Subject: Re: [PATCH 3/3] arm64: dts: meson: Describe G12b GPU as coherent

From: Boris Brezillon <[email-masked]>
Date: Mon, 5 Oct 2020 10:39:39 +0200

On Mon, 5 Oct 2020 09:34:06 +0100
Steven Price <[email-masked]> wrote:

> On 05/10/2020 09:15, Boris Brezillon wrote:
> > Hi Robin, Neil,
> > 
> > On Wed, 16 Sep 2020 10:26:43 +0200
> > Neil Armstrong <[email-masked]> wrote:
> >   
> >> Hi Robin,
> >>
> >> On 16/09/2020 01:51, Robin Murphy wrote:  
> >>> According to a downstream commit I found in the Khadas vendor kernel,
> >>> the GPU on G12b is wired up for ACE-lite, so (now that Panfrost knows
> >>> how to handle this properly) we should describe it as such. Otherwise
> >>> the mismatch leads to all manner of fun with mismatched attributes and
> >>> inadvertently snooping stale data from caches, which would account for
> >>> at least some of the brokenness observed on this platform.
> >>>
> >>> Signed-off-by: Robin Murphy <[email-masked]>
> >>> ---
> >>>   arch/arm64/boot/dts/amlogic/meson-g12b.dtsi | 4 ++++
> >>>   1 file changed, 4 insertions(+)
> >>>
> >>> diff --git a/arch/arm64/boot/dts/amlogic/meson-g12b.dtsi b/arch/arm64/boot/dts/amlogic/meson-g12b.dtsi
> >>> index 9b8548e5f6e5..ee8fcae9f9f0 100644
> >>> --- a/arch/arm64/boot/dts/amlogic/meson-g12b.dtsi
> >>> +++ b/arch/arm64/boot/dts/amlogic/meson-g12b.dtsi
> >>> @@ -135,3 +135,7 @@ map1 {
> >>>   		};
> >>>   	};
> >>>   };
> >>> +
> >>> +&mali {
> >>> +	dma-coherent;
> >>> +};
> >>>      
> >>
> >> Thanks a lot for digging, I'll run a test to confirm it fixes the issue !  
> > 
> > Sorry for the late reply. I triggered a dEQP run with this patch applied
> > and I see a bunch of "panfrost ffe40000.gpu: matching BO is not heap type"
> > errors (see below for a full backtrace). That doesn't seem to happen when
> > we drop this dma-coherent property.
> > 
> > [  690.945731] ------------[ cut here ]------------
> > [  690.950003] panfrost ffe40000.gpu: matching BO is not heap type (GPU VA = 319a000)
> > [  690.950051] WARNING: CPU: 0 PID: 120 at drivers/gpu/drm/panfrost/panfrost_mmu.c:465 panfrost_mmu_irq_handler_thread+0x47c/0x650
> > [  690.968854] Modules linked in:
> > [  690.971878] CPU: 0 PID: 120 Comm: irq/27-panfrost Tainted: G        W         5.9.0-rc5-02434-g7d8109ec5a42 #784
> > [  690.981964] Hardware name: Khadas VIM3 (DT)
> > [  690.986107] pstate: 60000005 (nZCv daif -PAN -UAO BTYPE=--)
> > [  690.991627] pc : panfrost_mmu_irq_handler_thread+0x47c/0x650
> > [  690.997232] lr : panfrost_mmu_irq_handler_thread+0x47c/0x650
> > [  691.002836] sp : ffff800011bcbcd0
> > [  691.006114] x29: ffff800011bcbcf0 x28: ffff0000f3fe3800
> > [  691.011375] x27: ffff0000ceaf5350 x26: ffff0000ca5fc500
> > [  691.016636] x25: ffff0000f32409c0 x24: 0000000000000001
> > [  691.021897] x23: ffff0000f3240880 x22: ffff0000f3e3a800
> > [  691.027159] x21: 0000000000000000 x20: 0000000000000000
> > [  691.032420] x19: 0000000000010001 x18: 0000000000000020
> > [  691.037681] x17: 0000000000000000 x16: 0000000000000000
> > [  691.042942] x15: ffff0000f3fe3c70 x14: ffffffffffffffff
> > [  691.048204] x13: ffff8000116c2428 x12: ffff8000116c2086
> > [  691.053466] x11: ffff800011bcbcd0 x10: ffff800011bcbcd0
> > [  691.058727] x9 : 00000000fffffffe x8 : 0000000000000000
> > [  691.063988] x7 : 7420706165682074 x6 : ffff8000116c1816
> > [  691.069249] x5 : 0000000000000000 x4 : 0000000000000000
> > [  691.074510] x3 : 00000000ffffffff x2 : ffff8000e348c000
> > [  691.079771] x1 : f1b91ff9af2df000 x0 : 0000000000000000
> > [  691.085033] Call trace:
> > [  691.087452]  panfrost_mmu_irq_handler_thread+0x47c/0x650
> > [  691.092712]  irq_thread_fn+0x2c/0xa0
> > [  691.096246]  irq_thread+0x184/0x208
> > [  691.099699]  kthread+0x140/0x160
> > [  691.102890]  ret_from_fork+0x10/0x34
> > [  691.106424] ---[ end trace b5dd8c2dfada8236 ]---
> >   
> 
> It's quite possible this is caused by the GPU seeing a stale page table 
> entry, so perhaps coherency isn't working as well as it should...
> 
> Do you get an "Unhandled Page fault" message after this?

Yep (see below).

--->8---

[  689.640491] ------------[ cut here ]------------
[  689.644754] panfrost ffe40000.gpu: matching BO is not heap type (GPU VA = 3146000)
[  689.644802] WARNING: CPU: 0 PID: 120 at drivers/gpu/drm/panfrost/panfrost_mmu.c:465 panfrost_mmu_irq_handler_thread+0x47c/0x650
[  689.663607] Modules linked in:
[  689.666631] CPU: 0 PID: 120 Comm: irq/27-panfrost Tainted: G        W         5.9.0-rc5-02434-g7d8109ec5a42 #784
[  689.676717] Hardware name: Khadas VIM3 (DT)
[  689.680860] pstate: 60000005 (nZCv daif -PAN -UAO BTYPE=--)
[  689.686380] pc : panfrost_mmu_irq_handler_thread+0x47c/0x650
[  689.691987] lr : panfrost_mmu_irq_handler_thread+0x47c/0x650
[  689.697590] sp : ffff800011bcbcd0
[  689.700867] x29: ffff800011bcbcf0 x28: ffff0000f3fe3800 
[  689.706128] x27: ffff0000d89cf750 x26: ffff0000da34a800 
[  689.711389] x25: ffff0000f32409c0 x24: 0000000000000001 
[  689.716650] x23: ffff0000f3240880 x22: ffff0000d456e000 
[  689.721911] x21: 0000000000000000 x20: 0000000000000000 
[  689.727173] x19: 0000000000010001 x18: 0000000000000020 
[  689.732434] x17: 0000000000000000 x16: 0000000000000000 
[  689.737695] x15: ffff0000f3fe3c70 x14: ffffffffffffffff 
[  689.742957] x13: ffff8000116c2428 x12: ffff8000116c2086 
[  689.748218] x11: ffff800011bcbcd0 x10: ffff800011bcbcd0 
[  689.753479] x9 : 00000000fffffffe x8 : 0000000000000000 
[  689.758740] x7 : 7420706165682074 x6 : ffff8000116c1816 
[  689.764001] x5 : 0000000000000000 x4 : 0000000000000000 
[  689.769263] x3 : 00000000ffffffff x2 : ffff8000e348c000 
[  689.774524] x1 : f1b91ff9af2df000 x0 : 0000000000000000 
[  689.779786] Call trace:
[  689.782204]  panfrost_mmu_irq_handler_thread+0x47c/0x650
[  689.787465]  irq_thread_fn+0x2c/0xa0
[  689.790999]  irq_thread+0x184/0x208
[  689.794451]  kthread+0x140/0x160
[  689.797642]  ret_from_fork+0x10/0x34
[  689.801177] ---[ end trace b5dd8c2dfada8235 ]---
[  689.805864] panfrost ffe40000.gpu: Unhandled Page fault in AS0 at VA 0x0000000003146080
[  689.805864] Reason: TODO
[  689.805864] raw fault status: 0x10003C3
[  689.805864] decoded fault status: SLAVE FAULT
[  689.805864] exception type 0xC3: TRANSLATION_FAULT_LEVEL3
[  689.805864] access type 0x3: WRITE
[  689.805864] source id 0x100
[  690.170419] panfrost ffe40000.gpu: gpu sched timeout, js=1, config=0x7300, status=0x8, head=0x3101100, tail=0x3101100, sched_job=000000004b442768
[  690.770373] panfrost ffe40000.gpu: error powering up gpu shader
[  690.945123] panfrost ffe40000.gpu: error powering up gpu shader
[  690.945731] ------------[ cut here ]------------

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