drm/fsl-dcu: use mode flags for hsync/vsync polarity

The current default configuration is as follows:
- Invert VSYNC signal (active LOW)
- Invert HSYNC signal (active LOW)

The mode flags allow to specify the required polarity per
mode. Furthermore, none of the current driver settings is
actually a standard polarity.

This patch applies the current driver default polarities as
explicit flags to the display which has been introduced with
the driver (NEC WQVGA "nec,nl4827hc19-05b"). The driver now
also parses the flags field and applies the configuration
accordingly, by using the following values as standard
polarities: (e.g. when no flags are specified):
- VSYNC signal not inverted (active HIGH)
- HSYNC signal not inverted (active HIGH)

Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Stefan Agner <stefan@agner.ch>

drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_crtc.c

@@ -74,7 +74,7 @@ static void fsl_dcu_drm_crtc_mode_set_nofb(struct drm_crtc *crtc)
 	struct drm_device *dev = crtc->dev;
 	struct fsl_dcu_drm_device *fsl_dev = dev->dev_private;
 	struct drm_display_mode *mode = &crtc->state->mode;
-	unsigned int hbp, hfp, hsw, vbp, vfp, vsw, div, index;
+	unsigned int hbp, hfp, hsw, vbp, vfp, vsw, div, index, pol = 0;
 	unsigned long dcuclk;
 
 	index = drm_crtc_index(crtc);
@@ -89,6 +89,12 @@ static void fsl_dcu_drm_crtc_mode_set_nofb(struct drm_crtc *crtc)
 	vfp = mode->vsync_start - mode->vdisplay;
 	vsw = mode->vsync_end - mode->vsync_start;
 
+	if (mode->flags & DRM_MODE_FLAG_NHSYNC)
+		pol |= DCU_SYN_POL_INV_HS_LOW;
+
+	if (mode->flags & DRM_MODE_FLAG_NVSYNC)
+		pol |= DCU_SYN_POL_INV_VS_LOW;
+
 	regmap_write(fsl_dev->regmap, DCU_HSYN_PARA,
 		     DCU_HSYN_PARA_BP(hbp) |
 		     DCU_HSYN_PARA_PW(hsw) |
@@ -101,8 +107,7 @@ static void fsl_dcu_drm_crtc_mode_set_nofb(struct drm_crtc *crtc)
 		     DCU_DISP_SIZE_DELTA_Y(mode->vdisplay) |
 		     DCU_DISP_SIZE_DELTA_X(mode->hdisplay));
 	regmap_write(fsl_dev->regmap, DCU_DIV_RATIO, div);
-	regmap_write(fsl_dev->regmap, DCU_SYN_POL,
-		     DCU_SYN_POL_INV_VS_LOW | DCU_SYN_POL_INV_HS_LOW);
+	regmap_write(fsl_dev->regmap, DCU_SYN_POL, pol);
 	regmap_write(fsl_dev->regmap, DCU_BGND, DCU_BGND_R(0) |
 		     DCU_BGND_G(0) | DCU_BGND_B(0));
 	regmap_write(fsl_dev->regmap, DCU_DCU_MODE,

drivers/gpu/drm/panel/panel-simple.c

@@ -1016,6 +1016,7 @@ static const struct drm_display_mode nec_nl4827hc19_05b_mode = {
 	.vsync_end = 272 + 2 + 4,
 	.vtotal = 272 + 2 + 4 + 2,
 	.vrefresh = 74,
+	.flags = DRM_MODE_FLAG_NVSYNC | DRM_MODE_FLAG_NHSYNC,
 };
 
 static const struct panel_desc nec_nl4827hc19_05b = {