[Intel-gfx] [PATCH 5/7] drm/i915/gt: Ignore stale context state upon resume

[Matthew Auld]

On Sun, 29 Dec 2019 at 18:32, Chris Wilson <chris at chris-wilson.co.uk> wrote:
>
> We leave the kernel_context on the HW as we suspend (and while idle).
> There is no guarantee that is complete in memory, so we try to inhibit
> restoration from the kernel_context. Reinforce the inhibition by
> scrubbing the context.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/gt/intel_lrc.c             | 17 +++++++++++++++--
>  drivers/gpu/drm/i915/gt/intel_ring_submission.c |  2 +-
>  2 files changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index 14e7e179855f..b1508dbd1063 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -2494,6 +2494,11 @@ static int execlists_context_alloc(struct intel_context *ce)
>
>  static void execlists_context_reset(struct intel_context *ce)
>  {
> +       u32 *regs;
> +
> +       CE_TRACE(ce, "reset\n");
> +       GEM_BUG_ON(!intel_context_is_pinned(ce));
> +
>         /*
>          * Because we emit WA_TAIL_DWORDS there may be a disparity
>          * between our bookkeeping in ce->ring->head and ce->ring->tail and
> @@ -2510,8 +2515,17 @@ static void execlists_context_reset(struct intel_context *ce)
>          * So to avoid that we reset the context images upon resume. For
>          * simplicity, we just zero everything out.
>          */
> -       intel_ring_reset(ce->ring, 0);
> +       intel_ring_reset(ce->ring, ce->ring->emit);
> +
> +       regs = memset(ce->lrc_reg_state, 0, PAGE_SIZE);
> +       execlists_init_reg_state(regs, ce, ce->engine, ce->ring, true);
>         __execlists_update_reg_state(ce, ce->engine);
> +
> +       /* Avoid trying to reload the garbage */
> +       regs[CTX_CONTEXT_CONTROL] |=
> +               _MASKED_BIT_ENABLE(CTX_CTRL_ENGINE_CTX_RESTORE_INHIBIT);
> +
> +       ce->lrc_desc |= CTX_DESC_FORCE_RESTORE;
>  }
>
>  static const struct intel_context_ops execlists_context_ops = {
> @@ -3968,7 +3982,6 @@ static void init_common_reg_state(u32 * const regs,
>                                             CTX_CTRL_RS_CTX_ENABLE);
>
>         regs[CTX_RING_CTL] = RING_CTL_SIZE(ring->size) | RING_VALID;
> -       regs[CTX_BB_STATE] = RING_BB_PPGTT;

Zero clue what that does...

Otherwise,
Reviewed-by: Matthew Auld <matthew.auld at intel.com>