Re: [PATCH v6 0/6] Allwinner H6 Mali GPU support

From: Robin Murphy <robin.murphy@arm.com>
To: "Tomeu Vizoso" <tomeu.vizoso@collabora.com>,
	"Clément Péron" <peron.clem@gmail.com>
Cc: David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Maxime Ripard <maxime.ripard@bootlin.com>,
	Chen-Yu Tsai <wens@csie.org>, Will Deacon <will.deacon@arm.com>,
	Joerg Roedel <joro@8bytes.org>,
	Neil Armstrong <narmstrong@baylibre.com>,
	Steven Price <steven.price@arm.com>,
	devicetree@vger.kernel.org,
	open list <linux-kernel@vger.kernel.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	Linux IOMMU <iommu@lists.linux-foundation.org>,
	"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v6 0/6] Allwinner H6 Mali GPU support
Date: Wed, 29 May 2019 18:38:29 +0100	[thread overview]
Message-ID: <4ff02295-6c34-791b-49f4-6558a92ad7a3@arm.com> (raw)
In-Reply-To: <CAAObsKD8bij1ANLqX6y11Y6mDEXiymNjrDkmHmvGWiFLKWu_FA@mail.gmail.com>

On 29/05/2019 16:09, Tomeu Vizoso wrote:
> On Tue, 21 May 2019 at 18:11, Clément Péron <peron.clem@gmail.com> wrote:
>>
> [snip]
>> [  345.204813] panfrost 1800000.gpu: mmu irq status=1
>> [  345.209617] panfrost 1800000.gpu: Unhandled Page fault in AS0 at VA
>> 0x0000000002400400
> 
>  From what I can see here, 0x0000000002400400 points to the first byte
> of the first submitted job descriptor.
> 
> So mapping buffers for the GPU doesn't seem to be working at all on
> 64-bit T-760.
> 
> Steven, Robin, do you have any idea of why this could be?

I tried rolling back to the old panfrost/nondrm shim, and it works fine 
with kbase, and I also found that T-820 falls over in the exact same 
manner, so the fact that it seemed to be common to the smaller 33-bit 
designs rather than anything to do with the other 
job_descriptor_size/v4/v5 complication turned out to be telling.

[ as an aside, are 64-bit jobs actually known not to work on v4 GPUs, or 
is it just that nobody's yet observed a 64-bit blob driving one? ]

Long story short, it appears that 'Mali LPAE' is also lacking the start 
level notion of VMSA, and expects a full 4-level table even for <40 bits 
when level 0 effectively redundant. Thus walking the 3-level table that 
io-pgtable comes back with ends up going wildly wrong. The hack below 
seems to do the job for me; if Clément can confirm (on T-720 you'll 
still need the userspace hack to force 32-bit jobs as well) then I think 
I'll cook up a proper refactoring of the allocator to put things right.

Robin.


----->8-----

diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index 546968d8a349..f29da6e8dc08 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -1023,12 +1023,14 @@ arm_mali_lpae_alloc_pgtable(struct 
io_pgtable_cfg *cfg, void *cookie)
  	iop = arm_64_lpae_alloc_pgtable_s1(cfg, cookie);
  	if (iop) {
  		u64 mair, ttbr;
+		struct arm_lpae_io_pgtable *data = io_pgtable_ops_to_data(&iop->ops);

+		data->levels = 4;
  		/* Copy values as union fields overlap */
  		mair = cfg->arm_lpae_s1_cfg.mair[0];
  		ttbr = cfg->arm_lpae_s1_cfg.ttbr[0];

