[PATCH 4/8] drm/fb-helper: Add fb_deferred_io support

Noralf Trønnes
2016-04-20T15:25:25Z

This adds deferred io support if CONFIG_FB_DEFERRED_IO is enabled.
Accumulated fbdev framebuffer changes are signaled using the callback
(struct drm_framebuffer_funcs *)->dirty()

The drm_fb_helper_sys_*() functions will accumulate changes and
schedule fb_info.deferred_work _if_ fb_info.fbdefio is set.
This worker is used by the deferred io mmap code to signal that it
has been collecting page faults. The page faults and/or other changes
are then merged into a drm_clip_rect and passed to the framebuffer
dirty() function.

The driver is responsible for setting up the fb_info.fbdefio structure
and calling fb_deferred_io_init() using the provided callback:
(struct fb_deferred_io).deferred_io = drm_fb_helper_deferred_io;

Signed-off-by: Noralf TrÃ¸nnes <noralf@tronnes.org>
---
drivers/gpu/drm/drm_fb_helper.c | 119 +++++++++++++++++++++++++++++++++++++++-
include/drm/drm_fb_helper.h | 15 +++++
2 files changed, 133 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 855108e..79c974a 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -40,6 +40,7 @@
#include <drm/drm_crtc_helper.h>
#include <drm/drm_atomic.h>
#include <drm/drm_atomic_helper.h>
+#include <drm/drm_rect.h>

static bool drm_fbdev_emulation = true;
module_param_named(fbdev_emulation, drm_fbdev_emulation, bool, 0600);
@@ -48,6 +49,9 @@ MODULE_PARM_DESC(fbdev_emulation,

static LIST_HEAD(kernel_fb_helper_list);

+static void drm_fb_helper_defer_dirty(struct fb_info *info, u32 x, u32 y,
+ u32 width, u32 height);
+
/**
* DOC: fbdev helpers
*
@@ -84,6 +88,13 @@ static LIST_HEAD(kernel_fb_helper_list);
* and set up an initial configuration using the detected hardware, drivers
* should call drm_fb_helper_single_add_all_connectors() followed by
* drm_fb_helper_initial_config().
+ *
+ * If CONFIG_FB_DEFERRED_IO is enabled and (struct fb_info).fbdefio is set,
+ * the drm_fb_helper_{cfb,sys}_{write,fillrect,copyarea,imageblit} functions
+ * will accumulate changes and schedule (struct fb_info).deferred_work to run.
+ * This is the same worker used by the mmap deferred io code path.
+ * drm_fb_helper_deferred_io() will call
+ * (struct drm_framebuffer_funcs)->dirty().
*/

/**
@@ -401,11 +412,14 @@ backoff:
static int restore_fbdev_mode(struct drm_fb_helper *fb_helper)
{
struct drm_device *dev = fb_helper->dev;
+ struct fb_info *info = fb_helper->fbdev;
struct drm_plane *plane;
int i;

drm_warn_on_modeset_not_all_locked(dev);

+ drm_fb_helper_defer_dirty(info, 0, 0, info->var.xres, info->var.yres);
+
if (fb_helper->atomic)
return restore_fbdev_mode_atomic(fb_helper);

@@ -650,6 +664,9 @@ void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper,
const struct drm_fb_helper_funcs *funcs)
{
INIT_LIST_HEAD(&helper->kernel_fb_list);
+#ifdef CONFIG_FB_DEFERRED_IO
+ spin_lock_init(&helper->dirty_lock);
+#endif
helper->funcs = funcs;
helper->dev = dev;
}
@@ -834,6 +851,87 @@ void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
}
EXPORT_SYMBOL(drm_fb_helper_unlink_fbi);

+#ifdef CONFIG_FB_DEFERRED_IO
+/**
+ * drm_fb_helper_deferred_io() - (struct fb_deferred_io *)->deferred_io callback
+ * function
+ *
+ * This function always runs in process context (struct delayed_work) and calls
+ * the (struct drm_framebuffer_funcs)->dirty function with the collected
+ * damage. There's no need to worry about the possibility that the fb_sys_*()
+ * functions could be running in atomic context. They only schedule the
+ * delayed worker which then calls this deferred_io callback.
+ */
+void drm_fb_helper_deferred_io(struct fb_info *info,
+ struct list_head *pagelist)
+{
+ struct drm_fb_helper *helper = info->par;
+ unsigned long start, end, min, max;
+ struct drm_clip_rect clip;
+ unsigned long flags;
+ struct page *page;
+
+ if (!helper->fb->funcs->dirty)
+ return;
+
+ spin_lock_irqsave(&helper->dirty_lock, flags);
+ clip = helper->dirty_clip;
+ drm_clip_rect_reset(&helper->dirty_clip);
+ spin_unlock_irqrestore(&helper->dirty_lock, flags);
+
+ min = ULONG_MAX;
+ max = 0;
+ list_for_each_entry(page, pagelist, lru) {
+ start = page->index << PAGE_SHIFT;
+ end = start + PAGE_SIZE - 1;
+ min = min(min, start);
+ max = max(max, end);
+ }
+
+ if (min < max) {
+ struct drm_clip_rect mmap_clip;
+
+ mmap_clip.x1 = 0;
+ mmap_clip.x2 = info->var.xres;
+ mmap_clip.y1 = min / info->fix.line_length;
+ mmap_clip.y2 = min_t(u32, max / info->fix.line_length,
+ info->var.yres);
+ drm_clip_rect_merge(&clip, &mmap_clip, 1, 0, 0, 0);
+ }
+
+ if (!drm_clip_rect_is_empty(&clip))
+ helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip, 1);
+}
+EXPORT_SYMBOL(drm_fb_helper_deferred_io);
+
+static void drm_fb_helper_defer_dirty(struct fb_info *info, u32 x, u32 y,
+ u32 width, u32 height)
+{
+ struct drm_fb_helper *helper = info->par;
+ struct drm_clip_rect clip;
+ unsigned long flags;
+
+ if (!info->fbdefio)
+ return;
+
+ clip.x1 = x;
+ clip.x2 = x + width;
+ clip.y1 = y;
+ clip.y2 = y + height;
+
+ spin_lock_irqsave(&helper->dirty_lock, flags);
+ drm_clip_rect_merge(&helper->dirty_clip, &clip, 1, 0, 0, 0);
+ spin_unlock_irqrestore(&helper->dirty_lock, flags);
+
+ schedule_delayed_work(&info->deferred_work, info->fbdefio->delay);
+}
+#else
+static void drm_fb_helper_defer_dirty(struct fb_info *info, u32 x, u32 y,
+ u32 width, u32 height)
+{
+}
+#endif
+
/**
* drm_fb_helper_sys_read - wrapper around fb_sys_read
* @info: fb_info struct pointer
@@ -862,7 +960,14 @@ EXPORT_SYMBOL(drm_fb_helper_sys_read);
ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
size_t count, loff_t *ppos)
{
- return fb_sys_write(info, buf, count, ppos);
+ ssize_t ret;
+
+ ret = fb_sys_write(info, buf, count, ppos);
+ if (ret > 0)
+ drm_fb_helper_defer_dirty(info, 0, 0,
+ info->var.xres, info->var.yres);
+
+ return ret;
}
EXPORT_SYMBOL(drm_fb_helper_sys_write);

@@ -877,6 +982,8 @@ void drm_fb_helper_sys_fillrect(struct fb_info *info,
const struct fb_fillrect *rect)
{
sys_fillrect(info, rect);
+ drm_fb_helper_defer_dirty(info, rect->dx, rect->dy,
+ rect->width, rect->height);
}
EXPORT_SYMBOL(drm_fb_helper_sys_fillrect);

@@ -891,6 +998,8 @@ void drm_fb_helper_sys_copyarea(struct fb_info *info,
const struct fb_copyarea *area)
{
sys_copyarea(info, area);
+ drm_fb_helper_defer_dirty(info, area->dx, area->dy,
+ area->width, area->height);
}
EXPORT_SYMBOL(drm_fb_helper_sys_copyarea);

@@ -905,6 +1014,8 @@ void drm_fb_helper_sys_imageblit(struct fb_info *info,
const struct fb_image *image)
{
sys_imageblit(info, image);
+ drm_fb_helper_defer_dirty(info, image->dx, image->dy,
+ image->width, image->height);
}
EXPORT_SYMBOL(drm_fb_helper_sys_imageblit);

@@ -919,6 +1030,8 @@ void drm_fb_helper_cfb_fillrect(struct fb_info *info,
const struct fb_fillrect *rect)
{
cfb_fillrect(info, rect);
+ drm_fb_helper_defer_dirty(info, rect->dx, rect->dy,
+ rect->width, rect->height);
}
EXPORT_SYMBOL(drm_fb_helper_cfb_fillrect);

@@ -933,6 +1046,8 @@ void drm_fb_helper_cfb_copyarea(struct fb_info *info,
const struct fb_copyarea *area)
{
cfb_copyarea(info, area);
+ drm_fb_helper_defer_dirty(info, area->dx, area->dy,
+ area->width, area->height);
}
EXPORT_SYMBOL(drm_fb_helper_cfb_copyarea);

@@ -947,6 +1062,8 @@ void drm_fb_helper_cfb_imageblit(struct fb_info *info,
const struct fb_image *image)
{
cfb_imageblit(info, image);
+ drm_fb_helper_defer_dirty(info, image->dx, image->dy,
+ image->width, image->height);
}
EXPORT_SYMBOL(drm_fb_helper_cfb_imageblit);

diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
index 062723b..c9e9271 100644
--- a/include/drm/drm_fb_helper.h
+++ b/include/drm/drm_fb_helper.h
@@ -172,6 +172,9 @@ struct drm_fb_helper_connector {
* @funcs: driver callbacks for fb helper
* @fbdev: emulated fbdev device info struct
* @pseudo_palette: fake palette of 16 colors
+ * @dirty_clip: clip rectangle used with deferred_io to accumulate damage to
+ * the screen buffer
+ * @dirty_lock: spinlock protecting @dirty_clip
*
* This is the main structure used by the fbdev helpers. Drivers supporting
* fbdev emulation should embedded this into their overall driver structure.
@@ -189,6 +192,10 @@ struct drm_fb_helper {
const struct drm_fb_helper_funcs *funcs;
struct fb_info *fbdev;
u32 pseudo_palette[17];
+#ifdef CONFIG_FB_DEFERRED_IO
+ struct drm_clip_rect dirty_clip;
+ spinlock_t dirty_lock;
+#endif

/**
* @kernel_fb_list:
@@ -245,6 +252,9 @@ void drm_fb_helper_fill_fix(struct fb_info *info, uint32_t pitch,

void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper);

+void drm_fb_helper_deferred_io(struct fb_info *info,
+ struct list_head *pagelist);
+
ssize_t drm_fb_helper_sys_read(struct fb_info *info, char __user *buf,
size_t count, loff_t *ppos);
ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
@@ -368,6 +378,11 @@ static inline void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
{
}

+static inline void drm_fb_helper_deferred_io(struct fb_info *info,
+ struct list_head *pagelist)
+{
+}
+
static inline ssize_t drm_fb_helper_sys_read(struct fb_info *info,
char __user *buf, size_t count,
loff_t *ppos)
--
2.2.2