[RFC] Deprecate AGP GART support for Radeon/Nouveau/TTM

[RFC] Deprecate AGP GART support for Radeon/Nouveau/TTM

[Christian König]

Unfortunately AGP is still to widely used as we could just drop support for using its GART.

Not using the AGP GART also doesn't mean a loss in functionality since drivers will just fallback to the driver specific PCI GART.

For now just deprecate the code and don't enable the AGP GART in TTM even when general AGP support is available.

Please comment,
Christian.


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[PATCH 1/2] drm/radeon: disable AGP by default

[Christian König]

Always use the PCI GART instead.

Signed-off-by: Christian König <christian.koenig@amd.com>
---
 drivers/gpu/drm/radeon/radeon_drv.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon_drv.c b/drivers/gpu/drm/radeon/radeon_drv.c
index bbb0883e8ce6..a71f13116d6b 100644
--- a/drivers/gpu/drm/radeon/radeon_drv.c
+++ b/drivers/gpu/drm/radeon/radeon_drv.c
@@ -171,12 +171,7 @@ int radeon_no_wb;
 int radeon_modeset = -1;
 int radeon_dynclks = -1;
 int radeon_r4xx_atom = 0;
-#ifdef __powerpc__
-/* Default to PCI on PowerPC (fdo #95017) */
 int radeon_agpmode = -1;
-#else
-int radeon_agpmode = 0;
-#endif
 int radeon_vram_limit = 0;
 int radeon_gart_size = -1; /* auto */
 int radeon_benchmarking = 0;
-- 
2.17.1

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[PATCH 2/2] drm/ttm: deprecate AGP support

[Christian König]

Even when core AGP support is compiled in Radeon and
Nouveau can also work with the PCI GART.

The AGP support was notorious unstable and hard to
maintain, so deprecate it for now and only enable it if
there is a good reason to do so.

Signed-off-by: Christian König <christian.koenig@amd.com>
---
 drivers/gpu/drm/Kconfig                       |  8 ++++++++
 drivers/gpu/drm/nouveau/nouveau_bo.c          |  8 ++++----
 drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h |  2 +-
 drivers/gpu/drm/radeon/radeon_agp.c           |  8 ++++----
 drivers/gpu/drm/radeon/radeon_ttm.c           | 10 +++++-----
 drivers/gpu/drm/ttm/Makefile                  |  2 +-
 6 files changed, 23 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 4f4e7fa001c1..52d834303766 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -182,6 +182,14 @@ config DRM_TTM
 	  GPU memory types. Will be enabled automatically if a device driver
 	  uses it.
 
+config DRM_TTM_AGP
+	bool "TTM AGP GART support (deprecated)"
+	depends on DRM_TTM && AGP
+	default n
+	help
+	  Enables deprecated AGP GART support in TTM.
+	  Less reliable than PCI GART, but faster in some cases.
+
 config DRM_TTM_DMA_PAGE_POOL
 	bool
 	depends on DRM_TTM && (SWIOTLB || INTEL_IOMMU)
diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
index c40f127de3d0..c73d4ae48f5c 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bo.c
+++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
@@ -635,7 +635,7 @@ nouveau_bo_wr32(struct nouveau_bo *nvbo, unsigned index, u32 val)
 static struct ttm_tt *
 nouveau_ttm_tt_create(struct ttm_buffer_object *bo, uint32_t page_flags)
 {
-#if IS_ENABLED(CONFIG_AGP)
+#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
 	struct nouveau_drm *drm = nouveau_bdev(bo->bdev);
 
 	if (drm->agp.bridge) {
@@ -1448,7 +1448,7 @@ nouveau_ttm_io_mem_reserve(struct ttm_bo_device *bdev, struct ttm_mem_reg *reg)
 		/* System memory */
 		return 0;
 	case TTM_PL_TT:
-#if IS_ENABLED(CONFIG_AGP)
+#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
 		if (drm->agp.bridge) {
 			reg->bus.offset = reg->start << PAGE_SHIFT;
 			reg->bus.base = drm->agp.base;
@@ -1603,7 +1603,7 @@ nouveau_ttm_tt_populate(struct ttm_tt *ttm, struct ttm_operation_ctx *ctx)
 	drm = nouveau_bdev(ttm->bdev);
 	dev = drm->dev->dev;
 
-#if IS_ENABLED(CONFIG_AGP)
+#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
 	if (drm->agp.bridge) {
 		return ttm_agp_tt_populate(ttm, ctx);
 	}
@@ -1656,7 +1656,7 @@ nouveau_ttm_tt_unpopulate(struct ttm_tt *ttm)
 	drm = nouveau_bdev(ttm->bdev);
 	dev = drm->dev->dev;
 
-#if IS_ENABLED(CONFIG_AGP)
+#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
 	if (drm->agp.bridge) {
 		ttm_agp_tt_unpopulate(ttm);
 		return;
diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h b/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h
index ad4d3621d02b..d572528da852 100644
--- a/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h
+++ b/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h
@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: MIT */
 #include "priv.h"
-#if defined(CONFIG_AGP) || (defined(CONFIG_AGP_MODULE) && defined(MODULE))
+#if defined(CONFIG_DRM_TTM_AGP)
 #ifndef __NVKM_PCI_AGP_H__
 #define __NVKM_PCI_AGP_H__
 
diff --git a/drivers/gpu/drm/radeon/radeon_agp.c b/drivers/gpu/drm/radeon/radeon_agp.c
index 0aca7bdf54c7..294d19301708 100644
--- a/drivers/gpu/drm/radeon/radeon_agp.c
+++ b/drivers/gpu/drm/radeon/radeon_agp.c
@@ -33,7 +33,7 @@
 
 #include "radeon.h"
 
-#if IS_ENABLED(CONFIG_AGP)
+#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
 
 struct radeon_agpmode_quirk {
 	u32 hostbridge_vendor;
@@ -131,7 +131,7 @@ static struct radeon_agpmode_quirk radeon_agpmode_quirk_list[] = {
 
 int radeon_agp_init(struct radeon_device *rdev)
 {
-#if IS_ENABLED(CONFIG_AGP)
+#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
 	struct radeon_agpmode_quirk *p = radeon_agpmode_quirk_list;
 	struct drm_agp_mode mode;
 	struct drm_agp_info info;
@@ -265,7 +265,7 @@ int radeon_agp_init(struct radeon_device *rdev)
 
 void radeon_agp_resume(struct radeon_device *rdev)
 {
-#if IS_ENABLED(CONFIG_AGP)
+#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
 	int r;
 	if (rdev->flags & RADEON_IS_AGP) {
 		r = radeon_agp_init(rdev);
@@ -277,7 +277,7 @@ void radeon_agp_resume(struct radeon_device *rdev)
 
 void radeon_agp_fini(struct radeon_device *rdev)
 {
-#if IS_ENABLED(CONFIG_AGP)
+#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
 	if (rdev->ddev->agp && rdev->ddev->agp->acquired) {
 		drm_agp_release(rdev->ddev);
 	}
diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
index 5d50c9edbe80..4f9c4e5f8263 100644
--- a/drivers/gpu/drm/radeon/radeon_ttm.c
+++ b/drivers/gpu/drm/radeon/radeon_ttm.c
@@ -86,7 +86,7 @@ static int radeon_init_mem_type(struct ttm_bo_device *bdev, uint32_t type,
 		man->available_caching = TTM_PL_MASK_CACHING;
 		man->default_caching = TTM_PL_FLAG_CACHED;
 		man->flags = TTM_MEMTYPE_FLAG_MAPPABLE | TTM_MEMTYPE_FLAG_CMA;
-#if IS_ENABLED(CONFIG_AGP)
+#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
 		if (rdev->flags & RADEON_IS_AGP) {
 			if (!rdev->ddev->agp) {
 				DRM_ERROR("AGP is not enabled for memory type %u\n",
@@ -411,7 +411,7 @@ static int radeon_ttm_io_mem_reserve(struct ttm_bo_device *bdev, struct ttm_mem_
 		/* system memory */
 		return 0;
 	case TTM_PL_TT:
-#if IS_ENABLED(CONFIG_AGP)
+#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
 		if (rdev->flags & RADEON_IS_AGP) {
 			/* RADEON_IS_AGP is set only if AGP is active */
 			mem->bus.offset = mem->start << PAGE_SHIFT;
@@ -631,7 +631,7 @@ static struct ttm_tt *radeon_ttm_tt_create(struct ttm_buffer_object *bo,
 	struct radeon_ttm_tt *gtt;
 
 	rdev = radeon_get_rdev(bo->bdev);
-#if IS_ENABLED(CONFIG_AGP)
+#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
 	if (rdev->flags & RADEON_IS_AGP) {
 		return ttm_agp_tt_create(bo, rdev->ddev->agp->bridge,
 					 page_flags);
@@ -683,7 +683,7 @@ static int radeon_ttm_tt_populate(struct ttm_tt *ttm,
 	}
 
 	rdev = radeon_get_rdev(ttm->bdev);
-#if IS_ENABLED(CONFIG_AGP)
+#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
 	if (rdev->flags & RADEON_IS_AGP) {
 		return ttm_agp_tt_populate(ttm, ctx);
 	}
@@ -714,7 +714,7 @@ static void radeon_ttm_tt_unpopulate(struct ttm_tt *ttm)
 		return;
 
 	rdev = radeon_get_rdev(ttm->bdev);
-#if IS_ENABLED(CONFIG_AGP)
+#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
 	if (rdev->flags & RADEON_IS_AGP) {
 		ttm_agp_tt_unpopulate(ttm);
 		return;
diff --git a/drivers/gpu/drm/ttm/Makefile b/drivers/gpu/drm/ttm/Makefile
index caea2a099496..aa772b198012 100644
--- a/drivers/gpu/drm/ttm/Makefile
+++ b/drivers/gpu/drm/ttm/Makefile
@@ -5,7 +5,7 @@
 ttm-y := ttm_memory.o ttm_tt.o ttm_bo.o \
 	ttm_bo_util.o ttm_bo_vm.o ttm_module.o \
 	ttm_execbuf_util.o ttm_page_alloc.o ttm_bo_manager.o
-ttm-$(CONFIG_AGP) += ttm_agp_backend.o
+ttm-$(CONFIG_DRM_TTM_AGP) += ttm_agp_backend.o
 ttm-$(CONFIG_DRM_TTM_DMA_PAGE_POOL) += ttm_page_alloc_dma.o
 
 obj-$(CONFIG_DRM_TTM) += ttm.o
-- 
2.17.1

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Re: [PATCH 1/2] drm/radeon: disable AGP by default

[Mathieu Malaterre]

On Wed, May 13, 2020 at 1:21 PM Christian König
<ckoenig.leichtzumerken@gmail.com> wrote:
>
> Always use the PCI GART instead.

Reviewed-by: Mathieu Malaterre <malat@debian.org>

> Signed-off-by: Christian König <christian.koenig@amd.com>
> ---
>  drivers/gpu/drm/radeon/radeon_drv.c | 5 -----
>  1 file changed, 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/radeon/radeon_drv.c b/drivers/gpu/drm/radeon/radeon_drv.c
> index bbb0883e8ce6..a71f13116d6b 100644
> --- a/drivers/gpu/drm/radeon/radeon_drv.c
> +++ b/drivers/gpu/drm/radeon/radeon_drv.c
> @@ -171,12 +171,7 @@ int radeon_no_wb;
>  int radeon_modeset = -1;
>  int radeon_dynclks = -1;
>  int radeon_r4xx_atom = 0;
> -#ifdef __powerpc__
> -/* Default to PCI on PowerPC (fdo #95017) */
>  int radeon_agpmode = -1;
> -#else
> -int radeon_agpmode = 0;
> -#endif
>  int radeon_vram_limit = 0;
>  int radeon_gart_size = -1; /* auto */
>  int radeon_benchmarking = 0;
> --
> 2.17.1
>


-- 
Mathieu
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Re: [PATCH 2/2] drm/ttm: deprecate AGP support

[Daniel Vetter]

On Wed, May 13, 2020 at 01:03:13PM +0200, Christian König wrote:
> Even when core AGP support is compiled in Radeon and
> Nouveau can also work with the PCI GART.
> 
> The AGP support was notorious unstable and hard to
> maintain, so deprecate it for now and only enable it if
> there is a good reason to do so.
> 
> Signed-off-by: Christian König <christian.koenig@amd.com>

So a lot more work, and more risk (but hey it's agp, how busted can it
get) could be to demidlayer this. I.e. a small set of helpers to create a
TTM_PL_TT manager, backed by agp. With zero agp code remaining in ttm
itself, and all the ttm agp code moved out to a ttm-agp-helper.ko module
that drivers would call.

But again a lot of work, so really only an option if we can't sunset agp
directly.
-Daniel

> ---
>  drivers/gpu/drm/Kconfig                       |  8 ++++++++
>  drivers/gpu/drm/nouveau/nouveau_bo.c          |  8 ++++----
>  drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h |  2 +-
>  drivers/gpu/drm/radeon/radeon_agp.c           |  8 ++++----
>  drivers/gpu/drm/radeon/radeon_ttm.c           | 10 +++++-----
>  drivers/gpu/drm/ttm/Makefile                  |  2 +-
>  6 files changed, 23 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index 4f4e7fa001c1..52d834303766 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -182,6 +182,14 @@ config DRM_TTM
>  	  GPU memory types. Will be enabled automatically if a device driver
>  	  uses it.
>  
> +config DRM_TTM_AGP
> +	bool "TTM AGP GART support (deprecated)"
> +	depends on DRM_TTM && AGP
> +	default n
> +	help
> +	  Enables deprecated AGP GART support in TTM.
> +	  Less reliable than PCI GART, but faster in some cases.
> +
>  config DRM_TTM_DMA_PAGE_POOL
>  	bool
>  	depends on DRM_TTM && (SWIOTLB || INTEL_IOMMU)
> diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
> index c40f127de3d0..c73d4ae48f5c 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_bo.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
> @@ -635,7 +635,7 @@ nouveau_bo_wr32(struct nouveau_bo *nvbo, unsigned index, u32 val)
>  static struct ttm_tt *
>  nouveau_ttm_tt_create(struct ttm_buffer_object *bo, uint32_t page_flags)
>  {
> -#if IS_ENABLED(CONFIG_AGP)
> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>  	struct nouveau_drm *drm = nouveau_bdev(bo->bdev);
>  
>  	if (drm->agp.bridge) {
> @@ -1448,7 +1448,7 @@ nouveau_ttm_io_mem_reserve(struct ttm_bo_device *bdev, struct ttm_mem_reg *reg)
>  		/* System memory */
>  		return 0;
>  	case TTM_PL_TT:
> -#if IS_ENABLED(CONFIG_AGP)
> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>  		if (drm->agp.bridge) {
>  			reg->bus.offset = reg->start << PAGE_SHIFT;
>  			reg->bus.base = drm->agp.base;
> @@ -1603,7 +1603,7 @@ nouveau_ttm_tt_populate(struct ttm_tt *ttm, struct ttm_operation_ctx *ctx)
>  	drm = nouveau_bdev(ttm->bdev);
>  	dev = drm->dev->dev;
>  
> -#if IS_ENABLED(CONFIG_AGP)
> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>  	if (drm->agp.bridge) {
>  		return ttm_agp_tt_populate(ttm, ctx);
>  	}
> @@ -1656,7 +1656,7 @@ nouveau_ttm_tt_unpopulate(struct ttm_tt *ttm)
>  	drm = nouveau_bdev(ttm->bdev);
>  	dev = drm->dev->dev;
>  
> -#if IS_ENABLED(CONFIG_AGP)
> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>  	if (drm->agp.bridge) {
>  		ttm_agp_tt_unpopulate(ttm);
>  		return;
> diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h b/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h
> index ad4d3621d02b..d572528da852 100644
> --- a/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h
> +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h
> @@ -1,6 +1,6 @@
>  /* SPDX-License-Identifier: MIT */
>  #include "priv.h"
> -#if defined(CONFIG_AGP) || (defined(CONFIG_AGP_MODULE) && defined(MODULE))
> +#if defined(CONFIG_DRM_TTM_AGP)
>  #ifndef __NVKM_PCI_AGP_H__
>  #define __NVKM_PCI_AGP_H__
>  
> diff --git a/drivers/gpu/drm/radeon/radeon_agp.c b/drivers/gpu/drm/radeon/radeon_agp.c
> index 0aca7bdf54c7..294d19301708 100644
> --- a/drivers/gpu/drm/radeon/radeon_agp.c
> +++ b/drivers/gpu/drm/radeon/radeon_agp.c
> @@ -33,7 +33,7 @@
>  
>  #include "radeon.h"
>  
> -#if IS_ENABLED(CONFIG_AGP)
> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>  
>  struct radeon_agpmode_quirk {
>  	u32 hostbridge_vendor;
> @@ -131,7 +131,7 @@ static struct radeon_agpmode_quirk radeon_agpmode_quirk_list[] = {
>  
>  int radeon_agp_init(struct radeon_device *rdev)
>  {
> -#if IS_ENABLED(CONFIG_AGP)
> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>  	struct radeon_agpmode_quirk *p = radeon_agpmode_quirk_list;
>  	struct drm_agp_mode mode;
>  	struct drm_agp_info info;
> @@ -265,7 +265,7 @@ int radeon_agp_init(struct radeon_device *rdev)
>  
>  void radeon_agp_resume(struct radeon_device *rdev)
>  {
> -#if IS_ENABLED(CONFIG_AGP)
> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>  	int r;
>  	if (rdev->flags & RADEON_IS_AGP) {
>  		r = radeon_agp_init(rdev);
> @@ -277,7 +277,7 @@ void radeon_agp_resume(struct radeon_device *rdev)
>  
>  void radeon_agp_fini(struct radeon_device *rdev)
>  {
> -#if IS_ENABLED(CONFIG_AGP)
> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>  	if (rdev->ddev->agp && rdev->ddev->agp->acquired) {
>  		drm_agp_release(rdev->ddev);
>  	}
> diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
> index 5d50c9edbe80..4f9c4e5f8263 100644
> --- a/drivers/gpu/drm/radeon/radeon_ttm.c
> +++ b/drivers/gpu/drm/radeon/radeon_ttm.c
> @@ -86,7 +86,7 @@ static int radeon_init_mem_type(struct ttm_bo_device *bdev, uint32_t type,
>  		man->available_caching = TTM_PL_MASK_CACHING;
>  		man->default_caching = TTM_PL_FLAG_CACHED;
>  		man->flags = TTM_MEMTYPE_FLAG_MAPPABLE | TTM_MEMTYPE_FLAG_CMA;
> -#if IS_ENABLED(CONFIG_AGP)
> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>  		if (rdev->flags & RADEON_IS_AGP) {
>  			if (!rdev->ddev->agp) {
>  				DRM_ERROR("AGP is not enabled for memory type %u\n",
> @@ -411,7 +411,7 @@ static int radeon_ttm_io_mem_reserve(struct ttm_bo_device *bdev, struct ttm_mem_
>  		/* system memory */
>  		return 0;
>  	case TTM_PL_TT:
> -#if IS_ENABLED(CONFIG_AGP)
> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>  		if (rdev->flags & RADEON_IS_AGP) {
>  			/* RADEON_IS_AGP is set only if AGP is active */
>  			mem->bus.offset = mem->start << PAGE_SHIFT;
> @@ -631,7 +631,7 @@ static struct ttm_tt *radeon_ttm_tt_create(struct ttm_buffer_object *bo,
>  	struct radeon_ttm_tt *gtt;
>  
>  	rdev = radeon_get_rdev(bo->bdev);
> -#if IS_ENABLED(CONFIG_AGP)
> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>  	if (rdev->flags & RADEON_IS_AGP) {
>  		return ttm_agp_tt_create(bo, rdev->ddev->agp->bridge,
>  					 page_flags);
> @@ -683,7 +683,7 @@ static int radeon_ttm_tt_populate(struct ttm_tt *ttm,
>  	}
>  
>  	rdev = radeon_get_rdev(ttm->bdev);
> -#if IS_ENABLED(CONFIG_AGP)
> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>  	if (rdev->flags & RADEON_IS_AGP) {
>  		return ttm_agp_tt_populate(ttm, ctx);
>  	}
> @@ -714,7 +714,7 @@ static void radeon_ttm_tt_unpopulate(struct ttm_tt *ttm)
>  		return;
>  
>  	rdev = radeon_get_rdev(ttm->bdev);
> -#if IS_ENABLED(CONFIG_AGP)
> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>  	if (rdev->flags & RADEON_IS_AGP) {
>  		ttm_agp_tt_unpopulate(ttm);
>  		return;
> diff --git a/drivers/gpu/drm/ttm/Makefile b/drivers/gpu/drm/ttm/Makefile
> index caea2a099496..aa772b198012 100644
> --- a/drivers/gpu/drm/ttm/Makefile
> +++ b/drivers/gpu/drm/ttm/Makefile
> @@ -5,7 +5,7 @@
>  ttm-y := ttm_memory.o ttm_tt.o ttm_bo.o \
>  	ttm_bo_util.o ttm_bo_vm.o ttm_module.o \
>  	ttm_execbuf_util.o ttm_page_alloc.o ttm_bo_manager.o
> -ttm-$(CONFIG_AGP) += ttm_agp_backend.o
> +ttm-$(CONFIG_DRM_TTM_AGP) += ttm_agp_backend.o
>  ttm-$(CONFIG_DRM_TTM_DMA_PAGE_POOL) += ttm_page_alloc_dma.o
>  
>  obj-$(CONFIG_DRM_TTM) += ttm.o
> -- 
> 2.17.1
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
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http://blog.ffwll.ch
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Re: [PATCH 2/2] drm/ttm: deprecate AGP support

[Christian König]

Am 13.05.20 um 14:34 schrieb Daniel Vetter:
> On Wed, May 13, 2020 at 01:03:13PM +0200, Christian König wrote:
>> Even when core AGP support is compiled in Radeon and
>> Nouveau can also work with the PCI GART.
>>
>> The AGP support was notorious unstable and hard to
>> maintain, so deprecate it for now and only enable it if
>> there is a good reason to do so.
>>
>> Signed-off-by: Christian König <christian.koenig@amd.com>
> So a lot more work, and more risk (but hey it's agp, how busted can it
> get) could be to demidlayer this. I.e. a small set of helpers to create a
> TTM_PL_TT manager, backed by agp. With zero agp code remaining in ttm
> itself, and all the ttm agp code moved out to a ttm-agp-helper.ko module
> that drivers would call.

Yes, exactly that's the idea which I have in mind for quite a while as well.

Problem is I have exactly one old x86 Mac to test this. Currently trying 
to get another old system up and running again.

That is not even remotely sufficient to test anything as large as this.

Regards,
Christian.

>
> But again a lot of work, so really only an option if we can't sunset agp
> directly.
> -Daniel
>
>> ---
>>   drivers/gpu/drm/Kconfig                       |  8 ++++++++
>>   drivers/gpu/drm/nouveau/nouveau_bo.c          |  8 ++++----
>>   drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h |  2 +-
>>   drivers/gpu/drm/radeon/radeon_agp.c           |  8 ++++----
>>   drivers/gpu/drm/radeon/radeon_ttm.c           | 10 +++++-----
>>   drivers/gpu/drm/ttm/Makefile                  |  2 +-
>>   6 files changed, 23 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
>> index 4f4e7fa001c1..52d834303766 100644
>> --- a/drivers/gpu/drm/Kconfig
>> +++ b/drivers/gpu/drm/Kconfig
>> @@ -182,6 +182,14 @@ config DRM_TTM
>>   	  GPU memory types. Will be enabled automatically if a device driver
>>   	  uses it.
>>   
>> +config DRM_TTM_AGP
>> +	bool "TTM AGP GART support (deprecated)"
>> +	depends on DRM_TTM && AGP
>> +	default n
>> +	help
>> +	  Enables deprecated AGP GART support in TTM.
>> +	  Less reliable than PCI GART, but faster in some cases.
>> +
>>   config DRM_TTM_DMA_PAGE_POOL
>>   	bool
>>   	depends on DRM_TTM && (SWIOTLB || INTEL_IOMMU)
>> diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
>> index c40f127de3d0..c73d4ae48f5c 100644
>> --- a/drivers/gpu/drm/nouveau/nouveau_bo.c
>> +++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
>> @@ -635,7 +635,7 @@ nouveau_bo_wr32(struct nouveau_bo *nvbo, unsigned index, u32 val)
>>   static struct ttm_tt *
>>   nouveau_ttm_tt_create(struct ttm_buffer_object *bo, uint32_t page_flags)
>>   {
>> -#if IS_ENABLED(CONFIG_AGP)
>> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>>   	struct nouveau_drm *drm = nouveau_bdev(bo->bdev);
>>   
>>   	if (drm->agp.bridge) {
>> @@ -1448,7 +1448,7 @@ nouveau_ttm_io_mem_reserve(struct ttm_bo_device *bdev, struct ttm_mem_reg *reg)
>>   		/* System memory */
>>   		return 0;
>>   	case TTM_PL_TT:
>> -#if IS_ENABLED(CONFIG_AGP)
>> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>>   		if (drm->agp.bridge) {
>>   			reg->bus.offset = reg->start << PAGE_SHIFT;
>>   			reg->bus.base = drm->agp.base;
>> @@ -1603,7 +1603,7 @@ nouveau_ttm_tt_populate(struct ttm_tt *ttm, struct ttm_operation_ctx *ctx)
>>   	drm = nouveau_bdev(ttm->bdev);
>>   	dev = drm->dev->dev;
>>   
>> -#if IS_ENABLED(CONFIG_AGP)
>> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>>   	if (drm->agp.bridge) {
>>   		return ttm_agp_tt_populate(ttm, ctx);
>>   	}
>> @@ -1656,7 +1656,7 @@ nouveau_ttm_tt_unpopulate(struct ttm_tt *ttm)
>>   	drm = nouveau_bdev(ttm->bdev);
>>   	dev = drm->dev->dev;
>>   
>> -#if IS_ENABLED(CONFIG_AGP)
>> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>>   	if (drm->agp.bridge) {
>>   		ttm_agp_tt_unpopulate(ttm);
>>   		return;
>> diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h b/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h
>> index ad4d3621d02b..d572528da852 100644
>> --- a/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h
>> +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/pci/agp.h
>> @@ -1,6 +1,6 @@
>>   /* SPDX-License-Identifier: MIT */
>>   #include "priv.h"
>> -#if defined(CONFIG_AGP) || (defined(CONFIG_AGP_MODULE) && defined(MODULE))
>> +#if defined(CONFIG_DRM_TTM_AGP)
>>   #ifndef __NVKM_PCI_AGP_H__
>>   #define __NVKM_PCI_AGP_H__
>>   
>> diff --git a/drivers/gpu/drm/radeon/radeon_agp.c b/drivers/gpu/drm/radeon/radeon_agp.c
>> index 0aca7bdf54c7..294d19301708 100644
>> --- a/drivers/gpu/drm/radeon/radeon_agp.c
>> +++ b/drivers/gpu/drm/radeon/radeon_agp.c
>> @@ -33,7 +33,7 @@
>>   
>>   #include "radeon.h"
>>   
>> -#if IS_ENABLED(CONFIG_AGP)
>> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>>   
>>   struct radeon_agpmode_quirk {
>>   	u32 hostbridge_vendor;
>> @@ -131,7 +131,7 @@ static struct radeon_agpmode_quirk radeon_agpmode_quirk_list[] = {
>>   
>>   int radeon_agp_init(struct radeon_device *rdev)
>>   {
>> -#if IS_ENABLED(CONFIG_AGP)
>> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>>   	struct radeon_agpmode_quirk *p = radeon_agpmode_quirk_list;
>>   	struct drm_agp_mode mode;
>>   	struct drm_agp_info info;
>> @@ -265,7 +265,7 @@ int radeon_agp_init(struct radeon_device *rdev)
>>   
>>   void radeon_agp_resume(struct radeon_device *rdev)
>>   {
>> -#if IS_ENABLED(CONFIG_AGP)
>> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>>   	int r;
>>   	if (rdev->flags & RADEON_IS_AGP) {
>>   		r = radeon_agp_init(rdev);
>> @@ -277,7 +277,7 @@ void radeon_agp_resume(struct radeon_device *rdev)
>>   
>>   void radeon_agp_fini(struct radeon_device *rdev)
>>   {
>> -#if IS_ENABLED(CONFIG_AGP)
>> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>>   	if (rdev->ddev->agp && rdev->ddev->agp->acquired) {
>>   		drm_agp_release(rdev->ddev);
>>   	}
>> diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
>> index 5d50c9edbe80..4f9c4e5f8263 100644
>> --- a/drivers/gpu/drm/radeon/radeon_ttm.c
>> +++ b/drivers/gpu/drm/radeon/radeon_ttm.c
>> @@ -86,7 +86,7 @@ static int radeon_init_mem_type(struct ttm_bo_device *bdev, uint32_t type,
>>   		man->available_caching = TTM_PL_MASK_CACHING;
>>   		man->default_caching = TTM_PL_FLAG_CACHED;
>>   		man->flags = TTM_MEMTYPE_FLAG_MAPPABLE | TTM_MEMTYPE_FLAG_CMA;
>> -#if IS_ENABLED(CONFIG_AGP)
>> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>>   		if (rdev->flags & RADEON_IS_AGP) {
>>   			if (!rdev->ddev->agp) {
>>   				DRM_ERROR("AGP is not enabled for memory type %u\n",
>> @@ -411,7 +411,7 @@ static int radeon_ttm_io_mem_reserve(struct ttm_bo_device *bdev, struct ttm_mem_
>>   		/* system memory */
>>   		return 0;
>>   	case TTM_PL_TT:
>> -#if IS_ENABLED(CONFIG_AGP)
>> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>>   		if (rdev->flags & RADEON_IS_AGP) {
>>   			/* RADEON_IS_AGP is set only if AGP is active */
>>   			mem->bus.offset = mem->start << PAGE_SHIFT;
>> @@ -631,7 +631,7 @@ static struct ttm_tt *radeon_ttm_tt_create(struct ttm_buffer_object *bo,
>>   	struct radeon_ttm_tt *gtt;
>>   
>>   	rdev = radeon_get_rdev(bo->bdev);
>> -#if IS_ENABLED(CONFIG_AGP)
>> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>>   	if (rdev->flags & RADEON_IS_AGP) {
>>   		return ttm_agp_tt_create(bo, rdev->ddev->agp->bridge,
>>   					 page_flags);
>> @@ -683,7 +683,7 @@ static int radeon_ttm_tt_populate(struct ttm_tt *ttm,
>>   	}
>>   
>>   	rdev = radeon_get_rdev(ttm->bdev);
>> -#if IS_ENABLED(CONFIG_AGP)
>> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>>   	if (rdev->flags & RADEON_IS_AGP) {
>>   		return ttm_agp_tt_populate(ttm, ctx);
>>   	}
>> @@ -714,7 +714,7 @@ static void radeon_ttm_tt_unpopulate(struct ttm_tt *ttm)
>>   		return;
>>   
>>   	rdev = radeon_get_rdev(ttm->bdev);
>> -#if IS_ENABLED(CONFIG_AGP)
>> +#if IS_ENABLED(CONFIG_DRM_TTM_AGP)
>>   	if (rdev->flags & RADEON_IS_AGP) {
>>   		ttm_agp_tt_unpopulate(ttm);
>>   		return;
>> diff --git a/drivers/gpu/drm/ttm/Makefile b/drivers/gpu/drm/ttm/Makefile
>> index caea2a099496..aa772b198012 100644
>> --- a/drivers/gpu/drm/ttm/Makefile
>> +++ b/drivers/gpu/drm/ttm/Makefile
>> @@ -5,7 +5,7 @@
>>   ttm-y := ttm_memory.o ttm_tt.o ttm_bo.o \
>>   	ttm_bo_util.o ttm_bo_vm.o ttm_module.o \
>>   	ttm_execbuf_util.o ttm_page_alloc.o ttm_bo_manager.o
>> -ttm-$(CONFIG_AGP) += ttm_agp_backend.o
>> +ttm-$(CONFIG_DRM_TTM_AGP) += ttm_agp_backend.o
>>   ttm-$(CONFIG_DRM_TTM_DMA_PAGE_POOL) += ttm_page_alloc_dma.o
>>   
>>   obj-$(CONFIG_DRM_TTM) += ttm.o
>> -- 
>> 2.17.1
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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Re: [RFC] Deprecate AGP GART support for Radeon/Nouveau/TTM

[Christian König]

Am 13.05.20 um 13:03 schrieb Christian König:
> Unfortunately AGP is still to widely used as we could just drop support for using its GART.
>
> Not using the AGP GART also doesn't mean a loss in functionality since drivers will just fallback to the driver specific PCI GART.
>
> For now just deprecate the code and don't enable the AGP GART in TTM even when general AGP support is available.

So I've used an ancient system (32bit) to setup a test box for this.


The first GPU I could test is an RV280 (Radeon 9200 PRO) which is easily 
15 years old.

What happens in AGP mode is that glxgears shows artifacts during 
rendering on this system.

In PCI mode those rendering artifacts are gone and glxgears seems to 
draw everything correctly now.

Performance is obviously not comparable, cause in AGP we don't render 
all triangles correctly.


The second GPU I could test is an RV630 PRO (Radeon HD 2600 PRO AGP) 
which is more than 10 years old.

As far as I can tell this one works in both AGP and PCIe mode perfectly 
fine.

Since this is only a 32bit system I couldn't really test any OpenGL game 
that well.

But for glxgears switching from AGP to PCIe mode seems to result in a 
roughly 5% performance drop.

The surprising reason for this is not the better TLB performance, but 
the lack of USWC support for the PCIe GART in radeon.


So if anybody wants to get his hands dirty and squeeze a bit more 
performance out of the old hardware, porting USWC from amdgpu to radeon 
shouldn't be to much of a problem.


Summing it up I'm still leaning towards disabling AGP completely by 
default for radeon and deprecate it in TTM as well.

Thoughts? Especially Alex what do you think.

Regards,
Christian.
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Re: [RFC] Deprecate AGP GART support for Radeon/Nouveau/TTM

[Rui Salvaterra]

Hi, Christian,

On Wed, 20 May 2020 at 16:00, Christian König
<ckoenig.leichtzumerken@gmail.com> wrote:
>
> So I've used an ancient system (32bit) to setup a test box for this.
>
>
> The first GPU I could test is an RV280 (Radeon 9200 PRO) which is easily
> 15 years old.

Oh, I have one of those in box somewhere, but no AGP machine to
install it (yet).

> What happens in AGP mode is that glxgears shows artifacts during
> rendering on this system.
>
> In PCI mode those rendering artifacts are gone and glxgears seems to
> draw everything correctly now.
>
> Performance is obviously not comparable, cause in AGP we don't render
> all triangles correctly.

I agree, correctness before performance, always.

> The second GPU I could test is an RV630 PRO (Radeon HD 2600 PRO AGP)
> which is more than 10 years old.
>
> As far as I can tell this one works in both AGP and PCIe mode perfectly
> fine.
>
> Since this is only a 32bit system I couldn't really test any OpenGL game
> that well.

I usually test with my distro's (Debian or Ubuntu, in my case) games.
For example, I used Nexuiz when wiring up the shader cache on r300g.

> But for glxgears switching from AGP to PCIe mode seems to result in a
> roughly 5% performance drop.
>
> The surprising reason for this is not the better TLB performance, but
> the lack of USWC support for the PCIe GART in radeon.
>
> So if anybody wants to get his hands dirty and squeeze a bit more
> performance out of the old hardware, porting USWC from amdgpu to radeon
> shouldn't be to much of a problem.

Well, FWIW, I would argue that a regression in performance, if
avoidable, should be avoided. I have not nearly enough knowledge of
the driver to do it myself, but I'll glady test any patches, on both
x86-64 (Radeon Xpress 1250) and ppc32 (Mobility Radeon 9550).

Cheers,
Rui
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Re: [RFC] Deprecate AGP GART support for Radeon/Nouveau/TTM

[Alex Deucher]

On Wed, May 20, 2020 at 10:43 AM Christian König
<ckoenig.leichtzumerken@gmail.com> wrote:
>
> Am 13.05.20 um 13:03 schrieb Christian König:
> > Unfortunately AGP is still to widely used as we could just drop support for using its GART.
> >
> > Not using the AGP GART also doesn't mean a loss in functionality since drivers will just fallback to the driver specific PCI GART.
> >
> > For now just deprecate the code and don't enable the AGP GART in TTM even when general AGP support is available.
>
> So I've used an ancient system (32bit) to setup a test box for this.
>
>
> The first GPU I could test is an RV280 (Radeon 9200 PRO) which is easily
> 15 years old.
>
> What happens in AGP mode is that glxgears shows artifacts during
> rendering on this system.
>
> In PCI mode those rendering artifacts are gone and glxgears seems to
> draw everything correctly now.
>
> Performance is obviously not comparable, cause in AGP we don't render
> all triangles correctly.
>
>
> The second GPU I could test is an RV630 PRO (Radeon HD 2600 PRO AGP)
> which is more than 10 years old.
>
> As far as I can tell this one works in both AGP and PCIe mode perfectly
> fine.
>
> Since this is only a 32bit system I couldn't really test any OpenGL game
> that well.
>
> But for glxgears switching from AGP to PCIe mode seems to result in a
> roughly 5% performance drop.
>
> The surprising reason for this is not the better TLB performance, but
> the lack of USWC support for the PCIe GART in radeon.
>
>
> So if anybody wants to get his hands dirty and squeeze a bit more
> performance out of the old hardware, porting USWC from amdgpu to radeon
> shouldn't be to much of a problem.

We do support USWC on radeon, although I think we had separate flags
for cached and WC.  That said we had a lot of problems with WC on 32
bit (see radeon_bo_create()).  The other problem is that, at least on
the really old radeons, the PCI gart didn't support snooped and
unsnooped.  It was always snooped.  It wasn't until pcie that the gart
hw got support for both.  For AGP, the expectation was that AGP
provided the uncached memory.

>
>
> Summing it up I'm still leaning towards disabling AGP completely by
> default for radeon and deprecate it in TTM as well.
>
> Thoughts? Especially Alex what do you think.

Works for me.

Alex
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Re: [RFC] Deprecate AGP GART support for Radeon/Nouveau/TTM

[Michel Dänzer]

On 2020-05-20 4:43 p.m., Christian König wrote:
> Am 13.05.20 um 13:03 schrieb Christian König:
>> Unfortunately AGP is still to widely used as we could just drop
>> support for using its GART.
>>
>> Not using the AGP GART also doesn't mean a loss in functionality since
>> drivers will just fallback to the driver specific PCI GART.
>>
>> For now just deprecate the code and don't enable the AGP GART in TTM
>> even when general AGP support is available.
> 
> So I've used an ancient system (32bit) to setup a test box for this.
> 
> 
> The first GPU I could test is an RV280 (Radeon 9200 PRO) which is easily
> 15 years old.
> 
> What happens in AGP mode is that glxgears shows artifacts during
> rendering on this system.
> 
> In PCI mode those rendering artifacts are gone and glxgears seems to
> draw everything correctly now.
> 
> Performance is obviously not comparable, cause in AGP we don't render
> all triangles correctly.
> 
> 
> The second GPU I could test is an RV630 PRO (Radeon HD 2600 PRO AGP)
> which is more than 10 years old.
> 
> As far as I can tell this one works in both AGP and PCIe mode perfectly
> fine.
> 
> Since this is only a 32bit system I couldn't really test any OpenGL game
> that well.
> 
> But for glxgears switching from AGP to PCIe mode seems to result in a
> roughly 5% performance drop.
> 
> The surprising reason for this is not the better TLB performance, but
> the lack of USWC support for the PCIe GART in radeon.

I suspect the main reason it's only 5% is that PCIe GART page tables are
stored in VRAM, so they don't need to be fetched across the PCIe link
(and presumably it has more than one TLB entry as well). The difference
is much bigger with native AGP ASICs with PCI GART.


-- 
Earthling Michel Dänzer               |               https://redhat.com
Libre software enthusiast             |             Mesa and X developer
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Re: [RFC] Deprecate AGP GART support for Radeon/Nouveau/TTM

[Christian König]

Am 20.05.20 um 18:25 schrieb Michel Dänzer:
> On 2020-05-20 4:43 p.m., Christian König wrote:
>> Am 13.05.20 um 13:03 schrieb Christian König:
>>> Unfortunately AGP is still to widely used as we could just drop
>>> support for using its GART.
>>>
>>> Not using the AGP GART also doesn't mean a loss in functionality since
>>> drivers will just fallback to the driver specific PCI GART.
>>>
>>> For now just deprecate the code and don't enable the AGP GART in TTM
>>> even when general AGP support is available.
>> So I've used an ancient system (32bit) to setup a test box for this.
>>
>>
>> The first GPU I could test is an RV280 (Radeon 9200 PRO) which is easily
>> 15 years old.
>>
>> What happens in AGP mode is that glxgears shows artifacts during
>> rendering on this system.
>>
>> In PCI mode those rendering artifacts are gone and glxgears seems to
>> draw everything correctly now.
>>
>> Performance is obviously not comparable, cause in AGP we don't render
>> all triangles correctly.
>>
>>
>> The second GPU I could test is an RV630 PRO (Radeon HD 2600 PRO AGP)
>> which is more than 10 years old.
>>
>> As far as I can tell this one works in both AGP and PCIe mode perfectly
>> fine.
>>
>> Since this is only a 32bit system I couldn't really test any OpenGL game
>> that well.
>>
>> But for glxgears switching from AGP to PCIe mode seems to result in a
>> roughly 5% performance drop.
>>
>> The surprising reason for this is not the better TLB performance, but
>> the lack of USWC support for the PCIe GART in radeon.
> I suspect the main reason it's only 5% is that PCIe GART page tables are
> stored in VRAM, so they don't need to be fetched across the PCIe link
> (and presumably it has more than one TLB entry as well). The difference
> is much bigger with native AGP ASICs with PCI GART.

Do you have some hardware you could give that a try on?

I mean the first card I put into the system obviously only worked 
correctly with AGP disabled.

While I agree that it means a performance regression, this is a rather 
high motivation to go ahead with at least the first patch.

Christian.
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Re: [RFC] Deprecate AGP GART support for Radeon/Nouveau/TTM

[Christian König]

Am 20.05.20 um 18:18 schrieb Alex Deucher:
> On Wed, May 20, 2020 at 10:43 AM Christian König
> <ckoenig.leichtzumerken@gmail.com> wrote:
>> Am 13.05.20 um 13:03 schrieb Christian König:
>>> Unfortunately AGP is still to widely used as we could just drop support for using its GART.
>>>
>>> Not using the AGP GART also doesn't mean a loss in functionality since drivers will just fallback to the driver specific PCI GART.
>>>
>>> For now just deprecate the code and don't enable the AGP GART in TTM even when general AGP support is available.
>> So I've used an ancient system (32bit) to setup a test box for this.
>>
>>
>> The first GPU I could test is an RV280 (Radeon 9200 PRO) which is easily
>> 15 years old.
>>
>> What happens in AGP mode is that glxgears shows artifacts during
>> rendering on this system.
>>
>> In PCI mode those rendering artifacts are gone and glxgears seems to
>> draw everything correctly now.
>>
>> Performance is obviously not comparable, cause in AGP we don't render
>> all triangles correctly.
>>
>>
>> The second GPU I could test is an RV630 PRO (Radeon HD 2600 PRO AGP)
>> which is more than 10 years old.
>>
>> As far as I can tell this one works in both AGP and PCIe mode perfectly
>> fine.
>>
>> Since this is only a 32bit system I couldn't really test any OpenGL game
>> that well.
>>
>> But for glxgears switching from AGP to PCIe mode seems to result in a
>> roughly 5% performance drop.
>>
>> The surprising reason for this is not the better TLB performance, but
>> the lack of USWC support for the PCIe GART in radeon.
>>
>>
>> So if anybody wants to get his hands dirty and squeeze a bit more
>> performance out of the old hardware, porting USWC from amdgpu to radeon
>> shouldn't be to much of a problem.
> We do support USWC on radeon, although I think we had separate flags
> for cached and WC.  That said we had a lot of problems with WC on 32
> bit (see radeon_bo_create()).  The other problem is that, at least on
> the really old radeons, the PCI gart didn't support snooped and
> unsnooped.  It was always snooped.  It wasn't until pcie that the gart
> hw got support for both.  For AGP, the expectation was that AGP
> provided the uncached memory.

Oh, indeed. I didn't remembered that.

Interesting is that in this case I have no idea where the performance 
difference is coming from.

>
>>
>> Summing it up I'm still leaning towards disabling AGP completely by
>> default for radeon and deprecate it in TTM as well.
>>
>> Thoughts? Especially Alex what do you think.
> Works for me.

I will take that as an rb and commit at least the first patch.

Thanks,
Christian.

>
> Alex

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Re: [RFC] Deprecate AGP GART support for Radeon/Nouveau/TTM

[Michel Dänzer]

On 2020-05-22 12:40 p.m., Christian König wrote:
> Am 20.05.20 um 18:25 schrieb Michel Dänzer:
>> On 2020-05-20 4:43 p.m., Christian König wrote:
>>> Am 13.05.20 um 13:03 schrieb Christian König:
>>>> Unfortunately AGP is still to widely used as we could just drop
>>>> support for using its GART.
>>>>
>>>> Not using the AGP GART also doesn't mean a loss in functionality since
>>>> drivers will just fallback to the driver specific PCI GART.
>>>>
>>>> For now just deprecate the code and don't enable the AGP GART in TTM
>>>> even when general AGP support is available.
>>> So I've used an ancient system (32bit) to setup a test box for this.
>>>
>>>
>>> The first GPU I could test is an RV280 (Radeon 9200 PRO) which is easily
>>> 15 years old.
>>>
>>> What happens in AGP mode is that glxgears shows artifacts during
>>> rendering on this system.
>>>
>>> In PCI mode those rendering artifacts are gone and glxgears seems to
>>> draw everything correctly now.
>>>
>>> Performance is obviously not comparable, cause in AGP we don't render
>>> all triangles correctly.
>>>
>>>
>>> The second GPU I could test is an RV630 PRO (Radeon HD 2600 PRO AGP)
>>> which is more than 10 years old.
>>>
>>> As far as I can tell this one works in both AGP and PCIe mode perfectly
>>> fine.
>>>
>>> Since this is only a 32bit system I couldn't really test any OpenGL game
>>> that well.
>>>
>>> But for glxgears switching from AGP to PCIe mode seems to result in a
>>> roughly 5% performance drop.
>>>
>>> The surprising reason for this is not the better TLB performance, but
>>> the lack of USWC support for the PCIe GART in radeon.
>> I suspect the main reason it's only 5% is that PCIe GART page tables are
>> stored in VRAM, so they don't need to be fetched across the PCIe link
>> (and presumably it has more than one TLB entry as well). The difference
>> is much bigger with native AGP ASICs with PCI GART.
> 
> Do you have some hardware you could give that a try on?

As I mentioned before, I tested this many times on my AGP PowerBooks
back in the day. The result was always a similar, big hit with PCI GART
vs AGP (even just 1x). I haven't seen any reason to believe this has
changed.


> While I agree that it means a performance regression, this is a rather
> high motivation to go ahead with at least the first patch.

I totally agree with the benefits, I just want everyone to be honest and
clear about the performance hit with native AGP Radeons, which already
have very weak performance by today's standards even with AGP.


-- 
Earthling Michel Dänzer               |               https://redhat.com
Libre software enthusiast             |             Mesa and X developer
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Re: [RFC] Deprecate AGP GART support for Radeon/Nouveau/TTM

[Alex Deucher]

On Fri, May 22, 2020 at 6:41 AM Christian König
<ckoenig.leichtzumerken@gmail.com> wrote:
>
> Am 20.05.20 um 18:18 schrieb Alex Deucher:
> > On Wed, May 20, 2020 at 10:43 AM Christian König
> > <ckoenig.leichtzumerken@gmail.com> wrote:
> >> Am 13.05.20 um 13:03 schrieb Christian König:
> >>> Unfortunately AGP is still to widely used as we could just drop support for using its GART.
> >>>
> >>> Not using the AGP GART also doesn't mean a loss in functionality since drivers will just fallback to the driver specific PCI GART.
> >>>
> >>> For now just deprecate the code and don't enable the AGP GART in TTM even when general AGP support is available.
> >> So I've used an ancient system (32bit) to setup a test box for this.
> >>
> >>
> >> The first GPU I could test is an RV280 (Radeon 9200 PRO) which is easily
> >> 15 years old.
> >>
> >> What happens in AGP mode is that glxgears shows artifacts during
> >> rendering on this system.
> >>
> >> In PCI mode those rendering artifacts are gone and glxgears seems to
> >> draw everything correctly now.
> >>
> >> Performance is obviously not comparable, cause in AGP we don't render
> >> all triangles correctly.
> >>
> >>
> >> The second GPU I could test is an RV630 PRO (Radeon HD 2600 PRO AGP)
> >> which is more than 10 years old.
> >>
> >> As far as I can tell this one works in both AGP and PCIe mode perfectly
> >> fine.
> >>
> >> Since this is only a 32bit system I couldn't really test any OpenGL game
> >> that well.
> >>
> >> But for glxgears switching from AGP to PCIe mode seems to result in a
> >> roughly 5% performance drop.
> >>
> >> The surprising reason for this is not the better TLB performance, but
> >> the lack of USWC support for the PCIe GART in radeon.
> >>
> >>
> >> So if anybody wants to get his hands dirty and squeeze a bit more
> >> performance out of the old hardware, porting USWC from amdgpu to radeon
> >> shouldn't be to much of a problem.
> > We do support USWC on radeon, although I think we had separate flags
> > for cached and WC.  That said we had a lot of problems with WC on 32
> > bit (see radeon_bo_create()).  The other problem is that, at least on
> > the really old radeons, the PCI gart didn't support snooped and
> > unsnooped.  It was always snooped.  It wasn't until pcie that the gart
> > hw got support for both.  For AGP, the expectation was that AGP
> > provided the uncached memory.
>
> Oh, indeed. I didn't remembered that.
>
> Interesting is that in this case I have no idea where the performance
> difference is coming from.
>
> >
> >>
> >> Summing it up I'm still leaning towards disabling AGP completely by
> >> default for radeon and deprecate it in TTM as well.
> >>
> >> Thoughts? Especially Alex what do you think.
> > Works for me.
>
> I will take that as an rb and commit at least the first patch.

Yeah, Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

>
> Thanks,
> Christian.
>
> >
> > Alex
>
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