With per-crtc locks modeset operations can run in parallel, and the cursor code uses the device-global evo master channel for hw frobbing. But the pageflip code can also sync with the master under some circumstances. Hence just wrap things up in a mutex to ensure that pushbuf access doesn't intermingle.
The approach here is a bit overkill since the per-crtc channels used to schedule the pageflips could probably be used without this pushbuf locking, but I'm not familiar enough with the nouveau codebase to be sure of that.
v2: Add missing mutex_init to avoid angering lockdep.
Signed-off-by: Daniel Vetter daniel.vetter@ffwll.ch --- drivers/gpu/drm/nouveau/nv50_display.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
diff --git a/drivers/gpu/drm/nouveau/nv50_display.c b/drivers/gpu/drm/nouveau/nv50_display.c index 3587408..d4cbea1 100644 --- a/drivers/gpu/drm/nouveau/nv50_display.c +++ b/drivers/gpu/drm/nouveau/nv50_display.c @@ -128,6 +128,11 @@ struct nv50_dmac { struct nv50_chan base; dma_addr_t handle; u32 *ptr; + + /* Protects against concurrent pushbuf access to this channel, lock is + * grabbed by evo_wait (if the pushbuf reservation is successful) and + * dropped again by evo_kick. */ + struct mutex lock; };
static void @@ -271,6 +276,8 @@ nv50_dmac_create(struct nouveau_object *core, u32 bclass, u8 head, u32 pushbuf = *(u32 *)data; int ret;
+ mutex_init(&dmac->lock); + dmac->ptr = pci_alloc_consistent(nv_device(core)->pdev, PAGE_SIZE, &dmac->handle); if (!dmac->ptr) @@ -395,11 +402,13 @@ evo_wait(void *evoc, int nr) struct nv50_dmac *dmac = evoc; u32 put = nv_ro32(dmac->base.user, 0x0000) / 4;
+ mutex_lock(&dmac->lock); if (put + nr >= (PAGE_SIZE / 4) - 8) { dmac->ptr[put] = 0x20000000;
nv_wo32(dmac->base.user, 0x0000, 0x00000000); if (!nv_wait(dmac->base.user, 0x0004, ~0, 0x00000000)) { + mutex_unlock(&dmac->lock); NV_ERROR(dmac->base.user, "channel stalled\n"); return NULL; } @@ -415,6 +424,7 @@ evo_kick(u32 *push, void *evoc) { struct nv50_dmac *dmac = evoc; nv_wo32(dmac->base.user, 0x0000, (push - dmac->ptr) << 2); + mutex_unlock(&dmac->lock); }
#define evo_mthd(p,m,s) *((p)++) = (((s) << 18) | (m))