drm/i915: Add psr_safest_params

This parameter is meant to be used when PSR issues are found as some
issues in the past was due wrong values set in VBT so this would be
a quick and easy way to ask users or for us to check if the issue is
due VBT values.

Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200520212756.354623-1-jose.souza@intel.com

drivers/gpu/drm/i915/i915_params.c

@@ -97,6 +97,11 @@ i915_param_named_unsafe(enable_psr, int, 0400,
 	"(0=disabled, 1=enabled) "
 	"Default: -1 (use per-chip default)");
 
+i915_param_named(psr_safest_params, bool, 0400,
+	"Replace PSR VBT parameters by the safest and not optimal ones. This "
+	"is helpfull to detect if PSR issues are related to bad values set in "
+	" VBT. (0=use VBT paramters, 1=use safest parameters)");
+
 i915_param_named_unsafe(force_probe, charp, 0400,
 	"Force probe the driver for specified devices. "
 	"See CONFIG_DRM_I915_FORCE_PROBE for details.");