diff mbox series

[1/2] drm/sun4i: backend: Make sure we enforce the clock rate

Message ID 20191219092000.949052-1-maxime@cerno.tech (mailing list archive)
State New, archived
Headers show
Series [1/2] drm/sun4i: backend: Make sure we enforce the clock rate | expand

Commit Message

Maxime Ripard Dec. 19, 2019, 9:19 a.m. UTC 
The backend 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>
---
 drivers/gpu/drm/sun4i/sun4i_backend.c | 3 +++
 1 file changed, 3 insertions(+)

Comments

Chen-Yu Tsai Jan. 7, 2020, 1:37 p.m. UTC | #1 
On Thu, Dec 19, 2019 at 5:20 PM Maxime Ripard <maxime@cerno.tech> wrote:
>
> The backend 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>

Reviewed-by: Chen-Yu Tsai <wens@csie.org>
diff mbox series

Patch

diff --git a/drivers/gpu/drm/sun4i/sun4i_backend.c b/drivers/gpu/drm/sun4i/sun4i_backend.c
index 4e29f4fe4a05..aa55eaeb8823 100644
--- a/drivers/gpu/drm/sun4i/sun4i_backend.c
+++ b/drivers/gpu/drm/sun4i/sun4i_backend.c
@@ -857,6 +857,7 @@  static int sun4i_backend_bind(struct device *dev, struct device *master,
 		goto err_disable_bus_clk;
 	}
 	clk_prepare_enable(backend->mod_clk);
+	clk_set_rate_exclusive(backend->mod_clk, 300000000);
 
 	backend->ram_clk = devm_clk_get(dev, "ram");
 	if (IS_ERR(backend->ram_clk)) {
@@ -932,6 +933,7 @@  static int sun4i_backend_bind(struct device *dev, struct device *master,
 err_disable_ram_clk:
 	clk_disable_unprepare(backend->ram_clk);
 err_disable_mod_clk:
+	clk_rate_exclusive_put(backend->mod_clk);
 	clk_disable_unprepare(backend->mod_clk);
 err_disable_bus_clk:
 	clk_disable_unprepare(backend->bus_clk);
@@ -952,6 +954,7 @@  static void sun4i_backend_unbind(struct device *dev, struct device *master,
 		sun4i_backend_free_sat(dev);
 
 	clk_disable_unprepare(backend->ram_clk);
+	clk_rate_exclusive_put(backend->mod_clk);
 	clk_disable_unprepare(backend->mod_clk);
 	clk_disable_unprepare(backend->bus_clk);
 	reset_control_assert(backend->reset);