[PATCH v2 4/7] drm/etnaviv: protect whole iommuv2 ctx alloc func under global mutex

[Icenowy Zheng]

As we are forced to use a global shared context on some
PTA-equipped-but-broken GPUs, the fine-grained mutex locking in the
current implemtnation of etnaviv_iommuv2_context_alloc() won't be
meaningful any more.

Make the whole function to be protected by the global lock, in order to
prevent reentrance when allocating global shared context.

Signed-off-by: Icenowy Zheng <u...@icenowy.me>
---
No changes in v2.

 drivers/gpu/drm/etnaviv/etnaviv_iommu_v2.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/etnaviv/etnaviv_iommu_v2.c 
b/drivers/gpu/drm/etnaviv/etnaviv_iommu_v2.c
index d664ae29ae209..5654a604c70cf 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_iommu_v2.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_iommu_v2.c
@@ -272,20 +272,18 @@ etnaviv_iommuv2_context_alloc(struct etnaviv_iommu_global 
*global)
        struct etnaviv_iommuv2_context *v2_context;
        struct etnaviv_iommu_context *context;
 
+       mutex_lock(&global->lock);
+
        v2_context = vzalloc(sizeof(*v2_context));
        if (!v2_context)
-               return NULL;
+               goto out_mutex_unlock;
 
-       mutex_lock(&global->lock);
        v2_context->id = find_first_zero_bit(global->v2.pta_alloc,
                                             ETNAVIV_PTA_ENTRIES);
-       if (v2_context->id < ETNAVIV_PTA_ENTRIES) {
+       if (v2_context->id < ETNAVIV_PTA_ENTRIES)
                set_bit(v2_context->id, global->v2.pta_alloc);
-       } else {
-               mutex_unlock(&global->lock);
+       else
                goto out_free;
-       }
-       mutex_unlock(&global->lock);
 
        v2_context->mtlb_cpu = dma_alloc_wc(global->dev, SZ_4K,
                                            &v2_context->mtlb_dma, GFP_KERNEL);
@@ -304,11 +302,14 @@ etnaviv_iommuv2_context_alloc(struct etnaviv_iommu_global 
*global)
        INIT_LIST_HEAD(&context->mappings);
        drm_mm_init(&context->mm, SZ_4K, (u64)SZ_1G * 4 - SZ_4K);
 
+       mutex_unlock(&global->lock);
        return context;
 
 out_free_id:
        clear_bit(v2_context->id, global->v2.pta_alloc);
 out_free:
        vfree(v2_context);
+out_mutex_unlock:
+       mutex_unlock(&global->lock);
        return NULL;
 }
-- 
2.51.0