drm/i915: Keep the CRC values into a circular buffer

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>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 0d8a9a397a245edd1c38731550dbfe42a32cc4ea..991abff94e1e6116b2d162e5af0138de0b67f3ea 100644 (file)
--- 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 bfaaaaee8a5b0536aea60ef20b6a49411c41bd6e..a29a4a1d300ab46dc6314ae49c730c3e3717ea76 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1230,11 +1230,11 @@ 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 d2074f129a364f1eb4c6f2156165ca742f4d38da..73d76af13ed438ccf2460f8fce8084ccc5b8be8b 100644 (file)
--- 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) {}