[Intel-gfx] [PATCH 08/18] drm/i915: Add a relay backed debugfs interface for capturing GuC logs

2016-10-12 Thread akash . goel 
From: Akash Goel 

Added a new debugfs interface '/sys/kernel/debug/dri/guc_log' for the
User to capture GuC firmware logs. Availed relay framework to implement
the interface, where Driver will have to just use a relay API to store
snapshots of the GuC log buffer in the buffer managed by relay.
The snapshot will be taken when GuC firmware sends a log buffer flush
interrupt and up to four snapshots could be stored in the relay buffer.
The relay buffer will be operated in a mode where it will overwrite the
data not yet collected by User.
Besides mmap method, through which User can directly access the relay
buffer contents, relay also supports the 'poll' method. Through the 'poll'
call on log file, User can come to know whenever a new snapshot of the
log buffer is taken by Driver, so can run in tandem with the Driver and
capture the logs in a sustained/streaming manner, without any loss of data.

v2: Defer the creation of relay channel & associated debugfs file, as
debugfs setup is now done at the end of i915 Driver load. (Chris)

v3:
- Switch to no-overwrite mode for relay.
- Fix the relay sub buffer switching sequence.

v4:
- Update i915 Kconfig to select RELAY config. (TvrtKo)
- Log a message when there is no sub buffer available to capture
  the GuC log buffer. (Tvrtko)
- Increase the number of relay sub buffers to 8 from 4, to have
  sufficient buffering for boot time logs

v5:
- Fix the alignment, indentation issues and some minor cleanup. (Tvrtko)
- Update the comment to elaborate on why a relay channel has to be
  associated with the debugfs file. (Tvrtko)

v6:
- Move the write to 'is_global' after the NULL check on parent directory
  dentry pointer. (Tvrtko)

v7: Add a BUG_ON to validate relay buffer allocation size. (Chris)

Testcase: igt/tools/intel_guc_logger

Suggested-by: Chris Wilson 
Signed-off-by: Sourab Gupta 
Signed-off-by: Akash Goel 
Reviewed-by: Tvrtko Ursulin 
---
 drivers/gpu/drm/i915/Kconfig   |   1 +
 drivers/gpu/drm/i915/i915_drv.c|   2 +
 drivers/gpu/drm/i915/i915_guc_submission.c | 213 -
 drivers/gpu/drm/i915/intel_guc.h   |   3 +
 4 files changed, 217 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
index 6aedc96..105c468 100644
--- a/drivers/gpu/drm/i915/Kconfig
+++ b/drivers/gpu/drm/i915/Kconfig
@@ -12,6 +12,7 @@ config DRM_I915
select DRM_KMS_HELPER
select DRM_PANEL
select DRM_MIPI_DSI
+   select RELAY
# i915 depends on ACPI_VIDEO when ACPI is enabled
# but for select to work, need to select ACPI_VIDEO's dependencies, ick
select BACKLIGHT_LCD_SUPPORT if ACPI
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 89d3222..09a2944 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1128,6 +1128,7 @@ static void i915_driver_register(struct drm_i915_private 
*dev_priv)
/* Reveal our presence to userspace */
if (drm_dev_register(dev, 0) == 0) {
i915_debugfs_register(dev_priv);
+   i915_guc_register(dev_priv);
i915_setup_sysfs(dev_priv);
} else
DRM_ERROR("Failed to register driver for userspace access!\n");
@@ -1166,6 +1167,7 @@ static void i915_driver_unregister(struct 
drm_i915_private *dev_priv)
intel_opregion_unregister(dev_priv);
 
i915_teardown_sysfs(dev_priv);
+   i915_guc_unregister(dev_priv);
i915_debugfs_unregister(dev_priv);
drm_dev_unregister(_priv->drm);
 
diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c 
b/drivers/gpu/drm/i915/i915_guc_submission.c
index b3c81a2..2cdc3ca 100644
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -23,6 +23,8 @@
  */
 #include 
 #include 
+#include 
+#include 
 #include "i915_drv.h"
 #include "intel_guc.h"
 
@@ -856,13 +858,160 @@ err:
return NULL;
 }
 
+/*
+ * Sub buffer switch callback. Called whenever relay has to switch to a new
+ * sub buffer, relay stays on the same sub buffer if 0 is returned.
+ */
+static int subbuf_start_callback(struct rchan_buf *buf,
+void *subbuf,
+void *prev_subbuf,
+size_t prev_padding)
+{
+   /* Use no-overwrite mode by default, where relay will stop accepting
+* new data if there are no empty sub buffers left.
+* There is no strict synchronization enforced by relay between Consumer
+* and Producer. In overwrite mode, there is a possibility of getting
+* inconsistent/garbled data, the producer could be writing on to the
+* same sub buffer from which Consumer is reading. This can't be avoided
+* unless Consumer is fast enough and

[Intel-gfx] [PATCH 08/18] drm/i915: Add a relay backed debugfs interface for capturing GuC logs

2016-09-08 Thread akash . goel 
From: Akash Goel 

Added a new debugfs interface '/sys/kernel/debug/dri/guc_log' for the
User to capture GuC firmware logs. Availed relay framework to implement
the interface, where Driver will have to just use a relay API to store
snapshots of the GuC log buffer in the buffer managed by relay.
The snapshot will be taken when GuC firmware sends a log buffer flush
interrupt and up to four snapshots could be stored in the relay buffer.
The relay buffer will be operated in a mode where it will overwrite the
data not yet collected by User.
Besides mmap method, through which User can directly access the relay
buffer contents, relay also supports the 'poll' method. Through the 'poll'
call on log file, User can come to know whenever a new snapshot of the
log buffer is taken by Driver, so can run in tandem with the Driver and
capture the logs in a sustained/streaming manner, without any loss of data.

v2: Defer the creation of relay channel & associated debugfs file, as
debugfs setup is now done at the end of i915 Driver load. (Chris)

v3:
- Switch to no-overwrite mode for relay.
- Fix the relay sub buffer switching sequence.

v4:
- Update i915 Kconfig to select RELAY config. (TvrtKo)
- Log a message when there is no sub buffer available to capture
  the GuC log buffer. (Tvrtko)
- Increase the number of relay sub buffers to 8 from 4, to have
  sufficient buffering for boot time logs

v5:
- Fix the alignment, indentation issues and some minor cleanup. (Tvrtko)
- Update the comment to elaborate on why a relay channel has to be
  associated with the debugfs file. (Tvrtko)

v6:
- Move the write to 'is_global' after the NULL check on parent directory
  dentry pointer. (Tvrtko)

v7: Add a BUG_ON to validate relay buffer allocation size. (Chris)

Testcase: igt/tools/intel_guc_logger

Suggested-by: Chris Wilson 
Signed-off-by: Sourab Gupta 
Signed-off-by: Akash Goel 
Reviewed-by: Tvrtko Ursulin 
---
 drivers/gpu/drm/i915/Kconfig   |   1 +
 drivers/gpu/drm/i915/i915_drv.c|   2 +
 drivers/gpu/drm/i915/i915_guc_submission.c | 213 -
 drivers/gpu/drm/i915/intel_guc.h   |   3 +
 4 files changed, 217 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
index 7769e46..fc900d2 100644
--- a/drivers/gpu/drm/i915/Kconfig
+++ b/drivers/gpu/drm/i915/Kconfig
@@ -11,6 +11,7 @@ config DRM_I915
select DRM_KMS_HELPER
select DRM_PANEL
select DRM_MIPI_DSI
+   select RELAY
# i915 depends on ACPI_VIDEO when ACPI is enabled
# but for select to work, need to select ACPI_VIDEO's dependencies, ick
select BACKLIGHT_LCD_SUPPORT if ACPI
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 02c34d6..b61f1c5 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1122,6 +1122,7 @@ static void i915_driver_register(struct drm_i915_private 
*dev_priv)
/* Reveal our presence to userspace */
if (drm_dev_register(dev, 0) == 0) {
i915_debugfs_register(dev_priv);
+   i915_guc_register(dev_priv);
i915_setup_sysfs(dev_priv);
} else
DRM_ERROR("Failed to register driver for userspace access!\n");
@@ -1160,6 +1161,7 @@ static void i915_driver_unregister(struct 
drm_i915_private *dev_priv)
intel_opregion_unregister(dev_priv);
 
i915_teardown_sysfs(dev_priv);
+   i915_guc_unregister(dev_priv);
i915_debugfs_unregister(dev_priv);
drm_dev_unregister(_priv->drm);
 
diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c 
b/drivers/gpu/drm/i915/i915_guc_submission.c
index 21e7c183..e2863b7 100644
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -23,6 +23,8 @@
  */
 #include 
 #include 
+#include 
+#include 
 #include "i915_drv.h"
 #include "intel_guc.h"
 
@@ -835,13 +837,160 @@ err:
return NULL;
 }
 
+/*
+ * Sub buffer switch callback. Called whenever relay has to switch to a new
+ * sub buffer, relay stays on the same sub buffer if 0 is returned.
+ */
+static int subbuf_start_callback(struct rchan_buf *buf,
+void *subbuf,
+void *prev_subbuf,
+size_t prev_padding)
+{
+   /* Use no-overwrite mode by default, where relay will stop accepting
+* new data if there are no empty sub buffers left.
+* There is no strict synchronization enforced by relay between Consumer
+* and Producer. In overwrite mode, there is a possibility of getting
+* inconsistent/garbled data, the producer could be writing on to the
+* same sub buffer from which Consumer is reading. This can't be avoided
+* unless Consumer is fast enough and

Re: [Intel-gfx] [PATCH 08/18] drm/i915: Add a relay backed debugfs interface for capturing GuC logs

2016-08-15 Thread Chris Wilson 
On Mon, Aug 15, 2016 at 10:08:15PM +0530, Goel, Akash wrote:
> 
> 
> On 8/15/2016 9:42 PM, Chris Wilson wrote:
> >On Mon, Aug 15, 2016 at 05:09:45PM +0100, Chris Wilson wrote:
> >>On Mon, Aug 15, 2016 at 08:19:49PM +0530, akash.g...@intel.com wrote:
> >>>+void i915_guc_register(struct drm_i915_private *dev_priv)
> >>>+{
> >>>+  if (!i915.enable_guc_submission)
> >>>+  return;
> >>
> >>The final state of i915.enable_guc_submission is not known at this time.
> 
> As per the below sequence, i915.enable_guc_submission would have
> been set to its final value by this time,
> 
> i915_driver_load
>   i915_load_modeset_init
>   i915_gem_init_hw
>   intel_guc_setup
>   i915_guc_submission_init
>   i915_guc_submission_enable
>   i915_driver_register
>   i915_debugfs_register
>   i915_guc_register

I was under the impression that intel_guc_setup() was asynchronous, that
it waited for the firmware to be loaded.
-Chris

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Re: [Intel-gfx] [PATCH 08/18] drm/i915: Add a relay backed debugfs interface for capturing GuC logs

2016-08-15 Thread Goel, Akash 



On 8/15/2016 9:42 PM, Chris Wilson wrote:

On Mon, Aug 15, 2016 at 05:09:45PM +0100, Chris Wilson wrote:

On Mon, Aug 15, 2016 at 08:19:49PM +0530, akash.g...@intel.com wrote:

+void i915_guc_register(struct drm_i915_private *dev_priv)
+{
+   if (!i915.enable_guc_submission)
+   return;


The final state of i915.enable_guc_submission is not known at this time.


As per the below sequence, i915.enable_guc_submission would have been 
set to its final value by this time,


i915_driver_load
i915_load_modeset_init
i915_gem_init_hw
intel_guc_setup
i915_guc_submission_init
i915_guc_submission_enable
i915_driver_register
i915_debugfs_register
i915_guc_register


Does it matter if you set up the log even though guc is not used?


I think it would be better to do setup only if guc submission is enabled.


Would this not be better driver from guc_submission_enable and
guc_submission_disable?





With the caveat that you probably need both. i.e. you have to wait for
both the GuC to be enabled and for sysfs to be available.

Sorry I am really confused.
Isn't this a right location ? creating the relay file after the debugfs 
registration has been done.

Other logging related setup is being done at i915_guc_submission_init().

Best regards
Akash


-Chris


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Re: [Intel-gfx] [PATCH 08/18] drm/i915: Add a relay backed debugfs interface for capturing GuC logs

2016-08-15 Thread Chris Wilson 
On Mon, Aug 15, 2016 at 05:09:45PM +0100, Chris Wilson wrote:
> On Mon, Aug 15, 2016 at 08:19:49PM +0530, akash.g...@intel.com wrote:
> > +void i915_guc_register(struct drm_i915_private *dev_priv)
> > +{
> > +   if (!i915.enable_guc_submission)
> > +   return;
> 
> The final state of i915.enable_guc_submission is not known at this time.
> Does it matter if you set up the log even though guc is not used?
> 
> Would this not be better driver from guc_submission_enable and
> guc_submission_disable?

With the caveat that you probably need both. i.e. you have to wait for
both the GuC to be enabled and for sysfs to be available.
-Chris

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Re: [Intel-gfx] [PATCH 08/18] drm/i915: Add a relay backed debugfs interface for capturing GuC logs

2016-08-15 Thread Chris Wilson 
On Mon, Aug 15, 2016 at 08:19:49PM +0530, akash.g...@intel.com wrote:
> +void i915_guc_register(struct drm_i915_private *dev_priv)
> +{
> + if (!i915.enable_guc_submission)
> + return;

The final state of i915.enable_guc_submission is not known at this time.
Does it matter if you set up the log even though guc is not used?

Would this not be better driver from guc_submission_enable and
guc_submission_disable?
-Chris

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Re: [Intel-gfx] [PATCH 08/18] drm/i915: Add a relay backed debugfs interface for capturing GuC logs

2016-08-15 Thread Goel, Akash 



On 8/15/2016 8:59 PM, Tvrtko Ursulin wrote:


On 15/08/16 15:49, akash.g...@intel.com wrote:

From: Akash Goel 

Added a new debugfs interface '/sys/kernel/debug/dri/guc_log' for the
User to capture GuC firmware logs. Availed relay framework to implement
the interface, where Driver will have to just use a relay API to store
snapshots of the GuC log buffer in the buffer managed by relay.
The snapshot will be taken when GuC firmware sends a log buffer flush
interrupt and up to four snapshots could be stored in the relay buffer.
The relay buffer will be operated in a mode where it will overwrite the
data not yet collected by User.
Besides mmap method, through which User can directly access the relay
buffer contents, relay also supports the 'poll' method. Through the
'poll'
call on log file, User can come to know whenever a new snapshot of the
log buffer is taken by Driver, so can run in tandem with the Driver and
capture the logs in a sustained/streaming manner, without any loss of
data.

v2: Defer the creation of relay channel & associated debugfs file, as
 debugfs setup is now done at the end of i915 Driver load. (Chris)

v3:
- Switch to no-overwrite mode for relay.
- Fix the relay sub buffer switching sequence.

v4:
- Update i915 Kconfig to select RELAY config. (TvrtKo)
- Log a message when there is no sub buffer available to capture
   the GuC log buffer. (Tvrtko)
- Increase the number of relay sub buffers to 8 from 4, to have
   sufficient buffering for boot time logs

v5:
- Fix the alignment, indentation issues and some minor cleanup. (Tvrtko)
- Update the comment to elaborate on why a relay channel has to be
   associated with the debugfs file. (Tvrtko)

Suggested-by: Chris Wilson 
Signed-off-by: Sourab Gupta 
Signed-off-by: Akash Goel 
---
  drivers/gpu/drm/i915/Kconfig   |   1 +
  drivers/gpu/drm/i915/i915_drv.c|   2 +
  drivers/gpu/drm/i915/i915_guc_submission.c | 211
-
  drivers/gpu/drm/i915/intel_guc.h   |   3 +
  4 files changed, 215 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
index 7769e46..fc900d2 100644
--- a/drivers/gpu/drm/i915/Kconfig
+++ b/drivers/gpu/drm/i915/Kconfig
@@ -11,6 +11,7 @@ config DRM_I915
  select DRM_KMS_HELPER
  select DRM_PANEL
  select DRM_MIPI_DSI
+select RELAY
  # i915 depends on ACPI_VIDEO when ACPI is enabled
  # but for select to work, need to select ACPI_VIDEO's
dependencies, ick
  select BACKLIGHT_LCD_SUPPORT if ACPI
diff --git a/drivers/gpu/drm/i915/i915_drv.c
b/drivers/gpu/drm/i915/i915_drv.c
index 13ae340..cdee60b 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1133,6 +1133,7 @@ static void i915_driver_register(struct
drm_i915_private *dev_priv)
  /* Reveal our presence to userspace */
  if (drm_dev_register(dev, 0) == 0) {
  i915_debugfs_register(dev_priv);
+i915_guc_register(dev_priv);
  i915_setup_sysfs(dev);
  } else
  DRM_ERROR("Failed to register driver for userspace access!\n");
@@ -1171,6 +1172,7 @@ static void i915_driver_unregister(struct
drm_i915_private *dev_priv)
  intel_opregion_unregister(dev_priv);

  i915_teardown_sysfs(_priv->drm);
+i915_guc_unregister(dev_priv);
  i915_debugfs_unregister(dev_priv);
  drm_dev_unregister(_priv->drm);

diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c
b/drivers/gpu/drm/i915/i915_guc_submission.c
index 2b27b87..9b1054c 100644
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -23,6 +23,8 @@
   */
  #include 
  #include 
+#include 
+#include 
  #include "i915_drv.h"
  #include "intel_guc.h"

@@ -837,13 +839,159 @@ err:
  return NULL;
  }

+/*
+ * Sub buffer switch callback. Called whenever relay has to switch to
a new
+ * sub buffer, relay stays on the same sub buffer if 0 is returned.
+ */
+static int subbuf_start_callback(struct rchan_buf *buf,
+ void *subbuf,
+ void *prev_subbuf,
+ size_t prev_padding)
+{
+/* Use no-overwrite mode by default, where relay will stop accepting
+ * new data if there are no empty sub buffers left.
+ * There is no strict synchronization enforced by relay between
Consumer
+ * and Producer. In overwrite mode, there is a possibility of
getting
+ * inconsistent/garbled data, the producer could be writing on to
the
+ * same sub buffer from which Consumer is reading. This can't be
avoided
+ * unless Consumer is fast enough and can always run in tandem with
+ * Producer.
+ */
+if (relay_buf_full(buf))
+return 0;
+
+return 1;
+}
+
+/*
+ * file_create() callback. Creates relay file in debugfs.
+ */
+static struct dentry *create_buf_file_callback(const char *filename,
+

Re: [Intel-gfx] [PATCH 08/18] drm/i915: Add a relay backed debugfs interface for capturing GuC logs

2016-08-15 Thread Tvrtko Ursulin 


On 15/08/16 15:49, akash.g...@intel.com wrote:

From: Akash Goel 

Added a new debugfs interface '/sys/kernel/debug/dri/guc_log' for the
User to capture GuC firmware logs. Availed relay framework to implement
the interface, where Driver will have to just use a relay API to store
snapshots of the GuC log buffer in the buffer managed by relay.
The snapshot will be taken when GuC firmware sends a log buffer flush
interrupt and up to four snapshots could be stored in the relay buffer.
The relay buffer will be operated in a mode where it will overwrite the
data not yet collected by User.
Besides mmap method, through which User can directly access the relay
buffer contents, relay also supports the 'poll' method. Through the 'poll'
call on log file, User can come to know whenever a new snapshot of the
log buffer is taken by Driver, so can run in tandem with the Driver and
capture the logs in a sustained/streaming manner, without any loss of data.

v2: Defer the creation of relay channel & associated debugfs file, as
 debugfs setup is now done at the end of i915 Driver load. (Chris)

v3:
- Switch to no-overwrite mode for relay.
- Fix the relay sub buffer switching sequence.

v4:
- Update i915 Kconfig to select RELAY config. (TvrtKo)
- Log a message when there is no sub buffer available to capture
   the GuC log buffer. (Tvrtko)
- Increase the number of relay sub buffers to 8 from 4, to have
   sufficient buffering for boot time logs

v5:
- Fix the alignment, indentation issues and some minor cleanup. (Tvrtko)
- Update the comment to elaborate on why a relay channel has to be
   associated with the debugfs file. (Tvrtko)

Suggested-by: Chris Wilson 
Signed-off-by: Sourab Gupta 
Signed-off-by: Akash Goel 
---
  drivers/gpu/drm/i915/Kconfig   |   1 +
  drivers/gpu/drm/i915/i915_drv.c|   2 +
  drivers/gpu/drm/i915/i915_guc_submission.c | 211 -
  drivers/gpu/drm/i915/intel_guc.h   |   3 +
  4 files changed, 215 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
index 7769e46..fc900d2 100644
--- a/drivers/gpu/drm/i915/Kconfig
+++ b/drivers/gpu/drm/i915/Kconfig
@@ -11,6 +11,7 @@ config DRM_I915
select DRM_KMS_HELPER
select DRM_PANEL
select DRM_MIPI_DSI
+   select RELAY
# i915 depends on ACPI_VIDEO when ACPI is enabled
# but for select to work, need to select ACPI_VIDEO's dependencies, ick
select BACKLIGHT_LCD_SUPPORT if ACPI
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 13ae340..cdee60b 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1133,6 +1133,7 @@ static void i915_driver_register(struct drm_i915_private 
*dev_priv)
/* Reveal our presence to userspace */
if (drm_dev_register(dev, 0) == 0) {
i915_debugfs_register(dev_priv);
+   i915_guc_register(dev_priv);
i915_setup_sysfs(dev);
} else
DRM_ERROR("Failed to register driver for userspace access!\n");
@@ -1171,6 +1172,7 @@ static void i915_driver_unregister(struct 
drm_i915_private *dev_priv)
intel_opregion_unregister(dev_priv);

i915_teardown_sysfs(_priv->drm);
+   i915_guc_unregister(dev_priv);
i915_debugfs_unregister(dev_priv);
drm_dev_unregister(_priv->drm);

diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c 
b/drivers/gpu/drm/i915/i915_guc_submission.c
index 2b27b87..9b1054c 100644
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -23,6 +23,8 @@
   */
  #include 
  #include 
+#include 
+#include 
  #include "i915_drv.h"
  #include "intel_guc.h"

@@ -837,13 +839,159 @@ err:
return NULL;
  }

+/*
+ * Sub buffer switch callback. Called whenever relay has to switch to a new
+ * sub buffer, relay stays on the same sub buffer if 0 is returned.
+ */
+static int subbuf_start_callback(struct rchan_buf *buf,
+void *subbuf,
+void *prev_subbuf,
+size_t prev_padding)
+{
+   /* Use no-overwrite mode by default, where relay will stop accepting
+* new data if there are no empty sub buffers left.
+* There is no strict synchronization enforced by relay between Consumer
+* and Producer. In overwrite mode, there is a possibility of getting
+* inconsistent/garbled data, the producer could be writing on to the
+* same sub buffer from which Consumer is reading. This can't be avoided
+* unless Consumer is fast enough and can always run in tandem with
+* Producer.
+*/
+   if (relay_buf_full(buf))
+   return 0;
+
+   return 1;
+}
+
+/*
+ * file_create() callback. Creates relay file in debugfs.

[Intel-gfx] [PATCH 08/18] drm/i915: Add a relay backed debugfs interface for capturing GuC logs

2016-08-15 Thread akash . goel 
From: Akash Goel 

Added a new debugfs interface '/sys/kernel/debug/dri/guc_log' for the
User to capture GuC firmware logs. Availed relay framework to implement
the interface, where Driver will have to just use a relay API to store
snapshots of the GuC log buffer in the buffer managed by relay.
The snapshot will be taken when GuC firmware sends a log buffer flush
interrupt and up to four snapshots could be stored in the relay buffer.
The relay buffer will be operated in a mode where it will overwrite the
data not yet collected by User.
Besides mmap method, through which User can directly access the relay
buffer contents, relay also supports the 'poll' method. Through the 'poll'
call on log file, User can come to know whenever a new snapshot of the
log buffer is taken by Driver, so can run in tandem with the Driver and
capture the logs in a sustained/streaming manner, without any loss of data.

v2: Defer the creation of relay channel & associated debugfs file, as
debugfs setup is now done at the end of i915 Driver load. (Chris)

v3:
- Switch to no-overwrite mode for relay.
- Fix the relay sub buffer switching sequence.

v4:
- Update i915 Kconfig to select RELAY config. (TvrtKo)
- Log a message when there is no sub buffer available to capture
  the GuC log buffer. (Tvrtko)
- Increase the number of relay sub buffers to 8 from 4, to have
  sufficient buffering for boot time logs

v5:
- Fix the alignment, indentation issues and some minor cleanup. (Tvrtko)
- Update the comment to elaborate on why a relay channel has to be
  associated with the debugfs file. (Tvrtko)

Suggested-by: Chris Wilson 
Signed-off-by: Sourab Gupta 
Signed-off-by: Akash Goel 
---
 drivers/gpu/drm/i915/Kconfig   |   1 +
 drivers/gpu/drm/i915/i915_drv.c|   2 +
 drivers/gpu/drm/i915/i915_guc_submission.c | 211 -
 drivers/gpu/drm/i915/intel_guc.h   |   3 +
 4 files changed, 215 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
index 7769e46..fc900d2 100644
--- a/drivers/gpu/drm/i915/Kconfig
+++ b/drivers/gpu/drm/i915/Kconfig
@@ -11,6 +11,7 @@ config DRM_I915
select DRM_KMS_HELPER
select DRM_PANEL
select DRM_MIPI_DSI
+   select RELAY
# i915 depends on ACPI_VIDEO when ACPI is enabled
# but for select to work, need to select ACPI_VIDEO's dependencies, ick
select BACKLIGHT_LCD_SUPPORT if ACPI
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 13ae340..cdee60b 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1133,6 +1133,7 @@ static void i915_driver_register(struct drm_i915_private 
*dev_priv)
/* Reveal our presence to userspace */
if (drm_dev_register(dev, 0) == 0) {
i915_debugfs_register(dev_priv);
+   i915_guc_register(dev_priv);
i915_setup_sysfs(dev);
} else
DRM_ERROR("Failed to register driver for userspace access!\n");
@@ -1171,6 +1172,7 @@ static void i915_driver_unregister(struct 
drm_i915_private *dev_priv)
intel_opregion_unregister(dev_priv);
 
i915_teardown_sysfs(_priv->drm);
+   i915_guc_unregister(dev_priv);
i915_debugfs_unregister(dev_priv);
drm_dev_unregister(_priv->drm);
 
diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c 
b/drivers/gpu/drm/i915/i915_guc_submission.c
index 2b27b87..9b1054c 100644
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -23,6 +23,8 @@
  */
 #include 
 #include 
+#include 
+#include 
 #include "i915_drv.h"
 #include "intel_guc.h"
 
@@ -837,13 +839,159 @@ err:
return NULL;
 }
 
+/*
+ * Sub buffer switch callback. Called whenever relay has to switch to a new
+ * sub buffer, relay stays on the same sub buffer if 0 is returned.
+ */
+static int subbuf_start_callback(struct rchan_buf *buf,
+void *subbuf,
+void *prev_subbuf,
+size_t prev_padding)
+{
+   /* Use no-overwrite mode by default, where relay will stop accepting
+* new data if there are no empty sub buffers left.
+* There is no strict synchronization enforced by relay between Consumer
+* and Producer. In overwrite mode, there is a possibility of getting
+* inconsistent/garbled data, the producer could be writing on to the
+* same sub buffer from which Consumer is reading. This can't be avoided
+* unless Consumer is fast enough and can always run in tandem with
+* Producer.
+*/
+   if (relay_buf_full(buf))
+   return 0;
+
+   return 1;
+}
+
+/*
+ * file_create() callback. Creates relay file in debugfs.
+ */
+static struct dentry *create_buf_file_callback(const