Re: [PATCH v2 2/4] drm/gem: Update client API to use struct drm_gem_membuf

[Daniel Vetter <daniel@ffwll.ch>]

On Thu, Aug 06, 2020 at 10:52:37AM +0200, Thomas Zimmermann wrote:
> GEM's vmap interface now wraps memory pointers in struct drm_gem_membuf.
> The structure represents a pointer into the framebuffer, which is either
> in I/O memory or in system memory. The structure contains a flag that
> distinguishes these cases.
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> ---
>  drivers/gpu/drm/drm_client.c    | 25 ++++++++++++-------------
>  drivers/gpu/drm/drm_fb_helper.c | 18 +++++++++---------
>  drivers/gpu/drm/drm_gem.c       | 19 +++++++++++--------
>  drivers/gpu/drm/drm_internal.h  |  5 +++--
>  drivers/gpu/drm/drm_prime.c     | 16 ++++++++++------
>  include/drm/drm_client.h        |  7 ++++---
>  include/drm/drm_device.h        | 26 ++++++++++++++++++++++++++
>  7 files changed, 75 insertions(+), 41 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
> index 495f47d23d87..0359b82928c1 100644
> --- a/drivers/gpu/drm/drm_client.c
> +++ b/drivers/gpu/drm/drm_client.c
> @@ -234,7 +234,7 @@ static void drm_client_buffer_delete(struct drm_client_buffer *buffer)
>  {
>  	struct drm_device *dev = buffer->client->dev;
>  
> -	drm_gem_vunmap(buffer->gem, buffer->vaddr);
> +	drm_gem_vunmap(buffer->gem, &buffer->membuf);
>  
>  	if (buffer->gem)
>  		drm_gem_object_put(buffer->gem);
> @@ -302,12 +302,13 @@ drm_client_buffer_create(struct drm_client_dev *client, u32 width, u32 height, u
>   * Returns:
>   *	The mapped memory's address
>   */
> -void *drm_client_buffer_vmap(struct drm_client_buffer *buffer)
> +const struct drm_gem_membuf *
> +drm_client_buffer_vmap(struct drm_client_buffer *buffer)
>  {
> -	void *vaddr;
> +	int ret;
>  
> -	if (buffer->vaddr)
> -		return buffer->vaddr;
> +	if (buffer->membuf.vaddr)
> +		return &buffer->membuf;
>  
>  	/*
>  	 * FIXME: The dependency on GEM here isn't required, we could
> @@ -317,13 +318,11 @@ void *drm_client_buffer_vmap(struct drm_client_buffer *buffer)
>  	 * fd_install step out of the driver backend hooks, to make that
>  	 * final step optional for internal users.
>  	 */
> -	vaddr = drm_gem_vmap(buffer->gem);
> -	if (IS_ERR(vaddr))
> -		return vaddr;
> -
> -	buffer->vaddr = vaddr;
> +	ret = drm_gem_vmap(buffer->gem, &buffer->membuf);
> +	if (ret)
> +		return ERR_PTR(ret);
>  
> -	return vaddr;
> +	return &buffer->membuf;
>  }
>  EXPORT_SYMBOL(drm_client_buffer_vmap);
>  
> @@ -337,8 +336,8 @@ EXPORT_SYMBOL(drm_client_buffer_vmap);
>   */
>  void drm_client_buffer_vunmap(struct drm_client_buffer *buffer)
>  {
> -	drm_gem_vunmap(buffer->gem, buffer->vaddr);
> -	buffer->vaddr = NULL;
> +	drm_gem_vunmap(buffer->gem, &buffer->membuf);
> +	buffer->membuf.vaddr = NULL;
>  }
>  EXPORT_SYMBOL(drm_client_buffer_vunmap);
>  
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 8697554ccd41..da24874247e7 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -394,7 +394,7 @@ static void drm_fb_helper_dirty_blit_real(struct drm_fb_helper *fb_helper,
>  	unsigned int cpp = fb->format->cpp[0];
>  	size_t offset = clip->y1 * fb->pitches[0] + clip->x1 * cpp;
>  	void *src = fb_helper->fbdev->screen_buffer + offset;
> -	void *dst = fb_helper->buffer->vaddr + offset;
> +	void *dst = fb_helper->buffer->membuf.vaddr + offset;
>  	size_t len = (clip->x2 - clip->x1) * cpp;
>  	unsigned int y;
>  
> @@ -416,7 +416,7 @@ static void drm_fb_helper_dirty_work(struct work_struct *work)
>  	struct drm_clip_rect *clip = &helper->dirty_clip;
>  	struct drm_clip_rect clip_copy;
>  	unsigned long flags;
> -	void *vaddr;
> +	const struct drm_gem_membuf *buf;
>  
>  	spin_lock_irqsave(&helper->dirty_lock, flags);
>  	clip_copy = *clip;
> @@ -429,8 +429,8 @@ static void drm_fb_helper_dirty_work(struct work_struct *work)
>  
>  		/* Generic fbdev uses a shadow buffer */
>  		if (helper->buffer) {
> -			vaddr = drm_client_buffer_vmap(helper->buffer);
> -			if (IS_ERR(vaddr))
> +			buf = drm_client_buffer_vmap(helper->buffer);
> +			if (IS_ERR(buf))
>  				return;
>  			drm_fb_helper_dirty_blit_real(helper, &clip_copy);
>  		}
> @@ -2076,7 +2076,7 @@ static int drm_fb_helper_generic_probe(struct drm_fb_helper *fb_helper,
>  	struct drm_framebuffer *fb;
>  	struct fb_info *fbi;
>  	u32 format;
> -	void *vaddr;
> +	const struct drm_gem_membuf *membuf;
>  
>  	drm_dbg_kms(dev, "surface width(%d), height(%d) and bpp(%d)\n",
>  		    sizes->surface_width, sizes->surface_height,
> @@ -2112,11 +2112,11 @@ static int drm_fb_helper_generic_probe(struct drm_fb_helper *fb_helper,
>  		fb_deferred_io_init(fbi);
>  	} else {
>  		/* buffer is mapped for HW framebuffer */
> -		vaddr = drm_client_buffer_vmap(fb_helper->buffer);
> -		if (IS_ERR(vaddr))
> -			return PTR_ERR(vaddr);
> +		membuf = drm_client_buffer_vmap(fb_helper->buffer);
> +		if (IS_ERR(membuf))
> +			return PTR_ERR(membuf);
>  
> -		fbi->screen_buffer = vaddr;
> +		fbi->screen_buffer = membuf->vaddr;
>  		/* Shamelessly leak the physical address to user-space */
>  #if IS_ENABLED(CONFIG_DRM_FBDEV_LEAK_PHYS_SMEM)
>  		if (drm_leak_fbdev_smem && fbi->fix.smem_start == 0)
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index 19d73868490e..36ded6a56fb2 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -1220,7 +1220,7 @@ void drm_gem_unpin(struct drm_gem_object *obj)
>  		obj->dev->driver->gem_prime_unpin(obj);
>  }
>  
> -void *drm_gem_vmap(struct drm_gem_object *obj)
> +int drm_gem_vmap(struct drm_gem_object *obj, struct drm_gem_membuf *buf)
>  {
>  	void *vaddr;
>  
> @@ -1229,23 +1229,26 @@ void *drm_gem_vmap(struct drm_gem_object *obj)
>  	else if (obj->dev->driver->gem_prime_vmap)
>  		vaddr = obj->dev->driver->gem_prime_vmap(obj);
>  	else
> -		vaddr = ERR_PTR(-EOPNOTSUPP);
> +		return -EOPNOTSUPP;
>  
>  	if (!vaddr)
> -		vaddr = ERR_PTR(-ENOMEM);
> +		return -ENOMEM;
> +
> +	buf->vaddr = vaddr;
> +	buf->is_iomem = false;
>  
> -	return vaddr;
> +	return 0;
>  }
>  
> -void drm_gem_vunmap(struct drm_gem_object *obj, void *vaddr)
> +void drm_gem_vunmap(struct drm_gem_object *obj, const struct drm_gem_membuf *buf)
>  {
> -	if (!vaddr)
> +	if (!buf || !buf->vaddr)
>  		return;
>  
>  	if (obj->funcs && obj->funcs->vunmap)
> -		obj->funcs->vunmap(obj, vaddr);
> +		obj->funcs->vunmap(obj, buf->vaddr);
>  	else if (obj->dev->driver->gem_prime_vunmap)
> -		obj->dev->driver->gem_prime_vunmap(obj, vaddr);
> +		obj->dev->driver->gem_prime_vunmap(obj, buf->vaddr);
>  }
>  
>  /**
> diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
> index 8e01caaf95cc..201d71249954 100644
> --- a/drivers/gpu/drm/drm_internal.h
> +++ b/drivers/gpu/drm/drm_internal.h
> @@ -36,6 +36,7 @@ struct dma_buf;
>  struct drm_connector;
>  struct drm_crtc;
>  struct drm_framebuffer;
> +struct drm_gem_membuf;
>  struct drm_gem_object;
>  struct drm_master;
>  struct drm_minor;
> @@ -186,8 +187,8 @@ void drm_gem_print_info(struct drm_printer *p, unsigned int indent,
>  
>  int drm_gem_pin(struct drm_gem_object *obj);
>  void drm_gem_unpin(struct drm_gem_object *obj);
> -void *drm_gem_vmap(struct drm_gem_object *obj);
> -void drm_gem_vunmap(struct drm_gem_object *obj, void *vaddr);
> +int drm_gem_vmap(struct drm_gem_object *obj, struct drm_gem_membuf *buf);
> +void drm_gem_vunmap(struct drm_gem_object *obj, const struct drm_gem_membuf *buf);
>  
>  /* drm_debugfs.c drm_debugfs_crc.c */
>  #if defined(CONFIG_DEBUG_FS)
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 1693aa7c14b5..d95a39030a93 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -671,13 +671,14 @@ EXPORT_SYMBOL(drm_gem_unmap_dma_buf);
>  void *drm_gem_dmabuf_vmap(struct dma_buf *dma_buf)
>  {
>  	struct drm_gem_object *obj = dma_buf->priv;
> -	void *vaddr;
> +	struct drm_gem_membuf buf;
> +	int ret;
>  
> -	vaddr = drm_gem_vmap(obj);
> -	if (IS_ERR(vaddr))
> -		vaddr = NULL;
> +	ret = drm_gem_vmap(obj, &buf);
> +	if (ret)
> +		buf.vaddr = NULL;
>  
> -	return vaddr;
> +	return buf.vaddr;
>  }
>  EXPORT_SYMBOL(drm_gem_dmabuf_vmap);
>  
> @@ -692,8 +693,11 @@ EXPORT_SYMBOL(drm_gem_dmabuf_vmap);
>  void drm_gem_dmabuf_vunmap(struct dma_buf *dma_buf, void *vaddr)
>  {
>  	struct drm_gem_object *obj = dma_buf->priv;
> +	struct drm_gem_membuf buf;
>  
> -	drm_gem_vunmap(obj, vaddr);
> +	buf.vaddr = vaddr;
> +	buf.is_iomem = false;
> +	drm_gem_vunmap(obj, &buf);
>  }
>  EXPORT_SYMBOL(drm_gem_dmabuf_vunmap);
>  
> diff --git a/include/drm/drm_client.h b/include/drm/drm_client.h
> index 7aaea665bfc2..5ed73c390619 100644
> --- a/include/drm/drm_client.h
> +++ b/include/drm/drm_client.h
> @@ -14,6 +14,7 @@ struct drm_client_dev;
>  struct drm_device;
>  struct drm_file;
>  struct drm_framebuffer;
> +struct drm_gem_membuf;
>  struct drm_gem_object;
>  struct drm_minor;
>  struct module;
> @@ -141,9 +142,9 @@ struct drm_client_buffer {
>  	struct drm_gem_object *gem;
>  
>  	/**
> -	 * @vaddr: Virtual address for the buffer
> +	 * @membuf: Virtual address for the buffer
>  	 */
> -	void *vaddr;
> +	struct drm_gem_membuf membuf;
>  
>  	/**
>  	 * @fb: DRM framebuffer
> @@ -155,7 +156,7 @@ struct drm_client_buffer *
>  drm_client_framebuffer_create(struct drm_client_dev *client, u32 width, u32 height, u32 format);
>  void drm_client_framebuffer_delete(struct drm_client_buffer *buffer);
>  int drm_client_framebuffer_flush(struct drm_client_buffer *buffer, struct drm_rect *rect);
> -void *drm_client_buffer_vmap(struct drm_client_buffer *buffer);
> +const struct drm_gem_membuf *drm_client_buffer_vmap(struct drm_client_buffer *buffer);
>  void drm_client_buffer_vunmap(struct drm_client_buffer *buffer);
>  
>  int drm_client_modeset_create(struct drm_client_dev *client);
> diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
> index 0988351d743c..6ecf03601c36 100644
> --- a/include/drm/drm_device.h
> +++ b/include/drm/drm_device.h
> @@ -381,4 +381,30 @@ struct drm_device {
>  #endif
>  };
>  
> +/**
> + * struct drm_gem_membuf - GEM memory buffer

This isn't gem specific, and membuf feels a bit strange - it's not a
memory buffer, but more a buffer mapping. I'd call these struct
drm_bufmap.

> + */
> +struct drm_gem_membuf {
> +	union {
> +		/**
> +		 * @vaddr:
> +		 *
> +		 * The virtual address for the buffer in system memory.
> +		 */
> +		void *vaddr;
> +		/**
> +		 * @vaddr_iomem:
> +		 *
> +		 * The virtual address for the buffer in I/O memory.
> +		 */
> +		void __iomem *vaddr_iomem;
> +	};
> +	/**
> +	 * @is_iomem:
> +	 *
> +	 * True if the memory is located in I/O memory, false otherwise.
> +	 */
> +	bool is_iomem;
> +};

I think if we do this we should go all in, i.e. create a new header, and
then start to add all kinds of helper functions to it, like:

static inline drm_memcpy_to_bufmap(bufmap, ...)
{
	if (bufmap->is_iomem)
		memcpy_toio(bufmap->vaddr_iomem, ...);
	else
		memcpy(bufmap->vaddr_iomem, ...);

}

totally wrong code of course, but I think you get the idea. If we add
helpers like this I think a new header file is also warranted, so maybe
put it all in drm_bufmap.h and then wire up the kerneldoc.

Also I think cc: ttm people for an ack would be good, maybe long-term we
want to roll this out through ttm too.

Cheers, Daniel


> +
>  #endif
> -- 
> 2.28.0
> 

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