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

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Message-ID: <4ff02295-6c34-791b-49f4-6558a92ad7a3@arm.com>
Date:   Wed, 29 May 2019 18:38:29 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Clément Péron <peron.clem@...il.com>
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Will Deacon <will.deacon@....com>,
        Joerg Roedel <joro@...tes.org>,
        Neil Armstrong <narmstrong@...libre.com>,
        Steven Price <steven.price@....com>,
        devicetree@...r.kernel.org,
        open list <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux IOMMU <iommu@...ts.linux-foundation.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v6 0/6] Allwinner H6 Mali GPU support

On 29/05/2019 16:09, Tomeu Vizoso wrote:
> On Tue, 21 May 2019 at 18:11, Clément Péron <peron.clem@...il.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];