imx-drm: PRE clock gating, panelless LDB, and VDIC CSI selection fixes

- Keep the external clock input to the PRE ungated and only use the internal
   soft reset to keep the module in low power state, to avoid sporadic startup
   failures.
 - Ignore -ENODEV return values from drm_of_find_panel_or_bridge in the LDB
   driver to fix probing for devices that still do not specify a panel in the
   device tree.
 - Fix the CSI input selection to the VDIC. According to experiments, the real
   behaviour differs a bit from the documentation.
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Merge tag 'imx-drm-fixes-2017-06-08' of git://git.pengutronix.de/git/pza/linux into drm-fixes

imx-drm: PRE clock gating, panelless LDB, and VDIC CSI selection fixes

- Keep the external clock input to the PRE ungated and only use the internal
  soft reset to keep the module in low power state, to avoid sporadic startup
  failures.
- Ignore -ENODEV return values from drm_of_find_panel_or_bridge in the LDB
  driver to fix probing for devices that still do not specify a panel in the
  device tree.
- Fix the CSI input selection to the VDIC. According to experiments, the real
  behaviour differs a bit from the documentation.

* tag 'imx-drm-fixes-2017-06-08' of git://git.pengutronix.de/git/pza/linux:
  gpu: ipu-v3: Fix CSI selection for VDIC
  drm/imx: imx-ldb: Accept drm_of_find_panel_or_bridge failure
  gpu: ipu-v3: pre: only use internal clock gating

drivers/gpu/drm/imx/imx-ldb.c

@@ -673,7 +673,7 @@ static int imx_ldb_bind(struct device *dev, struct device *master, void *data)
 		ret = drm_of_find_panel_or_bridge(child,
 						  imx_ldb->lvds_mux ? 4 : 2, 0,
 						  &channel->panel, &channel->bridge);
-		if (ret)
+		if (ret && ret != -ENODEV)
 			return ret;
 
 		/* panel ddc only if there is no bridge */

drivers/gpu/ipu-v3/ipu-common.c

@@ -725,15 +725,16 @@ void ipu_set_ic_src_mux(struct ipu_soc *ipu, int csi_id, bool vdi)
 	spin_lock_irqsave(&ipu->lock, flags);
 
 	val = ipu_cm_read(ipu, IPU_CONF);
-	if (vdi) {
+	if (vdi)
 		val |= IPU_CONF_IC_INPUT;
-	} else {
+	else
 		val &= ~IPU_CONF_IC_INPUT;
-		if (csi_id == 1)
-			val |= IPU_CONF_CSI_SEL;
-		else
-			val &= ~IPU_CONF_CSI_SEL;
-	}
+
+	if (csi_id == 1)
+		val |= IPU_CONF_CSI_SEL;
+	else
+		val &= ~IPU_CONF_CSI_SEL;
+
 	ipu_cm_write(ipu, val, IPU_CONF);
 
 	spin_unlock_irqrestore(&ipu->lock, flags);

drivers/gpu/ipu-v3/ipu-pre.c

@@ -131,8 +131,6 @@ int ipu_pre_get(struct ipu_pre *pre)
 	if (pre->in_use)
 		return -EBUSY;
 
-	clk_prepare_enable(pre->clk_axi);
-
 	/* first get the engine out of reset and remove clock gating */
 	writel(0, pre->regs + IPU_PRE_CTRL);
 
@@ -149,12 +147,7 @@ int ipu_pre_get(struct ipu_pre *pre)
 
 void ipu_pre_put(struct ipu_pre *pre)
 {
-	u32 val;
-
-	val = IPU_PRE_CTRL_SFTRST | IPU_PRE_CTRL_CLKGATE;
-	writel(val, pre->regs + IPU_PRE_CTRL);
-
-	clk_disable_unprepare(pre->clk_axi);
+	writel(IPU_PRE_CTRL_SFTRST, pre->regs + IPU_PRE_CTRL);
 
 	pre->in_use = false;
 }
@@ -249,6 +242,8 @@ static int ipu_pre_probe(struct platform_device *pdev)
 	if (!pre->buffer_virt)
 		return -ENOMEM;
 
+	clk_prepare_enable(pre->clk_axi);
+
 	pre->dev = dev;
 	platform_set_drvdata(pdev, pre);
 	mutex_lock(&ipu_pre_list_mutex);
@@ -268,6 +263,8 @@ static int ipu_pre_remove(struct platform_device *pdev)
 	available_pres--;
 	mutex_unlock(&ipu_pre_list_mutex);
 
+	clk_disable_unprepare(pre->clk_axi);
+
 	if (pre->buffer_virt)
 		gen_pool_free(pre->iram, (unsigned long)pre->buffer_virt,
 			      IPU_PRE_MAX_WIDTH * IPU_PRE_NUM_SCANLINES * 4);