drm/i915/gtt: Introduce release_pd_entry

By encapsulating the locking upper level and used check for entry
into a helper function, we can use it in all callsites.

v2: get rid of atomic_reads on lower level clears (Chris)

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190705215204.4559-4-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 0a55b09..236c964 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -811,7 +811,25 @@ __clear_pd_entry(struct i915_page_directory * const pd,
        __set_pd_entry((pd), (pde), px_base(to), gen8_pde_encode)
 
 #define clear_pd_entry(pd, pde, to) \
-       __clear_pd_entry((pd), (pde), px_base(to), gen8_pde_encode)
+       __clear_pd_entry((pd), (pde), (to), gen8_pde_encode)
+
+static bool
+release_pd_entry(struct i915_page_directory * const pd,
+                const unsigned short pde,
+                atomic_t *counter,
+                struct i915_page_dma * const scratch)
+{
+       bool free = false;
+
+       spin_lock(&pd->lock);
+       if (atomic_dec_and_test(counter)) {
+               clear_pd_entry(pd, pde, scratch);
+               free = true;
+       }
+       spin_unlock(&pd->lock);
+
+       return free;
+}
 
 /*
  * PDE TLBs are a pain to invalidate on GEN8+. When we modify
@@ -827,11 +845,11 @@ static void mark_tlbs_dirty(struct i915_ppgtt *ppgtt)
 /* Removes entries from a single page table, releasing it if it's empty.
  * Caller can use the return value to update higher-level entries.
  */
-static bool gen8_ppgtt_clear_pt(const struct i915_address_space *vm,
+static void gen8_ppgtt_clear_pt(const struct i915_address_space *vm,
                                struct i915_page_table *pt,
                                u64 start, u64 length)
 {
-       unsigned int num_entries = gen8_pte_count(start, length);
+       const unsigned int num_entries = gen8_pte_count(start, length);
        gen8_pte_t *vaddr;
 
        vaddr = kmap_atomic_px(pt);
@@ -839,10 +857,11 @@ static bool gen8_ppgtt_clear_pt(const struct i915_address_space *vm,
        kunmap_atomic(vaddr);
 
        GEM_BUG_ON(num_entries > atomic_read(&pt->used));
-       return !atomic_sub_return(num_entries, &pt->used);
+
+       atomic_sub(num_entries, &pt->used);
 }
 
-static bool gen8_ppgtt_clear_pd(struct i915_address_space *vm,
+static void gen8_ppgtt_clear_pd(struct i915_address_space *vm,
                                struct i915_page_directory *pd,
                                u64 start, u64 length)
 {
@@ -850,30 +869,20 @@ static bool gen8_ppgtt_clear_pd(struct i915_address_space *vm,
        u32 pde;
 
        gen8_for_each_pde(pt, pd, start, length, pde) {
-               bool free = false;
-
                GEM_BUG_ON(pt == vm->scratch_pt);
 
-               if (!gen8_ppgtt_clear_pt(vm, pt, start, length))
-                       continue;
-
-               spin_lock(&pd->lock);
-               if (!atomic_read(&pt->used)) {
-                       clear_pd_entry(pd, pde, vm->scratch_pt);
-                       free = true;
-               }
-               spin_unlock(&pd->lock);
-               if (free)
+               atomic_inc(&pt->used);
+               gen8_ppgtt_clear_pt(vm, pt, start, length);
+               if (release_pd_entry(pd, pde, &pt->used,
+                                    px_base(vm->scratch_pt)))
                        free_pt(vm, pt);
        }
-
-       return !atomic_read(&pd->used);
 }
 
 /* Removes entries from a single page dir pointer, releasing it if it's empty.
  * Caller can use the return value to update higher-level entries
  */
-static bool gen8_ppgtt_clear_pdp(struct i915_address_space *vm,
+static void gen8_ppgtt_clear_pdp(struct i915_address_space *vm,
                                 struct i915_page_directory * const pdp,
                                 u64 start, u64 length)
 {
@@ -881,24 +890,14 @@ static bool gen8_ppgtt_clear_pdp(struct i915_address_space *vm,
        unsigned int pdpe;
 
        gen8_for_each_pdpe(pd, pdp, start, length, pdpe) {
-               bool free = false;
-
                GEM_BUG_ON(pd == vm->scratch_pd);
 
-               if (!gen8_ppgtt_clear_pd(vm, pd, start, length))
-                       continue;
-
-               spin_lock(&pdp->lock);
-               if (!atomic_read(&pd->used)) {
-                       clear_pd_entry(pdp, pdpe, vm->scratch_pd);
-                       free = true;
-               }
-               spin_unlock(&pdp->lock);
-               if (free)
+               atomic_inc(&pd->used);
+               gen8_ppgtt_clear_pd(vm, pd, start, length);
+               if (release_pd_entry(pdp, pdpe, &pd->used,
+                                    px_base(vm->scratch_pd)))
                        free_pd(vm, pd);
        }
-
-       return !atomic_read(&pdp->used);
 }
 
 static void gen8_ppgtt_clear_3lvl(struct i915_address_space *vm,
@@ -922,19 +921,12 @@ static void gen8_ppgtt_clear_4lvl(struct i915_address_space *vm,
        GEM_BUG_ON(!i915_vm_is_4lvl(vm));
 
        gen8_for_each_pml4e(pdp, pml4, start, length, pml4e) {
-               bool free = false;
                GEM_BUG_ON(pdp == vm->scratch_pdp);
 
-               if (!gen8_ppgtt_clear_pdp(vm, pdp, start, length))
-                       continue;
-
-               spin_lock(&pml4->lock);
-               if (!atomic_read(&pdp->used)) {
-                       clear_pd_entry(pml4, pml4e, vm->scratch_pdp);
-                       free = true;
-               }
-               spin_unlock(&pml4->lock);
-               if (free)
+               atomic_inc(&pdp->used);
+               gen8_ppgtt_clear_pdp(vm, pdp, start, length);
+               if (release_pd_entry(pml4, pml4e, &pdp->used,
+                                    px_base(vm->scratch_pdp)))
                        free_pd(vm, pdp);
        }
 }
@@ -1457,17 +1449,8 @@ static int gen8_ppgtt_alloc_pdp(struct i915_address_space *vm,
        goto out;
 
 unwind_pd:
-       if (alloc) {
-               free_pd(vm, alloc);
-               alloc = NULL;
-       }
-       spin_lock(&pdp->lock);
-       if (atomic_dec_and_test(&pd->used)) {
-               GEM_BUG_ON(alloc);
-               alloc = pd; /* defer the free to after the lock */
-               clear_pd_entry(pdp, pdpe, vm->scratch_pd);
-       }
-       spin_unlock(&pdp->lock);
+       if (release_pd_entry(pdp, pdpe, &pd->used, px_base(vm->scratch_pd)))
+               free_pd(vm, pd);
 unwind:
        gen8_ppgtt_clear_pdp(vm, pdp, from, start - from);
 out:
@@ -1530,17 +1513,8 @@ static int gen8_ppgtt_alloc_4lvl(struct i915_address_space *vm,
        goto out;
 
 unwind_pdp:
-       if (alloc) {
-               free_pd(vm, alloc);
-               alloc = NULL;
-       }
-       spin_lock(&pml4->lock);
-       if (atomic_dec_and_test(&pdp->used)) {
-               GEM_BUG_ON(alloc);
-               alloc = pdp; /* defer the free until after the lock */
-               clear_pd_entry(pml4, pml4e, vm->scratch_pdp);
-       }
-       spin_unlock(&pml4->lock);
+       if (release_pd_entry(pml4, pml4e, &pdp->used, px_base(vm->scratch_pdp)))
+               free_pd(vm, pdp);
 unwind:
        gen8_ppgtt_clear_4lvl(vm, from, start - from);
 out:
@@ -1570,11 +1544,7 @@ static int gen8_preallocate_top_level_pdp(struct i915_ppgtt *ppgtt)
        return 0;
 
 unwind:
-       start -= from;
-       gen8_for_each_pdpe(pd, pdp, from, start, pdpe) {
-               clear_pd_entry(pdp, pdpe, vm->scratch_pd);
-               free_pd(vm, pd);
-       }
+       gen8_ppgtt_clear_pdp(vm, pdp, from, start - from);
        atomic_set(&pdp->used, 0);
        return -ENOMEM;
 }