drm/panfrost: Flush and disable address space when freeing page tables

Currently, page tables are freed without disabling the address space first.
This probably is fine as we'll switch to new page tables when the address
space is allocated again and runtime PM suspend will reset the GPU
clearing the registers. However, it's better to clean up after ourselves.
There is also a problem that we could be accessing the h/w in
tlb_inv_context() when suspended.

Rework the disable code to make sure we flush caches/TLBs and disable the
address space before freeing the page tables if we are not suspended. As
the tlb_inv_context() hook is only called when freeing the page tables and
we do a flush before disabling the AS, lets remove the flush from
tlb_inv_context and avoid any runtime PM issues.

Fixes: 7282f764 ("drm/panfrost: Implement per FD address spaces")
Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190826223317.28509-8-robh@kernel.org

drivers/gpu/drm/panfrost/panfrost_mmu.c

@@ -129,8 +129,10 @@ static void panfrost_mmu_enable(struct panfrost_device *pfdev, struct panfrost_m
 	write_cmd(pfdev, as_nr, AS_COMMAND_UPDATE);
 }
 
-static void mmu_disable(struct panfrost_device *pfdev, u32 as_nr)
+static void panfrost_mmu_disable(struct panfrost_device *pfdev, u32 as_nr)
 {
+	mmu_hw_do_operation_locked(pfdev, as_nr, 0, ~0UL, AS_COMMAND_FLUSH_MEM);
+
 	mmu_write(pfdev, AS_TRANSTAB_LO(as_nr), 0);
 	mmu_write(pfdev, AS_TRANSTAB_HI(as_nr), 0);
 
@@ -321,11 +323,7 @@ void panfrost_mmu_unmap(struct panfrost_gem_object *bo)
 }
 
 static void mmu_tlb_inv_context_s1(void *cookie)
-{
-	struct panfrost_file_priv *priv = cookie;
-
-	mmu_hw_do_operation(priv->pfdev, &priv->mmu, 0, ~0UL, AS_COMMAND_FLUSH_MEM);
-}
+{}
 
 static void mmu_tlb_inv_range_nosync(unsigned long iova, size_t size,
 				     size_t granule, bool leaf, void *cookie)
@@ -374,6 +372,11 @@ void panfrost_mmu_pgtable_free(struct panfrost_file_priv *priv)
 
 	spin_lock(&pfdev->as_lock);
 	if (mmu->as >= 0) {
+		pm_runtime_get_noresume(pfdev->dev);
+		if (pm_runtime_active(pfdev->dev))
+			panfrost_mmu_disable(pfdev, mmu->as);
+		pm_runtime_put_autosuspend(pfdev->dev);
+
 		clear_bit(mmu->as, &pfdev->as_alloc_mask);
 		clear_bit(mmu->as, &pfdev->as_in_use_mask);
 		list_del(&mmu->list);
@@ -618,5 +621,4 @@ int panfrost_mmu_init(struct panfrost_device *pfdev)
 void panfrost_mmu_fini(struct panfrost_device *pfdev)
 {
 	mmu_write(pfdev, MMU_INT_MASK, 0);
-	mmu_disable(pfdev, 0);
 }