23.06.2020 15:09, Mikko Perttunen пишет:
> /* Command is an opcode gather from a GEM handle */
> #define DRM_TEGRA_SUBMIT_COMMAND_GATHER 0
> /* Command is an opcode gather from a user pointer */
> #define DRM_TEGRA_SUBMIT_COMMAND_GATHER_UPTR 1
> /* Command is a wait for syncpt fence completion */
> #define DRM_TEGRA_SUBMIT_COMMAND_WAIT_SYNCPT 2
> /* Command is a wait for SYNC_FILE FD completion */
> #define DRM_TEGRA_SUBMIT_COMMAND_WAIT_SYNC_FILE 3
> /* Command is a wait for DRM syncobj completion */
> #define DRM_TEGRA_SUBMIT_COMMAND_WAIT_SYNCOBJ 4
>
> /*
> * Allow driver to skip command execution if engine
> * was not accessed by another channel between
> * submissions.
> */
> #define DRM_TEGRA_SUBMIT_CONTEXT_SETUP (1<<0)
>
> struct drm_tegra_submit_command {
> __u16 type;
> __u16 flags;
Shouldn't the "packed" attribute be needed if a non-32bit aligned fields
are used?
> union {
> struct {
> /* GEM handle */
> __u32 handle;
>
> /*
> * Offset into GEM object in bytes.
> * Must be aligned by 4.
> */
> __u64 offset;
64bits for a gather offset is a bit too much, in most cases gathers are
under 4K.
u32 should be more than enough (maybe even u16 if offset is given in a
dword granularity).
> /*
> * Length of gather in bytes.
> * Must be aligned by 4.
> */
> __u64 length;
u32/16
> } gather;
> struct {
> __u32 reserved[1];
>
> /*
> * Pointer to gather data.
> * Must be aligned by 4 bytes.
> */
> __u64 base;
> /*
> * Length of gather in bytes.
> * Must be aligned by 4.
> */
> __u64 length;
> } gather_uptr;
What about to inline the UPTR gather data and relocs into the
drm_tegra_submit_command[] buffer:
struct drm_tegra_submit_command {
struct {
u16 num_words;
u16 num_relocs;
gather_data[];
drm_tegra_submit_relocation relocs[];
} gather_uptr;
};
struct drm_tegra_channel_submit {
__u32 num_syncpt_incrs;
__u32 syncpt_idx;
__u64 commands_ptr;
__u32 commands_size;
...
};
struct drm_tegra_submit_command example[] = {
cmd.gather_uptr{},
...
gather_data[],
gather_relocs[],
cmd.wait_syncpt{},
...
};
This way we will have only a single copy_from_user() for the whole
cmdstream, which should be more efficient to do and nicer from both
userspace and kernel perspectives in regards to forming and parsing the
commands.
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