On Wed, Nov 30, 2016 at 02:19:18PM +0100, Benjamin Gaignard wrote:
> Some SoC without MMU have display driver where a drm/kms driver
> could be implemented.
> Before doing such kind of thing drm/kms must allow to use mmuless
> devices.
> This patch propose to remove MMU configuration flag and add some
> cma helpers functions to help implementing mmuless display driver
>
> version 2:
> - define get_fb_unmapped_area() in drivers/video/fbdev/core/fbmem.c
> if HAVE_ARCH_FB_UNMAPPED_AREA is set and get_fb_unmapped_area not
> already defined in the architecture
>
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxx>
> ---
> drivers/gpu/drm/Kconfig | 4 +--
> drivers/gpu/drm/drm_fb_cma_helper.c | 4 +++
> drivers/gpu/drm/drm_gem_cma_helper.c | 62 ++++++++++++++++++++++++++++++++++++
> drivers/gpu/drm/drm_vm.c | 4 +++
> drivers/video/fbdev/core/fbmem.c | 15 +++++++++
> include/drm/drm_gem_cma_helper.h | 6 ++++
> 6 files changed, 93 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index 8d9cf73..36c102b 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -6,7 +6,7 @@
> #
> menuconfig DRM
> tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)"
> - depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && MMU && HAS_DMA
> + depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
> select HDMI
> select FB_CMDLINE
> select I2C
> @@ -98,7 +98,7 @@ config DRM_LOAD_EDID_FIRMWARE
>
> config DRM_TTM
> tristate
> - depends on DRM
> + depends on DRM && MMU
> help
> GPU memory management subsystem for devices with multiple
> GPU memory types. Will be enabled automatically if a device driver
> diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c b/drivers/gpu/drm/drm_fb_cma_helper.c
> index 81b3558..b1414b6 100644
> --- a/drivers/gpu/drm/drm_fb_cma_helper.c
> +++ b/drivers/gpu/drm/drm_fb_cma_helper.c
> @@ -343,8 +343,12 @@ int drm_fb_cma_debugfs_show(struct seq_file *m, void *arg)
>
> static int drm_fb_cma_mmap(struct fb_info *info, struct vm_area_struct *vma)
> {
> +#ifdef CONFIG_MMU
> return dma_mmap_writecombine(info->device, vma, info->screen_base,
> info->fix.smem_start, info->fix.smem_len);
> +#else
> + return vm_iomap_memory(vma, vma->vm_start, info->fix.smem_len);
> +#endif
> }
>
> static struct fb_ops drm_fbdev_cma_ops = {
> diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c b/drivers/gpu/drm/drm_gem_cma_helper.c
> index 1d6c335..de13535 100644
> --- a/drivers/gpu/drm/drm_gem_cma_helper.c
> +++ b/drivers/gpu/drm/drm_gem_cma_helper.c
> @@ -318,11 +318,16 @@ static int drm_gem_cma_mmap_obj(struct drm_gem_cma_object *cma_obj,
> vma->vm_flags &= ~VM_PFNMAP;
> vma->vm_pgoff = 0;
>
> +#ifdef CONFIG_MMU
> ret = dma_mmap_wc(cma_obj->base.dev->dev, vma, cma_obj->vaddr,
> cma_obj->paddr, vma->vm_end - vma->vm_start);
> if (ret)
> drm_gem_vm_close(vma);
>
> +#else
> + ret = vm_iomap_memory(vma, vma->vm_start,
> + (vma->vm_end - vma->vm_start));
> +#endif
Ok, me asking for a separate helper was probably too much. The #ifdefs
here are still ugly, but on 2nd thought this just looks like the dma api
is broken on no-mmu? Shouldn't we instead have a patch somewhere which
gives us a working dma_mmap_wc on nommu platforms?
> return ret;
> }
>
> @@ -358,6 +363,63 @@ int drm_gem_cma_mmap(struct file *filp, struct vm_area_struct *vma)
> }
> EXPORT_SYMBOL_GPL(drm_gem_cma_mmap);
>
> +#ifdef CONFIG_MMU
> +#define drm_gem_cma_get_unmapped_area NULL
Depending upon how it's used it might be better to stub it out ...
> +#else
> +unsigned long drm_gem_cma_get_unmapped_area(struct file *filp,
> + unsigned long addr,
> + unsigned long len,
> + unsigned long pgoff,
> + unsigned long flags)
With no user and no kerneldoc I kinda have no idea what this is even for.
The name also doesn't help, it says "get_unmapped_area", but very clearly
you're returning a kernel vaddr cast to a long (and with ERR_PTR
semantics on top, but non-standard). Why is this not called get_vaddr?
-Daniel
> +{
> + struct drm_gem_cma_object *cma_obj;
> + struct drm_gem_object *obj = NULL;
> + struct drm_file *priv = filp->private_data;
> + struct drm_device *dev = priv->minor->dev;
> + struct drm_vma_offset_node *node;
> +
> + if (drm_device_is_unplugged(dev))
> + return -ENODEV;
> +
> + drm_vma_offset_lock_lookup(dev->vma_offset_manager);
> + node = drm_vma_offset_exact_lookup_locked(dev->vma_offset_manager,
> + pgoff,
> + len >> PAGE_SHIFT);
> + if (likely(node)) {
> + obj = container_of(node, struct drm_gem_object, vma_node);
> + /*
> + * When the object is being freed, after it hits 0-refcnt it
> + * proceeds to tear down the object. In the process it will
> + * attempt to remove the VMA offset and so acquire this
> + * mgr->vm_lock. Therefore if we find an object with a 0-refcnt
> + * that matches our range, we know it is in the process of being
> + * destroyed and will be freed as soon as we release the lock -
> + * so we have to check for the 0-refcnted object and treat it as
> + * invalid.
> + */
> + if (!kref_get_unless_zero(&obj->refcount))
> + obj = NULL;
> + }
> +
> + drm_vma_offset_unlock_lookup(dev->vma_offset_manager);
> +
> + if (!obj)
> + return -EINVAL;
> +
> + if (!drm_vma_node_is_allowed(node, priv)) {
> + drm_gem_object_unreference_unlocked(obj);
> + return -EACCES;
> + }
> +
> + cma_obj = to_drm_gem_cma_obj(obj);
> +
> + drm_gem_object_unreference_unlocked(obj);
> +
> + return cma_obj->vaddr ? (unsigned long)cma_obj->vaddr : -EINVAL;
> +}
> +#endif
> +EXPORT_SYMBOL_GPL(drm_gem_cma_get_unmapped_area);
> +
> #ifdef CONFIG_DEBUG_FS
> /**
> * drm_gem_cma_describe - describe a CMA GEM object for debugfs
> diff --git a/drivers/gpu/drm/drm_vm.c b/drivers/gpu/drm/drm_vm.c
> index caa4e4c..974e02b 100644
> --- a/drivers/gpu/drm/drm_vm.c
> +++ b/drivers/gpu/drm/drm_vm.c
> @@ -489,6 +489,7 @@ static int drm_mmap_dma(struct file *filp, struct vm_area_struct *vma)
> #if defined(__i386__) || defined(__x86_64__)
> pgprot_val(vma->vm_page_prot) &= ~_PAGE_RW;
> #else
> +#ifdef CONFIG_MMU
> /* Ye gads this is ugly. With more thought
> we could move this up higher and use
> `protection_map' instead. */
> @@ -497,6 +498,7 @@ static int drm_mmap_dma(struct file *filp, struct vm_area_struct *vma)
> (pte_wrprotect
> (__pte(pgprot_val(vma->vm_page_prot)))));
> #endif
> +#endif
> }
>
> vma->vm_ops = &drm_vm_dma_ops;
> @@ -573,6 +575,7 @@ static int drm_mmap_locked(struct file *filp, struct vm_area_struct *vma)
> #if defined(__i386__) || defined(__x86_64__)
> pgprot_val(vma->vm_page_prot) &= ~_PAGE_RW;
> #else
> +#ifdef CONFIG_MMU
> /* Ye gads this is ugly. With more thought
> we could move this up higher and use
> `protection_map' instead. */
> @@ -581,6 +584,7 @@ static int drm_mmap_locked(struct file *filp, struct vm_area_struct *vma)
> (pte_wrprotect
> (__pte(pgprot_val(vma->vm_page_prot)))));
> #endif
> +#endif
> }
>
> switch (map->type) {
> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> index 76c1ad9..54488ee 100644
> --- a/drivers/video/fbdev/core/fbmem.c
> +++ b/drivers/video/fbdev/core/fbmem.c
> @@ -1492,6 +1492,21 @@ static long fb_compat_ioctl(struct file *file, unsigned int cmd,
> return 0;
> }
>
> +#if defined(HAVE_ARCH_FB_UNMAPPED_AREA) && !defined(get_fb_unmapped_area)
> +unsigned long get_fb_unmapped_area(struct file *filp,
> + unsigned long addr, unsigned long len,
> + unsigned long pgoff, unsigned long flags)
> +{
> + struct fb_info * const info = filp->private_data;
> + unsigned long fb_size = PAGE_ALIGN(info->fix.smem_len);
> +
> + if (pgoff > fb_size || len > fb_size - pgoff)
> + return -EINVAL;
> +
> + return (unsigned long)info->screen_base + pgoff;
> +}
> +#endif
> +
> static const struct file_operations fb_fops = {
> .owner = THIS_MODULE,
> .read = fb_read,
> diff --git a/include/drm/drm_gem_cma_helper.h b/include/drm/drm_gem_cma_helper.h
> index acd6af8..177a20d 100644
> --- a/include/drm/drm_gem_cma_helper.h
> +++ b/include/drm/drm_gem_cma_helper.h
> @@ -53,6 +53,12 @@ struct drm_gem_cma_object *drm_gem_cma_create(struct drm_device *drm,
>
> extern const struct vm_operations_struct drm_gem_cma_vm_ops;
>
> +unsigned long drm_gem_cma_get_unmapped_area(struct file *filp,
> + unsigned long addr,
> + unsigned long len,
> + unsigned long pgoff,
> + unsigned long flags);
> +
> #ifdef CONFIG_DEBUG_FS
> void drm_gem_cma_describe(struct drm_gem_cma_object *obj, struct seq_file *m);
> #endif
> --
> 1.9.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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