On Wed, Jun 19, 2024 at 05:44:08PM +0300, Ville Syrjälä wrote: > On Wed, Jun 19, 2024 at 04:24:16PM +0300, Ville Syrjälä wrote: > > On Wed, Jun 19, 2024 at 04:11:08PM +0300, Jani Nikula wrote: > > > On Wed, 19 Jun 2024, Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> wrote: > > > > On Tue, Jun 18, 2024 at 02:07:56PM +0300, Jani Nikula wrote: > > > >> On Tue, 11 Jun 2024, Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx> wrote: > > > >> > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > > >> > > > > >> > 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@xxxxxxxxxxxxxxx> > > > >> > --- > > > >> > 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. > > > > > > I mean does any code actually look at the *module* parameter runtime? > > > It's only the initial value for the device param? > > > > You can change it via the debugfs i915_params/* thing. > > Apparently the modparam vs. debugfs permissions are specified in two > different places. This is rather confusing. > > Is there no way to put them in the same place? Or can we just nuke > the permission stuff from the modparam macro entirely so it won't > end up confusing me again? Looks like there is exactly one (gem related) > modparam that uses 0600, everything else seems to be 0400. And even that seems to use the per-device copy in the actual code. So looks to me like we can just rip out the macro argument and make it 0400 always. -- Ville Syrjälä Intel
