drm/i915: add enable_ips module option

IPS is still enabled by default. Feature requested by the power
management team.

This should also help testing the feature on some early pre-production
hardware where there were relationship problems between IPS and PSR.

v2: Rebase on top of the newest IPS implementation.
v3: Check i915_enable_ips at compute_config, not supports_ips, so the
    kernel parameter will be ignored at haswell_get_pipe_config.
Requested-by: Kristen Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.c

@@ -128,6 +128,10 @@ module_param_named(disable_power_well, i915_disable_power_well, int, 0600);
 MODULE_PARM_DESC(disable_power_well,
 		 "Disable the power well when possible (default: false)");
 
+int i915_enable_ips __read_mostly = 1;
+module_param_named(enable_ips, i915_enable_ips, int, 0600);
+MODULE_PARM_DESC(enable_ips, "Enable IPS (default: true)");
+
 static struct drm_driver driver;
 extern int intel_agp_enabled;
 

drivers/gpu/drm/i915/i915_drv.h

@@ -1470,6 +1470,7 @@ extern bool i915_enable_hangcheck __read_mostly;
 extern int i915_enable_ppgtt __read_mostly;
 extern unsigned int i915_preliminary_hw_support __read_mostly;
 extern int i915_disable_power_well __read_mostly;
+extern int i915_enable_ips __read_mostly;
 
 extern int i915_suspend(struct drm_device *dev, pm_message_t state);
 extern int i915_resume(struct drm_device *dev);

drivers/gpu/drm/i915/intel_display.c

@@ -4034,7 +4034,8 @@ static int ironlake_fdi_compute_config(struct intel_crtc *intel_crtc,
 static void hsw_compute_ips_config(struct intel_crtc *crtc,
 				   struct intel_crtc_config *pipe_config)
 {
-	pipe_config->ips_enabled = hsw_crtc_supports_ips(crtc) &&
+	pipe_config->ips_enabled = i915_enable_ips &&
+				   hsw_crtc_supports_ips(crtc) &&
 				   pipe_config->pipe_bpp == 24;
 }