[PATCH v2 2/2] drm/sun4i: drc: Make sure we enforce the clock rate

[Maxime Ripard <maxime@cerno.tech>]

The DRC needs to run at 300MHz to be functional. This was done so far
using assigned-clocks in the device tree, but that is easy to forget, and
dosen't provide any other guarantee than the rate is going to be roughly
the one requested at probe time.

Therefore it's pretty fragile, so let's just use the exclusive clock API to
enforce it.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>

---

Changes from v1:
  - Add test on the clk_set_rate_exclusive return value
---
 drivers/gpu/drm/sun4i/sun6i_drc.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/sun4i/sun6i_drc.c b/drivers/gpu/drm/sun4i/sun6i_drc.c
index f7ab72244796..4fbe9a6b5182 100644
--- a/drivers/gpu/drm/sun4i/sun6i_drc.c
+++ b/drivers/gpu/drm/sun4i/sun6i_drc.c
@@ -56,6 +56,13 @@ static int sun6i_drc_bind(struct device *dev, struct device *master,
 		ret = PTR_ERR(drc->mod_clk);
 		goto err_disable_bus_clk;
 	}
+
+	ret = clk_set_rate_exclusive(drc->mod_clk, 300000000);
+	if (ret) {
+		dev_err(dev, "Couldn't set the module clock frequency\n");
+		goto err_disable_bus_clk;
+	}
+
 	clk_prepare_enable(drc->mod_clk);
 
 	return 0;
@@ -72,6 +79,7 @@ static void sun6i_drc_unbind(struct device *dev, struct device *master,
 {
 	struct sun6i_drc *drc = dev_get_drvdata(dev);
 
+	clk_rate_exclusive_put(drc->mod_clk);
 	clk_disable_unprepare(drc->mod_clk);
 	clk_disable_unprepare(drc->bus_clk);
 	reset_control_assert(drc->reset);
-- 
2.24.1

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