Hi Maxime,

On 7/9/20 2:41 AM, Maxime Ripard wrote:

quoted

In order to prevent timeouts and stalls in the pipeline, the core clock
needs to be maxed at 500MHz during a modeset on the BCM2711.

Reviewed-by: Eric Anholt <redacted>
Signed-off-by: Maxime Ripard <redacted>
---
 drivers/gpu/drm/vc4/vc4_drv.h |  2 ++
 drivers/gpu/drm/vc4/vc4_hvs.c |  9 +++++++++
 drivers/gpu/drm/vc4/vc4_kms.c |  9 +++++++++
 3 files changed, 20 insertions(+)

diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
index e4cde1f9224b..6358f6ca8d56 100644
--- a/drivers/gpu/drm/vc4/vc4_drv.h
+++ b/drivers/gpu/drm/vc4/vc4_drv.h

@@ -320,6 +320,8 @@ struct vc4_hvs {
 	void __iomem *regs;
 	u32 __iomem *dlist;
 
+	struct clk *core_clk;
+
 	/* Memory manager for CRTCs to allocate space in the display
 	 * list.  Units are dwords.
 	 */

diff --git a/drivers/gpu/drm/vc4/vc4_hvs.c b/drivers/gpu/drm/vc4/vc4_hvs.c
index 836d8799d79e..091fdf4908aa 100644
--- a/drivers/gpu/drm/vc4/vc4_hvs.c
+++ b/drivers/gpu/drm/vc4/vc4_hvs.c

@@ -19,6 +19,7 @@
  * each CRTC.
  */
 
+#include <linux/clk.h>
 #include <linux/component.h>
 #include <linux/platform_device.h>
 

@@ -540,6 +541,14 @@ static int vc4_hvs_bind(struct device *dev, struct device *master, void *data)
 	hvs->regset.regs = hvs_regs;
 	hvs->regset.nregs = ARRAY_SIZE(hvs_regs);
 
+	if (hvs->hvs5) {
+		hvs->core_clk = devm_clk_get(&pdev->dev, NULL);
+		if (IS_ERR(hvs->core_clk)) {
+			dev_err(&pdev->dev, "Couldn't get core clock\n");
+			return PTR_ERR(hvs->core_clk);
+		}
+	}
+
 	if (!hvs->hvs5)
 		hvs->dlist = hvs->regs + SCALER_DLIST_START;
 	else

diff --git a/drivers/gpu/drm/vc4/vc4_kms.c b/drivers/gpu/drm/vc4/vc4_kms.c
index 08318e69061b..210cc2408087 100644
--- a/drivers/gpu/drm/vc4/vc4_kms.c
+++ b/drivers/gpu/drm/vc4/vc4_kms.c

@@ -11,6 +11,8 @@
  * crtc, HDMI encoder).
  */
 
+#include <linux/clk.h>
+
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_crtc.h>

@@ -149,6 +151,7 @@ vc4_atomic_complete_commit(struct drm_atomic_state *state)
 {
 	struct drm_device *dev = state->dev;
 	struct vc4_dev *vc4 = to_vc4_dev(dev);
+	struct vc4_hvs *hvs = vc4->hvs;
 	struct vc4_crtc *vc4_crtc;
 	int i;
 

@@ -160,6 +163,9 @@ vc4_atomic_complete_commit(struct drm_atomic_state *state)
 		vc4_hvs_mask_underrun(dev, vc4_crtc->channel);
 	}
 
+	if (vc4->hvs->hvs5)
+		clk_set_min_rate(hvs->core_clk, 500000000);
+
 	drm_atomic_helper_wait_for_fences(dev, state, false);
 
 	drm_atomic_helper_wait_for_dependencies(state);

@@ -182,6 +188,9 @@ vc4_atomic_complete_commit(struct drm_atomic_state *state)
 
 	drm_atomic_helper_commit_cleanup_done(state);
 
+	if (vc4->hvs->hvs5)
+		clk_set_min_rate(hvs->core_clk, 0);
+
 	drm_atomic_state_put(state);
 
 	up(&vc4->async_modeset);

This patch doesn't control the enable/disable of core_clk.
So, I think that it need to handle the clock as following:

diff --git a/drivers/gpu/drm/vc4/vc4_hvs.c b/drivers/gpu/drm/vc4/vc4_hvs.c
index 4ef88c0b51ab..355d67fd8beb 100644
--- a/drivers/gpu/drm/vc4/vc4_hvs.c
+++ b/drivers/gpu/drm/vc4/vc4_hvs.c

@@ -588,6 +588,12 @@ static int vc4_hvs_bind(struct device *dev, struct device *master, void *data)
                        dev_err(&pdev->dev, "Couldn't get core clock\n");
                        return PTR_ERR(hvs->core_clk);
                }
+
+               ret = clk_prepare_enable(hvs->core_clk);
+               if (ret) {
+                       dev_err(&pdev->dev, "Couldn't enable core clock\n");
+                       return ret;
+               }
        }
 
        if (!hvs->hvs5)

@@ -681,6 +687,8 @@ static void vc4_hvs_unbind(struct device *dev, struct device *master,
        drm_mm_takedown(&vc4->hvs->dlist_mm);
        drm_mm_takedown(&vc4->hvs->lbm_mm);
 
+       clk_prepare_enable(vc4->hvs->core_clk);