Den 29.03.2016 09:27, skrev Daniel Vetter:
On Fri, Mar 25, 2016 at 11:41:44AM +0100, Noralf Trønnes wrote:
Den 23.03.2016 18:28, skrev Daniel Vetter:
On Wed, Mar 23, 2016 at 06:07:56PM +0100, Noralf Trønnes wrote:
Den 18.03.2016 18:47, skrev Daniel Vetter:
On Thu, Mar 17, 2016 at 10:51:55PM +0100, Noralf Trønnes wrote:
Den 16.03.2016 16:11, skrev Daniel Vetter:
On Wed, Mar 16, 2016 at 02:34:15PM +0100, Noralf Trønnes wrote:
tinydrm provides a very simplified view of DRM for displays that has
onboard video memory and is connected through a slow bus like SPI/I2C.
Signed-off-by: Noralf Trønnes <noralf@xxxxxxxxxxx>
Yay, it finally happens! I already made a comment on the cover letter
about the fbdev stuff, I think that's the biggest part to split out from
tinydrm here. I'm not entirely sure a detailed code review makes sense
before that part is done (and hey we can start merging already), so just a
high level review for now:
[...]
In the case of tinydrm I think that means we should have a bunch of new
drm helpers, or extensions for existing ones:
- fbdev deferred io support using ->dirtyfb in drm_fb_helper.c.
Are you thinking something like this?
struct drm_fb_helper_funcs {
int (*dirtyfb)(struct drm_fb_helper *fb_helper,
struct drm_clip_rect *clip);
We already have a dirty_fb function in
dev->mode_config->funcs->dirty_fb(). This is the official interface native
drm/kms userspace is supposed to use to flush frontbuffer rendering. The
xfree86-video-modesetting driver uses it.
I couldn't find this dirty_fb() function, but I assume you mean
drm_framebuffer_funcs.dirty().
Yup.
};
struct drm_fb_helper {
spinlock_t dirty_lock;
struct drm_clip_rect *dirty_clip;
};
Yeah, this part is needed for the delayed work for the fbdev helper.
struct work dirty_fb_work; is missing.
This confuses me.
If we have this then there's no need for a fb->funcs->dirty() call,
the driver can just add a work function here instead.
Possible fb dirty() call chain:
Calls to drm_fb_helper_sys_* or mmap page writes will schedule
fb_info->deferred_work. The worker func fb_deferred_io_work() calls
fb_info->fbdefio->deferred_io().
Then deferred_io() can call fb_helper->fb->funcs->dirty().
In my use-case this dirty() function would schedule a delayed_work to run
immediately since it has already been deferred collecting changes.
The regular drm side framebuffer dirty() collects damage and schedules
the same worker to run deferred.
I don't see an easy way for a driver to set the dirty() function in
drm_fb_cma_helper apart from doing this:
struct drm_fbdev_cma {
struct drm_fb_helper fb_helper;
struct drm_fb_cma *fb;
+ int (*dirty)(struct drm_framebuffer *framebuffer,
+ struct drm_file *file_priv, unsigned flags,
+ unsigned color, struct drm_clip_rect *clips,
+ unsigned num_clips);
};
Well my point is that drm core already has a canonical interface
(drm_framebuffer_funcs.dirty) to flush out rendering. And it's supposed to
be called from process context, and userspace is supposed to batch up
dirty updates.
[...]
What I'd like is that the fbdev emulation uses exactly that interface,
without requiring drivers to write any additional fbdev code (like qxl and
udl currently have). Since the drm_framebuffer_funcs.dirty is already
expected to run in process context I think the only bit we need is the
deferred_work you already added in fbdev, so that we can schedule the
driver's ->dirty() function.
There shouldn't be any need to have another ->dirty() function anywhere
else.
I'll try and see if I can explain better with some code.
First the drm_fb_helper part:
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;
struct page *page;
if (!helper->fb->funcs->dirty)
return;
spin_lock(&helper->dirty_lock);
clip = *helper->dirty_clip;
/* reset dirty_clip */
spin_unlock(&helper->dirty_lock);
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) {
/* TODO merge with clip */
}
helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip, 1);
}
EXPORT_SYMBOL(drm_fb_helper_deferred_io);
/* Called by the drm_fb_helper_sys_*() functions */
static void drm_fb_helper_sys_deferred(struct fb_info *info, u32 x, u32 y,
u32 width, u32 height)
{
struct drm_fb_helper *helper = info->par;
struct drm_clip_rect clip;
if (!info->fbdefio)
return;
clip.x1 = x;
clip.x2 = x + width -1;
cliy.y1 = y;
clip.y2 = y + height - 1;
spin_lock(&helper->dirty_lock);
/* TODO merge clip with helper->dirty_clip */
spin_unlock(&helper->dirty_lock);
schedule_delayed_work(&info->deferred_work, info->fbdefio->delay);
}
So the question I have asked is this: How can the driver set the
dirty() function within drm_fb_cma_helper?
Having looked at the code over and over again, I have a suggestion,
but it assumes that it's allowed to change fb->funcs.
First the necessary drm_fb_cma_helper changes:
EXPORT_SYMBOL(drm_fb_cma_destroy);
EXPORT_SYMBOL(drm_fb_cma_create_handle);
EXPORT_SYMBOL(drm_fbdev_cma_create);
/* This is the drm_fbdev_cma_init() code with one change */
struct drm_fbdev_cma *drm_fbdev_cma_init_with_funcs(struct drm_device *dev,
unsigned int preferred_bpp, unsigned int num_crtc,
unsigned int max_conn_count, struct drm_framebuffer_funcs *funcs)
{
[...]
drm_fb_helper_prepare(dev, helper, funcs);
[...]
}
struct drm_fbdev_cma *drm_fbdev_cma_init(struct drm_device *dev,
unsigned int preferred_bpp, unsigned int num_crtc,
unsigned int max_conn_count)
{
return drm_fbdev_cma_init_with_funcs(dev, preferred_bpp, num_crtc,
max_conn_count,
&drm_fb_cma_helper_funcs);
}
Now tinydrm should be able to do this:
static int tinydrm_fbdev_dirty(struct drm_framebuffer *fb,
struct drm_file *file_priv,
unsigned flags, unsigned color,
struct drm_clip_rect *clips,
unsigned num_clips)
{
struct drm_fb_helper *helper = info->par;
struct tinydrm_device *tdev = helper->dev->dev_private;
struct drm_framebuffer *fb = helper->fb;
struct drm_gem_cma_object *cma_obj;
if (tdev->plane.fb != fb)
return 0;
cma_obj = drm_fb_cma_get_gem_obj(fb, 0);
if (!cma_obj) {
dev_err_once(info->dev, "Can't get cma_obj\n");
return -EINVAL;
}
return tdev->dirtyfb(fb, cma_obj->vaddr, flags, color, clips,
num_clips);
}
static struct drm_framebuffer_funcs tinydrm_fb_cma_funcs = {
.destroy = drm_fb_cma_destroy,
.create_handle = drm_fb_cma_create_handle,
.dirty = tinydrm_fbdev_dirty,
};
Ah, cma midlayer strikes again. We've had a similar discussion around the
gem side when vc4 landed for similar reasons iirc - it's hard to overwrite
specific helper functions to customize the behaviour.
I guess the simplest solution would be to export
drm_fb_cma_destroy/create_handle functions, and then add a
drm_fb_cma_create_with_funcs helper which you can use like this:
static int tinydrm_fbdev_create(struct drm_fb_helper *helper,
struct drm_fb_helper_surface_size *sizes)
{
return drm_fb_cma_create_with_funcs(helper, sizes, tinydrm_fb_cma_funcs);
}
Changing fb->funcs after drm_framebuffer_init is called is a no-go, since
that function also registers the framebuffer and makes it userspace
accessible. So after that point other threads can go&look at fb->funcs.
static int tinydrm_fbdev_create(struct drm_fb_helper *helper,
struct drm_fb_helper_surface_size *sizes)
{
struct tinydrm_device *tdev = helper->dev->dev_private;
struct fb_deferred_io *fbdefio;
struct fb_ops *fbops;
struct fb_info *info;
/*
* A per device structure is needed for:
* - fbops because fb_deferred_io_cleanup() clears fbops.fb_mmap
* - fbdefio to get per device delay
*/
fbops = devm_kzalloc(helper->dev->dev, sizeof(*fbops), GFP_KERNEL);
fbdefio = devm_kzalloc(helper->dev->dev, sizeof(*fbdefio),
GFP_KERNEL);
if (!fbops || !fbdefio)
return -ENOMEM;
ret = drm_fbdev_cma_create(helper, sizes);
if (ret)
return ret;
helper->fb->funcs = &tinydrm_fb_cma_funcs;
Ok, first thing I've forgotten is that the fbdev cma helper doesn't call
mode_config->funcs->fb_create and so gets the wrong fb->funcs. One thing
I've pondered for different reasons lately is whether the fbdev emulation
should grow a fake drm_file fpriv. With that we could just allocate a dumb
buffer and pass it to ->fb_create (it takes a handle, which means we need
a fake fpriv). I think that would fully demidlayer cma helpers. Or we
create a new helper function to do ->fb_create but with gem objects
instead of ids like what we've done for vc4. Or we just open-code it all.
Not sure which is better here.
info = fb_helper->fbdev;
/*
* fb_deferred_io requires a vmalloc address or a physical address.
* drm_fbdev_cma_create() sets smem_start to the dma address which
is
* a device address. This isn't always a physical address.
*/
info->smem_start = page_to_phys(virt_to_page(info->screen_buffer));
*fbops = *info->fbops;
info->fbops = fbops;
info->fbdefio = fbdefio;
fbdefio->deferred_io = drm_fb_helper_deferred_io;
fbdefio->delay = msecs_to_jiffies(tdev->deferred->defer_ms);
/* delay=0 is turned into delay=HZ, so use 1 as a minimum */
if (!fbdefio->delay)
fbdefio->delay = 1;
fb_deferred_io_init(info);
return 0;
}
static const struct drm_fb_helper_funcs tinydrm_fb_helper_funcs = {
.fb_probe = tinydrm_fbdev_create,
};
int tinydrm_fbdev_init(struct tinydrm_device *tdev)
{
struct drm_device *dev = tdev->base;
struct drm_fbdev_cma *cma;
cma = drm_fbdev_cma_init_with_funcs(dev, 16,
dev->mode_config.num_crtc,
dev->mode_config.num_connector,
&tinydrm_fb_helper_funcs);
if (IS_ERR(cma))
return PTR_ERR(cma);
I was wondering whether we couldn't avoid the _with_funcs here by setting
up fbdefio iff ->dirty is set. Then you could add the generic defio setup
code to drm_fbdev_cma_create after helper->fb is allocated, but only if
helper->fb->funcs->dirty is set. Makes for a bit less boilerplate.
Or did I miss something?
I don't see how I can avoid drm_fbdev_cma_init_with_funcs():
static struct drm_framebuffer_funcs tinydrm_fb_cma_funcs = {
.destroy = drm_fb_cma_destroy,
.create_handle = drm_fb_cma_create_handle,
.dirty = tinydrm_fbdev_dirty,
};
static int tinydrm_fbdev_create(struct drm_fb_helper *helper,
struct drm_fb_helper_surface_size *sizes)
{
return drm_fbdev_cma_create_with_funcs(helper, sizes,
&tinydrm_fb_cma_funcs);
}
static const struct drm_fb_helper_funcs tinydrm_fb_helper_funcs = {
.fb_probe = tinydrm_fbdev_create,
};
int tinydrm_fbdev_init(struct tinydrm_device *tdev)
{
struct drm_device *dev = tdev->base;
struct drm_fbdev_cma *cma;
cma = drm_fbdev_cma_init_with_funcs(dev, 16,
dev->mode_config.num_crtc,
dev->mode_config.num_connector,
&tinydrm_fb_helper_funcs);
if (IS_ERR(cma))
return PTR_ERR(cma);
tdev->fbdev_cma = cma;
return 0;
}
Thanks for your feedback so far Daniel, I quite like the direction this is
taking. I'll try and implement it in a new version of the patchset.
Noralf.
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