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

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

[Maxime Ripard]

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(+)

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);
-- 
2.23.0


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

[Maxime Ripard]

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>
---
 drivers/gpu/drm/sun4i/sun6i_drc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/sun4i/sun6i_drc.c b/drivers/gpu/drm/sun4i/sun6i_drc.c
index f7ab72244796..ddb52da90103 100644
--- a/drivers/gpu/drm/sun4i/sun6i_drc.c
+++ b/drivers/gpu/drm/sun4i/sun6i_drc.c
@@ -57,6 +57,7 @@ static int sun6i_drc_bind(struct device *dev, struct device *master,
 		goto err_disable_bus_clk;
 	}
 	clk_prepare_enable(drc->mod_clk);
+	clk_set_rate_exclusive(drc->mod_clk, 300000000);
 
 	return 0;
 
@@ -72,6 +73,7 @@ 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);
-- 
2.23.0


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

[Chen-Yu Tsai]

On Thu, Dec 19, 2019 at 5:20 PM Maxime Ripard <maxime@cerno.tech> wrote:
>
> 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>

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

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

[Chen-Yu Tsai]

On Thu, Dec 19, 2019 at 5:20 PM Maxime Ripard <maxime@cerno.tech> wrote:
>
> 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>
> ---
>  drivers/gpu/drm/sun4i/sun6i_drc.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/sun4i/sun6i_drc.c b/drivers/gpu/drm/sun4i/sun6i_drc.c
> index f7ab72244796..ddb52da90103 100644
> --- a/drivers/gpu/drm/sun4i/sun6i_drc.c
> +++ b/drivers/gpu/drm/sun4i/sun6i_drc.c
> @@ -57,6 +57,7 @@ static int sun6i_drc_bind(struct device *dev, struct device *master,
>                 goto err_disable_bus_clk;
>         }
>         clk_prepare_enable(drc->mod_clk);
> +       clk_set_rate_exclusive(drc->mod_clk, 300000000);

I wonder what would happen if this fails...
>
>         return 0;
>
> @@ -72,6 +73,7 @@ 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);

and we try to do the put regardless...

ChenYu

>         clk_disable_unprepare(drc->mod_clk);
>         clk_disable_unprepare(drc->bus_clk);
>         reset_control_assert(drc->reset);
> --
> 2.23.0
>

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

[Chen-Yu Tsai]

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>

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