[PATCH 2/2] drm: fsl-dcu: enable PIXCLK on LS1021A

[Alexander Stein]

From: Matthias Schiffer <matthias.schiffer at tq-group.com>

The PIXCLK needs to be enabled in SCFG before accessing certain DCU
registers, or the access will hang.

Signed-off-by: Matthias Schiffer <matthias.schiffer at tq-group.com>
Signed-off-by: Alexander Stein <alexander.stein at ew.tq-group.com>
---
 drivers/gpu/drm/fsl-dcu/Kconfig           |  1 +
 drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c | 14 ++++++++++++++
 drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h |  3 +++
 3 files changed, 18 insertions(+)

diff --git a/drivers/gpu/drm/fsl-dcu/Kconfig b/drivers/gpu/drm/fsl-dcu/Kconfig
index 5ca71ef87325..c9ee98693b48 100644
--- a/drivers/gpu/drm/fsl-dcu/Kconfig
+++ b/drivers/gpu/drm/fsl-dcu/Kconfig
@@ -8,6 +8,7 @@ config DRM_FSL_DCU
 	select DRM_PANEL
 	select REGMAP_MMIO
 	select VIDEOMODE_HELPERS
+	select MFD_SYSCON if SOC_LS1021A
 	help
 	  Choose this option if you have an Freescale DCU chipset.
 	  If M is selected the module will be called fsl-dcu-drm.
diff --git a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c
index 418887654bac..314cb8af89ee 100644
--- a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c
+++ b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c
@@ -100,12 +100,26 @@ static void fsl_dcu_irq_uninstall(struct drm_device *dev)
 static int fsl_dcu_load(struct drm_device *dev, unsigned long flags)
 {
 	struct fsl_dcu_drm_device *fsl_dev = dev->dev_private;
+	struct regmap *scfg;
 	int ret;
 
 	ret = fsl_dcu_drm_modeset_init(fsl_dev);
 	if (ret < 0)
 		return dev_err_probe(dev->dev, ret, "failed to initialize mode setting\n");
 
+	scfg = syscon_regmap_lookup_by_compatible("fsl,ls1021a-scfg");
+	if (PTR_ERR(scfg) != -ENODEV) {
+		/*
+		 * For simplicity, enable the PIXCLK unconditionally. Disabling
+		 * the clock in PM or on unload could be implemented as a future
+		 * improvement.
+		 */
+		ret = regmap_update_bits(scfg, SCFG_PIXCLKCR, SCFG_PIXCLKCR_PXCEN,
+					SCFG_PIXCLKCR_PXCEN);
+		if (ret < 0)
+			return dev_err_probe(dev->dev, ret, "failed to enable pixclk\n");
+	}
+
 	ret = drm_vblank_init(dev, dev->mode_config.num_crtc);
 	if (ret < 0) {
 		dev_err(dev->dev, "failed to initialize vblank\n");
diff --git a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h
index e2049a0e8a92..566396013c04 100644
--- a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h
+++ b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h
@@ -160,6 +160,9 @@
 #define FSL_DCU_ARGB4444		12
 #define FSL_DCU_YUV422			14
 
+#define SCFG_PIXCLKCR			0x28
+#define SCFG_PIXCLKCR_PXCEN		BIT(31)
+
 #define VF610_LAYER_REG_NUM		9
 #define LS1021A_LAYER_REG_NUM		10
 
-- 
2.34.1