drm/i915/glk: Fix maximum scaling factor for Geminilake scalers

Geminilake can output two pixels per clock, and that affects the maximum
scaling factor for its scalers. Take that into account and avoid the
following warning:

WARNING: CPU: 1 PID: 593 at drivers/gpu/drm/i915/intel_display.c:13223 skl_max_scale.part.129+0x78/0x80 [i915]
WARN_ON_ONCE(!crtc_clock || cdclk < crtc_clock)
Modules linked in: x86_pkg_temp_thermal i915 coretemp kvm_intel kvm i2c_algo_bit drm_kms_helper irqbypass crct10dif_pclmul prime_numbers crc32_pclmul drm ghash_clmulni_intel shpchp tpm_tis tpm_tis_core tpm nfsd authw
CPU: 1 PID: 593 Comm: kworker/u8:3 Tainted: G        W       4.10.0-rc8ander+ #330
Hardware name: Intel Corp. Geminilake/GLK RVP1 DDR4 (05), BIOS GELKRVPA.X64.0035.B33.1702150552 02/15/2017
Workqueue: events_unbound async_run_entry_fn
Call Trace:
 dump_stack+0x86/0xc3
 __warn+0xcb/0xf0
 warn_slowpath_fmt+0x5f/0x80
 skl_max_scale.part.129+0x78/0x80 [i915]
 intel_check_primary_plane+0xa6/0xc0 [i915]
 intel_plane_atomic_check_with_state+0xd1/0x1a0 [i915]
 ? drm_printk+0xb5/0xc0 [drm]
 intel_plane_atomic_check+0x3d/0x80 [i915]
 drm_atomic_helper_check_planes+0x7c/0x200 [drm_kms_helper]
 intel_atomic_check+0xa5b/0x11a0 [i915]
 drm_atomic_check_only+0x353/0x600 [drm]
 ? drm_atomic_add_affected_connectors+0x10c/0x120 [drm]
 drm_atomic_commit+0x18/0x50 [drm]
 restore_fbdev_mode+0x14c/0x2a0 [drm_kms_helper]
 drm_fb_helper_restore_fbdev_mode_unlocked+0x34/0x80 [drm_kms_helper]
 drm_fb_helper_set_par+0x2d/0x60 [drm_kms_helper]
 intel_fbdev_set_par+0x1a/0x70 [i915]
 fbcon_init+0x582/0x610
 visual_init+0xd6/0x130
 do_bind_con_driver+0x1da/0x3c0
 do_take_over_console+0x116/0x180
 do_fbcon_takeover+0x5c/0xb0
 fbcon_event_notify+0x772/0x8a0
 ? __blocking_notifier_call_chain+0x35/0x70
 notifier_call_chain+0x4a/0x70
 __blocking_notifier_call_chain+0x4d/0x70
 blocking_notifier_call_chain+0x16/0x20
 fb_notifier_call_chain+0x1b/0x20
 register_framebuffer+0x278/0x360
 drm_fb_helper_initial_config+0x253/0x440 [drm_kms_helper]
 intel_fbdev_initial_config+0x18/0x30 [i915]
 async_run_entry_fn+0x39/0x170
 process_one_work+0x212/0x670
 ? process_one_work+0x197/0x670
 worker_thread+0x4e/0x490
 kthread+0x101/0x140
 ? process_one_work+0x670/0x670
 ? kthread_create_on_node+0x60/0x60
 ret_from_fork+0x31/0x40

v2: s/max_pixclk/max_dotclk/ (Ville)
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170223071600.14356-3-ander.conselvan.de.oliveira@intel.com

drivers/gpu/drm/i915/intel_display.c

@@ -13291,16 +13291,22 @@ intel_cleanup_plane_fb(struct drm_plane *plane,
 int
 skl_max_scale(struct intel_crtc *intel_crtc, struct intel_crtc_state *crtc_state)
 {
+	struct drm_i915_private *dev_priv;
 	int max_scale;
-	int crtc_clock, cdclk;
+	int crtc_clock, max_dotclk;
 
 	if (!intel_crtc || !crtc_state->base.enable)
 		return DRM_PLANE_HELPER_NO_SCALING;
 
+	dev_priv = to_i915(intel_crtc->base.dev);
+
 	crtc_clock = crtc_state->base.adjusted_mode.crtc_clock;
-	cdclk = to_intel_atomic_state(crtc_state->base.state)->cdclk.logical.cdclk;
+	max_dotclk = to_intel_atomic_state(crtc_state->base.state)->cdclk.logical.cdclk;
+
+	if (IS_GEMINILAKE(dev_priv))
+		max_dotclk *= 2;
 
-	if (WARN_ON_ONCE(!crtc_clock || cdclk < crtc_clock))
+	if (WARN_ON_ONCE(!crtc_clock || max_dotclk < crtc_clock))
 		return DRM_PLANE_HELPER_NO_SCALING;
 
 	/*
@@ -13309,7 +13315,8 @@ skl_max_scale(struct intel_crtc *intel_crtc, struct intel_crtc_state *crtc_state
 	 *            or
 	 *    cdclk/crtc_clock
 	 */
-	max_scale = min((1 << 16) * 3 - 1, (1 << 8) * ((cdclk << 8) / crtc_clock));
+	max_scale = min((1 << 16) * 3 - 1,
+			(1 << 8) * ((max_dotclk << 8) / crtc_clock));
 
 	return max_scale;
 }