Hi
Am 20.02.24 um 11:16 schrieb Tony Lindgren:
* Thomas Zimmermann <tzimmermann@xxxxxxx> [240220 09:32]:
Am 20.02.24 um 09:56 schrieb Tony Lindgren:
Oh right, yes omapdrm is operating on memory.
With the latest kernels, you should see a warning if helpers operate on the
wrong type of memory. [1][2]
OK
[1] https://elixir.bootlin.com/linux/v6.8-rc5/source/drivers/video/fbdev/core/fb_io_fops.c#L16
[2] https://elixir.bootlin.com/linux/v6.8-rc5/source/drivers/video/fbdev/core/fb_sys_fops.c#L26
The following test patch works for me.. Not sure about the tracking though.
I know that i915 doesn't track mmap'ed pages correctly and I've see systems
that do not update the framebuffer. IDK how/why this works with omapdrm.
Sounds like the a similar issue might exist on omapdrm too then.
Do you mean that tracking needs to be implemented if fb_deferred_io_mmap()
did not work?
omap_fbdev_fb_mmap() appears to mmap the DMA memory pages directly to
userspace. So the fb_dirty callback won't be invoked when userspace writes
to this framebuffer memory.
To implement tracking, you'd need to set fb_mmap to fb_deferred_io_mmap().
If you init omap_fb_ops with FB_DEFAULT_DEFERRED_OPS(), [3] you'd get that
automatically. fb_deferred_io_mmap() sets up the tracking whenever
userspaces writes to a mapped page. You also need to init the write-back
mechanisms that calls fb_dirty for the tracked pages. You should be able to
duplicate the code from [4] into omapdrm.
OK great. Updated test patch below with FB_DEFAULT_DEFERRED_OPS, maybe that's
all there is to it if I follow you :) The fb_dirty part was already done in
patch 1/2.
The changes below look good. You can test by instrumenting
drm_fb_helper_deferred_io() with printk(). For testing, you can reduce
the write-back frequency by setting helper->fbdefio.delay to a higher
value. If you set it to HZ, it should only do a write-back once per
second. Then do an mmap() from userspace and copy data into the memory
region. It should print something from drm_fb_helper_deferred_io(). Best
regards Thomas
[3] https://elixir.bootlin.com/linux/latest/source/include/linux/fb.h#L704
[4] https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/drm_fbdev_generic.c#L119
Regards,
Tony
8< ---------------------------
diff --git a/drivers/gpu/drm/omapdrm/omap_fbdev.c b/drivers/gpu/drm/omapdrm/omap_fbdev.c
--- a/drivers/gpu/drm/omapdrm/omap_fbdev.c
+++ b/drivers/gpu/drm/omapdrm/omap_fbdev.c
@@ -51,6 +51,10 @@ static void pan_worker(struct work_struct *work)
omap_gem_roll(bo, fbi->var.yoffset * npages);
}
+FB_GEN_DEFAULT_DEFERRED_DMAMEM_OPS(omap_fbdev,
+ drm_fb_helper_damage_range,
+ drm_fb_helper_damage_area)
+
static int omap_fbdev_pan_display(struct fb_var_screeninfo *var,
struct fb_info *fbi)
{
@@ -76,15 +80,6 @@ static int omap_fbdev_pan_display(struct fb_var_screeninfo *var,
return drm_fb_helper_pan_display(var, fbi);
}
-static int omap_fbdev_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
-{
- struct drm_fb_helper *helper = info->par;
- struct drm_framebuffer *fb = helper->fb;
- struct drm_gem_object *bo = drm_gem_fb_get_obj(fb, 0);
-
- return drm_gem_mmap_obj(bo, omap_gem_mmap_size(bo), vma);
-}
-
static void omap_fbdev_fb_destroy(struct fb_info *info)
{
struct drm_fb_helper *helper = info->par;
@@ -94,6 +89,7 @@ static void omap_fbdev_fb_destroy(struct fb_info *info)
DBG();
+ fb_deferred_io_cleanup(info);
drm_fb_helper_fini(helper);
omap_gem_unpin(bo);
@@ -106,15 +102,13 @@ static void omap_fbdev_fb_destroy(struct fb_info *info)
static const struct fb_ops omap_fb_ops = {
.owner = THIS_MODULE,
- __FB_DEFAULT_DMAMEM_OPS_RDWR,
+ FB_DEFAULT_DEFERRED_OPS(omap_fbdev),
.fb_check_var = drm_fb_helper_check_var,
.fb_set_par = drm_fb_helper_set_par,
.fb_setcmap = drm_fb_helper_setcmap,
.fb_blank = drm_fb_helper_blank,
.fb_pan_display = omap_fbdev_pan_display,
- __FB_DEFAULT_DMAMEM_OPS_DRAW,
.fb_ioctl = drm_fb_helper_ioctl,
- .fb_mmap = omap_fbdev_fb_mmap,
.fb_destroy = omap_fbdev_fb_destroy,
};
@@ -213,6 +207,15 @@ static int omap_fbdev_create(struct drm_fb_helper *helper,
fbi->fix.smem_start = dma_addr;
fbi->fix.smem_len = bo->size;
+ /* deferred I/O */
+ helper->fbdefio.delay = HZ / 20;
+ helper->fbdefio.deferred_io = drm_fb_helper_deferred_io;
+
+ fbi->fbdefio = &helper->fbdefio;
+ ret = fb_deferred_io_init(fbi);
+ if (ret)
+ goto fail;
+
/* if we have DMM, then we can use it for scrolling by just
* shuffling pages around in DMM rather than doing sw blit.
*/
diff --git a/include/linux/fb.h b/include/linux/fb.h
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -686,6 +686,10 @@ extern int fb_deferred_io_fsync(struct file *file, loff_t start,
__FB_GEN_DEFAULT_DEFERRED_OPS_RDWR(__prefix, __damage_range, sys) \
__FB_GEN_DEFAULT_DEFERRED_OPS_DRAW(__prefix, __damage_area, sys)
+#define FB_GEN_DEFAULT_DEFERRED_DMAMEM_OPS(__prefix, __damage_range, __damage_area) \
+ __FB_GEN_DEFAULT_DEFERRED_OPS_RDWR(__prefix, __damage_range, sys) \
+ __FB_GEN_DEFAULT_DEFERRED_OPS_DRAW(__prefix, __damage_area, sys)
+
/*
* Initializes struct fb_ops for deferred I/O.
*/
--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)
