[PATCH 2/2] drm/panfrost: Use coherent pagetable walk on Juno
robin.murphy at arm.com
Mon Sep 30 17:54:23 UTC 2019
On 30/09/2019 17:26, Steven Price wrote:
> On 30/09/2019 16:24, Robin Murphy wrote:
>> Although going full "dma-coherent" ends badly due to GEM objects still
>> being forcibly mapped non-cacheable, we can at least take advantage of
>> Juno's ACE-lite integration to skip cache maintenance for pagetables.
>> CC: Rob Herring <robh at kernel.org>
>> CC: Tomeu Vizoso <tomeu.vizoso at collabora.com>
>> Signed-off-by: Robin Murphy <robin.murphy at arm.com>
>> This isn't really meant as a series, I'm just sending it together
>> with patch #1 for context.
>> drivers/gpu/drm/panfrost/panfrost_mmu.c | 3 +++
>> 1 file changed, 3 insertions(+)
>> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
>> index bdd990568476..560439f63277 100644
>> --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
>> +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
>> @@ -365,6 +365,9 @@ int panfrost_mmu_pgtable_alloc(struct panfrost_file_priv *priv)
>> .iommu_dev = pfdev->dev,
>> + if (of_device_is_compatible(pfdev->dev->of_node, "arm,juno-mali"))
>> + pfdev->mmu->pgtbl_cfg.coherent_walk = true;
> Should be:
> mmu->pgtbl_cfg.coherent_walk = true;
Oops, yes, rebase error.
> Also I'm not sure whether we should do this based on a compatible
> string. kbase has a "system-coherency" device-tree flag for it. In
> theory we could end up with a long list of compatibles here...
Right, ideally we'd just infer everything we need from "dma-coherent",
but to be able to set that without causing fireworks we need the GEM
mmap implementation to be able to play along too. Maybe this can wait
until I figure out how to address that at the same time...
And either way, it would probably be better to detect anything
SoC-specific once at probe and stash it in a feature flag - TBH this
patch is more of a proof-of-concept than anything.
>> mmu->pgtbl_ops = alloc_io_pgtable_ops(ARM_MALI_LPAE, &mmu->pgtbl_cfg,
>> if (!mmu->pgtbl_ops)
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