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drm/i915/guc: Simplify GuC doorbell logic 

All we're really doing is incrementing a simple counter in a
doorbell_info struct. We can do without extra variables and a separate
counter kept in guc_client. Since it's gone, we're also removing its
debugfs.
The only functional change here, is that we're no longer treating 0 as a
special value. GuC doesn't seem to care, why should we?

v2: Restore desc->tail update.
v3: Drop the retry loop, assert that doorbell cookie doesn't change
behind our back.
v4: WARN rather than BUG, use xchg. (Chris)

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170914105125.3031-1-michal.winiarski@intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
This commit is contained in:
Michał Winiarski 2017-09-14 12:51:23 +02:00 committed by Chris Wilson
parent 85e2fe679e
commit 59db36cf4d
3 changed files with 15 additions and 50 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/gpu/drm/i915/i915_debugfs.c
View File

@ -2445,8 +2445,8 @@ static void i915_guc_client_info(struct seq_file *m,
seq_printf(m, "\tPriority %d, GuC stage index: %u, PD offset 0x%x\n",
client->priority, client->stage_id, client->proc_desc_offset);
seq_printf(m, "\tDoorbell id %d, offset: 0x%lx, cookie 0x%x\n",
client->doorbell_id, client->doorbell_offset, client->doorbell_cookie);
seq_printf(m, "\tDoorbell id %d, offset: 0x%lx\n",
client->doorbell_id, client->doorbell_offset);
seq_printf(m, "\tWQ size %d, offset: 0x%x, tail %d\n",
client->wq_size, client->wq_offset, client->wq_tail);

60
drivers/gpu/drm/i915/i915_guc_submission.c
View File

@ -192,13 +192,12 @@ static int __create_doorbell(struct i915_guc_client *client)
doorbell = __get_doorbell(client);
doorbell->db_status = GUC_DOORBELL_ENABLED;
doorbell->cookie = client->doorbell_cookie;
doorbell->cookie = 0;
err = __guc_allocate_doorbell(client->guc, client->stage_id);
if (err) {
if (err)
doorbell->db_status = GUC_DOORBELL_DISABLED;
doorbell->cookie = 0;
}
return err;
}
@ -466,57 +465,24 @@ static void guc_reset_wq(struct i915_guc_client *client)
client->wq_tail = 0;
}
static int guc_ring_doorbell(struct i915_guc_client *client)
static void guc_ring_doorbell(struct i915_guc_client *client)
{
struct guc_process_desc *desc = __get_process_desc(client);
union guc_doorbell_qw db_cmp, db_exc, db_ret;
union guc_doorbell_qw *db;
int attempt = 2, ret = -EAGAIN;
struct guc_doorbell_info *db;
u32 cookie;
/* Update the tail so it is visible to GuC */
desc->tail = client->wq_tail;
/* current cookie */
db_cmp.db_status = GUC_DOORBELL_ENABLED;
db_cmp.cookie = client->doorbell_cookie;
/* cookie to be updated */
db_exc.db_status = GUC_DOORBELL_ENABLED;
db_exc.cookie = client->doorbell_cookie + 1;
if (db_exc.cookie == 0)
db_exc.cookie = 1;
/* pointer of current doorbell cacheline */
db = (union guc_doorbell_qw *)__get_doorbell(client);
db = __get_doorbell(client);
while (attempt--) {
/* lets ring the doorbell */
db_ret.value_qw = atomic64_cmpxchg((atomic64_t *)db,
db_cmp.value_qw, db_exc.value_qw);
/* we're not expecting the doorbell cookie to change behind our back */
cookie = READ_ONCE(db->cookie);
WARN_ON_ONCE(xchg(&db->cookie, cookie + 1) != cookie);
/* if the exchange was successfully executed */
if (db_ret.value_qw == db_cmp.value_qw) {
/* db was successfully rung */
client->doorbell_cookie = db_exc.cookie;
ret = 0;
break;
}
/* XXX: doorbell was lost and need to acquire it again */
if (db_ret.db_status == GUC_DOORBELL_DISABLED)
break;
DRM_WARN("Cookie mismatch. Expected %d, found %d\n",
db_cmp.cookie, db_ret.cookie);
/* update the cookie to newly read cookie from GuC */
db_cmp.cookie = db_ret.cookie;
db_exc.cookie = db_ret.cookie + 1;
if (db_exc.cookie == 0)
db_exc.cookie = 1;
}
return ret;
/* XXX: doorbell was lost and need to acquire it again */
GEM_BUG_ON(db->db_status != GUC_DOORBELL_ENABLED);
}
/**
@ -549,7 +515,7 @@ static void i915_guc_submit(struct intel_engine_cs *engine)
spin_lock(&client->wq_lock);
guc_wq_item_append(client, rq);
WARN_ON(guc_ring_doorbell(client));
guc_ring_doorbell(client);
client->submissions[engine_id] += 1;

1
drivers/gpu/drm/i915/intel_uc.h
View File

@ -66,7 +66,6 @@ struct i915_guc_client {
u16 doorbell_id;
unsigned long doorbell_offset;
u32 doorbell_cookie;
spinlock_t wq_lock;
uint32_t wq_offset;