[PATCH v2 1/3] vop2: Add clock resets support

[Detlev Casanova <detlev.casanova@xxxxxxxxxxxxx>]

At the end of initialization, each VP clock needs to be reset before
they can be used.

Failing to do so can put the VOP in an undefined state where the
generated HDMI signal is either lost or not matching the selected mode.

Signed-off-by: Detlev Casanova <detlev.casanova@xxxxxxxxxxxxx>
---
 drivers/gpu/drm/rockchip/rockchip_drm_vop2.c | 30 ++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
index fdd768bbd487c..e81a67161d29a 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
@@ -17,6 +17,7 @@
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
 #include <linux/regmap.h>
+#include <linux/reset.h>
 #include <linux/swab.h>
 
 #include <drm/drm.h>
@@ -157,6 +158,7 @@ struct vop2_win {
 struct vop2_video_port {
 	struct drm_crtc crtc;
 	struct vop2 *vop2;
+	struct reset_control *dclk_rst;
 	struct clk *dclk;
 	unsigned int id;
 	const struct vop2_video_port_data *data;
@@ -1915,6 +1917,26 @@ static int us_to_vertical_line(struct drm_display_mode *mode, int us)
 	return us * mode->clock / mode->htotal / 1000;
 }
 
+static int vop2_clk_reset(struct vop2_video_port *vp)
+{
+	struct reset_control *rstc = vp->dclk_rst;
+	struct vop2 *vop2 = vp->vop2;
+	int ret;
+
+	if (!rstc)
+		return 0;
+
+	ret = reset_control_assert(rstc);
+	if (ret < 0)
+		drm_warn(vop2->drm, "failed to assert reset\n");
+	udelay(10);
+	ret = reset_control_deassert(rstc);
+	if (ret < 0)
+		drm_warn(vop2->drm, "failed to deassert reset\n");
+
+	return ret;
+}
+
 static void vop2_crtc_atomic_enable(struct drm_crtc *crtc,
 				    struct drm_atomic_state *state)
 {
@@ -2055,6 +2077,8 @@ static void vop2_crtc_atomic_enable(struct drm_crtc *crtc,
 
 	vop2_vp_write(vp, RK3568_VP_DSP_CTRL, dsp_ctrl);
 
+	vop2_clk_reset(vp);
+
 	drm_crtc_vblank_on(crtc);
 
 	vop2_unlock(vop2);
@@ -2706,6 +2730,12 @@ static int vop2_create_crtcs(struct vop2 *vop2)
 		vp->data = vp_data;
 
 		snprintf(dclk_name, sizeof(dclk_name), "dclk_vp%d", vp->id);
+		vp->dclk_rst = devm_reset_control_get_optional(vop2->dev, dclk_name);
+		if (IS_ERR(vp->dclk_rst)) {
+		        drm_err(vop2->drm, "failed to get %s reset\n", dclk_name);
+		        return PTR_ERR(vp->dclk_rst);
+		}
+
 		vp->dclk = devm_clk_get(vop2->dev, dclk_name);
 		if (IS_ERR(vp->dclk)) {
 			drm_err(vop2->drm, "failed to get %s\n", dclk_name);
-- 
2.44.1