drm/fbdev-dma: Only install deferred I/O if necessary

Deferred I/O requires struct page for framebuffer memory, which is
not guaranteed for all DMA ranges. We thus only install deferred I/O
if we have a framebuffer that requires it.

A reported bug affected the ipu-v3 and pl111 drivers, which have video
memory in either Normal or HighMem zones

[    0.000000] Zone ranges:
[    0.000000]   Normal   [mem 0x0000000010000000-0x000000003fffffff]
[    0.000000]   HighMem  [mem 0x0000000040000000-0x000000004fffffff]

where deferred I/O only works correctly with HighMem. See the Closes
tags for bug reports.

v2:
- test if screen_buffer supports deferred I/O (Sima)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: 808a40b69468 ("drm/fbdev-dma: Implement damage handling and deferred I/O")
Reported-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Closes: https://lore.kernel.org/all/23636953.6Emhk5qWAg@steina-w/
Reported-by: Linus Walleij <linus.walleij@linaro.org>
Closes: https://lore.kernel.org/dri-devel/CACRpkdb+hb9AGavbWpY-=uQQ0apY9en_tWJioPKf_fAbXMP4Hg@mail.gmail.com/
Tested-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Reviewed-by: Simona Vetter <simona.vetter@ffwll.ch>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240904123750.31206-1-tzimmermann@suse.de

diff --git a/drivers/gpu/drm/drm_fbdev_dma.c b/drivers/gpu/drm/drm_fbdev_dma.c
index 7ef5a48c8029dd9a32c29daae9c577fa1d69acd6..b0602c4f3628305cc1261741142899446bdae44a 100644 (file)
--- a/drivers/gpu/drm/drm_fbdev_dma.c
+++ b/drivers/gpu/drm/drm_fbdev_dma.c
@@ -36,20 +36,11 @@ static int drm_fbdev_dma_fb_release(struct fb_info *info, int user)
        return 0;
 }
 
-FB_GEN_DEFAULT_DEFERRED_DMAMEM_OPS(drm_fbdev_dma,
-                                  drm_fb_helper_damage_range,
-                                  drm_fb_helper_damage_area);
-
 static int drm_fbdev_dma_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
 {
        struct drm_fb_helper *fb_helper = info->par;
-       struct drm_framebuffer *fb = fb_helper->fb;
-       struct drm_gem_dma_object *dma = drm_fb_dma_get_gem_obj(fb, 0);
 
-       if (!dma->map_noncoherent)
-               vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
-
-       return fb_deferred_io_mmap(info, vma);
+       return drm_gem_prime_mmap(fb_helper->buffer->gem, vma);
 }
 
 static void drm_fbdev_dma_fb_destroy(struct fb_info *info)
@@ -70,13 +61,40 @@ static void drm_fbdev_dma_fb_destroy(struct fb_info *info)
 }
 
 static const struct fb_ops drm_fbdev_dma_fb_ops = {
+       .owner = THIS_MODULE,
+       .fb_open = drm_fbdev_dma_fb_open,
+       .fb_release = drm_fbdev_dma_fb_release,
+       __FB_DEFAULT_DMAMEM_OPS_RDWR,
+       DRM_FB_HELPER_DEFAULT_OPS,
+       __FB_DEFAULT_DMAMEM_OPS_DRAW,
+       .fb_mmap = drm_fbdev_dma_fb_mmap,
+       .fb_destroy = drm_fbdev_dma_fb_destroy,
+};
+
+FB_GEN_DEFAULT_DEFERRED_DMAMEM_OPS(drm_fbdev_dma,
+                                  drm_fb_helper_damage_range,
+                                  drm_fb_helper_damage_area);
+
+static int drm_fbdev_dma_deferred_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
+{
+       struct drm_fb_helper *fb_helper = info->par;
+       struct drm_framebuffer *fb = fb_helper->fb;
+       struct drm_gem_dma_object *dma = drm_fb_dma_get_gem_obj(fb, 0);
+
+       if (!dma->map_noncoherent)
+               vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+
+       return fb_deferred_io_mmap(info, vma);
+}
+
+static const struct fb_ops drm_fbdev_dma_deferred_fb_ops = {
        .owner = THIS_MODULE,
        .fb_open = drm_fbdev_dma_fb_open,
        .fb_release = drm_fbdev_dma_fb_release,
        __FB_DEFAULT_DEFERRED_OPS_RDWR(drm_fbdev_dma),
        DRM_FB_HELPER_DEFAULT_OPS,
        __FB_DEFAULT_DEFERRED_OPS_DRAW(drm_fbdev_dma),
-       .fb_mmap = drm_fbdev_dma_fb_mmap,
+       .fb_mmap = drm_fbdev_dma_deferred_fb_mmap,
        .fb_destroy = drm_fbdev_dma_fb_destroy,
 };
 
@@ -89,6 +107,7 @@ static int drm_fbdev_dma_helper_fb_probe(struct drm_fb_helper *fb_helper,
 {
        struct drm_client_dev *client = &fb_helper->client;
        struct drm_device *dev = fb_helper->dev;
+       bool use_deferred_io = false;
        struct drm_client_buffer *buffer;
        struct drm_gem_dma_object *dma_obj;
        struct drm_framebuffer *fb;
@@ -111,6 +130,15 @@ static int drm_fbdev_dma_helper_fb_probe(struct drm_fb_helper *fb_helper,
 
        fb = buffer->fb;
 
+       /*
+        * Deferred I/O requires struct page for framebuffer memory,
+        * which is not guaranteed for all DMA ranges. We thus only
+        * install deferred I/O if we have a framebuffer that requires
+        * it.
+        */
+       if (fb->funcs->dirty)
+               use_deferred_io = true;
+
        ret = drm_client_buffer_vmap(buffer, &map);
        if (ret) {
                goto err_drm_client_buffer_delete;
@@ -130,7 +158,10 @@ static int drm_fbdev_dma_helper_fb_probe(struct drm_fb_helper *fb_helper,
 
        drm_fb_helper_fill_info(info, fb_helper, sizes);
 
-       info->fbops = &drm_fbdev_dma_fb_ops;
+       if (use_deferred_io)
+               info->fbops = &drm_fbdev_dma_deferred_fb_ops;
+       else
+               info->fbops = &drm_fbdev_dma_fb_ops;
 
        /* screen */
        info->flags |= FBINFO_VIRTFB; /* system memory */
@@ -144,14 +175,28 @@ static int drm_fbdev_dma_helper_fb_probe(struct drm_fb_helper *fb_helper,
        }
        info->fix.smem_len = info->screen_size;
 
-       /* deferred I/O */
-       fb_helper->fbdefio.delay = HZ / 20;
-       fb_helper->fbdefio.deferred_io = drm_fb_helper_deferred_io;
+       /*
+        * Only set up deferred I/O if the screen buffer supports
+        * it. If this disagrees with the previous test for ->dirty,
+        * mmap on the /dev/fb file might not work correctly.
+        */
+       if (!is_vmalloc_addr(info->screen_buffer) && info->fix.smem_start) {
+               unsigned long pfn = info->fix.smem_start >> PAGE_SHIFT;
 
-       info->fbdefio = &fb_helper->fbdefio;
-       ret = fb_deferred_io_init(info);
-       if (ret)
-               goto err_drm_fb_helper_release_info;
+               if (drm_WARN_ON(dev, !pfn_to_page(pfn)))
+                       use_deferred_io = false;
+       }
+
+       /* deferred I/O */
+       if (use_deferred_io) {
+               fb_helper->fbdefio.delay = HZ / 20;
+               fb_helper->fbdefio.deferred_io = drm_fb_helper_deferred_io;
+
+               info->fbdefio = &fb_helper->fbdefio;
+               ret = fb_deferred_io_init(info);
+               if (ret)
+                       goto err_drm_fb_helper_release_info;
+       }
 
        return 0;