[PATCH v6 16/20] drm/mediatek: Make sure the power-on sequence of LARB and RDMA

[Hsiao Chien Sung]

Since LARBs (Local ARBiter) have to be powered on before its users,
to ensure the power-on sequence, we created a device link between
RDMA and its LARB, and when pm_runtime_get_sync is called in RDMA,
system will guarantee the LARB is powered on before the RDMA.

Signed-off-by: Hsiao Chien Sung <shawn.sung at mediatek.com>
---
 drivers/gpu/drm/mediatek/mtk_mdp_rdma.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_mdp_rdma.c b/drivers/gpu/drm/mediatek/mtk_mdp_rdma.c
index c3adaeefd551..fce6fbb534b1 100644
--- a/drivers/gpu/drm/mediatek/mtk_mdp_rdma.c
+++ b/drivers/gpu/drm/mediatek/mtk_mdp_rdma.c
@@ -244,10 +244,23 @@ size_t mtk_mdp_rdma_get_num_formats(struct device *dev)

 int mtk_mdp_rdma_clk_enable(struct device *dev)
 {
+	int ret;
 	struct mtk_mdp_rdma *rdma = dev_get_drvdata(dev);

-	clk_prepare_enable(rdma->clk);
-	return 0;
+	/*
+	 * Since LARBs (Local ARBiter) have to be powered on before its users,
+	 * to ensure the power-on sequence, we created a device link between
+	 * RDMA and its LARB, and when pm_runtime_get_sync is called in RDMA,
+	 * system will make sure the LARB is powered on before the RDMA
+	 */
+	ret = pm_runtime_get_sync(dev);
+
+	if (ret < 0)
+		dev_err(dev, "pm_runtime_get_sync failed: %d\n", ret);
+	else
+		ret = clk_prepare_enable(rdma->clk);
+
+	return ret;
 }

 void mtk_mdp_rdma_clk_disable(struct device *dev)
@@ -255,6 +268,9 @@ void mtk_mdp_rdma_clk_disable(struct device *dev)
 	struct mtk_mdp_rdma *rdma = dev_get_drvdata(dev);

 	clk_disable_unprepare(rdma->clk);
+
+	/* Same reason as when enabling clock, turn the LARB off */
+	pm_runtime_put(dev);
 }

 static int mtk_mdp_rdma_bind(struct device *dev, struct device *master,
--
2.18.0