Address check for command buffer, etnaviv on Novena

Hello,

I am trying to get kernel 4.14-rc6 to run on my Novena imx6q board
with Debian experimental and Mesa 17.3.0-rc2 and ran into some problems with 
etnaviv complaining about "command buffer outside valid memory window".

I have a 256MB CMA allocation area set up at 0x70000000 in my 
devicetree.

While investigating how the buffer gets allocated at > 0x80000000,
I found the following suspicious part of a commit changing the address 
check:

commit c3ef4b8c3e108397980014a4616c56f50026d547
drm/etnaviv: wire up iova handling in new cmdbuf abstraction

@@ -703,7 +703,7 @@ int etnaviv_gpu_init(struct etnaviv_gpu *gpu)
         }

         if (gpu->mmu->version == ETNAVIV_IOMMU_V1 &&
-           gpu->buffer->paddr - gpu->memory_base > 0x80000000) {
+           etnaviv_cmdbuf_get_va(gpu->buffer) > 0x80000000) {
                 ret = -EINVAL;
                 dev_err(gpu->dev,
                         "command buffer outside valid memory window\n");


The implementations of in etnaviv_cmdbuf.c suggest that
etnaviv_cmdbuf_get_pa should be used to check physical addresses like
before the commit:

u32 etnaviv_cmdbuf_get_va(struct etnaviv_cmdbuf *buf)
{
	return buf->suballoc->iova + buf->suballoc_offset;
}

dma_addr_t etnaviv_cmdbuf_get_pa(struct etnaviv_cmdbuf *buf)
{
	return buf->suballoc->paddr + buf->suballoc_offset;
}

The values returned by etnaviv_cmdbuf_get_va are typically > 0xf0000000 
on my system, while etnaviv_cmdbuf_get_pa always returns a value between
0x70000000 and 0x80000000.

If I change etnaviv_cmdbuf_get_va to etnaviv_cmdbuf_get_pa, the address 
check
obviously passes, but I get gpu hangs.

I can either hang the GC320 unit starting X with xf86-video-armada:

[  189.026916] etnaviv-gpu 134000.gpu: hangcheck detected gpu lockup!
[  189.028946] etnaviv-gpu 134000.gpu:      completed fence: 29
[  189.030984] etnaviv-gpu 134000.gpu:      active fence: 34
[  189.033059] etnaviv-gpu 134000.gpu: hangcheck recover!

or the GC2000 unit when starting the Weston wayland compositor:

[  580.116792] etnaviv-gpu 130000.gpu: hangcheck detected gpu lockup!
[  580.116840] etnaviv-gpu 130000.gpu:      completed fence: 13
[  580.116855] etnaviv-gpu 130000.gpu:      active fence: 14
[  580.116893] etnaviv-gpu 130000.gpu: hangcheck recover!

Either way, I get a black screen and no other error indications than the dmesg 
messages.

I would love to hear your suggestions.

Jan Binder