On Fri, Aug 30, 2024 at 8:33 AM Antonino Maniscalco
<antomani103@xxxxxxxxx> wrote:
>
> This patch implements preemption feature for A6xx targets, this allows
> the GPU to switch to a higher priority ringbuffer if one is ready. A6XX
> hardware as such supports multiple levels of preemption granularities,
> ranging from coarse grained(ringbuffer level) to a more fine grained
> such as draw-call level or a bin boundary level preemption. This patch
> enables the basic preemption level, with more fine grained preemption
> support to follow.
>
> Signed-off-by: Sharat Masetty <smasetty@xxxxxxxxxxxxxx>
> Signed-off-by: Antonino Maniscalco <antomani103@xxxxxxxxx>
> Tested-by: Neil Armstrong <neil.armstrong@xxxxxxxxxx> # on SM8650-QRD
> ---
> drivers/gpu/drm/msm/Makefile | 1 +
> drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 323 +++++++++++++++++++++-
> drivers/gpu/drm/msm/adreno/a6xx_gpu.h | 168 ++++++++++++
> drivers/gpu/drm/msm/adreno/a6xx_preempt.c | 431 ++++++++++++++++++++++++++++++
> drivers/gpu/drm/msm/msm_ringbuffer.h | 7 +
> 5 files changed, 921 insertions(+), 9 deletions(-)
>
[snip]
> +void a6xx_preempt_trigger(struct msm_gpu *gpu)
> +{
> + struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
> + struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
> + u64 preempt_offset_priv_secure;
> + unsigned long flags;
> + struct msm_ringbuffer *ring;
> + uint64_t user_ctx_iova;
> + unsigned int cntl;
> +
> + if (gpu->nr_rings == 1)
> + return;
> +
> + /*
> + * Lock to make sure another thread attempting preemption doesn't skip it
> + * while we are still evaluating the next ring. This makes sure the other
> + * thread does start preemption if we abort it and avoids a soft lock.
> + */
> + spin_lock_irqsave(&a6xx_gpu->eval_lock, flags);
> +
> + /*
> + * Try to start preemption by moving from NONE to START. If
> + * unsuccessful, a preemption is already in flight
> + */
> + if (!try_preempt_state(a6xx_gpu, PREEMPT_NONE, PREEMPT_START)) {
> + spin_unlock_irqrestore(&a6xx_gpu->eval_lock, flags);
> + return;
> + }
> +
> + cntl = (((a6xx_gpu->preempt_level << 6) & 0xC0) |
> + ((a6xx_gpu->skip_save_restore << 9) & 0x200) |
> + ((a6xx_gpu->uses_gmem << 8) & 0x100) | 0x1);
nit, could we define these fields in the xml, and not open-code
register building?
BR,
-R
