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Date:   Tue, 1 Sep 2020 09:40:43 +0200
From:   Daniel Vetter <daniel@ffwll.ch>
To:     Gerd Hoffmann <kraxel@redhat.com>
Cc:     dri-devel@lists.freedesktop.org, christian.koenig@amd.com,
        Alex Deucher <alexander.deucher@amd.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Lucas Stach <l.stach@pengutronix.de>,
        Russell King <linux+etnaviv@armlinux.org.uk>,
        Christian Gmeiner <christian.gmeiner@gmail.com>,
        Rob Clark <robdclark@gmail.com>, Sean Paul <sean@poorly.run>,
        Ben Skeggs <bskeggs@redhat.com>,
        Sandy Huang <hjc@rock-chips.com>,
        Heiko =?iso-8859-1?Q?St=FCbner?= <heiko@sntech.de>,
        Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>,
        "open list:RADEON and AMDGPU DRM DRIVERS" 
        <amd-gfx@lists.freedesktop.org>,
        open list <linux-kernel@vger.kernel.org>,
        "moderated list:DRM DRIVERS FOR VIVANTE GPU IP" 
        <etnaviv@lists.freedesktop.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <linux-arm-msm@vger.kernel.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <freedreno@lists.freedesktop.org>,
        "open list:DRM DRIVER FOR NVIDIA GEFORCE/QUADRO GPUS" 
        <nouveau@lists.freedesktop.org>,
        "moderated list:ARM/Rockchip SoC support" 
        <linux-arm-kernel@lists.infradead.org>,
        "open list:ARM/Rockchip SoC support" 
        <linux-rockchip@lists.infradead.org>,
        "open list:DRM DRIVERS FOR NVIDIA TEGRA" 
        <linux-tegra@vger.kernel.org>,
        "moderated list:DRM DRIVERS FOR XEN" <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH v2 1/2] drm: allow limiting the scatter list size.
Message-ID: <20200901074043.GT2352366@phenom.ffwll.local>
Mail-Followup-To: Gerd Hoffmann <kraxel@redhat.com>,
        dri-devel@lists.freedesktop.org, christian.koenig@amd.com,
        Alex Deucher <alexander.deucher@amd.com>,
        David Airlie <airlied@linux.ie>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Lucas Stach <l.stach@pengutronix.de>,
        Russell King <linux+etnaviv@armlinux.org.uk>,
        Christian Gmeiner <christian.gmeiner@gmail.com>,
        Rob Clark <robdclark@gmail.com>, Sean Paul <sean@poorly.run>,
        Ben Skeggs <bskeggs@redhat.com>, Sandy Huang <hjc@rock-chips.com>,
        Heiko =?iso-8859-1?Q?St=FCbner?= <heiko@sntech.de>,
        Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>,
        "open list:RADEON and AMDGPU DRM DRIVERS" <amd-gfx@lists.freedesktop.org>,
        open list <linux-kernel@vger.kernel.org>,
        "moderated list:DRM DRIVERS FOR VIVANTE GPU IP" <etnaviv@lists.freedesktop.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" <linux-arm-msm@vger.kernel.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" <freedreno@lists.freedesktop.org>,
        "open list:DRM DRIVER FOR NVIDIA GEFORCE/QUADRO GPUS" <nouveau@lists.freedesktop.org>,
        "moderated list:ARM/Rockchip SoC support" <linux-arm-kernel@lists.infradead.org>,
        "open list:ARM/Rockchip SoC support" <linux-rockchip@lists.infradead.org>,
        "open list:DRM DRIVERS FOR NVIDIA TEGRA" <linux-tegra@vger.kernel.org>,
        "moderated list:DRM DRIVERS FOR XEN" <xen-devel@lists.xenproject.org>
References: <20200818092017.26290-1-kraxel@redhat.com>
 <20200818092017.26290-2-kraxel@redhat.com>
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On Tue, Aug 18, 2020 at 11:20:16AM +0200, Gerd Hoffmann wrote:
> Add max_segment argument to drm_prime_pages_to_sg().  When set pass it
> through to the __sg_alloc_table_from_pages() call, otherwise use
> SCATTERLIST_MAX_SEGMENT.
> 
> Also add max_segment field to drm driver and pass it to
> drm_prime_pages_to_sg() calls in drivers and helpers.
> 
> v2: place max_segment in drm driver not gem object.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  include/drm/drm_device.h                    |  8 ++++++++
>  include/drm/drm_prime.h                     |  3 ++-
>  drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c |  3 ++-
>  drivers/gpu/drm/drm_gem_shmem_helper.c      |  3 ++-
>  drivers/gpu/drm/drm_prime.c                 | 10 +++++++---
>  drivers/gpu/drm/etnaviv/etnaviv_gem.c       |  3 ++-
>  drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c |  3 ++-
>  drivers/gpu/drm/msm/msm_gem.c               |  3 ++-
>  drivers/gpu/drm/msm/msm_gem_prime.c         |  3 ++-
>  drivers/gpu/drm/nouveau/nouveau_prime.c     |  3 ++-
>  drivers/gpu/drm/radeon/radeon_prime.c       |  3 ++-
>  drivers/gpu/drm/rockchip/rockchip_drm_gem.c |  6 ++++--
>  drivers/gpu/drm/tegra/gem.c                 |  3 ++-
>  drivers/gpu/drm/vgem/vgem_drv.c             |  3 ++-
>  drivers/gpu/drm/xen/xen_drm_front_gem.c     |  3 ++-
>  15 files changed, 43 insertions(+), 17 deletions(-)
> 
> diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
> index 0988351d743c..47cb547a8115 100644
> --- a/include/drm/drm_device.h
> +++ b/include/drm/drm_device.h
> @@ -329,6 +329,14 @@ struct drm_device {
>  	 */
>  	struct drm_fb_helper *fb_helper;
>  
> +	/**
> +	 * @max_segment:
> +	 *
> +	 * Max size for scatter list segments.  When unset the default
> +	 * (SCATTERLIST_MAX_SEGMENT) is used.
> +	 */
> +	size_t max_segment;

Is there no better place for this then "at the bottom"? drm_device is a
huge structure, piling stuff up randomly doesn't make it better :-)

I think ideally we'd have a gem substruct like we have on the modeset side
at least.
-Daniel

> +
>  	/* Everything below here is for legacy driver, never use! */
>  	/* private: */
>  #if IS_ENABLED(CONFIG_DRM_LEGACY)
> diff --git a/include/drm/drm_prime.h b/include/drm/drm_prime.h
> index 9af7422b44cf..2c3689435cb4 100644
> --- a/include/drm/drm_prime.h
> +++ b/include/drm/drm_prime.h
> @@ -88,7 +88,8 @@ void drm_gem_dmabuf_vunmap(struct dma_buf *dma_buf, void *vaddr);
>  int drm_gem_prime_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma);
>  int drm_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct vm_area_struct *vma);
>  
> -struct sg_table *drm_prime_pages_to_sg(struct page **pages, unsigned int nr_pages);
> +struct sg_table *drm_prime_pages_to_sg(struct page **pages, unsigned int nr_pages,
> +				       size_t max_segment);
>  struct dma_buf *drm_gem_prime_export(struct drm_gem_object *obj,
>  				     int flags);
>  
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> index 519ce4427fce..8f6a647757e7 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> @@ -303,7 +303,8 @@ static struct sg_table *amdgpu_dma_buf_map(struct dma_buf_attachment *attach,
>  	switch (bo->tbo.mem.mem_type) {
>  	case TTM_PL_TT:
>  		sgt = drm_prime_pages_to_sg(bo->tbo.ttm->pages,
> -					    bo->tbo.num_pages);
> +					    bo->tbo.num_pages,
> +					    obj->dev->max_segment);
>  		if (IS_ERR(sgt))
>  			return sgt;
>  
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index 4b7cfbac4daa..8f47b41b0b2f 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -656,7 +656,8 @@ struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_object *obj)
>  
>  	WARN_ON(shmem->base.import_attach);
>  
> -	return drm_prime_pages_to_sg(shmem->pages, obj->size >> PAGE_SHIFT);
> +	return drm_prime_pages_to_sg(shmem->pages, obj->size >> PAGE_SHIFT,
> +				     obj->dev->max_segment);
>  }
>  EXPORT_SYMBOL_GPL(drm_gem_shmem_get_sg_table);
>  
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 1693aa7c14b5..27c783fd6633 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -802,7 +802,8 @@ static const struct dma_buf_ops drm_gem_prime_dmabuf_ops =  {
>   *
>   * This is useful for implementing &drm_gem_object_funcs.get_sg_table.
>   */
> -struct sg_table *drm_prime_pages_to_sg(struct page **pages, unsigned int nr_pages)
> +struct sg_table *drm_prime_pages_to_sg(struct page **pages, unsigned int nr_pages,
> +				       size_t max_segment)
>  {
>  	struct sg_table *sg = NULL;
>  	int ret;
> @@ -813,8 +814,11 @@ struct sg_table *drm_prime_pages_to_sg(struct page **pages, unsigned int nr_page
>  		goto out;
>  	}
>  
> -	ret = sg_alloc_table_from_pages(sg, pages, nr_pages, 0,
> -				nr_pages << PAGE_SHIFT, GFP_KERNEL);
> +	if (max_segment == 0 || max_segment > SCATTERLIST_MAX_SEGMENT)
> +		max_segment = SCATTERLIST_MAX_SEGMENT;
> +	ret = __sg_alloc_table_from_pages(sg, pages, nr_pages, 0,
> +					  nr_pages << PAGE_SHIFT,
> +					  max_segment, GFP_KERNEL);
>  	if (ret)
>  		goto out;
>  
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> index f06e19e7be04..90654246b335 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> @@ -103,7 +103,8 @@ struct page **etnaviv_gem_get_pages(struct etnaviv_gem_object *etnaviv_obj)
>  		int npages = etnaviv_obj->base.size >> PAGE_SHIFT;
>  		struct sg_table *sgt;
>  
> -		sgt = drm_prime_pages_to_sg(etnaviv_obj->pages, npages);
> +		sgt = drm_prime_pages_to_sg(etnaviv_obj->pages, npages,
> +					    etnaviv_obj->base.dev->max_segment);
>  		if (IS_ERR(sgt)) {
>  			dev_err(dev->dev, "failed to allocate sgt: %ld\n",
>  				PTR_ERR(sgt));
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c b/drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c
> index 6d9e5c3c4dd5..f65be0fffb3d 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c
> @@ -19,7 +19,8 @@ struct sg_table *etnaviv_gem_prime_get_sg_table(struct drm_gem_object *obj)
>  	if (WARN_ON(!etnaviv_obj->pages))  /* should have already pinned! */
>  		return ERR_PTR(-EINVAL);
>  
> -	return drm_prime_pages_to_sg(etnaviv_obj->pages, npages);
> +	return drm_prime_pages_to_sg(etnaviv_obj->pages, npages,
> +				     obj->dev->max_segment);
>  }
>  
>  void *etnaviv_gem_prime_vmap(struct drm_gem_object *obj)
> diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
> index b2f49152b4d4..dbf1437c3dac 100644
> --- a/drivers/gpu/drm/msm/msm_gem.c
> +++ b/drivers/gpu/drm/msm/msm_gem.c
> @@ -126,7 +126,8 @@ static struct page **get_pages(struct drm_gem_object *obj)
>  
>  		msm_obj->pages = p;
>  
> -		msm_obj->sgt = drm_prime_pages_to_sg(p, npages);
> +		msm_obj->sgt = drm_prime_pages_to_sg(p, npages,
> +						     obj->dev->max_segment);
>  		if (IS_ERR(msm_obj->sgt)) {
>  			void *ptr = ERR_CAST(msm_obj->sgt);
>  
> diff --git a/drivers/gpu/drm/msm/msm_gem_prime.c b/drivers/gpu/drm/msm/msm_gem_prime.c
> index d7c8948427fe..6337cd1f9428 100644
> --- a/drivers/gpu/drm/msm/msm_gem_prime.c
> +++ b/drivers/gpu/drm/msm/msm_gem_prime.c
> @@ -19,7 +19,8 @@ struct sg_table *msm_gem_prime_get_sg_table(struct drm_gem_object *obj)
>  	if (WARN_ON(!msm_obj->pages))  /* should have already pinned! */
>  		return NULL;
>  
> -	return drm_prime_pages_to_sg(msm_obj->pages, npages);
> +	return drm_prime_pages_to_sg(msm_obj->pages, npages,
> +				     obj->dev->max_segment);
>  }
>  
>  void *msm_gem_prime_vmap(struct drm_gem_object *obj)
> diff --git a/drivers/gpu/drm/nouveau/nouveau_prime.c b/drivers/gpu/drm/nouveau/nouveau_prime.c
> index bae6a3eccee0..dd0ff032ae16 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_prime.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_prime.c
> @@ -32,7 +32,8 @@ struct sg_table *nouveau_gem_prime_get_sg_table(struct drm_gem_object *obj)
>  	struct nouveau_bo *nvbo = nouveau_gem_object(obj);
>  	int npages = nvbo->bo.num_pages;
>  
> -	return drm_prime_pages_to_sg(nvbo->bo.ttm->pages, npages);
> +	return drm_prime_pages_to_sg(nvbo->bo.ttm->pages, npages,
> +				     obj->dev->max_segment);
>  }
>  
>  void *nouveau_gem_prime_vmap(struct drm_gem_object *obj)
> diff --git a/drivers/gpu/drm/radeon/radeon_prime.c b/drivers/gpu/drm/radeon/radeon_prime.c
> index b906e8fbd5f3..61a3fe147489 100644
> --- a/drivers/gpu/drm/radeon/radeon_prime.c
> +++ b/drivers/gpu/drm/radeon/radeon_prime.c
> @@ -36,7 +36,8 @@ struct sg_table *radeon_gem_prime_get_sg_table(struct drm_gem_object *obj)
>  	struct radeon_bo *bo = gem_to_radeon_bo(obj);
>  	int npages = bo->tbo.num_pages;
>  
> -	return drm_prime_pages_to_sg(bo->tbo.ttm->pages, npages);
> +	return drm_prime_pages_to_sg(bo->tbo.ttm->pages, npages,
> +				     obj->dev->max_segment);
>  }
>  
>  void *radeon_gem_prime_vmap(struct drm_gem_object *obj)
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
> index b9275ba7c5a5..5ddb2d31a607 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
> @@ -85,7 +85,8 @@ static int rockchip_gem_get_pages(struct rockchip_gem_object *rk_obj)
>  
>  	rk_obj->num_pages = rk_obj->base.size >> PAGE_SHIFT;
>  
> -	rk_obj->sgt = drm_prime_pages_to_sg(rk_obj->pages, rk_obj->num_pages);
> +	rk_obj->sgt = drm_prime_pages_to_sg(rk_obj->pages, rk_obj->num_pages,
> +					    rk_obj->base.dev->max_segment);
>  	if (IS_ERR(rk_obj->sgt)) {
>  		ret = PTR_ERR(rk_obj->sgt);
>  		goto err_put_pages;
> @@ -442,7 +443,8 @@ struct sg_table *rockchip_gem_prime_get_sg_table(struct drm_gem_object *obj)
>  	int ret;
>  
>  	if (rk_obj->pages)
> -		return drm_prime_pages_to_sg(rk_obj->pages, rk_obj->num_pages);
> +		return drm_prime_pages_to_sg(rk_obj->pages, rk_obj->num_pages,
> +					     obj->dev->max_segment);
>  
>  	sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
>  	if (!sgt)
> diff --git a/drivers/gpu/drm/tegra/gem.c b/drivers/gpu/drm/tegra/gem.c
> index 723df142a981..a0abde747e95 100644
> --- a/drivers/gpu/drm/tegra/gem.c
> +++ b/drivers/gpu/drm/tegra/gem.c
> @@ -284,7 +284,8 @@ static int tegra_bo_get_pages(struct drm_device *drm, struct tegra_bo *bo)
>  
>  	bo->num_pages = bo->gem.size >> PAGE_SHIFT;
>  
> -	bo->sgt = drm_prime_pages_to_sg(bo->pages, bo->num_pages);
> +	bo->sgt = drm_prime_pages_to_sg(bo->pages, bo->num_pages,
> +					bo->gem.dev->max_segment);
>  	if (IS_ERR(bo->sgt)) {
>  		err = PTR_ERR(bo->sgt);
>  		goto put_pages;
> diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
> index 313339bbff90..045461dc6319 100644
> --- a/drivers/gpu/drm/vgem/vgem_drv.c
> +++ b/drivers/gpu/drm/vgem/vgem_drv.c
> @@ -321,7 +321,8 @@ static struct sg_table *vgem_prime_get_sg_table(struct drm_gem_object *obj)
>  {
>  	struct drm_vgem_gem_object *bo = to_vgem_bo(obj);
>  
> -	return drm_prime_pages_to_sg(bo->pages, bo->base.size >> PAGE_SHIFT);
> +	return drm_prime_pages_to_sg(bo->pages, bo->base.size >> PAGE_SHIFT,
> +				     obj->dev->max_segment);
>  }
>  
>  static struct drm_gem_object* vgem_prime_import(struct drm_device *dev,
> diff --git a/drivers/gpu/drm/xen/xen_drm_front_gem.c b/drivers/gpu/drm/xen/xen_drm_front_gem.c
> index f0b85e094111..61a8c1a9fb04 100644
> --- a/drivers/gpu/drm/xen/xen_drm_front_gem.c
> +++ b/drivers/gpu/drm/xen/xen_drm_front_gem.c
> @@ -179,7 +179,8 @@ struct sg_table *xen_drm_front_gem_get_sg_table(struct drm_gem_object *gem_obj)
>  	if (!xen_obj->pages)
>  		return ERR_PTR(-ENOMEM);
>  
> -	return drm_prime_pages_to_sg(xen_obj->pages, xen_obj->num_pages);
> +	return drm_prime_pages_to_sg(xen_obj->pages, xen_obj->num_pages,
> +				     gem_obj->dev->max_segment);
>  }
>  
>  struct drm_gem_object *
> -- 
> 2.18.4
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch