2016-11-30 14:52 GMT+01:00 Daniel Vetter <daniel@xxxxxxxx>:
> On Wed, Nov 30, 2016 at 12:21:24PM +0100, Benjamin Gaignard wrote:
>> Some platforms without MMU have display drivers where a drm/kms driver
>> could be implemented.
>> Before doing such kind of thing drm/kms must allow to use mmuless
>> devices.
>> This patch proposes to remove MMU configuration flag and add some
>> cma helpers functions to help implementing mmuless display driver
>>
>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxx>
>> ---
>> drivers/gpu/drm/Kconfig | 4 +--
>> drivers/gpu/drm/drm_fb_cma_helper.c | 20 ++++++++++++
>> drivers/gpu/drm/drm_gem_cma_helper.c | 62 ++++++++++++++++++++++++++++++++++++
>
> Hacking this into cma helpers feels very wrong to me. mmu-less looks like
> it works substantially differently enough that it warrants a new set of
> mmu-less gem helpers. And maybe that will showcase more code-refactoring
> opportunities between cma helpers, mmu-less helpers and shmem-based gem
> objects. And if there's none, then I think copypasting is better than
> ending up in a mess.
Only the 2 calls to dma_mmap_wc() are problematic within ARM nommu architecture.
After Laurent remarks I have move get_fb_unmapped_area() to fbmem.c
it really limits the modifications in cma helpers...
>
>> drivers/gpu/drm/drm_vm.c | 4 +++
>> drivers/video/fbdev/core/fbmem.c | 8 +++++
>> include/drm/drm_gem_cma_helper.h | 6 ++++
>> 6 files changed, 102 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..a3cef79 100644
>> --- a/drivers/gpu/drm/drm_fb_cma_helper.c
>> +++ b/drivers/gpu/drm/drm_fb_cma_helper.c
>> @@ -343,10 +343,30 @@ 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
>> }
>>
>> +#ifdef HAVE_ARCH_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;
>> +}
>> +EXPORT_SYMBOL_GPL(get_fb_unmapped_area);
>> +#endif
>> +
>> static struct fb_ops drm_fbdev_cma_ops = {
>> .owner = THIS_MODULE,
>> DRM_FB_HELPER_DEFAULT_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
>> 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
>> +#else
>> +unsigned long drm_gem_cma_get_unmapped_area(struct file *filp,
>> + unsigned long addr,
>> + unsigned long len,
>> + unsigned long pgoff,
>> + unsigned long flags)
>> +{
>> + 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) {
>
> drm_vm.c is a legacy horror show. Instead of hacking even more garbage
> into this, can't we just not compile this for MMU-less platforms? A bunch
> of stubs in drm_internal.h is all that should be needed for this, since on
> MMU-less you should never be able to enable one of the legacy drivers
> which need the exported symbols from this file.
Following your advice I have removed drm_vm.c from the build if
CONFIG_MMU is not set
I only had to stub drm_legacy_vma_flush() to compile.
I will include that in v3
>
> Cheers, Daniel
>
>> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
>> index 76c1ad9..d6a83bd 100644
>> --- a/drivers/video/fbdev/core/fbmem.c
>> +++ b/drivers/video/fbdev/core/fbmem.c
>> @@ -1492,6 +1492,14 @@ static long fb_compat_ioctl(struct file *file, unsigned int cmd,
>> return 0;
>> }
>>
>> +#ifdef HAVE_ARCH_FB_UNMAPPED_AREA
>> +extern unsigned long get_fb_unmapped_area(struct file *filp,
>> + unsigned long addr,
>> + unsigned long len,
>> + unsigned long pgoff,
>> + unsigned long flags);
>> +#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..79e9dbd 100644
>> --- a/include/drm/drm_gem_cma_helper.h
>> +++ b/include/drm/drm_gem_cma_helper.h
>> @@ -51,6 +51,12 @@ int drm_gem_cma_dumb_map_offset(struct drm_file *file_priv,
>> struct drm_gem_cma_object *drm_gem_cma_create(struct drm_device *drm,
>> size_t size);
>>
>> +unsigned long drm_gem_cma_get_unmapped_area(struct file *filp,
>> + unsigned long addr,
>> + unsigned long len,
>> + unsigned long pgoff,
>> + unsigned long flags);
>> +
>> extern const struct vm_operations_struct drm_gem_cma_vm_ops;
>>
>> #ifdef CONFIG_DEBUG_FS
>> --
>> 1.9.1
>>
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
--
Benjamin Gaignard
Graphic Study Group
Linaro.org │ Open source software for ARM SoCs
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