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SubjectRe: [PATCH v7 2/4] soc: qcom: Add AOSS QMP driver
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Quoting Doug Anderson (2019-05-23 09:38:13)
> Hi,
>
> On Tue, Apr 30, 2019 at 9:38 PM Bjorn Andersson
> <bjorn.andersson@linaro.org> wrote:
>
> > +static int qmp_qdss_clk_add(struct qmp *qmp)
> > +{
> > + struct clk_init_data qdss_init = {
> > + .ops = &qmp_qdss_clk_ops,
> > + .name = "qdss",
> > + };
>
> Can't qdss_init be "static const"? That had the advantage of not
> needing to construct it on the stack and also of it having a longer
> lifetime. It looks like clk_register() stores the "hw" pointer in its
> structure and the "hw" structure will have a pointer here. While I
> can believe that it never looks at it again, it's nice if that pointer
> doesn't point somewhere on an old stack.
>
> I suppose we could go the other way and try to mark more stuff in this
> module as __init and __initdata, but even then at least the pointer
> won't be onto a stack. ;-)
>

Const would be nice, but otherwise making it static isn't a good idea.
The clk_init_data structure is all copied over, although we do leave a
dangling pointer to it stored inside the clk_hw structure we don't use
it after clk registration. Maybe we should overwrite the pointer with
NULL once we're done in clk_register() so that clk providers can't use
it. It might break somebody but would at least clarify this point.

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index aa51756fd4d6..56997a974408 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -3438,9 +3438,9 @@ static int clk_cpy_name(const char **dst_p, const char *src, bool must_exist)
return 0;
}

-static int clk_core_populate_parent_map(struct clk_core *core)
+static int clk_core_populate_parent_map(struct clk_core *core,
+ const struct clk_init_data *init)
{
- const struct clk_init_data *init = core->hw->init;
u8 num_parents = init->num_parents;
const char * const *parent_names = init->parent_names;
const struct clk_hw **parent_hws = init->parent_hws;
@@ -3520,6 +3520,14 @@ __clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw)
{
int ret;
struct clk_core *core;
+ const struct clk_init_data *init = hw->init;
+
+ /*
+ * The init data is not supposed to be used outside of registration path.
+ * Set it to NULL so that provider drivers can't use it either and so that
+ * we catch use of hw->init early on in the core.
+ */
+ hw->init = NULL;

core = kzalloc(sizeof(*core), GFP_KERNEL);
if (!core) {
@@ -3527,17 +3535,17 @@ __clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw)
goto fail_out;
}

- core->name = kstrdup_const(hw->init->name, GFP_KERNEL);
+ core->name = kstrdup_const(init->name, GFP_KERNEL);
if (!core->name) {
ret = -ENOMEM;
goto fail_name;
}

- if (WARN_ON(!hw->init->ops)) {
+ if (WARN_ON(!init->ops)) {
ret = -EINVAL;
goto fail_ops;
}
- core->ops = hw->init->ops;
+ core->ops = init->ops;

if (dev && pm_runtime_enabled(dev))
core->rpm_enabled = true;
@@ -3546,13 +3554,13 @@ __clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw)
if (dev && dev->driver)
core->owner = dev->driver->owner;
core->hw = hw;
- core->flags = hw->init->flags;
- core->num_parents = hw->init->num_parents;
+ core->flags = init->flags;
+ core->num_parents = init->num_parents;
core->min_rate = 0;
core->max_rate = ULONG_MAX;
hw->core = core;

- ret = clk_core_populate_parent_map(core);
+ ret = clk_core_populate_parent_map(core, init);
if (ret)
goto fail_parents;

>
>
> > +static void qmp_pd_remove(struct qmp *qmp)
> > +{
> > + struct genpd_onecell_data *data = &qmp->pd_data;
> > + struct device *dev = qmp->dev;
> > + int i;
> > +
> > + of_genpd_del_provider(dev->of_node);
> > +
> > + for (i = 0; i < data->num_domains; i++)
> > + pm_genpd_remove(data->domains[i]);
>
> Still feels like the above loop would be better as:
> for (i = data->num_domains - 1; i >= 0; i--)
>

Reason being to remove in reverse order? Otherwise this looks like an
opinion.

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