Re: [PATCH 08/11] drm/i915/dsb: Add i915.enable_dsb module parameter

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 11 Jun 2024, Ville Syrjala <ville.syrjala@linux.intel.com> wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> As we extend the use of DSB for critical pipe/plane register
> programming, it'll be nice to have an escape valve at hand,
> in case things go very poorly. To that end, add a i915.enable_dsb
> modparam by which we can force the driver to take the pure mmio
> path instead.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display_params.c | 3 +++
>  drivers/gpu/drm/i915/display/intel_display_params.h | 1 +
>  drivers/gpu/drm/i915/display/intel_dsb.c            | 3 +++
>  3 files changed, 7 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_display_params.c b/drivers/gpu/drm/i915/display/intel_display_params.c
> index aebdb7b59dbf..449a31767791 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_params.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_params.c
> @@ -54,6 +54,9 @@ intel_display_param_named_unsafe(enable_dc, int, 0400,
>  intel_display_param_named_unsafe(enable_dpt, bool, 0400,
>  	"Enable display page table (DPT) (default: true)");
>  
> +intel_display_param_named_unsafe(enable_dsb, bool, 0600,
> +	"Enable display state buffer (DSB) (default: true)");

Not much point in leaving the module param 0600, is there?

BR,
Jani.

> +
>  intel_display_param_named_unsafe(enable_sagv, bool, 0400,
>  	"Enable system agent voltage/frequency scaling (SAGV) (default: true)");
>  
> diff --git a/drivers/gpu/drm/i915/display/intel_display_params.h b/drivers/gpu/drm/i915/display/intel_display_params.h
> index 1208a62c16d2..48c29c55c939 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_params.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_params.h
> @@ -31,6 +31,7 @@ struct drm_i915_private;
>  	param(int, vbt_sdvo_panel_type, -1, 0400) \
>  	param(int, enable_dc, -1, 0400) \
>  	param(bool, enable_dpt, true, 0400) \
> +	param(bool, enable_dsb, true, 0600) \
>  	param(bool, enable_sagv, true, 0600) \
>  	param(int, disable_power_well, -1, 0400) \
>  	param(bool, enable_ips, true, 0600) \
> diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c b/drivers/gpu/drm/i915/display/intel_dsb.c
> index bee48ac419ce..2ab3765f6c06 100644
> --- a/drivers/gpu/drm/i915/display/intel_dsb.c
> +++ b/drivers/gpu/drm/i915/display/intel_dsb.c
> @@ -460,6 +460,9 @@ struct intel_dsb *intel_dsb_prepare(struct intel_atomic_state *state,
>  	if (!HAS_DSB(i915))
>  		return NULL;
>  
> +	if (!i915->display.params.enable_dsb)
> +		return NULL;
> +
>  	/* TODO: DSB is broken in Xe KMD, so disabling it until fixed */
>  	if (!IS_ENABLED(I915))
>  		return NULL;

-- 
Jani Nikula, Intel