diff mbox series

[RFC,v1,1/7] clk: meson: meson8b: run from the XTAL when changing the CPU frequency

Message ID 20181114225725.2821-2-martin.blumenstingl@googlemail.com (mailing list archive)
State Superseded, archived
Headers show
Series Meson8b: make the CPU clock mutable | expand

Commit Message

Martin Blumenstingl Nov. 14, 2018, 10:57 p.m. UTC 
Changing the CPU clock requires changing various clocks including the
SYS PLL. The existing meson clk-pll and clk-regmap drivers can change
all of the relevant clocks already.
However, changing for exampe the SYS PLL is problematic because as long
as the CPU is running off a clock derived from SYS PLL changing the
latter results in a full system lockup.
Fix this system lockup by switching the CPU clock to run off the XTAL
while we are changing the any of the clocks in the CPU clock tree.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
---
 drivers/clk/meson/meson8b.c | 63 +++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)

Comments

Jerome Brunet Nov. 15, 2018, 9:53 a.m. UTC | #1 
On Wed, 2018-11-14 at 23:57 +0100, Martin Blumenstingl wrote:
> Changing the CPU clock requires changing various clocks including the
> SYS PLL. The existing meson clk-pll and clk-regmap drivers can change
> all of the relevant clocks already.
> However, changing for exampe the SYS PLL is problematic because as long
> as the CPU is running off a clock derived from SYS PLL changing the
> latter results in a full system lockup.
> Fix this system lockup by switching the CPU clock to run off the XTAL
> while we are changing the any of the clocks in the CPU clock tree.
> 
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>

Original submission wasn't that far off after all ;)

Thanks for digging and fixing all the bugs around it ! It must have been quite
a challenge !

If you don't mind, I would prefer if your series put all the clock fixes
first, and this particular change just before the last one allowing RW ops.

Reviewed-by: Jerome Brunet <jbrunet@baylibre.com>

> ---
>  drivers/clk/meson/meson8b.c | 63 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 63 insertions(+)
> 
> diff --git a/drivers/clk/meson/meson8b.c b/drivers/clk/meson/meson8b.c
> index 9bd5920da0ff..40e77fe4ba7c 100644
> --- a/drivers/clk/meson/meson8b.c
> +++ b/drivers/clk/meson/meson8b.c
> @@ -1103,6 +1103,53 @@ static const struct reset_control_ops
> meson8b_clk_reset_ops = {
>  	.deassert = meson8b_clk_reset_deassert,
>  };
>  
> +struct meson8b_nb_data {
> +	struct notifier_block nb;
> +	struct clk_hw_onecell_data *onecell_data;
> +};
> +
> +static int meson8b_cpu_clk_notifier_cb(struct notifier_block *nb,
> +				       unsigned long event, void *data)
> +{
> +	struct meson8b_nb_data *nb_data =
> +		container_of(nb, struct meson8b_nb_data, nb);
> +	struct clk_hw **hws = nb_data->onecell_data->hws;
> +	struct clk_hw *cpu_clk_hw, *parent_clk_hw;
> +	struct clk *cpu_clk, *parent_clk;
> +	int ret;
> +
> +	switch (event) {
> +	case PRE_RATE_CHANGE:
> +		parent_clk_hw = hws[CLKID_XTAL];
> +		break;
> +
> +	case POST_RATE_CHANGE:
> +		parent_clk_hw = hws[CLKID_CPU_SCALE_OUT_SEL];
> +		break;
> +
> +	default:
> +		return NOTIFY_DONE;
> +	}
> +
> +	cpu_clk_hw = hws[CLKID_CPUCLK];
> +	cpu_clk = __clk_lookup(clk_hw_get_name(cpu_clk_hw));
> +
> +	parent_clk = __clk_lookup(clk_hw_get_name(parent_clk_hw));
> +
> +	ret = clk_set_parent(cpu_clk, parent_clk);
> +	if (ret)
> +		return notifier_from_errno(ret);
> +
> +	udelay(100);
> +
> +	return NOTIFY_OK;
> +}
> +
> +static struct meson8b_nb_data meson8b_cpu_nb_data = {
> +	.nb.notifier_call = meson8b_cpu_clk_notifier_cb,
> +	.onecell_data = &meson8b_hw_onecell_data,
> +};
> +
>  static const struct regmap_config clkc_regmap_config = {
>  	.reg_bits       = 32,
>  	.val_bits       = 32,
> @@ -1112,6 +1159,8 @@ static const struct regmap_config clkc_regmap_config =
> {
>  static void __init meson8b_clkc_init(struct device_node *np)
>  {
>  	struct meson8b_clk_reset *rstc;
> +	const char *notifier_clk_name;
> +	struct clk *notifier_clk;
>  	void __iomem *clk_base;
>  	struct regmap *map;
>  	int i, ret;
> @@ -1166,6 +1215,20 @@ static void __init meson8b_clkc_init(struct
> device_node *np)
>  			return;
>  	}
>  
> +	/*
> +	 * FIXME we shouldn't program the muxes in notifier handlers. The
> +	 * tricky programming sequence will be handled by the forthcoming
> +	 * coordinated clock rates mechanism once that feature is released.
> +	 */
> +	notifier_clk_name = clk_hw_get_name(&meson8b_cpu_scale_out_sel.hw);
> +	notifier_clk = __clk_lookup(notifier_clk_name);
> +	ret = clk_notifier_register(notifier_clk, &meson8b_cpu_nb_data.nb);
> +	if (ret) {
> +		pr_err("%s: failed to register the CPU clock notifier\n",
> +		       __func__);
> +		return;
> +	}
> +
>  	ret = of_clk_add_hw_provider(np, of_clk_hw_onecell_get,
>  				     &meson8b_hw_onecell_data);
>  	if (ret)
diff mbox series

Patch

diff --git a/drivers/clk/meson/meson8b.c b/drivers/clk/meson/meson8b.c
index 9bd5920da0ff..40e77fe4ba7c 100644
--- a/drivers/clk/meson/meson8b.c
+++ b/drivers/clk/meson/meson8b.c
@@ -1103,6 +1103,53 @@  static const struct reset_control_ops meson8b_clk_reset_ops = {
 	.deassert = meson8b_clk_reset_deassert,
 };
 
+struct meson8b_nb_data {
+	struct notifier_block nb;
+	struct clk_hw_onecell_data *onecell_data;
+};
+
+static int meson8b_cpu_clk_notifier_cb(struct notifier_block *nb,
+				       unsigned long event, void *data)
+{
+	struct meson8b_nb_data *nb_data =
+		container_of(nb, struct meson8b_nb_data, nb);
+	struct clk_hw **hws = nb_data->onecell_data->hws;
+	struct clk_hw *cpu_clk_hw, *parent_clk_hw;
+	struct clk *cpu_clk, *parent_clk;
+	int ret;
+
+	switch (event) {
+	case PRE_RATE_CHANGE:
+		parent_clk_hw = hws[CLKID_XTAL];
+		break;
+
+	case POST_RATE_CHANGE:
+		parent_clk_hw = hws[CLKID_CPU_SCALE_OUT_SEL];
+		break;
+
+	default:
+		return NOTIFY_DONE;
+	}
+
+	cpu_clk_hw = hws[CLKID_CPUCLK];
+	cpu_clk = __clk_lookup(clk_hw_get_name(cpu_clk_hw));
+
+	parent_clk = __clk_lookup(clk_hw_get_name(parent_clk_hw));
+
+	ret = clk_set_parent(cpu_clk, parent_clk);
+	if (ret)
+		return notifier_from_errno(ret);
+
+	udelay(100);
+
+	return NOTIFY_OK;
+}
+
+static struct meson8b_nb_data meson8b_cpu_nb_data = {
+	.nb.notifier_call = meson8b_cpu_clk_notifier_cb,
+	.onecell_data = &meson8b_hw_onecell_data,
+};
+
 static const struct regmap_config clkc_regmap_config = {
 	.reg_bits       = 32,
 	.val_bits       = 32,
@@ -1112,6 +1159,8 @@  static const struct regmap_config clkc_regmap_config = {
 static void __init meson8b_clkc_init(struct device_node *np)
 {
 	struct meson8b_clk_reset *rstc;
+	const char *notifier_clk_name;
+	struct clk *notifier_clk;
 	void __iomem *clk_base;
 	struct regmap *map;
 	int i, ret;
@@ -1166,6 +1215,20 @@  static void __init meson8b_clkc_init(struct device_node *np)
 			return;
 	}
 
+	/*
+	 * FIXME we shouldn't program the muxes in notifier handlers. The
+	 * tricky programming sequence will be handled by the forthcoming
+	 * coordinated clock rates mechanism once that feature is released.
+	 */
+	notifier_clk_name = clk_hw_get_name(&meson8b_cpu_scale_out_sel.hw);
+	notifier_clk = __clk_lookup(notifier_clk_name);
+	ret = clk_notifier_register(notifier_clk, &meson8b_cpu_nb_data.nb);
+	if (ret) {
+		pr_err("%s: failed to register the CPU clock notifier\n",
+		       __func__);
+		return;
+	}
+
 	ret = of_clk_add_hw_provider(np, of_clk_hw_onecell_get,
 				     &meson8b_hw_onecell_data);
 	if (ret)