[PATCH] [v3] drm/i915: Do remaps for all contexts

Ben Widawsky
2013-09-19T02:03:27Z

On both Ivybridge and Haswell, row remapping information is saved and
restored with context. This means, we never actually properly supported
the l3 remapping because our sysfs interface is asynchronous (and not
tied to any context), and the known faulty HW would be reused by the
next context to run.

Not that due to the asynchronous nature of the sysfs entry, there is no
point modifying the registers for the existing context. Instead we set a
flag for all contexts to load the correct remapping information on the
next run. Interested clients can use debugfs to determine whether or not
the row has been remapped.

One could propose at this point that we just do the remapping in the
kernel. I guess since we have to maintain the sysfs interface anyway,
I'm not sure how useful it is, and I do like keeping the policy in
userspace; (it wasn't my original decision to make the
interface the way it is, so I'm not attached).

v2: Force a context switch when we have a remap on the next switch.
(Ville)
Don't let userspace use the interface with disabled contexts.

v3: Don't force a context switch, just let it nop
Improper context slice remap initialization, 1<<1 instead of 1<<i, but I
rewrote it to avoid a second round of confusion.
Error print moved to error path (All Ville)
Added a comment on why the slice remap initialization happens.

CC: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
---
drivers/gpu/drm/i915/i915_debugfs.c | 8 +++++++
drivers/gpu/drm/i915/i915_drv.h | 1 +
drivers/gpu/drm/i915/i915_gem_context.c | 22 ++++++++++++++++----
drivers/gpu/drm/i915/i915_sysfs.c | 37 +++++++++++++--------------------
4 files changed, 41 insertions(+), 27 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index ada0950..80bed69 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -145,6 +145,13 @@ describe_obj(struct seq_file *m, struct drm_i915_gem_object *obj)
seq_printf(m, " (%s)", obj->ring->name);
}

+static void describe_ctx(struct seq_file *m, struct i915_hw_context *ctx)
+{
+ seq_putc(m, ctx->is_initialized ? 'I' : 'i');
+ seq_putc(m, ctx->remap_slice ? 'R' : 'r');
+ seq_putc(m, ' ');
+}
+
static int i915_gem_object_list_info(struct seq_file *m, void *data)
{
struct drm_info_node *node = (struct drm_info_node *) m->private;
@@ -1463,6 +1470,7 @@ static int i915_context_status(struct seq_file *m, void *unused)

list_for_each_entry(ctx, &dev_priv->context_list, link) {
seq_puts(m, "HW context ");
+ describe_ctx(m, ctx);
for_each_ring(ring, dev_priv, i)
if (ring->default_context == ctx)
seq_printf(m, "(default context %s) ", ring->name);
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 1795927..015df52 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -601,6 +601,7 @@ struct i915_hw_context {
struct kref ref;
int id;
bool is_initialized;
+ uint8_t remap_slice;
struct drm_i915_file_private *file_priv;
struct intel_ring_buffer *ring;
struct drm_i915_gem_object *obj;
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 2bbdce8..9af3fe7 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -181,6 +181,10 @@ create_hw_context(struct drm_device *dev,

ctx->file_priv = file_priv;
ctx->id = ret;
+ /* NB: Mark all slices as needing a remap so that when the context first
+ * loads it will restore whatever remap state already exists. If there
+ * is no remap info, it will be a NOP. */
+ ctx->remap_slice = (1 << NUM_L3_SLICES(dev)) - 1;

return ctx;

@@ -396,11 +400,11 @@ static int do_switch(struct i915_hw_context *to)
struct intel_ring_buffer *ring = to->ring;
struct i915_hw_context *from = ring->last_context;
u32 hw_flags = 0;
- int ret;
+ int ret, i;

BUG_ON(from != NULL && from->obj != NULL && from->obj->pin_count == 0);

- if (from == to)
+ if (from == to && !to->remap_slice)
return 0;

ret = i915_gem_obj_ggtt_pin(to->obj, CONTEXT_ALIGN, false, false);
@@ -423,8 +427,6 @@ static int do_switch(struct i915_hw_context *to)

if (!to->is_initialized || is_default_context(to))
hw_flags |= MI_RESTORE_INHIBIT;
- else if (WARN_ON_ONCE(from == to)) /* not yet expected */
- hw_flags |= MI_FORCE_RESTORE;

ret = mi_set_context(ring, to, hw_flags);
if (ret) {
@@ -432,6 +434,18 @@ static int do_switch(struct i915_hw_context *to)
return ret;
}

+ for (i = 0; i < MAX_L3_SLICES; i++) {
+ if (!(to->remap_slice & (1<<i)))
+ continue;
+
+ ret = i915_gem_l3_remap(ring, i);
+ /* If it failed, try again next round */
+ if (ret)
+ DRM_DEBUG_DRIVER("L3 remapping failed\n");
+ else
+ to->remap_slice &= ~(1<<i);
+ }
+
/* The backing object for the context is done after switching to the
* *next* context. Therefore we cannot retire the previous context until
* the next context has already started running. In fact, the below code
diff --git a/drivers/gpu/drm/i915/i915_sysfs.c b/drivers/gpu/drm/i915/i915_sysfs.c
index b07bdfb..deb8787 100644
--- a/drivers/gpu/drm/i915/i915_sysfs.c
+++ b/drivers/gpu/drm/i915/i915_sysfs.c
@@ -118,9 +118,8 @@ i915_l3_read(struct file *filp, struct kobject *kobj,
struct drm_minor *dminor = container_of(dev, struct drm_minor, kdev);
struct drm_device *drm_dev = dminor->dev;
struct drm_i915_private *dev_priv = drm_dev->dev_private;
- uint32_t misccpctl;
int slice = (int)(uintptr_t)attr->private;
- int i, ret;
+ int ret;

count = round_down(count, 4);

@@ -134,26 +133,13 @@ i915_l3_read(struct file *filp, struct kobject *kobj,
if (ret)
return ret;

- if (IS_HASWELL(drm_dev)) {
- if (dev_priv->l3_parity.remap_info[slice])
- memcpy(buf,
- dev_priv->l3_parity.remap_info[slice] + (offset/4),
- count);
- else
- memset(buf, 0, count);
-
- goto out;
- }
-
- misccpctl = I915_READ(GEN7_MISCCPCTL);
- I915_WRITE(GEN7_MISCCPCTL, misccpctl & ~GEN7_DOP_CLOCK_GATE_ENABLE);
-
- for (i = 0; i < count; i += 4)
- *((uint32_t *)(&buf[i])) = I915_READ(GEN7_L3LOG_BASE + offset + i);
-
- I915_WRITE(GEN7_MISCCPCTL, misccpctl);
+ if (dev_priv->l3_parity.remap_info[slice])
+ memcpy(buf,
+ dev_priv->l3_parity.remap_info[slice] + (offset/4),
+ count);
+ else
+ memset(buf, 0, count);

-out:
mutex_unlock(&drm_dev->struct_mutex);

return count;
@@ -168,6 +154,7 @@ i915_l3_write(struct file *filp, struct kobject *kobj,
struct drm_minor *dminor = container_of(dev, struct drm_minor, kdev);
struct drm_device *drm_dev = dminor->dev;
struct drm_i915_private *dev_priv = drm_dev->dev_private;
+ struct i915_hw_context *ctx;
u32 *temp = NULL; /* Just here to make handling failures easy */
int slice = (int)(uintptr_t)attr->private;
int ret;
@@ -176,6 +163,9 @@ i915_l3_write(struct file *filp, struct kobject *kobj,
if (ret)
return ret;

+ if (dev_priv->hw_contexts_disabled)
+ return -ENXIO;
+
ret = i915_mutex_lock_interruptible(drm_dev);
if (ret)
return ret;
@@ -204,8 +194,9 @@ i915_l3_write(struct file *filp, struct kobject *kobj,

memcpy(dev_priv->l3_parity.remap_info[slice] + (offset/4), buf, count);

- if (i915_gem_l3_remap(&dev_priv->ring[RCS], slice))
- count = 0;
+ /* NB: We defer the remapping until we switch to the context */
+ list_for_each_entry(ctx, &dev_priv->context_list, link)
+ ctx->remap_slice |= (1<<slice);

mutex_unlock(&drm_dev->struct_mutex);

--
1.8.4

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