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

[Ville Syrjälä]

On Tue, Jun 18, 2024 at 02:07:56PM +0300, Jani Nikula wrote:
> On Tue, 11 Jun 2024, Ville Syrjala <ville.syrjala at linux.intel.com> wrote:
> > From: Ville Syrjälä <ville.syrjala at 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 at 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?

It'll let you try both dsb and mmio paths at runtime without
having to do a full reboot/reload.

> 
> 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

-- 
Ville Syrjälä
Intel