[PATCH v7 10/10] drm/fb_helper: Support framebuffers in I/O memory

[Thomas Zimmermann <tzimmermann@xxxxxxx>]

At least sparc64 requires I/O-specific access to framebuffers. This
patch updates the fbdev console accordingly.

For drivers with direct access to the framebuffer memory, the callback
functions in struct fb_ops test for the type of memory and call the rsp
fb_sys_ of fb_cfb_ functions. Read and write operations are implemented
internally by DRM's fbdev helper.

For drivers that employ a shadow buffer, fbdev's blit function retrieves
the framebuffer address as struct dma_buf_map, and uses dma_buf_map
interfaces to access the buffer.

The bochs driver on sparc64 uses a workaround to flag the framebuffer as
I/O memory and avoid a HW exception. With the introduction of struct
dma_buf_map, this is not required any longer. The patch removes the rsp
code from both, bochs and fbdev.

v7:
        * use min_t(size_t,) (kernel test robot)
        * return the number of bytes read/written, if any (fbdev testcase)
v5:
        * implement fb_read/fb_write internally (Daniel, Sam)
v4:
        * move dma_buf_map changes into separate patch (Daniel)
        * TODO list: comment on fbdev updates (Daniel)

Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Reviewed-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
Tested-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
---
 Documentation/gpu/todo.rst        |  19 ++-
 drivers/gpu/drm/bochs/bochs_kms.c |   1 -
 drivers/gpu/drm/drm_fb_helper.c   | 220 ++++++++++++++++++++++++++++--
 include/drm/drm_mode_config.h     |  12 --
 4 files changed, 223 insertions(+), 29 deletions(-)

diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index 59f63f1d7680..acca232b025b 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -201,13 +201,28 @@ Convert drivers to use drm_fbdev_generic_setup()
 ------------------------------------------------
 
 Most drivers can use drm_fbdev_generic_setup(). Driver have to implement
-atomic modesetting and GEM vmap support. Current generic fbdev emulation
-expects the framebuffer in system memory (or system-like memory).
+atomic modesetting and GEM vmap support. Historically, generic fbdev emulation
+expected the framebuffer in system memory or system-like memory. By employing
+struct dma_buf_map, drivers with frambuffers in I/O memory can be supported
+as well.
 
 Contact: Maintainer of the driver you plan to convert
 
 Level: Intermediate
 
+Reimplement functions in drm_fbdev_fb_ops without fbdev
+-------------------------------------------------------
+
+A number of callback functions in drm_fbdev_fb_ops could benefit from
+being rewritten without dependencies on the fbdev module. Some of the
+helpers could further benefit from using struct dma_buf_map instead of
+raw pointers.
+
+Contact: Thomas Zimmermann <tzimmermann@xxxxxxx>, Daniel Vetter
+
+Level: Advanced
+
+
 drm_framebuffer_funcs and drm_mode_config_funcs.fb_create cleanup
 -----------------------------------------------------------------
 
diff --git a/drivers/gpu/drm/bochs/bochs_kms.c 
b/drivers/gpu/drm/bochs/bochs_kms.c
index 13d0d04c4457..853081d186d5 100644
--- a/drivers/gpu/drm/bochs/bochs_kms.c
+++ b/drivers/gpu/drm/bochs/bochs_kms.c
@@ -151,7 +151,6 @@ int bochs_kms_init(struct bochs_device *bochs)
        bochs->dev->mode_config.preferred_depth = 24;
        bochs->dev->mode_config.prefer_shadow = 0;
        bochs->dev->mode_config.prefer_shadow_fbdev = 1;
-       bochs->dev->mode_config.fbdev_use_iomem = true;
        bochs->dev->mode_config.quirk_addfb_prefer_host_byte_order = true;
 
        bochs->dev->mode_config.funcs = &bochs_mode_funcs;
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index a0d88130fedb..01ba1da28511 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -372,24 +372,22 @@ static void drm_fb_helper_resume_worker(struct 
work_struct *work)
 }
 
 static void drm_fb_helper_dirty_blit_real(struct drm_fb_helper *fb_helper,
-                                         struct drm_clip_rect *clip)
+                                         struct drm_clip_rect *clip,
+                                         struct dma_buf_map *dst)
 {
        struct drm_framebuffer *fb = fb_helper->fb;
        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->map.vaddr + offset;
        size_t len = (clip->x2 - clip->x1) * cpp;
        unsigned int y;
 
-       for (y = clip->y1; y < clip->y2; y++) {
-               if (!fb_helper->dev->mode_config.fbdev_use_iomem)
-                       memcpy(dst, src, len);
-               else
-                       memcpy_toio((void __iomem *)dst, src, len);
+       dma_buf_map_incr(dst, offset); /* go to first pixel within clip rect */
 
+       for (y = clip->y1; y < clip->y2; y++) {
+               dma_buf_map_memcpy_to(dst, src, len);
+               dma_buf_map_incr(dst, fb->pitches[0]);
                src += fb->pitches[0];
-               dst += fb->pitches[0];
        }
 }
 
@@ -417,8 +415,9 @@ static void drm_fb_helper_dirty_work(struct work_struct 
*work)
                        ret = drm_client_buffer_vmap(helper->buffer, &map);
                        if (ret)
                                return;
-                       drm_fb_helper_dirty_blit_real(helper, &clip_copy);
+                       drm_fb_helper_dirty_blit_real(helper, &clip_copy, &map);
                }
+
                if (helper->fb->funcs->dirty)
                        helper->fb->funcs->dirty(helper->fb, NULL, 0, 0,
                                                 &clip_copy, 1);
@@ -2027,6 +2026,199 @@ static int drm_fbdev_fb_mmap(struct fb_info *info, 
struct vm_area_struct *vma)
                return -ENODEV;
 }
 
+static bool drm_fbdev_use_iomem(struct fb_info *info)
+{
+       struct drm_fb_helper *fb_helper = info->par;
+       struct drm_client_buffer *buffer = fb_helper->buffer;
+
+       return !drm_fbdev_use_shadow_fb(fb_helper) && buffer->map.is_iomem;
+}
+
+static ssize_t fb_read_screen_base(struct fb_info *info, char __user *buf, 
size_t count,
+                                  loff_t pos)
+{
+       const char __iomem *src = info->screen_base + pos;
+       size_t alloc_size = min(count, PAGE_SIZE);
+       ssize_t ret = 0;
+       int err = 0;
+       char *tmp;
+
+       tmp = kmalloc(alloc_size, GFP_KERNEL);
+       if (!tmp)
+               return -ENOMEM;
+
+       while (count) {
+               size_t c = min_t(size_t, count, alloc_size);
+
+               memcpy_fromio(tmp, src, c);
+               if (copy_to_user(buf, tmp, c)) {
+                       err = -EFAULT;
+                       break;
+               }
+
+               src += c;
+               buf += c;
+               ret += c;
+               count -= c;
+       }
+
+       kfree(tmp);
+
+       return ret ? ret : err;
+}
+
+static ssize_t fb_read_screen_buffer(struct fb_info *info, char __user *buf, 
size_t count,
+                                    loff_t pos)
+{
+       const char *src = info->screen_buffer + pos;
+
+       if (copy_to_user(buf, src, count))
+               return -EFAULT;
+
+       return count;
+}
+
+static ssize_t drm_fbdev_fb_read(struct fb_info *info, char __user *buf,
+                                size_t count, loff_t *ppos)
+{
+       loff_t pos = *ppos;
+       size_t total_size;
+       ssize_t ret;
+
+       if (info->screen_size)
+               total_size = info->screen_size;
+       else
+               total_size = info->fix.smem_len;
+
+       if (pos >= total_size)
+               return 0;
+       if (count >= total_size)
+               count = total_size;
+       if (total_size - count < pos)
+               count = total_size - pos;
+
+       if (drm_fbdev_use_iomem(info))
+               ret = fb_read_screen_base(info, buf, count, pos);
+       else
+               ret = fb_read_screen_buffer(info, buf, count, pos);
+
+       if (ret > 0)
+               *ppos += ret;
+
+       return ret;
+}
+
+static ssize_t fb_write_screen_base(struct fb_info *info, const char __user 
*buf, size_t count,
+                                   loff_t pos)
+{
+       char __iomem *dst = info->screen_base + pos;
+       size_t alloc_size = min(count, PAGE_SIZE);
+       ssize_t ret = 0;
+       int err = 0;
+       u8 *tmp;
+
+       tmp = kmalloc(alloc_size, GFP_KERNEL);
+       if (!tmp)
+               return -ENOMEM;
+
+       while (count) {
+               size_t c = min_t(size_t, count, alloc_size);
+
+               if (copy_from_user(tmp, buf, c)) {
+                       err = -EFAULT;
+                       break;
+               }
+               memcpy_toio(dst, tmp, c);
+
+               dst += c;
+               buf += c;
+               ret += c;
+               count -= c;
+       }
+
+       kfree(tmp);
+
+       return ret ? ret : err;
+}
+
+static ssize_t fb_write_screen_buffer(struct fb_info *info, const char __user 
*buf, size_t count,
+                                     loff_t pos)
+{
+       char *dst = info->screen_buffer + pos;
+
+       if (copy_from_user(dst, buf, count))
+               return -EFAULT;
+
+       return count;
+}
+
+static ssize_t drm_fbdev_fb_write(struct fb_info *info, const char __user *buf,
+                                 size_t count, loff_t *ppos)
+{
+       loff_t pos = *ppos;
+       size_t total_size;
+       ssize_t ret;
+       int err = 0;
+
+       if (info->screen_size)
+               total_size = info->screen_size;
+       else
+               total_size = info->fix.smem_len;
+
+       if (pos > total_size)
+               return -EFBIG;
+       if (count > total_size) {
+               err = -EFBIG;
+               count = total_size;
+       }
+       if (total_size - count < pos) {
+               if (!err)
+                       err = -ENOSPC;
+               count = total_size - pos;
+       }
+
+       /*
+        * Copy to framebuffer even if we already logged an error. Emulates
+        * the behavior of the original fbdev implementation.
+        */
+       if (drm_fbdev_use_iomem(info))
+               ret = fb_write_screen_base(info, buf, count, pos);
+       else
+               ret = fb_write_screen_buffer(info, buf, count, pos);
+
+       if (ret > 0)
+               *ppos += ret;
+
+       return ret ? ret : err;
+}
+
+static void drm_fbdev_fb_fillrect(struct fb_info *info,
+                                 const struct fb_fillrect *rect)
+{
+       if (drm_fbdev_use_iomem(info))
+               drm_fb_helper_cfb_fillrect(info, rect);
+       else
+               drm_fb_helper_sys_fillrect(info, rect);
+}
+
+static void drm_fbdev_fb_copyarea(struct fb_info *info,
+                                 const struct fb_copyarea *area)
+{
+       if (drm_fbdev_use_iomem(info))
+               drm_fb_helper_cfb_copyarea(info, area);
+       else
+               drm_fb_helper_sys_copyarea(info, area);
+}
+
+static void drm_fbdev_fb_imageblit(struct fb_info *info,
+                                  const struct fb_image *image)
+{
+       if (drm_fbdev_use_iomem(info))
+               drm_fb_helper_cfb_imageblit(info, image);
+       else
+               drm_fb_helper_sys_imageblit(info, image);
+}
+
 static const struct fb_ops drm_fbdev_fb_ops = {
        .owner          = THIS_MODULE,
        DRM_FB_HELPER_DEFAULT_OPS,
@@ -2034,11 +2226,11 @@ static const struct fb_ops drm_fbdev_fb_ops = {
        .fb_release     = drm_fbdev_fb_release,
        .fb_destroy     = drm_fbdev_fb_destroy,
        .fb_mmap        = drm_fbdev_fb_mmap,
-       .fb_read        = drm_fb_helper_sys_read,
-       .fb_write       = drm_fb_helper_sys_write,
-       .fb_fillrect    = drm_fb_helper_sys_fillrect,
-       .fb_copyarea    = drm_fb_helper_sys_copyarea,
-       .fb_imageblit   = drm_fb_helper_sys_imageblit,
+       .fb_read        = drm_fbdev_fb_read,
+       .fb_write       = drm_fbdev_fb_write,
+       .fb_fillrect    = drm_fbdev_fb_fillrect,
+       .fb_copyarea    = drm_fbdev_fb_copyarea,
+       .fb_imageblit   = drm_fbdev_fb_imageblit,
 };
 
 static struct fb_deferred_io drm_fbdev_defio = {
diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
index 5ffbb4ed5b35..ab424ddd7665 100644
--- a/include/drm/drm_mode_config.h
+++ b/include/drm/drm_mode_config.h
@@ -877,18 +877,6 @@ struct drm_mode_config {
         */
        bool prefer_shadow_fbdev;
 
-       /**
-        * @fbdev_use_iomem:
-        *
-        * Set to true if framebuffer reside in iomem.
-        * When set to true memcpy_toio() is used when copying the framebuffer 
in
-        * drm_fb_helper.drm_fb_helper_dirty_blit_real().
-        *
-        * FIXME: This should be replaced with a per-mapping is_iomem
-        * flag (like ttm does), and then used everywhere in fbdev code.
-        */
-       bool fbdev_use_iomem;
-
        /**
         * @quirk_addfb_prefer_xbgr_30bpp:
         *
-- 
2.29.0