From: Martin Sperl <kernel@xxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxx>
---
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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