Messages in this thread | | | Subject | Re: [RFC PATCH 2/4] DRM: Add support of AI Processor Unit (APU) | From | Christian König <> | Date | Thu, 23 Sep 2021 08:17:33 +0200 |
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Am 23.09.21 um 02:58 schrieb Dave Airlie: > On Sat, 18 Sept 2021 at 07:57, Alexandre Bailon <abailon@baylibre.com> wrote: >> Some Mediatek SoC provides hardware accelerator for AI / ML. >> This driver provides the infrastructure to manage memory >> shared between host CPU and the accelerator, and to submit >> jobs to the accelerator. >> The APU itself is managed by remoteproc so this drivers >> relies on remoteproc to found the APU and get some important data >> from it. But, the driver is quite generic and it should possible >> to manage accelerator using another ways. >> This driver doesn't manage itself the data transmitions. >> It must be registered by another driver implementing the transmitions. >> >> Signed-off-by: Alexandre Bailon <abailon@baylibre.com> >> [SNIP]
>> Please refer to >> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.kernel.org%2Fdoc%2FDocumentation%2Fioctl%2Fbotching-up-ioctls.rst&data=04%7C01%7Cchristian.koenig%40amd.com%7C53a0ef2630404ddc4d9408d97e2d409c%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637679555123878415%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=6oVXAAOjQX%2FnDzJxZIAALqjDourHdrdGF6QVQKR58KI%3D&reserved=0 >> >> here and below in many places. >> >> There's a lot of missing padding/alignment here.
There is also the pahole utility which show you nicely where you need padding for your IOCTL structures.
For example "pahole drivers/gpu/drm/amd/amdgpu/amdgpu.ko -C drm_amdgpu_gem_va" gives you:
struct drm_amdgpu_gem_va { __u32 handle; /* 0 4 */ __u32 _pad; /* 4 4 */ __u32 operation; /* 8 4 */ __u32 flags; /* 12 4 */ __u64 va_address; /* 16 8 */ __u64 offset_in_bo; /* 24 8 */ __u64 map_size; /* 32 8 */
/* size: 40, cachelines: 1, members: 7 */ /* last cacheline: 40 bytes */ };
And as you can see we have added the _pad field to our IOCTL parameter structure to properly align the 64bit members.
Regards, Christian.
>> >> I'm trying to find the time to review this stack in full, any writeups >> on how this is used from userspace would be useful (not just the code >> repo, but some sort of how do I get at it) it reads as kinda generic >> (calling it apu), but then has some specifics around device binding. >> >> Dave.
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