[PATCH v2] drm: fsl-dcu: enable PIXCLK on LS1021A

[Matthias Schiffer]

The PIXCLK needs to be enabled in SCFG before accessing the DCU on LS1021A,
or the access will hang.

Signed-off-by: Matthias Schiffer <matthias.schiffer@xxxxxxxxxxxxxxx>
---

v2:
- rebase
- remove unnecessary argument of fsl_dcu_scfg_config_ls1021a()


 drivers/gpu/drm/fsl-dcu/Kconfig           |  1 +
 drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c | 25 +++++++++++++++++++++++
 drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h |  3 +++
 3 files changed, 29 insertions(+)

diff --git a/drivers/gpu/drm/fsl-dcu/Kconfig b/drivers/gpu/drm/fsl-dcu/Kconfig
index d7dd8ba90e3a..9e5a35e7c00c 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 660fe573db96..b6b1cb75fc41 100644
--- a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c
+++ b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c
@@ -50,6 +50,23 @@ static const struct regmap_config fsl_dcu_regmap_config = {
 	.volatile_reg = fsl_dcu_drm_is_volatile_reg,
 };
 
+static int fsl_dcu_scfg_config_ls1021a(void)
+{
+	struct regmap *scfg;
+
+	scfg = syscon_regmap_lookup_by_compatible("fsl,ls1021a-scfg");
+	if (IS_ERR(scfg))
+		return PTR_ERR(scfg);
+
+	/*
+	 * For simplicity, enable the PIXCLK unconditionally. It might
+	 * be possible to disable the clock in PM or on unload as a future
+	 * improvement.
+	 */
+	return regmap_update_bits(scfg, SCFG_PIXCLKCR, SCFG_PIXCLKCR_PXCEN,
+				  SCFG_PIXCLKCR_PXCEN);
+}
+
 static void fsl_dcu_irq_reset(struct drm_device *dev)
 {
 	struct fsl_dcu_drm_device *fsl_dev = dev->dev_private;
@@ -108,6 +125,14 @@ static int fsl_dcu_load(struct drm_device *dev, unsigned long flags)
 		return ret;
 	}
 
+	if (of_device_is_compatible(fsl_dev->np, "fsl,ls1021a-dcu")) {
+		ret = fsl_dcu_scfg_config_ls1021a();
+		if (ret < 0) {
+			dev_err(dev->dev, "failed to enable pixclk\n");
+			goto done_vblank;
+		}
+	}
+
 	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
 
-- 
2.17.1