[PATCH v4 2/3] drm/amd/display: Destroy DC context while keeping DML

[Alex Deucher]

On Wed, Oct 4, 2023 at 1:37 PM Mario Limonciello
<mario.limonciello at amd.com> wrote:
>
> If there is memory pressure at suspend time then dynamically
> allocating a large structure as part of DC suspend code will
> fail.
>
> Instead re-use the same structure and clear all members except
> those that should be maintained.
>
> Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2362
> Signed-off-by: Mario Limonciello <mario.limonciello at amd.com>
> ---
>  drivers/gpu/drm/amd/display/dc/core/dc.c      | 25 -------------------
>  .../gpu/drm/amd/display/dc/core/dc_resource.c | 12 +++++++++
>  2 files changed, 12 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/core/dc.c b/drivers/gpu/drm/amd/display/dc/core/dc.c
> index 39e291a467e2..cb8c7c5a8807 100644
> --- a/drivers/gpu/drm/amd/display/dc/core/dc.c
> +++ b/drivers/gpu/drm/amd/display/dc/core/dc.c
> @@ -4728,9 +4728,6 @@ bool dc_set_power_state(
>         struct dc *dc,
>         enum dc_acpi_cm_power_state power_state)
>  {
> -       struct kref refcount;
> -       struct display_mode_lib *dml;
> -
>         if (!dc->current_state)
>                 return true;
>
> @@ -4750,30 +4747,8 @@ bool dc_set_power_state(
>                 break;
>         default:
>                 ASSERT(dc->current_state->stream_count == 0);
> -               /* Zero out the current context so that on resume we start with
> -                * clean state, and dc hw programming optimizations will not
> -                * cause any trouble.
> -                */
> -               dml = kzalloc(sizeof(struct display_mode_lib),
> -                               GFP_KERNEL);
> -
> -               ASSERT(dml);
> -               if (!dml)
> -                       return false;
> -
> -               /* Preserve refcount */
> -               refcount = dc->current_state->refcount;
> -               /* Preserve display mode lib */
> -               memcpy(dml, &dc->current_state->bw_ctx.dml, sizeof(struct display_mode_lib));
>
>                 dc_resource_state_destruct(dc->current_state);
> -               memset(dc->current_state, 0,
> -                               sizeof(*dc->current_state));
> -
> -               dc->current_state->refcount = refcount;
> -               dc->current_state->bw_ctx.dml = *dml;

The dml dance seems a bit weird.  I guess it's here because
dc_resource_state_destruct() might change it?  Can we safely drop
this?  If we do need it, we could pre-allocate a dml structure and use
that.

Alex

> -
> -               kfree(dml);
>
>                 break;
>         }
> diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_resource.c b/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
> index aa7b5db83644..e487c966c118 100644
> --- a/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
> +++ b/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
> @@ -4350,6 +4350,18 @@ void dc_resource_state_destruct(struct dc_state *context)
>                 context->streams[i] = NULL;
>         }
>         context->stream_count = 0;
> +       context->stream_mask = 0;
> +       memset(&context->res_ctx, 0, sizeof(context->res_ctx));
> +       memset(&context->pp_display_cfg, 0, sizeof(context->pp_display_cfg));
> +       memset(&context->dcn_bw_vars, 0, sizeof(context->dcn_bw_vars));
> +       context->clk_mgr = NULL;
> +       memset(&context->bw_ctx.bw, 0, sizeof(context->bw_ctx.bw));
> +       memset(context->block_sequence, 0, sizeof(context->block_sequence));
> +       context->block_sequence_steps = 0;
> +       memset(context->dc_dmub_cmd, 0, sizeof(context->dc_dmub_cmd));
> +       context->dmub_cmd_count = 0;
> +       memset(&context->perf_params, 0, sizeof(context->perf_params));
> +       memset(&context->scratch, 0, sizeof(context->scratch));
>  }
>
>  void dc_resource_state_copy_construct(
> --
> 2.34.1
>