Re: [RFC v2 4/5] clk: per-user clock accounting for debug

From: Tomeu Vizoso
Date: Thu Jul 10 2014 - 06:52:09 EST

On 07/09/2014 10:01 PM, Tomasz Figa wrote:
Hi Tomeu, Rabin,

Please see my comments inline.

On 03.07.2014 16:38, Tomeu Vizoso wrote:
From: Rabin Vincent <rabin.vincent@xxxxxxxxxxxxxx>

When a clock has multiple users, the WARNING on imbalance of
enable/disable may not show the guilty party since although they may
have commited the error earlier, the warning is emitted later when some
other user, presumably innocent, disables the clock.


diff --git a/drivers/clk/clk-devres.c b/drivers/clk/clk-devres.c
index 5f2aba9..d6a5e59 100644
--- a/drivers/clk/clk-devres.c
+++ b/drivers/clk/clk-devres.c
@@ -37,7 +37,8 @@ EXPORT_SYMBOL(devm_clk_provider_get);

struct clk *devm_clk_get(struct device *dev, const char *id)
- return clk_core_to_clk(devm_clk_provider_get(dev, id));
+ const char *dev_id = dev ? dev_name(dev) : NULL;
+ return clk_core_to_clk(devm_clk_provider_get(dev, id), dev_id, id);

Hmm, correct me if I'm missing something but you're just calling
devm_clk_provider() which guarantees calling of clk_provider_put() on
device removal, but what about the consumer struct being created here?

Shouldn't you rather call normal clk_provider_get() here, then create a
consumer struct for it and then wrap it up using devres, providing
appropriate release function?

You are totally right.


diff --git a/drivers/clk/clk-highbank.c b/drivers/clk/clk-highbank.c
index cc1bae1..4e38856 100644
--- a/drivers/clk/clk-highbank.c
+++ b/drivers/clk/clk-highbank.c
@@ -331,7 +331,7 @@ CLK_OF_DECLARE(hb_a9periph, "calxeda,hb-a9periph-clock", hb_a9periph_init);
static void __init hb_a9bus_init(struct device_node *node)
struct clk_core *clk = hb_clk_init(node, &a9bclk_ops);
- clk_prepare_enable(clk_core_to_clk(clk));
+ clk_prepare_enable(clk_core_to_clk(clk, node->full_name, NULL));
CLK_OF_DECLARE(hb_a9bus, "calxeda,hb-a9bus-clock", hb_a9bus_init);

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 644a824..b887c69 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -568,6 +568,28 @@ static int clk_disable_unused(void)

+struct clk *clk_core_to_clk(struct clk_core *clk_core, const char *dev,
+ const char *con)

Name of this function suggests that this is just a simple conversion,
while it creates new object. I would suggest calling this
clk_create_consumer() or something along these lines.

Agreed, that sounds better.

+ struct clk *clk;
+ clk = kzalloc(sizeof(*clk), GFP_KERNEL);
+ if (!clk)
+ return ERR_PTR(-ENOMEM);


+static void clk_free_clk(struct clk *clk)
+ kfree(clk);

Any need for this one-liner? Seems to be used just once below.

Yeah, should probably remove it from this patch and only reintroduce it later when it's actually needed.

void clk_put(struct clk *clk)
- __clk_put(clk_to_clk_core(clk));
+ clk_core_t *core = clk_to_clk_core(clk);
+ clk_free_clk(clk);
+ __clk_put(core);

diff --git a/drivers/clk/qcom/mmcc-msm8960.c b/drivers/clk/qcom/mmcc-msm8960.c
index 28a5d30..47f21ea 100644
--- a/drivers/clk/qcom/mmcc-msm8960.c
+++ b/drivers/clk/qcom/mmcc-msm8960.c
@@ -470,7 +470,8 @@ static int pix_rdi_set_parent(struct clk_hw *hw, u8 index)
* needs to be on at what time.
for (i = 0; i < num_parents; i++) {
- ret = clk_prepare_enable(clk_core_to_clk(clk_get_parent_by_index(clk, i)));
+ struct clk_core *parent = clk_get_parent_by_index(clk, i);
+ ret = clk_prepare_enable(clk_core_to_clk(parent, NULL, __clk_get_name(parent)));

Shouldn't this use clk_provider_*() instead? IMHO clk_core_to_clk() and
clk_to_clk_core() shouldn't be available to clock drivers, just the core
clock code. Consumers should operate on struct clks alone, clock drivers
should operate only on struct clk_cores and only the core code should be
responsible for necessary conversions.

Totally, this is already fixed in my local version.

if (ret)
goto err;
@@ -498,8 +499,10 @@ static int pix_rdi_set_parent(struct clk_hw *hw, u8 index)

- for (i--; i >= 0; i--)
- clk_disable_unprepare(clk_core_to_clk(clk_get_parent_by_index(clk, i)));
+ for (i--; i >= 0; i--) {
+ struct clk_core *parent = clk_get_parent_by_index(clk, i);
+ clk_disable_unprepare(clk_core_to_clk(parent, NULL, __clk_get_name(parent)));

Hmm. Memory leak? Every time this operation is called you create a
consumer struct for each parent two times.

Yes, fortunately this won't be needed as we'll have clk_provider_disable_unprepare and friends.

+ }

return ret;
diff --git a/drivers/clk/sunxi/clk-sunxi.c b/drivers/clk/sunxi/clk-sunxi.c
index 5de44c1..550a691 100644
--- a/drivers/clk/sunxi/clk-sunxi.c
+++ b/drivers/clk/sunxi/clk-sunxi.c
@@ -1196,7 +1196,7 @@ static void __init sunxi_init_clocks(const char *clocks[], int nclocks)
struct clk_core *clk = clk_provider_get(NULL, clocks[i]);

if (!IS_ERR(clk))
- clk_prepare_enable(clk_core_to_clk(clk));
+ clk_prepare_enable(clk_core_to_clk(clk, NULL, clocks[i]));

Probably should use clk_provider_*()?


diff --git a/drivers/clk/tegra/clk.c b/drivers/clk/tegra/clk.c
index 385d101..2a03d47 100644
--- a/drivers/clk/tegra/clk.c
+++ b/drivers/clk/tegra/clk.c
@@ -228,7 +228,7 @@ void __init tegra_init_from_table(struct tegra_clk_init_table *tbl,

if (tbl->state)
- if (clk_prepare_enable(clk_core_to_clk(clk))) {
+ if (clk_prepare_enable(clk_core_to_clk(clk, NULL, __clk_get_name(clk)))) {

Ditto. And all similar cases below which I skipped due to lack of any
added value to this review.

pr_err("%s: Failed to enable %s\n", __func__,


diff --git a/include/linux/clk-private.h b/include/linux/clk-private.h
index 2c1ece9..9657fc8 100644
--- a/include/linux/clk-private.h
+++ b/include/linux/clk-private.h
@@ -57,6 +57,10 @@ struct clk_core {

struct clk {
struct clk_core *core;
+ unsigned int enable_count;
+ const char *dev_id;
+ const char *con_id;
+ void *last_disable;

Probably the same as for enables should be done for prepares.

Yes, I think it would be useful as well.


diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 87de32c..abfc31a 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -533,7 +533,8 @@ struct clk_core *clk_provider_get_sys(const char *dev_id, const char *con_id);
struct clk_core *clk_provider_get(struct device *dev, const char *con_id);
struct clk_core *devm_clk_provider_get(struct device *dev, const char *id);

-#define clk_core_to_clk(core) ((struct clk *)(core))

Btw. this should have been a static inline.




Best regards,

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