Linaro-mm-sig November 2013

linaro-mm-sig@lists.linaro.org

24 participants
11 discussions

by Laura Abbott

Hi, I noticed there is currently no CMA support for AArch64. Is this already on someone's TODO list or is this still open? Thanks, Laura -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation

10 years, 9 months

Move wayland-drm protocol from Mesa to wayland-core

by Benjamin Gaignard

Hi all, I'm working for Linaro on enabling a zero copy path in GStreamer by using dmabuf. To make this possible I have patched gst wayland sink to use wayland drm protocol: https://bugzilla.gnome.org/show_bug.cgi?id=711155 Today wayland drm protocol is limited to Mesa so I have decided to move it into wayland-core. My hardware doesn't have gpu support yet so I have patched weston (pixman) to allow usage of wl_drm buffers. With this I able to share/use a buffer allocated by DRM in gstreamer pipeline even if I don't have gpu and EGL. What do you think about make wayland drm protocol available like this ? Please note those patches are for wayland/weston 1.1.0 Regards, Benjamin -- Benjamin Gaignard Graphic Working Group Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog

11 years

Re: [Linaro-mm-sig] [Mesa-dev] [PATCH] dri3, i915, i965: Add __DRI_IMAGE_FOURCC_SARGB8888

by Daniel Vetter

On Fri, Nov 22, 2013 at 12:01 PM, Keith Packard <keithp(a)keithp.com> wrote: > Daniel Vetter <daniel(a)ffwll.ch> writes: > >> Hm, where do we have the canonical source for all these fourcc codes? I'm >> asking since we have our own copy in the kernel as drm_fourcc.h, and that >> one is part of the userspace ABI since we use it to pass around >> framebuffer formats and format lists. > > I think it's the kernel? I really don't know, as the whole notion of > fourcc codes seems crazy to me... > > Feel free to steal this code and stick it in the kernel if you like. Well, I wasn't ever in favour of using fourcc codes since they're just not standardized at all, highly redundant in some cases and also miss lots of stuff we actually need (like all the rgb formats). Cc'ing the heck out of this to get kernel people to hopefully notice. Maybe someone takes charge of this ... Otherwise meh. >> Just afraid to create long-term maintainance madness here with the >> kernel's iron thou-shalt-not-break-userspace-ever rule ... Not likely >> we'll ever accept srgb for framebuffers though. > > Would suck to collide with something we do want though. Yeah, it'd suck. But given how fourcc works we probably have that already, just haven't noticed yet :( -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch

11 years

[PATCH 0/2] Revert support for reserved memory regions defined in device tree

by Marek Szyprowski

Hi all! Benjamin Herrenschmidt pointed a few issues in the proposed design of device tree bindings for contiguous memory allocator and reserved memory regions: https://lkml.org/lkml/2013/9/15/151 http://www.spinics.net/lists/arm-kernel/msg273548.html Some time has passed, but there is still no consensus on the bindings for the reserved memory and various drawback of this solution has been shown, so in my opinion the best I can do now is to revert them completely and start from scratch again later. This patch series reverts patches related to device tree bindings proposed in the following thread: http://thread.gmane.org/gmane.linux.ports.arm.kernel/263216 and merged by commit 64c353864e3f7ccba0ade1bd6f562f9a3bc7e68d ("Merge branch 'for-v3.12' of git://git.linaro.org/people/mszyprowski/linux-dma-mapping"). Best regards Marek Szyprowski Samsung R&D Institute Poland Marek Szyprowski (2): Revert "ARM: init: add support for reserved memory defined by device tree" Revert "drivers: of: add initialization code for dma reserved memory" Documentation/devicetree/bindings/memory.txt | 168 ------------------------- arch/arm/mm/init.c | 3 - drivers/of/Kconfig | 6 - drivers/of/Makefile | 1 - drivers/of/of_reserved_mem.c | 173 -------------------------- drivers/of/platform.c | 4 - include/linux/of_reserved_mem.h | 14 --- 7 files changed, 369 deletions(-) delete mode 100644 Documentation/devicetree/bindings/memory.txt delete mode 100644 drivers/of/of_reserved_mem.c delete mode 100644 include/linux/of_reserved_mem.h -- 1.7.9.5

11 years, 1 month

[PATCH RFC] dma-buf/fs Add get_[file|dma_buf]_unless_doomed

by Thomas Hellstrom

In this context, a "doomed" object is an object whose refcount has reached zero, but that has not yet been freed. To avoid mutual refcounting vmwgfx need to have a non-refcounted pointer to a dma-buf in a lookup structure. The pointer is removed in the dma-buf destructor. To allow lookup-structure private locks we need get_dma_buf_unless_doomed(). This common refcounting scenario is described with examples in detail in the kref documentaion. The solution with local locks is under kref_get_unless_zero(). See also kobject_get_unless_zero() and its commit message. Since dma-bufs are using the attached file for refcounting, get_dma_buf_unless_doomed maps directly to a get_file_unless_doomed. Signed-off-by: Thomas Hellstrom <thellstrom(a)vmware.com> --- include/linux/dma-buf.h | 16 ++++++++++++++++ include/linux/fs.h | 15 +++++++++++++++ 2 files changed, 31 insertions(+) diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index dfac5ed..6e58144 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -162,6 +162,22 @@ static inline void get_dma_buf(struct dma_buf *dmabuf) get_file(dmabuf->file); } +/** + * get_dma_buf_unless_doomed - convenience wrapper for get_file_unless_doomed + * + * @dmabuf: [in] pointer to dma_buf + * + * Obtain a dma-buf reference from a lookup structure that doesn't refcount + * the dma-buf, but synchronizes with its release method to make sure it has + * not been freed yet. See for example kref_get_unless_zero documentation. + * Returns true if refcounting succeeds, false otherwise. + */ +static inline bool __must_check +get_dma_buf_unless_doomed(struct dma_buf *dmabuf) +{ + return get_file_unless_doomed(dmabuf->file); +} + struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf, struct device *dev); void dma_buf_detach(struct dma_buf *dmabuf, diff --git a/include/linux/fs.h b/include/linux/fs.h index 3f40547..a96c333 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -824,6 +824,21 @@ static inline struct file *get_file(struct file *f) atomic_long_inc(&f->f_count); return f; } + +/** + * get_file_unless_doomed - convenience wrapper for get_file_unless_doomed + * @file: [in] pointer to file + * + * Obtain a file reference from a lookup structure that doesn't refcount + * the file, but synchronizes with its release method to make sure it has + * not been freed yet. See for example kref_get_unless_zero documentation. + * Returns true if refcounting succeeds, false otherwise. + */ +static inline bool __must_check get_file_unless_doomed(struct file *f) +{ + return atomic_long_inc_not_zero(&f->f_count) != 0L; +} + #define fput_atomic(x) atomic_long_add_unless(&(x)->f_count, -1, 1) #define file_count(x) atomic_long_read(&(x)->f_count) -- 1.7.10.4

11 years, 1 month

Re: [Linaro-mm-sig] thoughts of looking at android fences

by Maarten Lankhorst

11 years, 1 month

Re: [Linaro-mm-sig] thoughts of looking at android fences

by Maarten Lankhorst

op 07-11-13 22:11, Rom Lemarchand schreef: > Hi Maarten, I tested your changes and needed the attached patch: behavior > now seems equivalent as android sync. I haven't tested performance. > > The issue resolved by this patch happens when i_b < b->num_fences and > i_a >= a->num_fences (or vice versa). Then, pt_a is invalid and so > dereferencing pt_a->context causes a crash. Oops, thinko. :) Originally I had it correct by doing this: + /* + * Assume sync_fence a and b are both ordered and have no + * duplicates with the same context. + * + * If a sync_fence can only be created with sync_fence_merge + * and sync_fence_create, this is a reasonable assumption. + */ + for (i = i_a = i_b = 0; i_a < a->num_fences && i_b < b->num_fences; ) { + struct fence *pt_a = a->cbs[i_a].sync_pt; + struct fence *pt_b = b->cbs[i_b].sync_pt; + + if (pt_a->context < pt_b->context) { + sync_fence_add_pt(fence, &i, pt_a); + + i_a++; + } else if (pt_a->context > pt_b->context) { + sync_fence_add_pt(fence, &i, pt_b); + + i_b++; + } else { + if (pt_a->seqno - pt_b->seqno <= INT_MAX) + sync_fence_add_pt(fence, &i, pt_a); + else + sync_fence_add_pt(fence, &i, pt_b); + + i_a++; + i_b++; + } + } + + /* Add remaining fences from a or b*/ + for (; i_a < a->num_fences; i_a++) + sync_fence_add_pt(fence, &i, a->cbs[i_a].sync_pt); + + for (; i_b < b->num_fences; i_b++) + sync_fence_add_pt(fence, &i, b->cbs[i_b].sync_pt); Then I thought I could clean it up by merging it, but that ended up being more unreadable and crashing... so I guess I'll revert back to this version. :)

11 years, 1 month

RFC: get_dma_buf_unless_zero ?

by Thomas Hellstrom

Anyone else but me that feels such a function could be useful? My main use-case is that it would resolve the mutual refcounting problem: 1) drm buffer object caches a dma_buf pointer which it refcounts 2) The dma-buf holds a refcount to the buffer. This is resolved today by having the user-space visible part of the drm-buffer holding the refcount to the dma_buf. When user-space closes the drm-buffer, the reference goes away, and eventually the buffer is freed, when all external dma-buf users are done with the dma-buf However, this also means that the dma-buf remains for the buffer lifetime even when there are no external users, which bugs me a bit. This can be resolved by viewing the drm buffer as a lookup structure that doesn't hold a refcount to the dma-buf, but that means that the lookup structure (buffer) would need to share locks with the dma-buf implementation, unless we have a get_dma_buf_unless_zero, which means we can use locks local to the lookup structure, the drm buffer. (See the last part of the kref documentation for a detailed discussion of this). Now I don't think keeping the dma_buf for the drm buffer lifetime is a HUGE problem, but I just wanted to get people's views of this. Thanks, Thomas

11 years, 1 month

dma-buf non-coherent mmap

by Thomas Hellstrom

Hi! I'm just looking over what's needed to implement drm Prime / dma-buf exports + imports in the vmwgfx driver. It seems like most dma-bufs ops are quite straightforward to implement except user-space mmap(). The reason being that vmwgfx dma-bufs will be using completely non-coherent memory, whenever there needs to be CPU accesses. The accelerated contents resides in an opaque structure on the device into which we can DMA to and from, so for mmap to work we need to zap ptes and DMA to the device when doing something accelerated, and on the first page-fault DMA data back and wait for idle if the device did a write to the dma-buf. Now this shouldn't really be a problem if dma-bufs were only used for cross-device sharing, but since people apparently want to use dma-buf file handles to share CPU data between processes it really becomes a serious problem. Needless to say we'd want to limit the size of the DMAs, and have mmap users request regions for read, and mark regions dirty for write, something similar to gallium's texture transfer objects. Any ideas? /Thomas

11 years, 1 month

thoughts of looking at android fences

by Maarten Lankhorst

Hey, So I took a look at the sync stuff in android, in a lot of ways I believe that they're similar, yet subtly different. Most of the stuff I looked at is from the sync.h header in drivers/staging, so maybe my knowledge is incomplete. The timeline is similar to what I called a fence context. Each command stream on a gpu can have a context. Because nvidia hardware can have 4095 separate timelines, I didn't want to keep the bookkeeping for each timeline, although I guess that it's already done. Maybe it could be done in a unified way for each driver, making a transition to timelines that can be used by android easier. I did not have an explicit syncpoint addition, but I think that sync points + sync_fence were similar to what I did with my dma-fence stuff, except slightly different. In my approach the dma-fence is signaled after all sync_points are done AND the queued commands are executed. In effect the dma-fence becomes the next syncpoint, depending on all previous dma-fence syncpoints. An important thing to note is that dma-fence is kernelspace only, so it might be better to rename it to syncpoint, and use fence for the userspace interface. A big difference is locking, I assume in my code that most fences emitted are not waited on, so the fastpath fence_signal is a test_and_set_bit plus test_bit. A single lock is used for the waitqueue and callbacks, with the waitqueue being implemented internally as an asynchronous callback. The lock is provided by the driver, which makes adding support for old hardware that has no reliable way of notifying completion of events easier. I avoided using global locks, but I think for debugfs support I may end up having to add some. The dma fence looks similar overall, except that I allow overriding some stuff and keep less track about state. I do believe that I can create a userspace interface around dma_fence that works similar to android, and the kernel space interface could be done in a similar way too. One thing though: is it really required to merge fences? It seems to me that if I add a poll callback userspace could simply do a poll on a list of fences. This would give userspace all the information it needs about each individual fence. The thing about wait/wound mutexes can be ignored for this discussion. It's really just a method of adding a fence to a dma-buf, and building a list of all dma-fences to wait on in the kernel before starting a command buffer, and setting a new fence to all the dma-bufs to signal completion of the event. Regardless of the sync mechanism we'll decide on, this stuff wouldn't change. Depending on feedback I'll try reflashing my nexus 7 to stock android, and work on trying to convert android syncpoints to dma-fence, which I'll probably rename to syncpoints. ~Maarten

11 years, 1 month

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Linaro-mm-sig November 2013