[PATCH] clk: Add clk_set_parent debugfs node

[PATCH] clk: Add clk_set_parent debugfs node

[Sam Protsenko]

Useful for testing mux clocks. One can write the index of the parent to
set into clk_set_parent node, starting from 0. Example

    # cat clk_possible_parrents
      dout_shared0_div4 dout_shared1_div4
    # cat clk_parent
      dout_shared0_div4
    # echo 1 > clk_set_parent
    # cat clk_parent
      dout_shared1_div4

Define CLOCK_ALLOW_WRITE_DEBUGFS in drivers/clk/clk.c in order to use
this feature.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
---
 drivers/clk/clk.c | 31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 65508eb89ec9..3e5456580db9 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -3214,6 +3214,30 @@ static int current_parent_show(struct seq_file *s, void *data)
 }
 DEFINE_SHOW_ATTRIBUTE(current_parent);
 
+#ifdef CLOCK_ALLOW_WRITE_DEBUGFS
+static int clk_set_parent_set(void *data, u64 val)
+{
+	struct clk_core *core = data, *parent;
+	int ret;
+
+	if (val >= core->num_parents)
+		return -EINVAL;
+
+	parent = clk_core_get_parent_by_index(core, val);
+	if (IS_ERR_OR_NULL(parent))
+		return PTR_ERR(parent);
+
+	clk_prepare_lock();
+	ret = clk_core_set_parent_nolock(core, parent);
+	clk_prepare_unlock();
+
+	return ret;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(clk_set_parent_fops, NULL, clk_set_parent_set,
+			 "%llu\n");
+#endif
+
 static int clk_duty_cycle_show(struct seq_file *s, void *data)
 {
 	struct clk_core *core = s->private;
@@ -3285,9 +3309,14 @@ static void clk_debug_create_one(struct clk_core *core, struct dentry *pdentry)
 		debugfs_create_file("clk_parent", 0444, root, core,
 				    &current_parent_fops);
 
-	if (core->num_parents > 1)
+	if (core->num_parents > 1) {
 		debugfs_create_file("clk_possible_parents", 0444, root, core,
 				    &possible_parents_fops);
+#ifdef CLOCK_ALLOW_WRITE_DEBUGFS
+		debugfs_create_file("clk_set_parent", 0200, root, core,
+				    &clk_set_parent_fops);
+#endif
+	}
 
 	if (core->ops->debug_init)
 		core->ops->debug_init(core->hw, core->dentry);
-- 
2.30.2

Re: [PATCH] clk: Add clk_set_parent debugfs node

[Sam Protsenko]

On Tue, 14 Sept 2021 at 17:19, Sam Protsenko <semen.protsenko@linaro.org> wrote:
>
> Useful for testing mux clocks. One can write the index of the parent to
> set into clk_set_parent node, starting from 0. Example
>
>     # cat clk_possible_parrents
>       dout_shared0_div4 dout_shared1_div4
>     # cat clk_parent
>       dout_shared0_div4
>     # echo 1 > clk_set_parent
>     # cat clk_parent
>       dout_shared1_div4
>
> Define CLOCK_ALLOW_WRITE_DEBUGFS in drivers/clk/clk.c in order to use
> this feature.
>
> Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
> ---

+ Adding more folks for review

Guys, can you please review this one?

>  drivers/clk/clk.c | 31 ++++++++++++++++++++++++++++++-
>  1 file changed, 30 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 65508eb89ec9..3e5456580db9 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -3214,6 +3214,30 @@ static int current_parent_show(struct seq_file *s, void *data)
>  }
>  DEFINE_SHOW_ATTRIBUTE(current_parent);
>
> +#ifdef CLOCK_ALLOW_WRITE_DEBUGFS
> +static int clk_set_parent_set(void *data, u64 val)
> +{
> +       struct clk_core *core = data, *parent;
> +       int ret;
> +
> +       if (val >= core->num_parents)
> +               return -EINVAL;
> +
> +       parent = clk_core_get_parent_by_index(core, val);
> +       if (IS_ERR_OR_NULL(parent))
> +               return PTR_ERR(parent);
> +
> +       clk_prepare_lock();
> +       ret = clk_core_set_parent_nolock(core, parent);
> +       clk_prepare_unlock();
> +
> +       return ret;
> +}
> +
> +DEFINE_DEBUGFS_ATTRIBUTE(clk_set_parent_fops, NULL, clk_set_parent_set,
> +                        "%llu\n");
> +#endif
> +
>  static int clk_duty_cycle_show(struct seq_file *s, void *data)
>  {
>         struct clk_core *core = s->private;
> @@ -3285,9 +3309,14 @@ static void clk_debug_create_one(struct clk_core *core, struct dentry *pdentry)
>                 debugfs_create_file("clk_parent", 0444, root, core,
>                                     &current_parent_fops);
>
> -       if (core->num_parents > 1)
> +       if (core->num_parents > 1) {
>                 debugfs_create_file("clk_possible_parents", 0444, root, core,
>                                     &possible_parents_fops);
> +#ifdef CLOCK_ALLOW_WRITE_DEBUGFS
> +               debugfs_create_file("clk_set_parent", 0200, root, core,
> +                                   &clk_set_parent_fops);
> +#endif
> +       }
>
>         if (core->ops->debug_init)
>                 core->ops->debug_init(core->hw, core->dentry);
> --
> 2.30.2
>

Re: [PATCH] clk: Add clk_set_parent debugfs node

[Geert Uytterhoeven]

Hi Sam,

On Tue, Oct 5, 2021 at 12:11 PM Sam Protsenko
<semen.protsenko@linaro.org> wrote:
> On Tue, 14 Sept 2021 at 17:19, Sam Protsenko <semen.protsenko@linaro.org> wrote:
> > Useful for testing mux clocks. One can write the index of the parent to
> > set into clk_set_parent node, starting from 0. Example
> >
> >     # cat clk_possible_parrents
> >       dout_shared0_div4 dout_shared1_div4
> >     # cat clk_parent
> >       dout_shared0_div4
> >     # echo 1 > clk_set_parent
> >     # cat clk_parent
> >       dout_shared1_div4
> >
> > Define CLOCK_ALLOW_WRITE_DEBUGFS in drivers/clk/clk.c in order to use
> > this feature.
> >
> > Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
> > ---
>
> + Adding more folks for review
>
> Guys, can you please review this one?

Thanks for your patch!

> > --- a/drivers/clk/clk.c
> > +++ b/drivers/clk/clk.c
> > @@ -3214,6 +3214,30 @@ static int current_parent_show(struct seq_file *s, void *data)
> >  }
> >  DEFINE_SHOW_ATTRIBUTE(current_parent);
> >
> > +#ifdef CLOCK_ALLOW_WRITE_DEBUGFS
> > +static int clk_set_parent_set(void *data, u64 val)

u64 is overkill, num_parents is u8.

> > +{
> > +       struct clk_core *core = data, *parent;
> > +       int ret;
> > +
> > +       if (val >= core->num_parents)
> > +               return -EINVAL;

clk_core_get_parent_by_index() called below already checks this.

> > +
> > +       parent = clk_core_get_parent_by_index(core, val);
> > +       if (IS_ERR_OR_NULL(parent))
> > +               return PTR_ERR(parent);
> > +
> > +       clk_prepare_lock();
> > +       ret = clk_core_set_parent_nolock(core, parent);
> > +       clk_prepare_unlock();
> > +
> > +       return ret;
> > +}
> > +
> > +DEFINE_DEBUGFS_ATTRIBUTE(clk_set_parent_fops, NULL, clk_set_parent_set,
> > +                        "%llu\n");
> > +#endif
> > +
> >  static int clk_duty_cycle_show(struct seq_file *s, void *data)
> >  {
> >         struct clk_core *core = s->private;
> > @@ -3285,9 +3309,14 @@ static void clk_debug_create_one(struct clk_core *core, struct dentry *pdentry)
> >                 debugfs_create_file("clk_parent", 0444, root, core,
> >                                     &current_parent_fops);
> >
> > -       if (core->num_parents > 1)
> > +       if (core->num_parents > 1) {
> >                 debugfs_create_file("clk_possible_parents", 0444, root, core,
> >                                     &possible_parents_fops);
> > +#ifdef CLOCK_ALLOW_WRITE_DEBUGFS
> > +               debugfs_create_file("clk_set_parent", 0200, root, core,
> > +                                   &clk_set_parent_fops);
> > +#endif

Why add a new file, instead of making the existing "clk_parent" file
writable, like is done for "clk_rate"?
Yes, "clk_parent" prints a name, while you use a parent number, but
I guess that can be fixed? Or even both can be accepted?

> > +       }
> >
> >         if (core->ops->debug_init)
> >                 core->ops->debug_init(core->hw, core->dentry);

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH] clk: Add clk_set_parent debugfs node

[Sam Protsenko]

Hi Geert,

On Tue, 5 Oct 2021 at 13:43, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Sam,
>
> On Tue, Oct 5, 2021 at 12:11 PM Sam Protsenko
> <semen.protsenko@linaro.org> wrote:
> > On Tue, 14 Sept 2021 at 17:19, Sam Protsenko <semen.protsenko@linaro.org> wrote:
> > > Useful for testing mux clocks. One can write the index of the parent to
> > > set into clk_set_parent node, starting from 0. Example
> > >
> > >     # cat clk_possible_parrents
> > >       dout_shared0_div4 dout_shared1_div4
> > >     # cat clk_parent
> > >       dout_shared0_div4
> > >     # echo 1 > clk_set_parent
> > >     # cat clk_parent
> > >       dout_shared1_div4
> > >
> > > Define CLOCK_ALLOW_WRITE_DEBUGFS in drivers/clk/clk.c in order to use
> > > this feature.
> > >
> > > Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
> > > ---
> >
> > + Adding more folks for review
> >
> > Guys, can you please review this one?
>
> Thanks for your patch!
>

Thanks for review! :)

> > > --- a/drivers/clk/clk.c
> > > +++ b/drivers/clk/clk.c
> > > @@ -3214,6 +3214,30 @@ static int current_parent_show(struct seq_file *s, void *data)
> > >  }
> > >  DEFINE_SHOW_ATTRIBUTE(current_parent);
> > >
> > > +#ifdef CLOCK_ALLOW_WRITE_DEBUGFS
> > > +static int clk_set_parent_set(void *data, u64 val)
>
> u64 is overkill, num_parents is u8.
>

u64 is required by simple_attr_open() signature, because
clk_set_parent_set() is being passed there as a parameter eventually
(via DEFINE_DEBUGFS_ATTRIBUTE()). But yeah, I'll use u8 when reworking
the code for using with existing 'clk_parent' file.

> > > +{
> > > +       struct clk_core *core = data, *parent;
> > > +       int ret;
> > > +
> > > +       if (val >= core->num_parents)
> > > +               return -EINVAL;
>
> clk_core_get_parent_by_index() called below already checks this.
>

Thanks, will remove this.

> > > +
> > > +       parent = clk_core_get_parent_by_index(core, val);
> > > +       if (IS_ERR_OR_NULL(parent))
> > > +               return PTR_ERR(parent);

Also just noticed that this block is incorrect. I should've used just
'if (!parent)' here instead. I remember Russel King was raising the
question about removing that API for good, as too many people tend to
use that incorrectly, and now I can see why.

> > > +
> > > +       clk_prepare_lock();
> > > +       ret = clk_core_set_parent_nolock(core, parent);
> > > +       clk_prepare_unlock();
> > > +
> > > +       return ret;
> > > +}
> > > +
> > > +DEFINE_DEBUGFS_ATTRIBUTE(clk_set_parent_fops, NULL, clk_set_parent_set,
> > > +                        "%llu\n");
> > > +#endif
> > > +
> > >  static int clk_duty_cycle_show(struct seq_file *s, void *data)
> > >  {
> > >         struct clk_core *core = s->private;
> > > @@ -3285,9 +3309,14 @@ static void clk_debug_create_one(struct clk_core *core, struct dentry *pdentry)
> > >                 debugfs_create_file("clk_parent", 0444, root, core,
> > >                                     &current_parent_fops);
> > >
> > > -       if (core->num_parents > 1)
> > > +       if (core->num_parents > 1) {
> > >                 debugfs_create_file("clk_possible_parents", 0444, root, core,
> > >                                     &possible_parents_fops);
> > > +#ifdef CLOCK_ALLOW_WRITE_DEBUGFS
> > > +               debugfs_create_file("clk_set_parent", 0200, root, core,
> > > +                                   &clk_set_parent_fops);
> > > +#endif
>
> Why add a new file, instead of making the existing "clk_parent" file
> writable, like is done for "clk_rate"?
> Yes, "clk_parent" prints a name, while you use a parent number, but
> I guess that can be fixed? Or even both can be accepted?
>

Ok, I'll merge that feature into existing 'clk_parent' file. At the
time I implemented this I was busy with something else, and use
existing code around as an example. But it's not too hard to do this
properly, by defining 'struct file_operations' manually, like it's
done for example in dwc3_lsp_write(). Will send v2 with fixes shortly.

> > > +       }
> > >
> > >         if (core->ops->debug_init)
> > >                 core->ops->debug_init(core->hw, core->dentry);
>
> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds