Allow a clock to specify a "prerequisite" clock, identified by its
name. The prerequisite clock must be prepared and enabled before a
clock that depends on it is used. In order to simplify locking, we
require a clock and its prerequisite to be associated with the same
CCU. (We'll just trust--but not verify--that nobody defines a cycle
of prerequisite clocks.)
Rework the KONA_CLK() macro, and define a new KONA_CLK_PREREQ()
variant that allows a prerequisite clock to be specified.
Signed-off-by: Alex Elder <el...@linaro.org>
---
drivers/clk/bcm/clk-kona.c | 70 ++++++++++++++++++++++++++++++++++++++++++++--
drivers/clk/bcm/clk-kona.h | 20 +++++++++++--
2 files changed, 85 insertions(+), 5 deletions(-)
diff --git a/drivers/clk/bcm/clk-kona.c b/drivers/clk/bcm/clk-kona.c
index 2e27924..51b4edb 100644
--- a/drivers/clk/bcm/clk-kona.c
+++ b/drivers/clk/bcm/clk-kona.c
@@ -1037,6 +1037,42 @@ static bool __peri_clk_init(struct kona_clk *bcm_clk)
/* Clock operations */
+static int kona_prereq_prepare_enable(struct kona_clk *bcm_clk)
+{
+ const char *clk_name = bcm_clk->init_data.name;
+ const char *prereq_name = bcm_clk->prereq.name;
+ struct clk *prereq_clk = bcm_clk->prereq.clk;
+ int ret;
+
+ BUG_ON(!clk_name);
+
+ /* Look up the prerequisite clock if we haven't already */
+ if (!prereq_clk) {
+ prereq_clk = __clk_lookup(prereq_name);
+ if (WARN_ON_ONCE(!prereq_clk))
+ return -ENOENT;
+ bcm_clk->prereq.clk = prereq_clk;
+ }
+
+ /* Dependent clock already holds the prepare lock */
+ ret = __clk_prepare(prereq_clk);
+ if (ret) {
+ pr_err("%s: unable to prepare prereq clock %s for %s\n",
+ __func__, prereq_name, clk_name);
+ return ret;
+ }
+
+ ret = clk_enable(prereq_clk);
+ if (ret) {
+ __clk_unprepare(prereq_clk);
+ pr_err("%s: unable to enable prereq clock %s for %s\n",
+ __func__, prereq_name, clk_name);
+ return ret;
+ }
+
+ return 0;
+}
+
static int kona_clk_prepare(struct clk_hw *hw)
{
struct kona_clk *bcm_clk = to_kona_clk(hw);
@@ -1044,6 +1080,13 @@ static int kona_clk_prepare(struct clk_hw *hw)
unsigned long flags;
int ret = 0;
+ /* Prepare the prerequisite clock first */
+ if (bcm_clk->prereq.name) {
+ ret = kona_prereq_prepare_enable(bcm_clk);
+ if (ret)
+ goto out;
+ }
+
if (clk_is_initialized(bcm_clk))
return 0;
@@ -1062,19 +1105,42 @@ static int kona_clk_prepare(struct clk_hw *hw)
__ccu_write_disable(ccu);
ccu_unlock(ccu, flags);
-
+out:
if (!ret)
clk_set_initialized(bcm_clk);
return ret;
}
+/*
+ * Disable and unprepare a prerequisite clock, and drop our
+ * reference to it.
+ */
+static void kona_prereq_disable_unprepare(struct kona_clk *bcm_clk)
+{
+ struct clk *prereq_clk = bcm_clk->prereq.clk;
+
+ BUG_ON(!bcm_clk->prereq.name);
+ WARN_ON_ONCE(!prereq_clk);
+
+ clk_disable(prereq_clk);
+ __clk_unprepare(prereq_clk);
+}
+
static void kona_clk_unprepare(struct clk_hw *hw)
{
struct kona_clk *bcm_clk = to_kona_clk(hw);
WARN_ON(!clk_is_initialized(bcm_clk));
- /* Nothing to do. */
+
+ /*
+ * We don't do anything to unprepare Kona clocks themselves,
+ * but if there's a prerequisite we'll need to unprepare it.
+ */
+ if (!bcm_clk->prereq.name)
+ return;
+
+ kona_prereq_disable_unprepare(bcm_clk);
}
static int kona_peri_clk_enable(struct clk_hw *hw)
diff --git a/drivers/clk/bcm/clk-kona.h b/drivers/clk/bcm/clk-kona.h
index ea77ec1..98b6fa1 100644
--- a/drivers/clk/bcm/clk-kona.h
+++ b/drivers/clk/bcm/clk-kona.h
@@ -407,6 +407,10 @@ struct kona_clk {
struct ccu_data *ccu; /* ccu this clock is associated with */
enum bcm_clk_type type;
u32 flags; /* BCM_CLK_KONA_FLAGS_* below */
+ struct {
+ const char *name;
+ struct clk *clk;
+ } prereq;
union {
void *data;
struct peri_clk_data *peri;
@@ -422,16 +426,26 @@ struct kona_clk {
#define BCM_CLK_KONA_FLAGS_INITIALIZED ((u32)1 << 0) /* Clock initialized */
/* Initialization macro for an entry in a CCU's kona_clks[] array. */
-#define KONA_CLK(_ccu_name, _clk_name, _type) \
- { \
+#define ___KONA_CLK_COMMON(_ccu_name, _clk_name, _type)
\
.init_data = { \
.name = #_clk_name, \
.ops = &kona_ ## _type ## _clk_ops, \
}, \
.ccu = &_ccu_name ## _ccu_data, \
.type = bcm_clk_ ## _type, \
- .u.data = &_clk_name ## _data, \
+ .u.data = &_clk_name ## _data
+
+#define KONA_CLK_PREREQ(_ccu_name, _clk_name, _type, _prereq) \
+ { \
+ .prereq.name = #_prereq, \
+ ___KONA_CLK_COMMON(_ccu_name, _clk_name, _type), \
}
+
+#define KONA_CLK(_ccu_name, _clk_name, _type) \
+ { \
+ ___KONA_CLK_COMMON(_ccu_name, _clk_name, _type), \
+ }
+
#define LAST_KONA_CLK { .type = bcm_clk_none }
/*
--
1.9.1
--
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