Unfortunately the GC620 GPU seems to have broken PTA capibility, and
switching page table ID in command stream after it's running won't work.
As directly switching mtlb isn't working either, there will be no
reliable way to switch page table in the command stream, and a shared
context, like iommuv1, is needed.
Add support for this shared context situation. Shared context is set
when the broken PTA is known, and the context allocation code will be
made short circuit when a shared context is set.
Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
---
drivers/gpu/drm/etnaviv/etnaviv_iommu_v2.c | 8 ++++++++
drivers/gpu/drm/etnaviv/etnaviv_mmu.c | 1 +
drivers/gpu/drm/etnaviv/etnaviv_mmu.h | 2 ++
3 files changed, 11 insertions(+)
diff --git a/drivers/gpu/drm/etnaviv/etnaviv_iommu_v2.c b/drivers/gpu/drm/etnaviv/etnaviv_iommu_v2.c
index 5654a604c70cf..960ba3d659dc5 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_iommu_v2.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_iommu_v2.c
@@ -273,6 +273,12 @@ etnaviv_iommuv2_context_alloc(struct etnaviv_iommu_global *global)
struct etnaviv_iommu_context *context;
mutex_lock(&global->lock);
+ if (global->shared_context) {
+ context = global->shared_context;
+ etnaviv_iommu_context_get(context);
+ mutex_unlock(&global->lock);
+ return context;
+ }
v2_context = vzalloc(sizeof(*v2_context));
if (!v2_context)
@@ -301,6 +307,8 @@ etnaviv_iommuv2_context_alloc(struct etnaviv_iommu_global *global)
mutex_init(&context->lock);
INIT_LIST_HEAD(&context->mappings);
drm_mm_init(&context->mm, SZ_4K, (u64)SZ_1G * 4 - SZ_4K);
+ if (global->v2.broken_pta)
+ global->shared_context = context;
mutex_unlock(&global->lock);
return context;
diff --git a/drivers/gpu/drm/etnaviv/etnaviv_mmu.c b/drivers/gpu/drm/etnaviv/etnaviv_mmu.c
index df5192083b201..a0f9c950504e0 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_mmu.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_mmu.c
@@ -504,6 +504,7 @@ int etnaviv_iommu_global_init(struct etnaviv_gpu *gpu)
memset32(global->bad_page_cpu, 0xdead55aa, SZ_4K / sizeof(u32));
if (version == ETNAVIV_IOMMU_V2) {
+ global->v2.broken_pta = gpu->identity.model == chipModel_GC620;
global->v2.pta_cpu = dma_alloc_wc(dev, ETNAVIV_PTA_SIZE,
&global->v2.pta_dma, GFP_KERNEL);
if (!global->v2.pta_cpu)
diff --git a/drivers/gpu/drm/etnaviv/etnaviv_mmu.h b/drivers/gpu/drm/etnaviv/etnaviv_mmu.h
index 2ec4acda02bc6..5627d2a0d0237 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_mmu.h
+++ b/drivers/gpu/drm/etnaviv/etnaviv_mmu.h
@@ -55,6 +55,8 @@ struct etnaviv_iommu_global {
u64 *pta_cpu;
dma_addr_t pta_dma;
DECLARE_BITMAP(pta_alloc, ETNAVIV_PTA_ENTRIES);
+ /* Whether runtime switching page table ID will fail */
+ bool broken_pta;
} v2;
};
--
2.50.1在 2025-08-16星期六的 15:47 +0800，Icenowy Zheng写道：
> Unfortunately the GC620 GPU seems to have broken PTA capibility, and
> switching page table ID in command stream after it's running won't
> work.
> As directly switching mtlb isn't working either, there will be no
> reliable way to switch page table in the command stream, and a shared
> context, like iommuv1, is needed.
>
> Add support for this shared context situation. Shared context is set
> when the broken PTA is known, and the context allocation code will be
> made short circuit when a shared context is set.
>
> Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
> ---
> drivers/gpu/drm/etnaviv/etnaviv_iommu_v2.c | 8 ++++++++
> drivers/gpu/drm/etnaviv/etnaviv_mmu.c | 1 +
> drivers/gpu/drm/etnaviv/etnaviv_mmu.h | 2 ++
> 3 files changed, 11 insertions(+)
>
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_iommu_v2.c
> b/drivers/gpu/drm/etnaviv/etnaviv_iommu_v2.c
> index 5654a604c70cf..960ba3d659dc5 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_iommu_v2.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_iommu_v2.c
Well, I forgot to clean shared_context in etnaviv_iommuv2_free() when
the shared context is torn down...
> @@ -273,6 +273,12 @@ etnaviv_iommuv2_context_alloc(struct
> etnaviv_iommu_global *global)
> struct etnaviv_iommu_context *context;
>
> mutex_lock(&global->lock);
> + if (global->shared_context) {
> + context = global->shared_context;
> + etnaviv_iommu_context_get(context);
> + mutex_unlock(&global->lock);
> + return context;
> + }
>
> v2_context = vzalloc(sizeof(*v2_context));
> if (!v2_context)
> @@ -301,6 +307,8 @@ etnaviv_iommuv2_context_alloc(struct
> etnaviv_iommu_global *global)
> mutex_init(&context->lock);
> INIT_LIST_HEAD(&context->mappings);
> drm_mm_init(&context->mm, SZ_4K, (u64)SZ_1G * 4 - SZ_4K);
> + if (global->v2.broken_pta)
> + global->shared_context = context;
>
> mutex_unlock(&global->lock);
> return context;
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_mmu.c
> b/drivers/gpu/drm/etnaviv/etnaviv_mmu.c
> index df5192083b201..a0f9c950504e0 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_mmu.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_mmu.c
> @@ -504,6 +504,7 @@ int etnaviv_iommu_global_init(struct etnaviv_gpu
> *gpu)
> memset32(global->bad_page_cpu, 0xdead55aa, SZ_4K /
> sizeof(u32));
>
> if (version == ETNAVIV_IOMMU_V2) {
> + global->v2.broken_pta = gpu->identity.model ==
> chipModel_GC620;
> global->v2.pta_cpu = dma_alloc_wc(dev,
> ETNAVIV_PTA_SIZE,
> &global->v2.pta_dma,
> GFP_KERNEL);
> if (!global->v2.pta_cpu)
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_mmu.h
> b/drivers/gpu/drm/etnaviv/etnaviv_mmu.h
> index 2ec4acda02bc6..5627d2a0d0237 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_mmu.h
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_mmu.h
> @@ -55,6 +55,8 @@ struct etnaviv_iommu_global {
> u64 *pta_cpu;
> dma_addr_t pta_dma;
> DECLARE_BITMAP(pta_alloc, ETNAVIV_PTA_ENTRIES);
> + /* Whether runtime switching page table ID will fail
> */
> + bool broken_pta;
> } v2;
> };
>
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