[PATCH v2 5/5] drm/msm/dpu1: Handle the reg bus ICC path

[Konrad Dybcio <konrad.dybcio@linaro.org>]

Apart from the already handled data bus (MAS_MDP_Pn<->DDR), there's
another path that needs to be handled to ensure MDSS functions properly,
namely the "reg bus", a.k.a the CPU-MDSS interconnect.

Gating that path may have a variety of effects.. from none to otherwise
inexplicable DSI timeouts..

On the DPU side, we need to keep the bus alive. The vendor driver
kickstarts it to max (300Mbps) throughput on first commit, but in
exchange for some battery life in rare DPU-enabled-panel-disabled
usecases, we can request it at DPU init and gate it at suspend.

Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c | 22 ++++++++++++++++++++--
 drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h |  1 +
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
index dd6c1c40ab9e..5e1ed338114d 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
@@ -384,15 +384,17 @@ static int dpu_kms_global_obj_init(struct dpu_kms *dpu_kms)
 	return 0;
 }
 
-static int dpu_kms_parse_data_bus_icc_path(struct dpu_kms *dpu_kms)
+static int dpu_kms_parse_icc_paths(struct dpu_kms *dpu_kms)
 {
 	struct icc_path *path0;
 	struct icc_path *path1;
+	struct icc_path *reg_bus_path;
 	struct drm_device *dev = dpu_kms->dev;
 	struct device *dpu_dev = dev->dev;
 
 	path0 = msm_icc_get(dpu_dev, "mdp0-mem");
 	path1 = msm_icc_get(dpu_dev, "mdp1-mem");
+	reg_bus_path = msm_icc_get(dpu_dev, "cpu-cfg");
 
 	if (IS_ERR_OR_NULL(path0))
 		return PTR_ERR_OR_ZERO(path0);
@@ -404,6 +406,10 @@ static int dpu_kms_parse_data_bus_icc_path(struct dpu_kms *dpu_kms)
 		dpu_kms->mdp_path[1] = path1;
 		dpu_kms->num_mdp_paths++;
 	}
+
+	if (!IS_ERR_OR_NULL(reg_bus_path))
+		dpu_kms->reg_bus_path = reg_bus_path;
+
 	return 0;
 }
 
@@ -1039,7 +1045,7 @@ static int dpu_kms_hw_init(struct msm_kms *kms)
 		DPU_DEBUG("REG_DMA is not defined");
 	}
 
-	dpu_kms_parse_data_bus_icc_path(dpu_kms);
+	dpu_kms_parse_icc_paths(dpu_kms);
 
 	rc = pm_runtime_resume_and_get(&dpu_kms->pdev->dev);
 	if (rc < 0)
@@ -1241,6 +1247,9 @@ static int __maybe_unused dpu_runtime_suspend(struct device *dev)
 	for (i = 0; i < dpu_kms->num_mdp_paths; i++)
 		icc_set_bw(dpu_kms->mdp_path[i], 0, 0);
 
+	if (dpu_kms->reg_bus_path)
+		icc_set_bw(dpu_kms->reg_bus_path, 0, 0);
+
 	return 0;
 }
 
@@ -1261,6 +1270,15 @@ static int __maybe_unused dpu_runtime_resume(struct device *dev)
 		return rc;
 	}
 
+	/*
+	 * The vendor driver supports setting 76.8 / 150 / 300 MBps on this
+	 * path, but it seems to go for the highest level when display output
+	 * is enabled and zero otherwise. For simplicity, we can assume that
+	 * DPU being enabled and running implies that.
+	 */
+	if (dpu_kms->reg_bus_path)
+		icc_set_bw(dpu_kms->reg_bus_path, 0, MBps_to_icc(300));
+
 	dpu_vbif_init_memtypes(dpu_kms);
 
 	drm_for_each_encoder(encoder, ddev)
diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h
index d5d9bec90705..c332381d58c4 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h
@@ -111,6 +111,7 @@ struct dpu_kms {
 	atomic_t bandwidth_ref;
 	struct icc_path *mdp_path[2];
 	u32 num_mdp_paths;
+	struct icc_path *reg_bus_path;
 };
 
 struct vsync_info {

-- 
2.40.0