[PATCH 03/16] drm/i915: Keep the CRC values into a circular buffer

Damien Lespiau
2013-10-15T17:55:54Z

There are a few good properties to a circular buffer, for instance it
has a number of entries (before we were always dumping the full buffer).

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
---
drivers/gpu/drm/i915/i915_debugfs.c | 20 ++++++++++++--------
drivers/gpu/drm/i915/i915_drv.h | 4 ++--
drivers/gpu/drm/i915/i915_irq.c | 19 +++++++++++++++----
3 files changed, 29 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 0d8a9a3..991abff 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -27,6 +27,7 @@
*/

#include <linux/seq_file.h>
+#include <linux/circ_buf.h>
#include <linux/ctype.h>
#include <linux/debugfs.h>
#include <linux/slab.h>
@@ -1739,25 +1740,28 @@ static int i915_pipe_crc(struct seq_file *m, void *data)
struct drm_device *dev = node->minor->dev;
struct drm_i915_private *dev_priv = dev->dev_private;
enum pipe pipe = (enum pipe)node->info_ent->data;
- const struct intel_pipe_crc *pipe_crc = &dev_priv->pipe_crc[pipe];
- int i;
- int start;
+ struct intel_pipe_crc *pipe_crc = &dev_priv->pipe_crc[pipe];
+ int head, tail;

if (dev_priv->pipe_crc[pipe].source == INTEL_PIPE_CRC_SOURCE_NONE) {
seq_puts(m, "none\n");
return 0;
}

- start = atomic_read(&pipe_crc->slot) + 1;
seq_puts(m, " timestamp CRC1 CRC2 CRC3 CRC4 CRC5\n");
- for (i = 0; i < INTEL_PIPE_CRC_ENTRIES_NR; i++) {
- const struct intel_pipe_crc_entry *entry =
- &pipe_crc->entries[(start + i) %
- INTEL_PIPE_CRC_ENTRIES_NR];
+ head = atomic_read(&pipe_crc->head);
+ tail = atomic_read(&pipe_crc->tail);
+
+ while (CIRC_CNT(head, tail, INTEL_PIPE_CRC_ENTRIES_NR) >= 1) {
+ struct intel_pipe_crc_entry *entry = &pipe_crc->entries[tail];

seq_printf(m, "%12u %8x %8x %8x %8x %8x\n", entry->timestamp,
entry->crc[0], entry->crc[1], entry->crc[2],
entry->crc[3], entry->crc[4]);
+
+ BUILD_BUG_ON_NOT_POWER_OF_2(INTEL_PIPE_CRC_ENTRIES_NR);
+ tail = (tail + 1) & (INTEL_PIPE_CRC_ENTRIES_NR - 1);
+ atomic_set(&pipe_crc->tail, tail);
}

return 0;
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 0d564eb..7a1ed3a 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1232,11 +1232,11 @@ struct intel_pipe_crc_entry {
uint32_t crc[5];
};

-#define INTEL_PIPE_CRC_ENTRIES_NR 200
+#define INTEL_PIPE_CRC_ENTRIES_NR 128
struct intel_pipe_crc {
struct intel_pipe_crc_entry entries[INTEL_PIPE_CRC_ENTRIES_NR];
enum intel_pipe_crc_source source;
- atomic_t slot;
+ atomic_t head, tail;
};

typedef struct drm_i915_private {
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index d2074f1..73d76af 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -30,6 +30,7 @@

#include <linux/sysrq.h>
#include <linux/slab.h>
+#include <linux/circ_buf.h>
#include <drm/drmP.h>
#include <drm/i915_drm.h>
#include "i915_drv.h"
@@ -1195,20 +1196,30 @@ static void ivb_pipe_crc_update(struct drm_device *dev, enum pipe pipe)
struct intel_pipe_crc *pipe_crc = &dev_priv->pipe_crc[pipe];
struct intel_pipe_crc_entry *entry;
ktime_t now;
- int ts, slot;
+ int ts, head, tail;
+
+ head = atomic_read(&pipe_crc->head);
+ tail = atomic_read(&pipe_crc->tail);
+
+ if (CIRC_SPACE(head, tail, INTEL_PIPE_CRC_ENTRIES_NR) < 1) {
+ DRM_ERROR("CRC buffer overflowing\n");
+ return;
+ }
+
+ entry = &pipe_crc->entries[head];

now = ktime_get();
ts = ktime_to_us(now);

- slot = (atomic_read(&pipe_crc->slot) + 1) % INTEL_PIPE_CRC_ENTRIES_NR;
- entry = &pipe_crc->entries[slot];
entry->timestamp = ts;
entry->crc[0] = I915_READ(PIPE_CRC_RES_1_IVB(pipe));
entry->crc[1] = I915_READ(PIPE_CRC_RES_2_IVB(pipe));
entry->crc[2] = I915_READ(PIPE_CRC_RES_3_IVB(pipe));
entry->crc[3] = I915_READ(PIPE_CRC_RES_4_IVB(pipe));
entry->crc[4] = I915_READ(PIPE_CRC_RES_5_IVB(pipe));
- atomic_set(&dev_priv->pipe_crc[pipe].slot, slot);
+
+ head = (head + 1) & (INTEL_PIPE_CRC_ENTRIES_NR - 1);
+ atomic_set(&pipe_crc->head, head);
}
#else
static void ivb_pipe_crc_update(struct drm_device *dev, int pipe) {}
--
1.8.3.1