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drm/i915: Dumb down the semaphore logic
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While I think the previous code is correct, it was hard to follow and
hard to debug. Since we already have a ring abstraction, might as well
use it to handle the semaphore updates and compares.

I don't expect this code to make semaphores better or worse, but you
never know...

v2:
Remove magic per Keith's suggestions.
Ran Daniel's gem_ring_sync_loop test on this.

v3:
Ignored one of Keith's suggestions.

v4:
Removed some bloat per Daniel's recommendation.

Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Keith Packard <keithp@keithp.com>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Keith Packard <keithp@keithp.com>
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Ben Widawsky authored and Keith Packard committed Sep 21, 2011
1 parent e0dac65 commit c8c99b0
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Showing 4 changed files with 126 additions and 47 deletions.
3 changes: 2 additions & 1 deletion drivers/gpu/drm/i915/i915_gem_execbuffer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -784,7 +784,8 @@ i915_gem_execbuffer_sync_rings(struct drm_i915_gem_object *obj,
}

from->sync_seqno[idx] = seqno;
return intel_ring_sync(to, from, seqno - 1);

return to->sync_to(to, from, seqno - 1);
}

static int
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13 changes: 13 additions & 0 deletions drivers/gpu/drm/i915/i915_reg.h
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Original file line number Diff line number Diff line change
Expand Up @@ -194,6 +194,13 @@
#define MI_SEMAPHORE_UPDATE (1<<21)
#define MI_SEMAPHORE_COMPARE (1<<20)
#define MI_SEMAPHORE_REGISTER (1<<18)
#define MI_SEMAPHORE_SYNC_RV (2<<16)
#define MI_SEMAPHORE_SYNC_RB (0<<16)
#define MI_SEMAPHORE_SYNC_VR (0<<16)
#define MI_SEMAPHORE_SYNC_VB (2<<16)
#define MI_SEMAPHORE_SYNC_BR (2<<16)
#define MI_SEMAPHORE_SYNC_BV (0<<16)
#define MI_SEMAPHORE_SYNC_INVALID (1<<0)
/*
* 3D instructions used by the kernel
*/
Expand Down Expand Up @@ -296,6 +303,12 @@
#define RING_CTL(base) ((base)+0x3c)
#define RING_SYNC_0(base) ((base)+0x40)
#define RING_SYNC_1(base) ((base)+0x44)
#define GEN6_RVSYNC (RING_SYNC_0(RENDER_RING_BASE))
#define GEN6_RBSYNC (RING_SYNC_1(RENDER_RING_BASE))
#define GEN6_VRSYNC (RING_SYNC_1(GEN6_BSD_RING_BASE))
#define GEN6_VBSYNC (RING_SYNC_0(GEN6_BSD_RING_BASE))
#define GEN6_BRSYNC (RING_SYNC_0(BLT_RING_BASE))
#define GEN6_BVSYNC (RING_SYNC_1(BLT_RING_BASE))
#define RING_MAX_IDLE(base) ((base)+0x54)
#define RING_HWS_PGA(base) ((base)+0x80)
#define RING_HWS_PGA_GEN6(base) ((base)+0x2080)
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149 changes: 106 additions & 43 deletions drivers/gpu/drm/i915/intel_ringbuffer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -315,79 +315,127 @@ static void render_ring_cleanup(struct intel_ring_buffer *ring)
}

static void
update_semaphore(struct intel_ring_buffer *ring, int i, u32 seqno)
update_mboxes(struct intel_ring_buffer *ring,
u32 seqno,
u32 mmio_offset)
{
struct drm_device *dev = ring->dev;
struct drm_i915_private *dev_priv = dev->dev_private;
int id;

/*
* cs -> 1 = vcs, 0 = bcs
* vcs -> 1 = bcs, 0 = cs,
* bcs -> 1 = cs, 0 = vcs.
*/
id = ring - dev_priv->ring;
id += 2 - i;
id %= 3;

intel_ring_emit(ring,
MI_SEMAPHORE_MBOX |
MI_SEMAPHORE_REGISTER |
MI_SEMAPHORE_UPDATE);
intel_ring_emit(ring, MI_SEMAPHORE_MBOX |
MI_SEMAPHORE_GLOBAL_GTT |
MI_SEMAPHORE_REGISTER |
MI_SEMAPHORE_UPDATE);
intel_ring_emit(ring, seqno);
intel_ring_emit(ring,
RING_SYNC_0(dev_priv->ring[id].mmio_base) + 4*i);
intel_ring_emit(ring, mmio_offset);
}

/**
* gen6_add_request - Update the semaphore mailbox registers
*
* @ring - ring that is adding a request
* @seqno - return seqno stuck into the ring
*
* Update the mailbox registers in the *other* rings with the current seqno.
* This acts like a signal in the canonical semaphore.
*/
static int
gen6_add_request(struct intel_ring_buffer *ring,
u32 *result)
u32 *seqno)
{
u32 seqno;
u32 mbox1_reg;
u32 mbox2_reg;
int ret;

ret = intel_ring_begin(ring, 10);
if (ret)
return ret;

seqno = i915_gem_get_seqno(ring->dev);
update_semaphore(ring, 0, seqno);
update_semaphore(ring, 1, seqno);
mbox1_reg = ring->signal_mbox[0];
mbox2_reg = ring->signal_mbox[1];

*seqno = i915_gem_get_seqno(ring->dev);

update_mboxes(ring, *seqno, mbox1_reg);
update_mboxes(ring, *seqno, mbox2_reg);
intel_ring_emit(ring, MI_STORE_DWORD_INDEX);
intel_ring_emit(ring, I915_GEM_HWS_INDEX << MI_STORE_DWORD_INDEX_SHIFT);
intel_ring_emit(ring, seqno);
intel_ring_emit(ring, *seqno);
intel_ring_emit(ring, MI_USER_INTERRUPT);
intel_ring_advance(ring);

*result = seqno;
return 0;
}

int
intel_ring_sync(struct intel_ring_buffer *ring,
struct intel_ring_buffer *to,
/**
* intel_ring_sync - sync the waiter to the signaller on seqno
*
* @waiter - ring that is waiting
* @signaller - ring which has, or will signal
* @seqno - seqno which the waiter will block on
*/
static int
intel_ring_sync(struct intel_ring_buffer *waiter,
struct intel_ring_buffer *signaller,
int ring,
u32 seqno)
{
int ret;
u32 dw1 = MI_SEMAPHORE_MBOX |
MI_SEMAPHORE_COMPARE |
MI_SEMAPHORE_REGISTER;

ret = intel_ring_begin(ring, 4);
ret = intel_ring_begin(waiter, 4);
if (ret)
return ret;

intel_ring_emit(ring,
MI_SEMAPHORE_MBOX |
MI_SEMAPHORE_REGISTER |
intel_ring_sync_index(ring, to) << 17 |
MI_SEMAPHORE_COMPARE);
intel_ring_emit(ring, seqno);
intel_ring_emit(ring, 0);
intel_ring_emit(ring, MI_NOOP);
intel_ring_advance(ring);
intel_ring_emit(waiter, dw1 | signaller->semaphore_register[ring]);
intel_ring_emit(waiter, seqno);
intel_ring_emit(waiter, 0);
intel_ring_emit(waiter, MI_NOOP);
intel_ring_advance(waiter);

return 0;
}

/* VCS->RCS (RVSYNC) or BCS->RCS (RBSYNC) */
int
render_ring_sync_to(struct intel_ring_buffer *waiter,
struct intel_ring_buffer *signaller,
u32 seqno)
{
WARN_ON(signaller->semaphore_register[RCS] == MI_SEMAPHORE_SYNC_INVALID);
return intel_ring_sync(waiter,
signaller,
RCS,
seqno);
}

/* RCS->VCS (VRSYNC) or BCS->VCS (VBSYNC) */
int
gen6_bsd_ring_sync_to(struct intel_ring_buffer *waiter,
struct intel_ring_buffer *signaller,
u32 seqno)
{
WARN_ON(signaller->semaphore_register[VCS] == MI_SEMAPHORE_SYNC_INVALID);
return intel_ring_sync(waiter,
signaller,
VCS,
seqno);
}

/* RCS->BCS (BRSYNC) or VCS->BCS (BVSYNC) */
int
gen6_blt_ring_sync_to(struct intel_ring_buffer *waiter,
struct intel_ring_buffer *signaller,
u32 seqno)
{
WARN_ON(signaller->semaphore_register[BCS] == MI_SEMAPHORE_SYNC_INVALID);
return intel_ring_sync(waiter,
signaller,
BCS,
seqno);
}



#define PIPE_CONTROL_FLUSH(ring__, addr__) \
do { \
intel_ring_emit(ring__, GFX_OP_PIPE_CONTROL | PIPE_CONTROL_QW_WRITE | \
Expand Down Expand Up @@ -1027,6 +1075,11 @@ static const struct intel_ring_buffer render_ring = {
.irq_put = render_ring_put_irq,
.dispatch_execbuffer = render_ring_dispatch_execbuffer,
.cleanup = render_ring_cleanup,
.sync_to = render_ring_sync_to,
.semaphore_register = {MI_SEMAPHORE_SYNC_INVALID,
MI_SEMAPHORE_SYNC_RV,
MI_SEMAPHORE_SYNC_RB},
.signal_mbox = {GEN6_VRSYNC, GEN6_BRSYNC},
};

/* ring buffer for bit-stream decoder */
Expand Down Expand Up @@ -1154,6 +1207,11 @@ static const struct intel_ring_buffer gen6_bsd_ring = {
.irq_get = gen6_bsd_ring_get_irq,
.irq_put = gen6_bsd_ring_put_irq,
.dispatch_execbuffer = gen6_ring_dispatch_execbuffer,
.sync_to = gen6_bsd_ring_sync_to,
.semaphore_register = {MI_SEMAPHORE_SYNC_VR,
MI_SEMAPHORE_SYNC_INVALID,
MI_SEMAPHORE_SYNC_VB},
.signal_mbox = {GEN6_RVSYNC, GEN6_BVSYNC},
};

/* Blitter support (SandyBridge+) */
Expand Down Expand Up @@ -1281,10 +1339,15 @@ static const struct intel_ring_buffer gen6_blt_ring = {
.flush = blt_ring_flush,
.add_request = gen6_add_request,
.get_seqno = ring_get_seqno,
.irq_get = blt_ring_get_irq,
.irq_put = blt_ring_put_irq,
.irq_get = blt_ring_get_irq,
.irq_put = blt_ring_put_irq,
.dispatch_execbuffer = gen6_ring_dispatch_execbuffer,
.cleanup = blt_ring_cleanup,
.cleanup = blt_ring_cleanup,
.sync_to = gen6_blt_ring_sync_to,
.semaphore_register = {MI_SEMAPHORE_SYNC_BR,
MI_SEMAPHORE_SYNC_BV,
MI_SEMAPHORE_SYNC_INVALID},
.signal_mbox = {GEN6_RBSYNC, GEN6_VBSYNC},
};

int intel_init_render_ring_buffer(struct drm_device *dev)
Expand Down
8 changes: 5 additions & 3 deletions drivers/gpu/drm/i915/intel_ringbuffer.h
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Original file line number Diff line number Diff line change
Expand Up @@ -75,7 +75,12 @@ struct intel_ring_buffer {
int (*dispatch_execbuffer)(struct intel_ring_buffer *ring,
u32 offset, u32 length);
void (*cleanup)(struct intel_ring_buffer *ring);
int (*sync_to)(struct intel_ring_buffer *ring,
struct intel_ring_buffer *to,
u32 seqno);

u32 semaphore_register[3]; /*our mbox written by others */
u32 signal_mbox[2]; /* mboxes this ring signals to */
/**
* List of objects currently involved in rendering from the
* ringbuffer.
Expand Down Expand Up @@ -180,9 +185,6 @@ static inline void intel_ring_emit(struct intel_ring_buffer *ring,
void intel_ring_advance(struct intel_ring_buffer *ring);

u32 intel_ring_get_seqno(struct intel_ring_buffer *ring);
int intel_ring_sync(struct intel_ring_buffer *ring,
struct intel_ring_buffer *to,
u32 seqno);

int intel_init_render_ring_buffer(struct drm_device *dev);
int intel_init_bsd_ring_buffer(struct drm_device *dev);
Expand Down

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