct pwc_frame_buf*, fbuf)
> +		__field(int, urb__status)
> +		__field(u32, urb__actual_length)
> +		__field(int, fbuf__filled)
> +		__string(name, pdev->v4l2_dev.name)
> +	),
> +	TP_fast_assign(
> +		__entry->urb = urb;
> +		__entry->fbuf = pdev->fill_buf;
> +		__entry->urb__status = urb->status;
> +		__entry->urb__actual_length = urb->actual_length;
> +		__entry->fbuf__filled = (pdev->fill_buf
> +					 ? pdev->fill_buf->filled : 0);
> +		__assign_str(name, pdev->v4l2_dev.name);
> +	),
> +	TP_printk("dev=%s (fbuf=%p filled=%d) urb=%p (status=%d actual_length=%u)",
> +		__get_str(name),
> +		__entry->fbuf,
> +		__entry->fbuf__filled,
> +		__entry->urb,
> +		__entry->urb__status,
> +		__entry->urb__actual_length)
> +);
> +
> +TRACE_EVENT(pwc_handler_exit,
> +	TP_PROTO(struct urb *urb, struct pwc_device *pdev),
> +	TP_ARGS(urb, pdev),
> +	TP_STRUCT__entry(
> +		__field(struct urb*, urb)
> +		__field(struct pwc_frame_buf*, fbuf)
> +		__field(int, fbuf__filled)
> +		__string(name, pdev->v4l2_dev.name)
> +	),
> +	TP_fast_assign(
> +		__entry->urb = urb;
> +		__entry->fbuf = pdev->fill_buf;
> +		__entry->fbuf__filled = pdev->fill_buf->filled;
> +		__assign_str(name, pdev->v4l2_dev.name);
> +	),
> +	TP_printk(" dev=%s (fbuf=%p filled=%d) urb=%p",
> +		__get_str(name),
> +		__entry->fbuf,
> +		__entry->fbuf__filled,
> +		__entry->urb)
> +);
> +
> +#endif /* _TRACE_PWC_H */
> +
> +/* This part must be outside protection */
> +#include <trace/define_trace.h>

Re: [PATCH v6 2/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

[Matwey V. Kornilov]

пт, 9 нояб. 2018 г. в 22:03, Matwey V. Kornilov <matwey@sai.msu.ru>:
>
> DMA cocherency slows the transfer down on systems without hardware
> coherent DMA.
> Instead we use noncocherent DMA memory and explicit sync at data receive
> handler.
>
> Based on previous commit the following performance benchmarks have been
> carried out. Average memcpy() data transfer rate (rate) and handler
> completion time (time) have been measured when running video stream at
> 640x480 resolution at 10fps.
>
> x86_64 based system (Intel Core i5-3470). This platform has hardware
> coherent DMA support and proposed change doesn't make big difference here.
>
>  * kmalloc:            rate = (2.0 +- 0.4) GBps
>                        time = (5.0 +- 3.0) usec
>  * usb_alloc_coherent: rate = (3.4 +- 1.2) GBps
>                        time = (3.5 +- 3.0) usec
>
> We see that the measurements agree within error ranges in this case.
> So theoretically predicted performance downgrade cannot be reliably
> measured here.
>
> armv7l based system (TI AM335x BeagleBone Black @ 300MHz). This platform
> has no hardware coherent DMA support. DMA coherence is implemented via
> disabled page caching that slows down memcpy() due to memory controller
> behaviour.
>
>  * kmalloc:            rate =  ( 94 +- 4) MBps
>                        time =  (101 +- 4) usec
>  * usb_alloc_coherent: rate = (28.1 +- 0.1) MBps
>                        time =  (341 +- 2) usec
>
> Note, that quantative difference leads (this commit leads to 3.3 times
> acceleration) to qualitative behavior change in this case. As it was
> stated before, the video stream cannot be successfully received at AM335x
> platforms with MUSB based USB host controller due to performance issues
> [1].
>
> [1] https://www.spinics.net/lists/linux-usb/msg165735.html
>
> Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>

Ping

> ---
>  drivers/media/usb/pwc/pwc-if.c | 62 +++++++++++++++++++++++++++++++++---------
>  1 file changed, 49 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/media/usb/pwc/pwc-if.c b/drivers/media/usb/pwc/pwc-if.c
> index 53c111bd5a22..a81fb319b339 100644
> --- a/drivers/media/usb/pwc/pwc-if.c
> +++ b/drivers/media/usb/pwc/pwc-if.c
> @@ -159,6 +159,32 @@ static const struct video_device pwc_template = {
>  /***************************************************************************/
>  /* Private functions */
>
> +static void *pwc_alloc_urb_buffer(struct device *dev,
> +                                 size_t size, dma_addr_t *dma_handle)
> +{
> +       void *buffer = kmalloc(size, GFP_KERNEL);
> +
> +       if (!buffer)
> +               return NULL;
> +
> +       *dma_handle = dma_map_single(dev, buffer, size, DMA_FROM_DEVICE);
> +       if (dma_mapping_error(dev, *dma_handle)) {
> +               kfree(buffer);
> +               return NULL;
> +       }
> +
> +       return buffer;
> +}
> +
> +static void pwc_free_urb_buffer(struct device *dev,
> +                               size_t size,
> +                               void *buffer,
> +                               dma_addr_t dma_handle)
> +{
> +       dma_unmap_single(dev, dma_handle, size, DMA_FROM_DEVICE);
> +       kfree(buffer);
> +}
> +
>  static struct pwc_frame_buf *pwc_get_next_fill_buf(struct pwc_device *pdev)
>  {
>         unsigned long flags = 0;
> @@ -306,6 +332,11 @@ static void pwc_isoc_handler(struct urb *urb)
>         /* Reset ISOC error counter. We did get here, after all. */
>         pdev->visoc_errors = 0;
>
> +       dma_sync_single_for_cpu(&urb->dev->dev,
> +                               urb->transfer_dma,
> +                               urb->transfer_buffer_length,
> +                               DMA_FROM_DEVICE);
> +
>         /* vsync: 0 = don't copy data
>                   1 = sync-hunt
>                   2 = synched
> @@ -352,6 +383,11 @@ static void pwc_isoc_handler(struct urb *urb)
>                 pdev->vlast_packet_size = flen;
>         }
>
> +       dma_sync_single_for_device(&urb->dev->dev,
> +                                  urb->transfer_dma,
> +                                  urb->transfer_buffer_length,
> +                                  DMA_FROM_DEVICE);
> +
>  handler_end:
>         trace_pwc_handler_exit(urb, pdev);
>
> @@ -428,16 +464,15 @@ static int pwc_isoc_init(struct pwc_device *pdev)
>                 urb->dev = udev;
>                 urb->pipe = usb_rcvisocpipe(udev, pdev->vendpoint);
>                 urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
> -               urb->transfer_buffer = usb_alloc_coherent(udev,
> -                                                         ISO_BUFFER_SIZE,
> -                                                         GFP_KERNEL,
> -                                                         &urb->transfer_dma);
> +               urb->transfer_buffer_length = ISO_BUFFER_SIZE;
> +               urb->transfer_buffer = pwc_alloc_urb_buffer(&udev->dev,
> +                                                           urb->transfer_buffer_length,
> +                                                           &urb->transfer_dma);
>                 if (urb->transfer_buffer == NULL) {
>                         PWC_ERROR("Failed to allocate urb buffer %d\n", i);
>                         pwc_isoc_cleanup(pdev);
>                         return -ENOMEM;
>                 }
> -               urb->transfer_buffer_length = ISO_BUFFER_SIZE;
>                 urb->complete = pwc_isoc_handler;
>                 urb->context = pdev;
>                 urb->start_frame = 0;
> @@ -488,15 +523,16 @@ static void pwc_iso_free(struct pwc_device *pdev)
>
>         /* Freeing ISOC buffers one by one */
>         for (i = 0; i < MAX_ISO_BUFS; i++) {
> -               if (pdev->urbs[i]) {
> +               struct urb *urb = pdev->urbs[i];
> +
> +               if (urb) {
>                         PWC_DEBUG_MEMORY("Freeing URB\n");
> -                       if (pdev->urbs[i]->transfer_buffer) {
> -                               usb_free_coherent(pdev->udev,
> -                                       pdev->urbs[i]->transfer_buffer_length,
> -                                       pdev->urbs[i]->transfer_buffer,
> -                                       pdev->urbs[i]->transfer_dma);
> -                       }
> -                       usb_free_urb(pdev->urbs[i]);
> +                       if (urb->transfer_buffer)
> +                               pwc_free_urb_buffer(&urb->dev->dev,
> +                                                   urb->transfer_buffer_length,
> +                                                   urb->transfer_buffer,
> +                                                   urb->transfer_dma);
> +                       usb_free_urb(urb);
>                         pdev->urbs[i] = NULL;
>                 }
>         }
> --
> 2.16.4
>


-- 
With best regards,
Matwey V. Kornilov

Re: [PATCH v6 2/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

[Matwey V. Kornilov]

ср, 21 нояб. 2018 г. в 21:15, Matwey V. Kornilov <matwey.kornilov@gmail.com>:
>
> пт, 9 нояб. 2018 г. в 22:03, Matwey V. Kornilov <matwey@sai.msu.ru>:
> >
> > DMA cocherency slows the transfer down on systems without hardware
> > coherent DMA.
> > Instead we use noncocherent DMA memory and explicit sync at data receive
> > handler.
> >
> > Based on previous commit the following performance benchmarks have been
> > carried out. Average memcpy() data transfer rate (rate) and handler
> > completion time (time) have been measured when running video stream at
> > 640x480 resolution at 10fps.
> >
> > x86_64 based system (Intel Core i5-3470). This platform has hardware
> > coherent DMA support and proposed change doesn't make big difference here.
> >
> >  * kmalloc:            rate = (2.0 +- 0.4) GBps
> >                        time = (5.0 +- 3.0) usec
> >  * usb_alloc_coherent: rate = (3.4 +- 1.2) GBps
> >                        time = (3.5 +- 3.0) usec
> >
> > We see that the measurements agree within error ranges in this case.
> > So theoretically predicted performance downgrade cannot be reliably
> > measured here.
> >
> > armv7l based system (TI AM335x BeagleBone Black @ 300MHz). This platform
> > has no hardware coherent DMA support. DMA coherence is implemented via
> > disabled page caching that slows down memcpy() due to memory controller
> > behaviour.
> >
> >  * kmalloc:            rate =  ( 94 +- 4) MBps
> >                        time =  (101 +- 4) usec
> >  * usb_alloc_coherent: rate = (28.1 +- 0.1) MBps
> >                        time =  (341 +- 2) usec
> >
> > Note, that quantative difference leads (this commit leads to 3.3 times
> > acceleration) to qualitative behavior change in this case. As it was
> > stated before, the video stream cannot be successfully received at AM335x
> > platforms with MUSB based USB host controller due to performance issues
> > [1].
> >
> > [1] https://www.spinics.net/lists/linux-usb/msg165735.html
> >
> > Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>
>
> Ping

Ping

>
> > ---
> >  drivers/media/usb/pwc/pwc-if.c | 62 +++++++++++++++++++++++++++++++++---------
> >  1 file changed, 49 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/media/usb/pwc/pwc-if.c b/drivers/media/usb/pwc/pwc-if.c
> > index 53c111bd5a22..a81fb319b339 100644
> > --- a/drivers/media/usb/pwc/pwc-if.c
> > +++ b/drivers/media/usb/pwc/pwc-if.c
> > @@ -159,6 +159,32 @@ static const struct video_device pwc_template = {
> >  /***************************************************************************/
> >  /* Private functions */
> >
> > +static void *pwc_alloc_urb_buffer(struct device *dev,
> > +                                 size_t size, dma_addr_t *dma_handle)
> > +{
> > +       void *buffer = kmalloc(size, GFP_KERNEL);
> > +
> > +       if (!buffer)
> > +               return NULL;
> > +
> > +       *dma_handle = dma_map_single(dev, buffer, size, DMA_FROM_DEVICE);
> > +       if (dma_mapping_error(dev, *dma_handle)) {
> > +               kfree(buffer);
> > +               return NULL;
> > +       }
> > +
> > +       return buffer;
> > +}
> > +
> > +static void pwc_free_urb_buffer(struct device *dev,
> > +                               size_t size,
> > +                               void *buffer,
> > +                               dma_addr_t dma_handle)
> > +{
> > +       dma_unmap_single(dev, dma_handle, size, DMA_FROM_DEVICE);
> > +       kfree(buffer);
> > +}
> > +
> >  static struct pwc_frame_buf *pwc_get_next_fill_buf(struct pwc_device *pdev)
> >  {
> >         unsigned long flags = 0;
> > @@ -306,6 +332,11 @@ static void pwc_isoc_handler(struct urb *urb)
> >         /* Reset ISOC error counter. We did get here, after all. */
> >         pdev->visoc_errors = 0;
> >
> > +       dma_sync_single_for_cpu(&urb->dev->dev,
> > +                               urb->transfer_dma,
> > +                               urb->transfer_buffer_length,
> > +                               DMA_FROM_DEVICE);
> > +
> >         /* vsync: 0 = don't copy data
> >                   1 = sync-hunt
> >                   2 = synched
> > @@ -352,6 +383,11 @@ static void pwc_isoc_handler(struct urb *urb)
> >                 pdev->vlast_packet_size = flen;
> >         }
> >
> > +       dma_sync_single_for_device(&urb->dev->dev,
> > +                                  urb->transfer_dma,
> > +                                  urb->transfer_buffer_length,
> > +                                  DMA_FROM_DEVICE);
> > +
> >  handler_end:
> >         trace_pwc_handler_exit(urb, pdev);
> >
> > @@ -428,16 +464,15 @@ static int pwc_isoc_init(struct pwc_device *pdev)
> >                 urb->dev = udev;
> >                 urb->pipe = usb_rcvisocpipe(udev, pdev->vendpoint);
> >                 urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
> > -               urb->transfer_buffer = usb_alloc_coherent(udev,
> > -                                                         ISO_BUFFER_SIZE,
> > -                                                         GFP_KERNEL,
> > -                                                         &urb->transfer_dma);
> > +               urb->transfer_buffer_length = ISO_BUFFER_SIZE;
> > +               urb->transfer_buffer = pwc_alloc_urb_buffer(&udev->dev,
> > +                                                           urb->transfer_buffer_length,
> > +                                                           &urb->transfer_dma);
> >                 if (urb->transfer_buffer == NULL) {
> >                         PWC_ERROR("Failed to allocate urb buffer %d\n", i);
> >                         pwc_isoc_cleanup(pdev);
> >                         return -ENOMEM;
> >                 }
> > -               urb->transfer_buffer_length = ISO_BUFFER_SIZE;
> >                 urb->complete = pwc_isoc_handler;
> >                 urb->context = pdev;
> >                 urb->start_frame = 0;
> > @@ -488,15 +523,16 @@ static void pwc_iso_free(struct pwc_device *pdev)
> >
> >         /* Freeing ISOC buffers one by one */
> >         for (i = 0; i < MAX_ISO_BUFS; i++) {
> > -               if (pdev->urbs[i]) {
> > +               struct urb *urb = pdev->urbs[i];
> > +
> > +               if (urb) {
> >                         PWC_DEBUG_MEMORY("Freeing URB\n");
> > -                       if (pdev->urbs[i]->transfer_buffer) {
> > -                               usb_free_coherent(pdev->udev,
> > -                                       pdev->urbs[i]->transfer_buffer_length,
> > -                                       pdev->urbs[i]->transfer_buffer,
> > -                                       pdev->urbs[i]->transfer_dma);
> > -                       }
> > -                       usb_free_urb(pdev->urbs[i]);
> > +                       if (urb->transfer_buffer)
> > +                               pwc_free_urb_buffer(&urb->dev->dev,
> > +                                                   urb->transfer_buffer_length,
> > +                                                   urb->transfer_buffer,
> > +                                                   urb->transfer_dma);
> > +                       usb_free_urb(urb);
> >                         pdev->urbs[i] = NULL;
> >                 }
> >         }
> > --
> > 2.16.4
> >
>
>
> --
> With best regards,
> Matwey V. Kornilov



-- 
With best regards,
Matwey V. Kornilov

Re: [PATCH v6 2/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

[Matwey V. Kornilov]

пт, 30 нояб. 2018 г. в 15:20, Matwey V. Kornilov <matwey.kornilov@gmail.com>:
>
> ср, 21 нояб. 2018 г. в 21:15, Matwey V. Kornilov <matwey.kornilov@gmail.com>:
> >
> > пт, 9 нояб. 2018 г. в 22:03, Matwey V. Kornilov <matwey@sai.msu.ru>:
> > >
> > > DMA cocherency slows the transfer down on systems without hardware
> > > coherent DMA.
> > > Instead we use noncocherent DMA memory and explicit sync at data receive
> > > handler.
> > >
> > > Based on previous commit the following performance benchmarks have been
> > > carried out. Average memcpy() data transfer rate (rate) and handler
> > > completion time (time) have been measured when running video stream at
> > > 640x480 resolution at 10fps.
> > >
> > > x86_64 based system (Intel Core i5-3470). This platform has hardware
> > > coherent DMA support and proposed change doesn't make big difference here.
> > >
> > >  * kmalloc:            rate = (2.0 +- 0.4) GBps
> > >                        time = (5.0 +- 3.0) usec
> > >  * usb_alloc_coherent: rate = (3.4 +- 1.2) GBps
> > >                        time = (3.5 +- 3.0) usec
> > >
> > > We see that the measurements agree within error ranges in this case.
> > > So theoretically predicted performance downgrade cannot be reliably
> > > measured here.
> > >
> > > armv7l based system (TI AM335x BeagleBone Black @ 300MHz). This platform
> > > has no hardware coherent DMA support. DMA coherence is implemented via
> > > disabled page caching that slows down memcpy() due to memory controller
> > > behaviour.
> > >
> > >  * kmalloc:            rate =  ( 94 +- 4) MBps
> > >                        time =  (101 +- 4) usec
> > >  * usb_alloc_coherent: rate = (28.1 +- 0.1) MBps
> > >                        time =  (341 +- 2) usec
> > >
> > > Note, that quantative difference leads (this commit leads to 3.3 times
> > > acceleration) to qualitative behavior change in this case. As it was
> > > stated before, the video stream cannot be successfully received at AM335x
> > > platforms with MUSB based USB host controller due to performance issues
> > > [1].
> > >
> > > [1] https://www.spinics.net/lists/linux-usb/msg165735.html
> > >
> > > Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>
> >
> > Ping
>
> Ping

Ping

>
> >
> > > ---
> > >  drivers/media/usb/pwc/pwc-if.c | 62 +++++++++++++++++++++++++++++++++---------
> > >  1 file changed, 49 insertions(+), 13 deletions(-)
> > >
> > > diff --git a/drivers/media/usb/pwc/pwc-if.c b/drivers/media/usb/pwc/pwc-if.c
> > > index 53c111bd5a22..a81fb319b339 100644
> > > --- a/drivers/media/usb/pwc/pwc-if.c
> > > +++ b/drivers/media/usb/pwc/pwc-if.c
> > > @@ -159,6 +159,32 @@ static const struct video_device pwc_template = {
> > >  /***************************************************************************/
> > >  /* Private functions */
> > >
> > > +static void *pwc_alloc_urb_buffer(struct device *dev,
> > > +                                 size_t size, dma_addr_t *dma_handle)
> > > +{
> > > +       void *buffer = kmalloc(size, GFP_KERNEL);
> > > +
> > > +       if (!buffer)
> > > +               return NULL;
> > > +
> > > +       *dma_handle = dma_map_single(dev, buffer, size, DMA_FROM_DEVICE);
> > > +       if (dma_mapping_error(dev, *dma_handle)) {
> > > +               kfree(buffer);
> > > +               return NULL;
> > > +       }
> > > +
> > > +       return buffer;
> > > +}
> > > +
> > > +static void pwc_free_urb_buffer(struct device *dev,
> > > +                               size_t size,
> > > +                               void *buffer,
> > > +                               dma_addr_t dma_handle)
> > > +{
> > > +       dma_unmap_single(dev, dma_handle, size, DMA_FROM_DEVICE);
> > > +       kfree(buffer);
> > > +}
> > > +
> > >  static struct pwc_frame_buf *pwc_get_next_fill_buf(struct pwc_device *pdev)
> > >  {
> > >         unsigned long flags = 0;
> > > @@ -306,6 +332,11 @@ static void pwc_isoc_handler(struct urb *urb)
> > >         /* Reset ISOC error counter. We did get here, after all. */
> > >         pdev->visoc_errors = 0;
> > >
> > > +       dma_sync_single_for_cpu(&urb->dev->dev,
> > > +                               urb->transfer_dma,
> > > +                               urb->transfer_buffer_length,
> > > +                               DMA_FROM_DEVICE);
> > > +
> > >         /* vsync: 0 = don't copy data
> > >                   1 = sync-hunt
> > >                   2 = synched
> > > @@ -352,6 +383,11 @@ static void pwc_isoc_handler(struct urb *urb)
> > >                 pdev->vlast_packet_size = flen;
> > >         }
> > >
> > > +       dma_sync_single_for_device(&urb->dev->dev,
> > > +                                  urb->transfer_dma,
> > > +                                  urb->transfer_buffer_length,
> > > +                                  DMA_FROM_DEVICE);
> > > +
> > >  handler_end:
> > >         trace_pwc_handler_exit(urb, pdev);
> > >
> > > @@ -428,16 +464,15 @@ static int pwc_isoc_init(struct pwc_device *pdev)
> > >                 urb->dev = udev;
> > >                 urb->pipe = usb_rcvisocpipe(udev, pdev->vendpoint);
> > >                 urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
> > > -               urb->transfer_buffer = usb_alloc_coherent(udev,
> > > -                                                         ISO_BUFFER_SIZE,
> > > -                                                         GFP_KERNEL,
> > > -                                                         &urb->transfer_dma);
> > > +               urb->transfer_buffer_length = ISO_BUFFER_SIZE;
> > > +               urb->transfer_buffer = pwc_alloc_urb_buffer(&udev->dev,
> > > +                                                           urb->transfer_buffer_length,
> > > +                                                           &urb->transfer_dma);
> > >                 if (urb->transfer_buffer == NULL) {
> > >                         PWC_ERROR("Failed to allocate urb buffer %d\n", i);
> > >                         pwc_isoc_cleanup(pdev);
> > >                         return -ENOMEM;
> > >                 }
> > > -               urb->transfer_buffer_length = ISO_BUFFER_SIZE;
> > >                 urb->complete = pwc_isoc_handler;
> > >                 urb->context = pdev;
> > >                 urb->start_frame = 0;
> > > @@ -488,15 +523,16 @@ static void pwc_iso_free(struct pwc_device *pdev)
> > >
> > >         /* Freeing ISOC buffers one by one */
> > >         for (i = 0; i < MAX_ISO_BUFS; i++) {
> > > -               if (pdev->urbs[i]) {
> > > +               struct urb *urb = pdev->urbs[i];
> > > +
> > > +               if (urb) {
> > >                         PWC_DEBUG_MEMORY("Freeing URB\n");
> > > -                       if (pdev->urbs[i]->transfer_buffer) {
> > > -                               usb_free_coherent(pdev->udev,
> > > -                                       pdev->urbs[i]->transfer_buffer_length,
> > > -                                       pdev->urbs[i]->transfer_buffer,
> > > -                                       pdev->urbs[i]->transfer_dma);
> > > -                       }
> > > -                       usb_free_urb(pdev->urbs[i]);
> > > +                       if (urb->transfer_buffer)
> > > +                               pwc_free_urb_buffer(&urb->dev->dev,
> > > +                                                   urb->transfer_buffer_length,
> > > +                                                   urb->transfer_buffer,
> > > +                                                   urb->transfer_dma);
> > > +                       usb_free_urb(urb);
> > >                         pdev->urbs[i] = NULL;
> > >                 }
> > >         }
> > > --
> > > 2.16.4
> > >
> >
> >
> > --
> > With best regards,
> > Matwey V. Kornilov
>
>
>
> --
> With best regards,
> Matwey V. Kornilov



-- 
With best regards,
Matwey V. Kornilov

Re: [PATCH v6 2/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

[Steven Rostedt]

Can someone please take this patch or at least say what's wrong with it
if you have a problem?

Matwey has been patiently pinging us once every other week for over a
month asking for a reply. I've already given my Reviewed-by from a
tracing perspective.

Ignoring patches is not a friendly gesture.

-- Steve


On Wed, 12 Dec 2018 16:07:38 +0300
"Matwey V. Kornilov" <matwey.kornilov@gmail.com> wrote:

> пт, 30 нояб. 2018 г. в 15:20, Matwey V. Kornilov <matwey.kornilov@gmail.com>:
> >
> > ср, 21 нояб. 2018 г. в 21:15, Matwey V. Kornilov <matwey.kornilov@gmail.com>:  
> > >
> > > пт, 9 нояб. 2018 г. в 22:03, Matwey V. Kornilov <matwey@sai.msu.ru>:  
> > > >
> > > > DMA cocherency slows the transfer down on systems without hardware
> > > > coherent DMA.
> > > > Instead we use noncocherent DMA memory and explicit sync at data receive
> > > > handler.
> > > >
> > > > Based on previous commit the following performance benchmarks have been
> > > > carried out. Average memcpy() data transfer rate (rate) and handler
> > > > completion time (time) have been measured when running video stream at
> > > > 640x480 resolution at 10fps.
> > > >
> > > > x86_64 based system (Intel Core i5-3470). This platform has hardware
> > > > coherent DMA support and proposed change doesn't make big difference here.
> > > >
> > > >  * kmalloc:            rate = (2.0 +- 0.4) GBps
> > > >                        time = (5.0 +- 3.0) usec
> > > >  * usb_alloc_coherent: rate = (3.4 +- 1.2) GBps
> > > >                        time = (3.5 +- 3.0) usec
> > > >
> > > > We see that the measurements agree within error ranges in this case.
> > > > So theoretically predicted performance downgrade cannot be reliably
> > > > measured here.
> > > >
> > > > armv7l based system (TI AM335x BeagleBone Black @ 300MHz). This platform
> > > > has no hardware coherent DMA support. DMA coherence is implemented via
> > > > disabled page caching that slows down memcpy() due to memory controller
> > > > behaviour.
> > > >
> > > >  * kmalloc:            rate =  ( 94 +- 4) MBps
> > > >                        time =  (101 +- 4) usec
> > > >  * usb_alloc_coherent: rate = (28.1 +- 0.1) MBps
> > > >                        time =  (341 +- 2) usec
> > > >
> > > > Note, that quantative difference leads (this commit leads to 3.3 times
> > > > acceleration) to qualitative behavior change in this case. As it was
> > > > stated before, the video stream cannot be successfully received at AM335x
> > > > platforms with MUSB based USB host controller due to performance issues
> > > > [1].
> > > >
> > > > [1] https://www.spinics.net/lists/linux-usb/msg165735.html
> > > >
> > > > Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>  
> > >
> > > Ping  
> >
> > Ping  
> 
> Ping
> 
> >  
> > >  
> > > > ---
> > > >  drivers/media/usb/pwc/pwc-if.c | 62 +++++++++++++++++++++++++++++++++---------
> > > >  1 file changed, 49 insertions(+), 13 deletions(-)
> > > >
> > > > diff --git a/drivers/media/usb/pwc/pwc-if.c b/drivers/media/usb/pwc/pwc-if.c
> > > > index 53c111bd5a22..a81fb319b339 100644
> > > > --- a/drivers/media/usb/pwc/pwc-if.c
> > > > +++ b/drivers/media/usb/pwc/pwc-if.c
> > > > @@ -159,6 +159,32 @@ static const struct video_device pwc_template = {
> > > >  /***************************************************************************/
> > > >  /* Private functions */
> > > >
> > > > +static void *pwc_alloc_urb_buffer(struct device *dev,
> > > > +                                 size_t size, dma_addr_t *dma_handle)
> > > > +{
> > > > +       void *buffer = kmalloc(size, GFP_KERNEL);
> > > > +
> > > > +       if (!buffer)
> > > > +               return NULL;
> > > > +
> > > > +       *dma_handle = dma_map_single(dev, buffer, size, DMA_FROM_DEVICE);
> > > > +       if (dma_mapping_error(dev, *dma_handle)) {
> > > > +               kfree(buffer);
> > > > +               return NULL;
> > > > +       }
> > > > +
> > > > +       return buffer;
> > > > +}
> > > > +
> > > > +static void pwc_free_urb_buffer(struct device *dev,
> > > > +                               size_t size,
> > > > +                               void *buffer,
> > > > +                               dma_addr_t dma_handle)
> > > > +{
> > > > +       dma_unmap_single(dev, dma_handle, size, DMA_FROM_DEVICE);
> > > > +       kfree(buffer);
> > > > +}
> > > > +
> > > >  static struct pwc_frame_buf *pwc_get_next_fill_buf(struct pwc_device *pdev)
> > > >  {
> > > >         unsigned long flags = 0;
> > > > @@ -306,6 +332,11 @@ static void pwc_isoc_handler(struct urb *urb)
> > > >         /* Reset ISOC error counter. We did get here, after all. */
> > > >         pdev->visoc_errors = 0;
> > > >
> > > > +       dma_sync_single_for_cpu(&urb->dev->dev,
> > > > +                               urb->transfer_dma,
> > > > +                               urb->transfer_buffer_length,
> > > > +                               DMA_FROM_DEVICE);
> > > > +
> > > >         /* vsync: 0 = don't copy data
> > > >                   1 = sync-hunt
> > > >                   2 = synched
> > > > @@ -352,6 +383,11 @@ static void pwc_isoc_handler(struct urb *urb)
> > > >                 pdev->vlast_packet_size = flen;
> > > >         }
> > > >
> > > > +       dma_sync_single_for_device(&urb->dev->dev,
> > > > +                                  urb->transfer_dma,
> > > > +                                  urb->transfer_buffer_length,
> > > > +                                  DMA_FROM_DEVICE);
> > > > +
> > > >  handler_end:
> > > >         trace_pwc_handler_exit(urb, pdev);
> > > >
> > > > @@ -428,16 +464,15 @@ static int pwc_isoc_init(struct pwc_device *pdev)
> > > >                 urb->dev = udev;
> > > >                 urb->pipe = usb_rcvisocpipe(udev, pdev->vendpoint);
> > > >                 urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
> > > > -               urb->transfer_buffer = usb_alloc_coherent(udev,
> > > > -                                                         ISO_BUFFER_SIZE,
> > > > -                                                         GFP_KERNEL,
> > > > -                                                         &urb->transfer_dma);
> > > > +               urb->transfer_buffer_length = ISO_BUFFER_SIZE;
> > > > +               urb->transfer_buffer = pwc_alloc_urb_buffer(&udev->dev,
> > > > +                                                           urb->transfer_buffer_length,
> > > > +                                                           &urb->transfer_dma);
> > > >                 if (urb->transfer_buffer == NULL) {
> > > >                         PWC_ERROR("Failed to allocate urb buffer %d\n", i);
> > > >                         pwc_isoc_cleanup(pdev);
> > > >                         return -ENOMEM;
> > > >                 }
> > > > -               urb->transfer_buffer_length = ISO_BUFFER_SIZE;
> > > >                 urb->complete = pwc_isoc_handler;
> > > >                 urb->context = pdev;
> > > >                 urb->start_frame = 0;
> > > > @@ -488,15 +523,16 @@ static void pwc_iso_free(struct pwc_device *pdev)
> > > >
> > > >         /* Freeing ISOC buffers one by one */
> > > >         for (i = 0; i < MAX_ISO_BUFS; i++) {
> > > > -               if (pdev->urbs[i]) {
> > > > +               struct urb *urb = pdev->urbs[i];
> > > > +
> > > > +               if (urb) {
> > > >                         PWC_DEBUG_MEMORY("Freeing URB\n");
> > > > -                       if (pdev->urbs[i]->transfer_buffer) {
> > > > -                               usb_free_coherent(pdev->udev,
> > > > -                                       pdev->urbs[i]->transfer_buffer_length,
> > > > -                                       pdev->urbs[i]->transfer_buffer,
> > > > -                                       pdev->urbs[i]->transfer_dma);
> > > > -                       }
> > > > -                       usb_free_urb(pdev->urbs[i]);
> > > > +                       if (urb->transfer_buffer)
> > > > +                               pwc_free_urb_buffer(&urb->dev->dev,
> > > > +                                                   urb->transfer_buffer_length,
> > > > +                                                   urb->transfer_buffer,
> > > > +                                                   urb->transfer_dma);
> > > > +                       usb_free_urb(urb);
> > > >                         pdev->urbs[i] = NULL;
> > > >                 }
> > > >         }
> > > > --
> > > > 2.16.4
> > > >  
> > >
> > >
> > > --
> > > With best regards,
> > > Matwey V. Kornilov  
> >
> >
> >
> > --
> > With best regards,
> > Matwey V. Kornilov  
> 
> 
> 

Re: [PATCH v6 2/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

[Steven Rostedt]

On Wed, 12 Dec 2018 08:56:22 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> Can someone please take this patch or at least say what's wrong with it
> if you have a problem?
> 
> Matwey has been patiently pinging us once every other week for over a
> month asking for a reply. I've already given my Reviewed-by from a
> tracing perspective.
> 
> Ignoring patches is not a friendly gesture.
> 

Nevermind, it appears that v5 is still under discussion.

Matwey, does v6 address the comments made in v5?

-- Steve

Re: [PATCH v6 2/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

[Matwey V. Kornilov]

ср, 12 дек. 2018 г. в 17:01, Steven Rostedt <rostedt@goodmis.org>:
>
> On Wed, 12 Dec 2018 08:56:22 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
> > Can someone please take this patch or at least say what's wrong with it
> > if you have a problem?
> >
> > Matwey has been patiently pinging us once every other week for over a
> > month asking for a reply. I've already given my Reviewed-by from a
> > tracing perspective.
> >
> > Ignoring patches is not a friendly gesture.
> >
>
> Nevermind, it appears that v5 is still under discussion.
>
> Matwey, does v6 address the comments made in v5?

Hi,

v6 addresses the comments made by Laurent Pinchart on Oct, 31:

https://www.spinics.net/lists/linux-media/msg142216.html

namely, dma_sync_single_for_device() is introduced in the proper place



>
> -- Steve



-- 
With best regards,
Matwey V. Kornilov

Re: [PATCH v6 0/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

[Laurent Pinchart]

Hi Matwey,

Thank you for the patches.

For the whole series,

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

On Friday, 9 November 2018 21:03:25 EET Matwey V. Kornilov wrote:
> DMA cocherency slows the transfer down on systems without hardware coherent
> DMA. In order to demontrate this we introduce performance measurement
> facilities in patch 1 and fix the performance issue in patch 2 in order to
> obtain 3.3 times speedup.
> 
> Changes since v5:
>  * add dma_sync_single_for_device() as required by Laurent Pinchart
> 
> Changes since v4:
>  * fix fields order in trace events
>  * minor style fixes
> 
> Changes since v3:
>  * fix scripts/checkpatch.pl errors
>  * use __string to store name in trace events
> 
> Changes since v2:
>  * use dma_sync_single_for_cpu() to achive better performance
>  * remeasured performance
> 
> Changes since v1:
>  * trace_pwc_handler_exit() call moved to proper place
>  * detailed description added for commit 1
>  * additional output added to trace to track separate frames
> 
> Matwey V. Kornilov (2):
>   media: usb: pwc: Introduce TRACE_EVENTs for pwc_isoc_handler()
>   media: usb: pwc: Don't use coherent DMA buffers for ISO transfer
> 
>  drivers/media/usb/pwc/pwc-if.c | 69 +++++++++++++++++++++++++++++++--------
>  include/trace/events/pwc.h     | 65 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 121 insertions(+), 13 deletions(-)
>  create mode 100644 include/trace/events/pwc.h

-- 
Regards,

Laurent Pinchart

[PATCH v6 3/2] MAINTAINERS: added include/trace/events/pwc.h

[Hans Verkuil]

Added include/trace/events/pwc.h to the list of files.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
---
Will include this patch as part of the pull request.
---
 MAINTAINERS | 1 +
 1 file changed, 1 insertion(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 3e9f1710ed13..3ce9533bca26 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12191,6 +12191,7 @@ L:	linux-media@vger.kernel.org
 T:	git git://linuxtv.org/media_tree.git
 S:	Odd Fixes
 F:	drivers/media/usb/pwc/*
+F:	include/trace/events/pwc.h

 PWM FAN DRIVER
 M:	Kamil Debski <kamil@wypas.org>
-- 
2.19.2

Re: [PATCH v6 0/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

[Ezequiel Garcia]

On Wed, 12 Dec 2018 at 14:27, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Matwey,
>
> Thank you for the patches.
>
> For the whole series,
>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>

Thanks Laurent.

Matwey, given your detailed analysis of this issue,
and given you have pwc hardware to test, I think
you should consider co-maintaining this driver.

Thanks,
-- 
Ezequiel García, VanguardiaSur
www.vanguardiasur.com.ar

Re: [PATCH v6 0/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

[Matwey V. Kornilov]

ср, 12 дек. 2018 г. в 20:41, Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>:
>
> On Wed, 12 Dec 2018 at 14:27, Laurent Pinchart
> <laurent.pinchart@ideasonboard.com> wrote:
> >
> > Hi Matwey,
> >
> > Thank you for the patches.
> >
> > For the whole series,
> >
> > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> >
>
> Thanks Laurent.
>
> Matwey, given your detailed analysis of this issue,
> and given you have pwc hardware to test, I think
> you should consider co-maintaining this driver.
>

Well, It would be great if I could help. Is there some guide how to apply?

> Thanks,
> --
> Ezequiel García, VanguardiaSur
> www.vanguardiasur.com.ar



-- 
With best regards,
Matwey V. Kornilov