[RFC 0/9] Allow modifications of specific clocks via DT and more

[RFC 0/9] Allow modifications of specific clocks via DT and more

[kernel-TqfNSX0MhmxHKSADF0wUEw]

From: Martin Sperl <kernel-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org>

This patch series (which requires the patch-series-v4 of
"clk: bcm2835: add clocks and add MASH support") allows to configure
specific aspects (mostly with regards to clock selection) of individual
clocks to get configured via the device-tree.

Also - for debug purposes - a patch has been added that exposes the
raw clock registers read-only via debugfs.

Martin Sperl (9):
  clk: bcm2835: add basic device tree support for per clock settings
  clk: bcm2835: add support for parent selection in DT
  clk: bcm2835: add ability to control mash level via device-tree
  clk: bcm2835: reorganize bcm2835_clock_determine_rate
  clk: bcm2835: prefer clocks that use integer dividers
  clk: bcm2835: allow to define a minimum fractional divider in DT
  clk: bcm2835: allow clock choosing mechanims to be selected in DT
  dt-bindings: bcm2835: document optional per clock dt-nodes
  clk: bcm2835: expose raw clock-registers via debugfs

 .../bindings/clock/brcm,bcm2835-cprman.txt         |   33 ++
 drivers/clk/bcm/clk-bcm2835.c                      |  508 ++++++++++++++++++--
 include/dt-bindings/clock/bcm2835.h                |   15 +
 3 files changed, 512 insertions(+), 44 deletions(-)

-- 
1.7.10.4

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[RFC 1/9] clk: bcm2835: add basic device tree support for per clock settings

[kernel-TqfNSX0MhmxHKSADF0wUEw]

From: Martin Sperl <kernel-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org>

Add basic device tree support for per clock settings taken from the
device tree.

Signed-off-by: Martin Sperl <kernel-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org>
---
 drivers/clk/bcm/clk-bcm2835.c |   72 +++++++++++++++++++++++++++++++++++++----
 1 file changed, 66 insertions(+), 6 deletions(-)

diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c
index 637f8ae..1c714d0 100644
--- a/drivers/clk/bcm/clk-bcm2835.c
+++ b/drivers/clk/bcm/clk-bcm2835.c
@@ -1757,8 +1757,38 @@ static const struct clk_ops bcm2835_vpu_clock_clk_ops = {
 	.get_parent = bcm2835_clock_get_parent,
 };
 
+static struct device_node *bcm2835_find_dt_node(
+	struct bcm2835_cprman *cprman, int id)
+{
+	struct device *dev = cprman->dev;
+	struct device_node *nc, *ncp = dev->of_node;
+	u32 value;
+	int err;
+
+	/* if no dt, then use the constant version */
+	if (!ncp)
+		return NULL;
+
+	/* try to find the devicetree with the id */
+	for_each_available_child_of_node(ncp, nc) {
+		/* get reg value */
+		err = of_property_read_u32(nc, "reg", &value);
+		if (err) {
+			dev_err(dev, "%s has no valid 'reg' property (%d)\n",
+				nc->full_name, err);
+		} else {
+			if (value == id)
+				return nc;
+		}
+	}
+
+	/* not found */
+	return NULL;
+}
+
 static struct clk *bcm2835_register_pll(struct bcm2835_cprman *cprman,
-					const struct bcm2835_pll_data *data)
+					const struct bcm2835_pll_data *data,
+					size_t id)
 {
 	struct bcm2835_pll *pll;
 	struct clk_init_data init;
@@ -1785,7 +1815,8 @@ static struct clk *bcm2835_register_pll(struct bcm2835_cprman *cprman,
 
 static struct clk *
 bcm2835_register_pll_divider(struct bcm2835_cprman *cprman,
-			     const struct bcm2835_pll_divider_data *data)
+			     const struct bcm2835_pll_divider_data *data,
+			     size_t id)
 {
 	struct bcm2835_pll_divider *divider;
 	struct clk_init_data init;
@@ -1843,14 +1874,42 @@ bcm2835_register_pll_divider(struct bcm2835_cprman *cprman,
 	return clk;
 }
 
+static const struct bcm2835_clock_data *bcm2835_register_clock_of(
+	struct bcm2835_cprman *cprman,
+	const struct bcm2835_clock_data *data_orig,
+	size_t id)
+{
+	struct device *dev = cprman->dev;
+	struct device_node *nc;
+	struct bcm2835_clock_data *data;
+
+	/* find the corresponding dt-node */
+	nc = bcm2835_find_dt_node(cprman, id);
+	if (!nc)
+		return data_orig;
+
+	/* create a copy of data */
+	data = devm_kmalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return data_orig;
+	memcpy(data, data_orig, sizeof(*data));
+
+	/* and return the result */
+	return data;
+}
+
 static struct clk *bcm2835_register_clock(struct bcm2835_cprman *cprman,
-					  const struct bcm2835_clock_data *data)
+					  const struct bcm2835_clock_data *data,
+					  size_t id)
 {
 	struct bcm2835_clock *clock;
 	struct clk_init_data init;
 	const char *parents[1 << CM_SRC_BITS];
 	size_t i;
 
+	/* update default values from the device_tree */
+	data = bcm2835_register_clock_of(cprman, data, id);
+
 	/*
 	 * Replace our "xosc" references with the oscillator's
 	 * actual name.
@@ -1887,7 +1946,8 @@ static struct clk *bcm2835_register_clock(struct bcm2835_cprman *cprman,
 }
 
 static struct clk *bcm2835_register_gate(struct bcm2835_cprman *cprman,
-					 const struct bcm2835_gate_data *data)
+					 const struct bcm2835_gate_data *data,
+					 size_t id)
 {
 	return clk_register_gate(cprman->dev, data->name, data->parent,
 				 CLK_IGNORE_UNUSED | CLK_SET_RATE_GATE,
@@ -1896,7 +1956,7 @@ static struct clk *bcm2835_register_gate(struct bcm2835_cprman *cprman,
 }
 
 typedef struct clk *(*bcm2835_clk_register)(struct bcm2835_cprman *cprman,
-					    const void *data);
+					    const void *data, size_t id);
 struct bcm2835_clk_desc {
 	bcm2835_clk_register clk_register;
 	const void *data;
@@ -2007,7 +2067,7 @@ static int bcm2835_clk_probe(struct platform_device *pdev)
 	for (i = 0; i < asize; i++) {
 		desc = &clk_desc_array[i];
 		if (desc->clk_register && desc->data)
-			clks[i] = desc->clk_register(cprman, desc->data);
+			clks[i] = desc->clk_register(cprman, desc->data, i);
 	}
 
 	return of_clk_add_provider(dev->of_node, of_clk_src_onecell_get,
-- 
1.7.10.4

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[RFC 7/9] clk: bcm2835: allow clock choosing mechanims to be selected in DT

[kernel-TqfNSX0MhmxHKSADF0wUEw]

From: Martin Sperl <kernel-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org>

Allow the clock choosing mechanism to be selected in the
devicetree.

There are 3 options that can get selected right now:
* BCM2835_CHOOSE_CLOCK_INTEGER
  - only integer dividers are used (fails otherwise)
* BCM2835_CHOOSE_CLOCK_CLOSEST
  - choose the clock that is closest to the target rate
* BCM2835_CHOOSE_CLOCK_INTEGER_THEN_FRAC
  - integer dividers are preferred,
    otherwise uses the clock that is closest to
    the target rate
  - this is the default implementation used

If there is a need for a different policy, then that can
get implemented and selected using this mechanism.

Signed-off-by: Martin Sperl <kernel-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org>
---
 drivers/clk/bcm/clk-bcm2835.c       |   92 ++++++++++++++++++++++++++---------
 include/dt-bindings/clock/bcm2835.h |    6 +++
 2 files changed, 74 insertions(+), 24 deletions(-)

diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c
index 7048ca5..c381cb1 100644
--- a/drivers/clk/bcm/clk-bcm2835.c
+++ b/drivers/clk/bcm/clk-bcm2835.c
@@ -697,6 +697,14 @@ static const struct bcm2835_pll_divider_data bcm2835_pllh_pix_data = {
 	.fixed_divider = 10,
 };
 
+struct bcm2835_rates {
+	struct clk_hw *parent;
+	unsigned long rate;
+	unsigned long prate;
+	u32 div;
+	divmash dmash;
+};
+
 struct bcm2835_clock_data {
 	const char *name;
 
@@ -718,6 +726,12 @@ struct bcm2835_clock_data {
 	bool mash_forced;
 
 	bool is_vpu_clock;
+
+	/* the determine rate function */
+	int (*choose_clock)(struct clk_hw *hw,
+			    struct clk_rate_request *req,
+			    struct bcm2835_rates *rates,
+			    size_t rate_cnt);
 };
 
 static const char *const bcm2835_clock_per_parents[] = {
@@ -1670,14 +1684,6 @@ unlock_exit:
 	return 0;
 }
 
-struct bcm2835_rates {
-	struct clk_hw *parent;
-	unsigned long rate;
-	unsigned long prate;
-	u32 div;
-	divmash dmash;
-};
-
 static int bcm2835_clock_determine_rate_set(struct clk_rate_request *req,
 					    struct bcm2835_rates *best)
 {
@@ -1688,10 +1694,10 @@ static int bcm2835_clock_determine_rate_set(struct clk_rate_request *req,
 	return 0;
 }
 
-static int bcm2835_clock_determine_integer_rate(struct clk_hw *hw,
-						struct clk_rate_request *req,
-						struct bcm2835_rates *rates,
-						size_t rate_cnt)
+static int bcm2835_clock_choose_integer_div(struct clk_hw *hw,
+					    struct clk_rate_request *req,
+					    struct bcm2835_rates *rates,
+					    size_t rate_cnt)
 {
 	size_t i;
 
@@ -1706,10 +1712,10 @@ static int bcm2835_clock_determine_integer_rate(struct clk_hw *hw,
 	return -EINVAL;
 }
 
-static int bcm2835_clock_determine_closest_rate(struct clk_hw *hw,
-						struct clk_rate_request *req,
-						struct bcm2835_rates *rates,
-						size_t rate_cnt)
+static int bcm2835_clock_choose_closest_rate(struct clk_hw *hw,
+					     struct clk_rate_request *req,
+					     struct bcm2835_rates *rates,
+					     size_t rate_cnt)
 {
 	struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
 	const struct bcm2835_clock_data *data = clock->data;
@@ -1750,14 +1756,30 @@ static int bcm2835_clock_determine_closest_rate(struct clk_hw *hw,
 	return -EINVAL;
 }
 
+static int bcm2835_clock_choose_int_then_frac(struct clk_hw *hw,
+					      struct clk_rate_request *req,
+					      struct bcm2835_rates *rates,
+					      size_t rate_cnt)
+{
+	int err;
+
+	/* find integer rates with preference */
+	err = bcm2835_clock_choose_integer_div(hw, req, rates, rate_cnt);
+	if (!err)
+		return 0;
+
+	/* find the closest rate */
+	return bcm2835_clock_choose_closest_rate(hw, req, rates, rate_cnt);
+}
+
 static int bcm2835_clock_determine_rate(struct clk_hw *hw,
 					struct clk_rate_request *req)
 {
 	struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
+	const struct bcm2835_clock_data *data = clock->data;
 	struct bcm2835_rates rates[BIT(CM_SRC_BITS)];
 	size_t i, rate_cnt = 0;
 	divmash dm;
-	int err;
 
 	/* fill in rates */
 	for (i = 0; i < clk_hw_get_num_parents(hw); ++i) {
@@ -1774,14 +1796,12 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw,
 		rate_cnt++;
 	}
 
-	/* find integer rates with preference */
-	err = bcm2835_clock_determine_integer_rate(hw, req, rates, rate_cnt);
-	if (!err)
-		return 0;
+	/* if we have a custom rate selection , then use that one */
+	if (data->choose_clock)
+		return data->choose_clock(hw, req, rates, rate_cnt);
 
-	/* otherwise choose the "closest" one */
-	return bcm2835_clock_determine_closest_rate(hw, req, rates,
-						    rate_cnt);
+	/* otherwise choose the "int-then-frac" one */
+	return bcm2835_clock_choose_int_then_frac(hw, req, rates, rate_cnt);
 }
 
 static int _bcm2835_clk_set_parent(struct bcm2835_cprman *cprman,
@@ -2108,6 +2128,30 @@ static const struct bcm2835_clock_data *bcm2835_register_clock_of(
 	err = of_property_read_u32(nc, "brcm,min-fract-div", &value);
 	if (!err)
 		data->min_frac_div = value << CM_DIV_FRAC_BITS;
+	/* choose alternate clock selector */
+	err = of_property_read_u32(nc, "brcm,clock-selector", &value);
+	if (!err) {
+		switch (value) {
+		case BCM2835_CHOOSE_CLOCK_DEFAULT:
+		case BCM2835_CHOOSE_CLOCK_INTEGER_THEN_FRAC:
+			data->choose_clock =
+				bcm2835_clock_choose_int_then_frac;
+			break;
+		case BCM2835_CHOOSE_CLOCK_INTEGER:
+			data->choose_clock =
+				bcm2835_clock_choose_integer_div;
+			break;
+		case BCM2835_CHOOSE_CLOCK_CLOSEST:
+			data->choose_clock =
+				bcm2835_clock_choose_closest_rate;
+			break;
+		default:
+			dev_err(dev,
+				"clock %s: undefined clock-selector: %d\n",
+				data->name, value);
+			break;
+		}
+	}
 
 	/* and return the result */
 	return data;
diff --git a/include/dt-bindings/clock/bcm2835.h b/include/dt-bindings/clock/bcm2835.h
index eb73380..b00880e 100644
--- a/include/dt-bindings/clock/bcm2835.h
+++ b/include/dt-bindings/clock/bcm2835.h
@@ -76,3 +76,9 @@
 
 #define BCM2835_MASH_INTEGER		BCM2835_MASH_NONE
 #define BCM2835_MASH_FRAC		BCM2835_MASH_ORDER_1
+
+/* the possible clock selectors */
+#define BCM2835_CHOOSE_CLOCK_DEFAULT		0
+#define BCM2835_CHOOSE_CLOCK_INTEGER		1
+#define BCM2835_CHOOSE_CLOCK_INTEGER_THEN_FRAC	2
+#define BCM2835_CHOOSE_CLOCK_CLOSEST		3
-- 
1.7.10.4

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[RFC 2/9] clk: bcm2835: add support for parent selection in DT

[kernel]

From: Martin Sperl <kernel@martin.sperl.org>

Allow for a per clock custom selection of clocks in the device tree.

Basic setup in dt looks like this:
  clock@BCM2835_CLOCK_PCM {
    reg = <BCM2835_CLOCK_PCM>;
    parent-clock-names = "xosc", "plld_per", "plla_per", "pll_aux_per";
  };

Special care had to be taken when only a single clock is assigned,
as then set_parent_rate is not called - so the register has to get
set up immediately.

To allow for custom order of the clocks (giving preference)
an additional mapping between IDs is required when handling
get/set parent.

The default parent clocks are assumed to be all available clocks
against which the "selected" parents are checked.

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
---
 drivers/clk/bcm/clk-bcm2835.c |  124 +++++++++++++++++++++++++++++++++++++++--
 1 file changed, 119 insertions(+), 5 deletions(-)

diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c
index 1c714d0..8fccbd3 100644
--- a/drivers/clk/bcm/clk-bcm2835.c
+++ b/drivers/clk/bcm/clk-bcm2835.c
@@ -702,6 +702,7 @@ struct bcm2835_clock_data {
 
 	const char *const *parents;
 	int num_mux_parents;
+	u8 *parents_idx;
 
 	u32 ctl_reg;
 	u32 div_reg;
@@ -1706,15 +1707,30 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw,
 	return 0;
 }
 
+static int _bcm2835_clk_set_parent(struct bcm2835_cprman *cprman,
+				   const struct bcm2835_clock_data *data,
+				   u8 index)
+{
+	u8 src;
+
+	/* map the index if we got a map */
+	if (data->parents_idx)
+		index = data->parents_idx[index];
+
+	/* calc the source */
+	src = (index << CM_SRC_SHIFT) & CM_SRC_MASK;
+
+	cprman_write(cprman, data->ctl_reg, src);
+	return 0;
+}
+
 static int bcm2835_clock_set_parent(struct clk_hw *hw, u8 index)
 {
 	struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
 	struct bcm2835_cprman *cprman = clock->cprman;
 	const struct bcm2835_clock_data *data = clock->data;
-	u8 src = (index << CM_SRC_SHIFT) & CM_SRC_MASK;
 
-	cprman_write(cprman, data->ctl_reg, src);
-	return 0;
+	return _bcm2835_clk_set_parent(cprman, data, index);
 }
 
 static u8 bcm2835_clock_get_parent(struct clk_hw *hw)
@@ -1723,10 +1739,23 @@ static u8 bcm2835_clock_get_parent(struct clk_hw *hw)
 	struct bcm2835_cprman *cprman = clock->cprman;
 	const struct bcm2835_clock_data *data = clock->data;
 	u32 src = cprman_read(cprman, data->ctl_reg);
+	int i;
 
-	return (src & CM_SRC_MASK) >> CM_SRC_SHIFT;
-}
+	/* translate src to default index */
+	src = (src & CM_SRC_MASK) >> CM_SRC_SHIFT;
+
+	/* without overrides overrides return the value */
+	if (!data->parents_idx)
+		return src;
 
+	/* otherwise iterate over fields to find it */
+	for (i = 0; i < data->num_mux_parents ; i++)
+		if (data->parents_idx[i] == src)
+			return i;
+
+	/* if not found */
+	return -EINVAL;
+}
 
 static const struct clk_ops bcm2835_clock_clk_ops = {
 	.is_prepared = bcm2835_clock_is_on,
@@ -1874,6 +1903,88 @@ bcm2835_register_pll_divider(struct bcm2835_cprman *cprman,
 	return clk;
 }
 
+static void bcm2835_register_clock_of_parents(
+	struct bcm2835_cprman *cprman,
+	struct bcm2835_clock_data *data,
+	struct device_node *nc)
+{
+	struct device *dev = cprman->dev;
+	u8 *parents_idx;
+	const char **parents;
+	const char *name;
+	int err, names, i, j;
+
+	/* check number of strings */
+	names = of_property_count_strings(nc, "parent-clock-names");
+	if (names < 0)
+		return;
+	if (names > data->num_mux_parents) {
+		dev_err(dev,
+			"%s: dt-property parent-clock-names has more entries (%d) than available parent clocks (%d)\n",
+			of_node_full_name(nc), names, data->num_mux_parents);
+		return;
+	}
+
+	/* allocate parents */
+	parents = devm_kzalloc(dev, sizeof(*parents) * names, GFP_KERNEL);
+	if (!parents)
+		return;
+
+	/* allocate parents index */
+	parents_idx = devm_kzalloc(dev, sizeof(*parents_idx) * names,
+				   GFP_KERNEL);
+	if (!parents_idx) {
+		devm_kfree(dev, parents);
+		return;
+	}
+
+	/* and check the parents against list of allowed parents */
+	for (i = 0; i < names; i++) {
+		/* get the string */
+		err = of_property_read_string_index(nc, "parent-clock-names",
+						    i, &name);
+		if (err) {
+			devm_kfree(dev, parents_idx);
+			devm_kfree(dev, parents);
+			dev_err(dev,
+				"%s: could not get parent-clock-names[%d] - %d\n",
+				of_node_full_name(nc), i, err);
+			return;
+		}
+		/* check against available parents - the default list */
+		for (j = 0; j < data->num_mux_parents; j++) {
+			if (strcmp(data->parents[j],  name) == 0) {
+				parents[i] = data->parents[j];
+				parents_idx[i] = j;
+				break;
+			}
+		}
+		/* if there was no match */
+		if (!parents[i]) {
+			devm_kfree(dev, parents_idx);
+			devm_kfree(dev, parents);
+			dev_err(dev,
+				"%s: could not find %s in list of allowed parent clocks\n",
+				of_node_full_name(nc), name);
+			return;
+		}
+	}
+
+	/* finally assign it */
+	data->num_mux_parents = names;
+	data->parents = parents;
+	data->parents_idx = parents_idx;
+
+	/*
+	 * if there is only one parent, then use that one immediately,
+	 * as with only one parent clock_set_parent does not get called
+	 * and it is assumed that everything is set up, so
+	 * we need to do that before anything else...
+	 */
+	if (names == 1)
+		_bcm2835_clk_set_parent(cprman, data, 0);
+}
+
 static const struct bcm2835_clock_data *bcm2835_register_clock_of(
 	struct bcm2835_cprman *cprman,
 	const struct bcm2835_clock_data *data_orig,
@@ -1894,6 +2005,9 @@ static const struct bcm2835_clock_data *bcm2835_register_clock_of(
 		return data_orig;
 	memcpy(data, data_orig, sizeof(*data));
 
+	/* apply overrides */
+	bcm2835_register_clock_of_parents(cprman, data, nc);
+
 	/* and return the result */
 	return data;
 }
-- 
1.7.10.4

Re: [RFC 2/9] clk: bcm2835: add support for parent selection in DT

[Sascha Hauer]

Martin,

On Tue, Jan 19, 2016 at 02:51:33PM +0000, kernel@martin.sperl.org wrote:
> From: Martin Sperl <kernel@martin.sperl.org>
> 
> Allow for a per clock custom selection of clocks in the device tree.
> 
> Basic setup in dt looks like this:
>   clock@BCM2835_CLOCK_PCM {
>     reg = <BCM2835_CLOCK_PCM>;
>     parent-clock-names = "xosc", "plld_per", "plla_per", "pll_aux_per";
>   };

Isn't this the same as the already existing assigned-clock-parents property?
If yes, that should be used.

Sascha


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Re: [RFC 2/9] clk: bcm2835: add support for parent selection in DT

[Martin Sperl]

On 21.01.2016 09:26, Sascha Hauer wrote:
> Martin,
>
> On Tue, Jan 19, 2016 at 02:51:33PM +0000, kernel@martin.sperl.org wrote:
>> From: Martin Sperl <kernel@martin.sperl.org>
>>
>> Allow for a per clock custom selection of clocks in the device tree.
>>
>> Basic setup in dt looks like this:
>>    clock@BCM2835_CLOCK_PCM {
>>      reg = <BCM2835_CLOCK_PCM>;
>>      parent-clock-names = "xosc", "plld_per", "plla_per", "pll_aux_per";
>>    };
>
> Isn't this the same as the already existing assigned-clock-parents property?
> If yes, that should be used.
It is not 100% identical, as the parent-clock-names do provide ordering
of clocks to be selected, which - under some circumstances may be
beneficial - e.g: when having a parent clock with 500MHz and 1000MHz,
then the higher clock could get given preference by switching ordering...

Also when using:
assigned-clock-parents = <&clk_osc 0>, <&clocks BCM2835_PLLD_PER>;

I get strange indexes passed when calling set_parent - so this would
need to get rewritten to support assigned-clock-parents correctly -
calculating the index on the fly...

[RFC 3/9] clk: bcm2835: add ability to control mash level via device-tree

[kernel]

From: Martin Sperl <kernel@martin.sperl.org>

Control maximum mash levels that can get used via the device tree.

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
---
 drivers/clk/bcm/clk-bcm2835.c       |   39 +++++++++++++++++++++++++++--------
 include/dt-bindings/clock/bcm2835.h |    9 ++++++++
 2 files changed, 39 insertions(+), 9 deletions(-)

diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c
index 8fccbd3..48c1ad0 100644
--- a/drivers/clk/bcm/clk-bcm2835.c
+++ b/drivers/clk/bcm/clk-bcm2835.c
@@ -303,10 +303,10 @@
 #define BCM2835_MASH_MAX_FREQ	25000000u
 
 enum bcm2835_clock_mash_type {
-	MASH_NONE = 0,
-	MASH_FRAC = 1,
-	MASH_2ND_ORDER = 2,
-	MASH_3RD_ORDER = 3
+	MASH_NONE = BCM2835_MASH_NONE,
+	MASH_FRAC = BCM2835_MASH_FRAC,
+	MASH_ORDER_2 = BCM2835_MASH_ORDER_2,
+	MASH_ORDER_3 = BCM2835_MASH_ORDER_3
 };
 
 /*
@@ -713,6 +713,7 @@ struct bcm2835_clock_data {
 	u32 frac_bits;
 	/* the mash value to use - see CM_MASH */
 	enum bcm2835_clock_mash_type mash;
+	bool mash_forced;
 
 	bool is_vpu_clock;
 };
@@ -1508,7 +1509,7 @@ static divmash bcm2835_clock_choose_div(struct clk_hw *hw,
 
 	/* select mash mode */
 	if (data->frac_bits && divf)
-		mash = data->mash ? data->mash : MASH_FRAC;
+		mash = data->mash_forced ? data->mash : MASH_FRAC;
 
 	/*
 	 * handle possible limits for different mash levels with fall-tru
@@ -1517,17 +1518,17 @@ static divmash bcm2835_clock_choose_div(struct clk_hw *hw,
 	 *   http://elinux.org/BCM2835_datasheet_errata#p105_table
 	 */
 	switch (mash) {
-	case MASH_3RD_ORDER:
+	case MASH_ORDER_3:
 		if ((divi >= divi_min + 3) &&
 		    (divi + 4 <= divi_max) &&
 		    (parent_rate / (divi - 3) <= BCM2835_MASH_MAX_FREQ))
-			return divmash_calc(MASH_3RD_ORDER, div);
+			return divmash_calc(MASH_ORDER_3, div);
 		/* fall tru if not in bounds */
-	case MASH_2ND_ORDER:
+	case MASH_ORDER_2:
 		if ((divi >= divi_min + 1) &&
 		    (divi + 2 <= divi_max) &&
 		    (parent_rate / (divi - 1) <= BCM2835_MASH_MAX_FREQ))
-			return divmash_calc(MASH_2ND_ORDER, div);
+			return divmash_calc(MASH_ORDER_2, div);
 		/* fall tru if not in bounds */
 	case MASH_FRAC:
 		if ((divi >= divi_min) &&
@@ -1993,6 +1994,8 @@ static const struct bcm2835_clock_data *bcm2835_register_clock_of(
 	struct device *dev = cprman->dev;
 	struct device_node *nc;
 	struct bcm2835_clock_data *data;
+	int err;
+	u32 value;
 
 	/* find the corresponding dt-node */
 	nc = bcm2835_find_dt_node(cprman, id);
@@ -2008,6 +2011,24 @@ static const struct bcm2835_clock_data *bcm2835_register_clock_of(
 	/* apply overrides */
 	bcm2835_register_clock_of_parents(cprman, data, nc);
 
+	/* check for mash */
+	err = of_property_read_u32(nc, "brcm,mash-max-order", &value);
+	if (!err) {
+		switch (value) {
+		case MASH_NONE:
+		case MASH_FRAC:
+		case MASH_ORDER_2:
+		case MASH_ORDER_3:
+			data->mash = value;
+			data->mash_forced = 1;
+			break;
+		default:
+			dev_err(dev, "clock %s: undefined mash type: %d\n",
+				data->name, value);
+			break;
+		}
+	}
+
 	/* and return the result */
 	return data;
 }
diff --git a/include/dt-bindings/clock/bcm2835.h b/include/dt-bindings/clock/bcm2835.h
index d29f181..eb73380 100644
--- a/include/dt-bindings/clock/bcm2835.h
+++ b/include/dt-bindings/clock/bcm2835.h
@@ -67,3 +67,12 @@
 #define BCM2835_CLOCK_TD0		51
 #define BCM2835_CLOCK_TD1		52
 #define BCM2835_CLOCK_TEC		53
+
+/* the mash divider options */
+#define BCM2835_MASH_NONE		0
+#define BCM2835_MASH_ORDER_1		1
+#define BCM2835_MASH_ORDER_2		2
+#define BCM2835_MASH_ORDER_3		3
+
+#define BCM2835_MASH_INTEGER		BCM2835_MASH_NONE
+#define BCM2835_MASH_FRAC		BCM2835_MASH_ORDER_1
-- 
1.7.10.4

[RFC 4/9] clk: bcm2835: reorganize bcm2835_clock_determine_rate

[kernel]

From: Martin Sperl <kernel@martin.sperl.org>

Reorganize bcm2835_clock_determine_rate so that the per
clock frequency calculation is separated from the
selection logic.

This allows for different clock selection policies
to be use while keeping code common.

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
---
 drivers/clk/bcm/clk-bcm2835.c |   98 +++++++++++++++++++++++++++++------------
 1 file changed, 70 insertions(+), 28 deletions(-)

diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c
index 48c1ad0..f1ab525 100644
--- a/drivers/clk/bcm/clk-bcm2835.c
+++ b/drivers/clk/bcm/clk-bcm2835.c
@@ -1668,44 +1668,86 @@ unlock_exit:
 	return 0;
 }
 
-static int bcm2835_clock_determine_rate(struct clk_hw *hw,
-		struct clk_rate_request *req)
+struct bcm2835_rates {
+	struct clk_hw *parent;
+	unsigned long rate;
+	unsigned long prate;
+	u32 div;
+	divmash dmash;
+};
+
+static int bcm2835_clock_determine_rate_set(struct clk_rate_request *req,
+					    struct bcm2835_rates *best)
 {
-	struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
-	struct clk_hw *parent, *best_parent = NULL;
-	unsigned long rate, best_rate = 0;
-	unsigned long prate, best_prate = 0;
+	req->best_parent_hw = best->parent;
+	req->best_parent_rate = best->prate;
+	req->rate = best->rate;
+
+	return 0;
+}
+
+static int bcm2835_clock_determine_closest_rate(struct clk_hw *hw,
+						struct clk_rate_request *req,
+						struct bcm2835_rates *rates,
+						size_t rate_cnt)
+{
+	struct bcm2835_rates *best = NULL;
 	size_t i;
-	divmash dm;
-	u32 div;
 
-	/*
-	 * Select parent clock that results in the closest but lower rate
-	 */
-	for (i = 0; i < clk_hw_get_num_parents(hw); ++i) {
-		parent = clk_hw_get_parent_by_index(hw, i);
-		if (!parent)
+	/* find best matching */
+	for (i = 0; i < rate_cnt; i++) {
+		if (rates[i].rate > req->rate)
+			continue;
+		if (!best) {
+			best = &rates[i];
+			continue;
+		}
+		/* find the closest */
+		if (rates[i].rate > best->rate) {
+			best = &rates[i];
+			continue;
+		}
+		/* if identical then use highest divider */
+		if ((rates[i].rate == best->rate) &&
+		    (rates[i].div > best->div)) {
+			best = &rates[i];
 			continue;
-		prate = clk_hw_get_rate(parent);
-		dm = bcm2835_clock_choose_div(hw, req->rate, prate, true);
-		div = divmash_get_div(dm);
-		rate = bcm2835_clock_rate_from_divisor(clock, prate, div);
-		if (rate > best_rate && rate <= req->rate) {
-			best_parent = parent;
-			best_prate = prate;
-			best_rate = rate;
 		}
 	}
 
-	if (!best_parent)
-		return -EINVAL;
+	if (best)
+		return bcm2835_clock_determine_rate_set(req, best);
+
+	/* nothing found */
+	return -EINVAL;
+}
 
-	req->best_parent_hw = best_parent;
-	req->best_parent_rate = best_prate;
+static int bcm2835_clock_determine_rate(struct clk_hw *hw,
+					struct clk_rate_request *req)
+{
+	struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
+	struct bcm2835_rates rates[BIT(CM_SRC_BITS)];
+	size_t i, rate_cnt = 0;
+	divmash dm;
 
-	req->rate = best_rate;
+	/* fill in rates */
+	for (i = 0; i < clk_hw_get_num_parents(hw); ++i) {
+		rates[rate_cnt].parent = clk_hw_get_parent_by_index(hw, i);
+		if (!rates[rate_cnt].parent)
+			continue;
+		rates[rate_cnt].prate = clk_hw_get_rate(
+			rates[rate_cnt].parent);
+		dm = bcm2835_clock_choose_div(
+			hw, req->rate, rates[rate_cnt].prate, true);
+		rates[rate_cnt].div =  divmash_get_div(dm);
+		rates[rate_cnt].rate = bcm2835_clock_rate_from_divisor(
+			clock, rates[rate_cnt].prate, rates[rate_cnt].div);
+		rate_cnt++;
+	}
 
-	return 0;
+	/* choose the "closest" one */
+	return bcm2835_clock_determine_closest_rate(hw, req, rates,
+						    rate_cnt);
 }
 
 static int _bcm2835_clk_set_parent(struct bcm2835_cprman *cprman,
-- 
1.7.10.4

[RFC 5/9] clk: bcm2835: prefer clocks that use integer dividers

[kernel]

From: Martin Sperl <kernel@martin.sperl.org>

To reduce possible jitter prefer integer dividers over
fractional dividers.

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
---
 drivers/clk/bcm/clk-bcm2835.c |   26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c
index f1ab525..e5313ba 100644
--- a/drivers/clk/bcm/clk-bcm2835.c
+++ b/drivers/clk/bcm/clk-bcm2835.c
@@ -1686,6 +1686,24 @@ static int bcm2835_clock_determine_rate_set(struct clk_rate_request *req,
 	return 0;
 }
 
+static int bcm2835_clock_determine_integer_rate(struct clk_hw *hw,
+						struct clk_rate_request *req,
+						struct bcm2835_rates *rates,
+						size_t rate_cnt)
+{
+	size_t i;
+
+	/* find first matching */
+	for (i = 0; i < rate_cnt; i++) {
+		if (!divmash_get_divf(rates[i].dmash))
+			return bcm2835_clock_determine_rate_set(req,
+								&rates[i]);
+	}
+
+	/* nothing found */
+	return -EINVAL;
+}
+
 static int bcm2835_clock_determine_closest_rate(struct clk_hw *hw,
 						struct clk_rate_request *req,
 						struct bcm2835_rates *rates,
@@ -1729,6 +1747,7 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw,
 	struct bcm2835_rates rates[BIT(CM_SRC_BITS)];
 	size_t i, rate_cnt = 0;
 	divmash dm;
+	int err;
 
 	/* fill in rates */
 	for (i = 0; i < clk_hw_get_num_parents(hw); ++i) {
@@ -1745,7 +1764,12 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw,
 		rate_cnt++;
 	}
 
-	/* choose the "closest" one */
+	/* find integer rates with preference */
+	err = bcm2835_clock_determine_integer_rate(hw, req, rates, rate_cnt);
+	if (!err)
+		return 0;
+
+	/* otherwise choose the "closest" one */
 	return bcm2835_clock_determine_closest_rate(hw, req, rates,
 						    rate_cnt);
 }
-- 
1.7.10.4

[RFC 6/9] clk: bcm2835: allow to define a minimum fractional divider in DT

[kernel]

From: Martin Sperl <kernel@martin.sperl.org>

Allow to define a minimum fractional divider to use
in the devicetree.

This is primarily used to reduce clock-jitter introduced
by the fractional/MASH divider.

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
---
 drivers/clk/bcm/clk-bcm2835.c |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c
index e5313ba..7048ca5 100644
--- a/drivers/clk/bcm/clk-bcm2835.c
+++ b/drivers/clk/bcm/clk-bcm2835.c
@@ -711,6 +711,8 @@ struct bcm2835_clock_data {
 	u32 int_bits;
 	/* Number of fractional bits in the divider */
 	u32 frac_bits;
+	/* the minimum divider to allow when fractional */
+	u32 min_frac_div;
 	/* the mash value to use - see CM_MASH */
 	enum bcm2835_clock_mash_type mash;
 	bool mash_forced;
@@ -1709,13 +1711,21 @@ static int bcm2835_clock_determine_closest_rate(struct clk_hw *hw,
 						struct bcm2835_rates *rates,
 						size_t rate_cnt)
 {
+	struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
+	const struct bcm2835_clock_data *data = clock->data;
 	struct bcm2835_rates *best = NULL;
 	size_t i;
 
 	/* find best matching */
 	for (i = 0; i < rate_cnt; i++) {
+		/* do not look at anything above the requested rate */
 		if (rates[i].rate > req->rate)
 			continue;
+		/* if we have a divider that is not "safe", then ignore */
+		if (divmash_get_divf(rates[i].dmash) &&
+		    (rates[i].div < data->min_frac_div))
+			continue;
+		/* if we are the first */
 		if (!best) {
 			best = &rates[i];
 			continue;
@@ -2094,6 +2104,10 @@ static const struct bcm2835_clock_data *bcm2835_register_clock_of(
 			break;
 		}
 	}
+	/* add support for min fractional divider */
+	err = of_property_read_u32(nc, "brcm,min-fract-div", &value);
+	if (!err)
+		data->min_frac_div = value << CM_DIV_FRAC_BITS;
 
 	/* and return the result */
 	return data;
-- 
1.7.10.4

[RFC 8/9] dt-bindings: bcm2835: document optional per clock dt-nodes

[kernel]

From: Martin Sperl <kernel@martin.sperl.org>

Document how to modify per clock default behaviour
via the device-tree.

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
---
 .../bindings/clock/brcm,bcm2835-cprman.txt         |   33 ++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/Documentation/devicetree/bindings/clock/brcm,bcm2835-cprman.txt b/Documentation/devicetree/bindings/clock/brcm,bcm2835-cprman.txt
index e56a1df..794c4ac 100644
--- a/Documentation/devicetree/bindings/clock/brcm,bcm2835-cprman.txt
+++ b/Documentation/devicetree/bindings/clock/brcm,bcm2835-cprman.txt
@@ -17,6 +17,26 @@ Required properties:
 		  found in include/dt-bindings/clock/bcm2835.h
 - reg:		Specifies base physical address and size of the registers
 - clocks:	The external oscillator clock phandle
+- #address-cells number of cells required to define a clock
+- #size-cells    Should be 0
+
+Subnodes:
+
+It is possible to apply optional settings per clock to modify clock
+selection behaviour.
+For each clock there may be a subnode that may contain the following:
+
+Required properties:
+- reg                 -  clock id
+
+Optional properties:
+- parent-clock-names  - list of parrent-clock names
+  		        this list is validated againt the default list
+		        of parent clocks and is used in this order.
+- brcm,clock-selector - the clock selector to use
+- brcm,mash-max-order - the maximum order of the fractional divider
+- brcm,min-fract-div  - the minimum divider required when using
+  		      	the fractional divider
 
 Example:
 
@@ -33,6 +53,19 @@ Example:
 		#clock-cells = <1>;
 		reg = <0x7e101000 0x2000>;
 		clocks = <&clk_osc>;
+
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		/* custom settings for the PCM clock */
+		clock@BCM2835_CLOCK_PCM {
+			 reg = <BCM2835_CLOCK_PCM>;
+			 parent-clock-names = "xosc", "plld_per";
+			 brcm,clock-selector =
+				  <BCM2835_CHOOSE_CLOCK_INTEGER_THEN_FRAC>;
+			 brcm,mash-max-order = <BCM2835_MASH_ORDER_3>;
+			 brcm,min-fract-div = <20>;
+		};
 	};
 
 	i2c0: i2c@7e205000 {
-- 
1.7.10.4

[RFC 9/9] clk: bcm2835: expose raw clock-registers via debugfs

[kernel]

From: Martin Sperl <kernel@martin.sperl.org>

For debugging purposes under some circumstance
it helps to be able to see the actual clock registers.

E.g: when looking at the clock divider it is helpful to
see what the actual clock divider is.

This patch exposes all the clock registers specific to each
clock/pll/pll-divider via debugfs.

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
---
 drivers/clk/bcm/clk-bcm2835.c |  101 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)

diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c
index c381cb1..29abae6 100644
--- a/drivers/clk/bcm/clk-bcm2835.c
+++ b/drivers/clk/bcm/clk-bcm2835.c
@@ -40,6 +40,7 @@
 #include <linux/clk-provider.h>
 #include <linux/clkdev.h>
 #include <linux/clk/bcm2835.h>
+#include <linux/debugfs.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
@@ -379,6 +380,27 @@ static inline u32 cprman_read(struct bcm2835_cprman *cprman, u32 reg)
 	return readl(cprman->regs + reg);
 }
 
+static int bcm2835_debugfs_regset(struct bcm2835_cprman *cprman, u32 base,
+				  struct debugfs_reg32 *regs, size_t nregs,
+				  struct dentry *dentry)
+{
+	struct dentry *regdump;
+	struct debugfs_regset32 *regset;
+
+	regset = devm_kzalloc(cprman->dev, sizeof(*regset), GFP_KERNEL);
+	if (!regset)
+		return -ENOMEM;
+
+	regset->regs = regs;
+	regset->nregs = nregs;
+	regset->base = cprman->regs + base;
+
+	regdump = debugfs_create_regset32("regdump", S_IRUGO, dentry,
+					  regset);
+
+	return regdump ? 0 : -ENOMEM;
+}
+
 /*
  * These are fixed clocks. They're probably not all root clocks and it may
  * be possible to turn them on and off but until this is mapped out better
@@ -1360,6 +1382,36 @@ static int bcm2835_pll_set_rate(struct clk_hw *hw,
 	return 0;
 }
 
+static int bcm2835_pll_debug_init(struct clk_hw *hw,
+				  struct dentry *dentry)
+{
+	struct bcm2835_pll *pll = container_of(hw, struct bcm2835_pll, hw);
+	struct bcm2835_cprman *cprman = pll->cprman;
+	const struct bcm2835_pll_data *data = pll->data;
+	struct debugfs_reg32 *regs;
+
+	regs = devm_kzalloc(cprman->dev, 7 * sizeof(*regs), GFP_KERNEL);
+	if (!regs)
+		return -ENOMEM;
+
+	regs[0].name = "cm_ctrl";
+	regs[0].offset = data->cm_ctrl_reg;
+	regs[1].name = "a2w_ctrl";
+	regs[1].offset = data->a2w_ctrl_reg;
+	regs[2].name = "frac";
+	regs[2].offset = data->frac_reg;
+	regs[3].name = "ana0";
+	regs[3].offset = data->ana_reg_base + 0 * 4;
+	regs[4].name = "ana1";
+	regs[4].offset = data->ana_reg_base + 1 * 4;
+	regs[5].name = "ana2";
+	regs[5].offset = data->ana_reg_base + 2 * 4;
+	regs[6].name = "ana3";
+	regs[6].offset = data->ana_reg_base + 3 * 4;
+
+	return bcm2835_debugfs_regset(cprman, 0, regs, 7, dentry);
+}
+
 static const struct clk_ops bcm2835_pll_clk_ops = {
 	.is_prepared = bcm2835_pll_is_on,
 	.prepare = bcm2835_pll_on,
@@ -1367,6 +1419,7 @@ static const struct clk_ops bcm2835_pll_clk_ops = {
 	.recalc_rate = bcm2835_pll_get_rate,
 	.set_rate = bcm2835_pll_set_rate,
 	.round_rate = bcm2835_pll_round_rate,
+	.debug_init = bcm2835_pll_debug_init,
 };
 
 struct bcm2835_pll_divider {
@@ -1461,6 +1514,26 @@ static int bcm2835_pll_divider_set_rate(struct clk_hw *hw,
 	return 0;
 }
 
+static int bcm2835_pll_divider_debug_init(struct clk_hw *hw,
+					  struct dentry *dentry)
+{
+	struct bcm2835_pll_divider *divider = bcm2835_pll_divider_from_hw(hw);
+	struct bcm2835_cprman *cprman = divider->cprman;
+	const struct bcm2835_pll_divider_data *data = divider->data;
+	struct debugfs_reg32 *regs;
+
+	regs = devm_kzalloc(cprman->dev, 7 * sizeof(*regs), GFP_KERNEL);
+	if (!regs)
+		return -ENOMEM;
+
+	regs[0].name = "cm";
+	regs[0].offset = data->cm_reg;
+	regs[1].name = "a2w";
+	regs[1].offset = data->a2w_reg;
+
+	return bcm2835_debugfs_regset(cprman, 0, regs, 2, dentry);
+}
+
 static const struct clk_ops bcm2835_pll_divider_clk_ops = {
 	.is_prepared = bcm2835_pll_divider_is_on,
 	.prepare = bcm2835_pll_divider_on,
@@ -1468,6 +1541,7 @@ static const struct clk_ops bcm2835_pll_divider_clk_ops = {
 	.recalc_rate = bcm2835_pll_divider_get_rate,
 	.set_rate = bcm2835_pll_divider_set_rate,
 	.round_rate = bcm2835_pll_divider_round_rate,
+	.debug_init = bcm2835_pll_divider_debug_init,
 };
 
 /*
@@ -1854,6 +1928,31 @@ static u8 bcm2835_clock_get_parent(struct clk_hw *hw)
 	return -EINVAL;
 }
 
+static struct debugfs_reg32 bcm2835_debugfs_clock_reg32[] = {
+	{
+		.name = "ctl",
+		.offset = 0,
+	},
+	{
+		.name = "div",
+		.offset = 4,
+	},
+};
+
+static int bcm2835_clock_debug_init(struct clk_hw *hw,
+				    struct dentry *dentry)
+{
+	struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
+	struct bcm2835_cprman *cprman = clock->cprman;
+	const struct bcm2835_clock_data *data = clock->data;
+
+	return bcm2835_debugfs_regset(
+		cprman, data->ctl_reg,
+		bcm2835_debugfs_clock_reg32,
+		ARRAY_SIZE(bcm2835_debugfs_clock_reg32),
+		dentry);
+}
+
 static const struct clk_ops bcm2835_clock_clk_ops = {
 	.is_prepared = bcm2835_clock_is_on,
 	.prepare = bcm2835_clock_on,
@@ -1863,6 +1962,7 @@ static const struct clk_ops bcm2835_clock_clk_ops = {
 	.determine_rate = bcm2835_clock_determine_rate,
 	.set_parent = bcm2835_clock_set_parent,
 	.get_parent = bcm2835_clock_get_parent,
+	.debug_init = bcm2835_clock_debug_init,
 };
 
 static int bcm2835_vpu_clock_is_on(struct clk_hw *hw)
@@ -1881,6 +1981,7 @@ static const struct clk_ops bcm2835_vpu_clock_clk_ops = {
 	.determine_rate = bcm2835_clock_determine_rate,
 	.set_parent = bcm2835_clock_set_parent,
 	.get_parent = bcm2835_clock_get_parent,
+	.debug_init = bcm2835_clock_debug_init,
 };
 
 static struct device_node *bcm2835_find_dt_node(
-- 
1.7.10.4