From d9b42dfab513c9130ee0458f2e6febb75c89d1c8 Mon Sep 17 00:00:00 2001 From: Thomas Zimmermann Date: Wed, 3 Jul 2019 09:58:18 +0200 Subject: drm/client: Support unmapping of DRM client buffers MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit DRM clients, such as the fbdev emulation, have their buffer objects mapped by default. Mapping a buffer implicitly prevents its relocation. Hence, the buffer may permanently consume video memory while it's allocated. This is a problem for drivers of low-memory devices, such as ast, mgag200 or older framebuffer hardware, which will then not have enough memory to display other content (e.g., X11). This patch introduces drm_client_buffer_vmap() and _vunmap(). Internal DRM clients can use these functions to unmap and remap buffer objects as needed. There's no reference counting for vmap operations. Callers are expected to either keep buffers mapped (as it is now), or call vmap and vunmap in pairs around code that accesses the mapped memory. v2: * remove several duplicated NULL-pointer checks v3: * style and typo fixes Signed-off-by: Thomas Zimmermann Reviewed-by: Noralf Trønnes Link: https://patchwork.freedesktop.org/patch/315831/ Signed-off-by: Gerd Hoffmann --- drivers/gpu/drm/drm_client.c | 66 +++++++++++++++++++++++++++++++++++++------- 1 file changed, 56 insertions(+), 10 deletions(-) (limited to 'drivers/gpu/drm/drm_client.c') diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c index 410572f14257..fb107b24baae 100644 --- a/drivers/gpu/drm/drm_client.c +++ b/drivers/gpu/drm/drm_client.c @@ -281,6 +281,42 @@ drm_client_buffer_create(struct drm_client_dev *client, u32 width, u32 height, u buffer->gem = obj; + vaddr = drm_client_buffer_vmap(buffer); + if (IS_ERR(vaddr)) { + ret = PTR_ERR(vaddr); + goto err_delete; + } + + return buffer; + +err_delete: + drm_client_buffer_delete(buffer); + + return ERR_PTR(ret); +} + +/** + * drm_client_buffer_vmap - Map DRM client buffer into address space + * @buffer: DRM client buffer + * + * This function maps a client buffer into kernel address space. If the + * buffer is already mapped, it returns the mapping's address. + * + * Client buffer mappings are not ref'counted. Each call to + * drm_client_buffer_vmap() should be followed by a call to + * drm_client_buffer_vunmap(); or the client buffer should be mapped + * throughout its lifetime. The latter is the default. + * + * Returns: + * The mapped memory's address + */ +void *drm_client_buffer_vmap(struct drm_client_buffer *buffer) +{ + void *vaddr; + + if (buffer->vaddr) + return buffer->vaddr; + /* * FIXME: The dependency on GEM here isn't required, we could * convert the driver handle to a dma-buf instead and use the @@ -289,21 +325,31 @@ drm_client_buffer_create(struct drm_client_dev *client, u32 width, u32 height, u * fd_install step out of the driver backend hooks, to make that * final step optional for internal users. */ - vaddr = drm_gem_vmap(obj); - if (IS_ERR(vaddr)) { - ret = PTR_ERR(vaddr); - goto err_delete; - } + vaddr = drm_gem_vmap(buffer->gem); + if (IS_ERR(vaddr)) + return vaddr; buffer->vaddr = vaddr; - return buffer; - -err_delete: - drm_client_buffer_delete(buffer); + return vaddr; +} +EXPORT_SYMBOL(drm_client_buffer_vmap); - return ERR_PTR(ret); +/** + * drm_client_buffer_vunmap - Unmap DRM client buffer + * @buffer: DRM client buffer + * + * This function removes a client buffer's memory mapping. This + * function is only required by clients that manage their buffers + * by themselves. By default, DRM client buffers are mapped throughout + * their entire lifetime. + */ +void drm_client_buffer_vunmap(struct drm_client_buffer *buffer) +{ + drm_gem_vunmap(buffer->gem, buffer->vaddr); + buffer->vaddr = NULL; } +EXPORT_SYMBOL(drm_client_buffer_vunmap); static void drm_client_buffer_rmfb(struct drm_client_buffer *buffer) { -- cgit From 87e281f88f3aa4ed401554f793685bcb2463580a Mon Sep 17 00:00:00 2001 From: Thomas Zimmermann Date: Wed, 3 Jul 2019 09:58:24 +0200 Subject: drm/fb-helper: Map DRM client buffer only when required MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This patch changes DRM clients to not map the buffer by default. The buffer, like any buffer object, should be mapped and unmapped when needed. An unmapped buffer object can be evicted to system memory and does not consume video ram until displayed. This allows to use generic fbdev emulation with drivers for low-memory devices, such as ast and mgag200. This change affects the generic framebuffer console. HW-based consoles map their console buffer once and keep it mapped. Userspace can mmap this buffer into its address space. The shadow-buffered framebuffer console only needs the buffer object to be mapped during updates. While not being updated from the shadow buffer, the buffer object can remain unmapped. Userspace will always mmap the shadow buffer. v2: * change DRM client to not map buffer by default * manually map client buffer for fbdev with HW framebuffer Signed-off-by: Thomas Zimmermann Reviewed-by: Noralf Trønnes Link: https://patchwork.freedesktop.org/patch/315830/ Signed-off-by: Gerd Hoffmann --- drivers/gpu/drm/drm_client.c | 16 ++++------------ drivers/gpu/drm/drm_fb_helper.c | 33 +++++++++++++++++++++++++-------- 2 files changed, 29 insertions(+), 20 deletions(-) (limited to 'drivers/gpu/drm/drm_client.c') diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c index fb107b24baae..e1dafb0cc5e2 100644 --- a/drivers/gpu/drm/drm_client.c +++ b/drivers/gpu/drm/drm_client.c @@ -254,7 +254,6 @@ drm_client_buffer_create(struct drm_client_dev *client, u32 width, u32 height, u struct drm_device *dev = client->dev; struct drm_client_buffer *buffer; struct drm_gem_object *obj; - void *vaddr; int ret; buffer = kzalloc(sizeof(*buffer), GFP_KERNEL); @@ -281,12 +280,6 @@ drm_client_buffer_create(struct drm_client_dev *client, u32 width, u32 height, u buffer->gem = obj; - vaddr = drm_client_buffer_vmap(buffer); - if (IS_ERR(vaddr)) { - ret = PTR_ERR(vaddr); - goto err_delete; - } - return buffer; err_delete: @@ -305,7 +298,7 @@ err_delete: * Client buffer mappings are not ref'counted. Each call to * drm_client_buffer_vmap() should be followed by a call to * drm_client_buffer_vunmap(); or the client buffer should be mapped - * throughout its lifetime. The latter is the default. + * throughout its lifetime. * * Returns: * The mapped memory's address @@ -339,10 +332,9 @@ EXPORT_SYMBOL(drm_client_buffer_vmap); * drm_client_buffer_vunmap - Unmap DRM client buffer * @buffer: DRM client buffer * - * This function removes a client buffer's memory mapping. This - * function is only required by clients that manage their buffers - * by themselves. By default, DRM client buffers are mapped throughout - * their entire lifetime. + * This function removes a client buffer's memory mapping. Calling this + * function is only required by clients that manage their buffer mappings + * by themselves. */ void drm_client_buffer_vunmap(struct drm_client_buffer *buffer) { diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index 1984e5c54d58..7ba6a0255821 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -403,6 +403,7 @@ 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; spin_lock_irqsave(&helper->dirty_lock, flags); clip_copy = *clip; @@ -412,10 +413,18 @@ static void drm_fb_helper_dirty_work(struct work_struct *work) /* call dirty callback only when it has been really touched */ if (clip_copy.x1 < clip_copy.x2 && clip_copy.y1 < clip_copy.y2) { + /* Generic fbdev uses a shadow buffer */ - if (helper->buffer) + if (helper->buffer) { + vaddr = drm_client_buffer_vmap(helper->buffer); + if (IS_ERR(vaddr)) + return; drm_fb_helper_dirty_blit_real(helper, &clip_copy); + } helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip_copy, 1); + + if (helper->buffer) + drm_client_buffer_vunmap(helper->buffer); } } @@ -2178,6 +2187,7 @@ int drm_fb_helper_generic_probe(struct drm_fb_helper *fb_helper, struct drm_framebuffer *fb; struct fb_info *fbi; u32 format; + void *vaddr; DRM_DEBUG_KMS("surface width(%d), height(%d) and bpp(%d)\n", sizes->surface_width, sizes->surface_height, @@ -2200,13 +2210,7 @@ int drm_fb_helper_generic_probe(struct drm_fb_helper *fb_helper, fbi->fbops = &drm_fbdev_fb_ops; fbi->screen_size = fb->height * fb->pitches[0]; fbi->fix.smem_len = fbi->screen_size; - fbi->screen_buffer = buffer->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) - fbi->fix.smem_start = - page_to_phys(virt_to_page(fbi->screen_buffer)); -#endif + drm_fb_helper_fill_info(fbi, fb_helper, sizes); if (fb->funcs->dirty) { @@ -2231,6 +2235,19 @@ int drm_fb_helper_generic_probe(struct drm_fb_helper *fb_helper, fbi->fbdefio = &drm_fbdev_defio; 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); + + fbi->screen_buffer = 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) + fbi->fix.smem_start = + page_to_phys(virt_to_page(fbi->screen_buffer)); +#endif } return 0; -- cgit