Re: [PATCH v2] clk: Add clk_set_parent debugfs node

[Sam Protsenko]

On Thu, 7 Oct 2021 at 16:50, Sam Protsenko <semen.protsenko@xxxxxxxxxx> wrote:
>
> Useful for testing mux clocks. One can write the index of the parent to
> set into clk_parent node, starting from 0. Example
>
>     # cd /sys/kernel/debug/clk/mout_peri_bus
>     # cat clk_possible_parrents
>       dout_shared0_div4 dout_shared1_div4
>     # cat clk_parent
>       dout_shared0_div4
>     # echo 1 > clk_parent
>     # cat clk_parent
>       dout_shared1_div4
>
> One needs to define CLOCK_ALLOW_WRITE_DEBUGFS in drivers/clk/clk.c in
> order to use this feature.
>
> Signed-off-by: Sam Protsenko <semen.protsenko@xxxxxxxxxx>
> ---

Please ignore this one, it has unwanted changes added by mistake. I'll
send v3 soon.

> Changes in v2:
>   - Merged write() function into existing 'clk_parent' file
>   - Removed 'if (val >= core->num_parents)' check
>   - Removed incorrect usage of IS_ERR_OR_NULL()
>
>  drivers/clk/clk.c | 56 +++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 54 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 806c55f0991b..5776efab4739 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -3224,6 +3224,46 @@ static int current_parent_show(struct seq_file *s, void *data)
>  }
>  DEFINE_SHOW_ATTRIBUTE(current_parent);
>
> +#ifdef CLOCK_ALLOW_WRITE_DEBUGFS
> +static ssize_t current_parent_write(struct file *file, const char __user *ubuf,
> +                                   size_t count, loff_t *ppos)
> +{
> +       struct seq_file *s = file->private_data;
> +       struct clk_core *core = s->private;
> +       struct clk_core *parent;
> +       char buf[4] = { 0 };
> +       u8 idx;
> +       int err;
> +
> +       if (copy_from_user(&buf, ubuf, min_t(size_t, sizeof(buf) - 1, count)))
> +               return -EFAULT;
> +
> +       err = kstrtou8(buf, 0, &idx);
> +       if (err)
> +               return err;
> +
> +       parent = clk_core_get_parent_by_index(core, idx);
> +       if (!parent)
> +               return -ENOENT;
> +
> +       clk_prepare_lock();
> +       err = clk_core_set_parent_nolock(core, parent);
> +       clk_prepare_unlock();
> +       if (err)
> +               return err;
> +
> +       return count;
> +}
> +
> +static const struct file_operations current_parent_rw_fops = {
> +       .open           = current_parent_open,
> +       .write          = current_parent_write,
> +       .read           = seq_read,
> +       .llseek         = seq_lseek,
> +       .release        = single_release,
> +};
> +#endif
> +
>  static int clk_duty_cycle_show(struct seq_file *s, void *data)
>  {
>         struct clk_core *core = s->private;
> @@ -3291,13 +3331,25 @@ static void clk_debug_create_one(struct clk_core *core, struct dentry *pdentry)
>                             &clk_prepare_enable_fops);
>  #endif
>
> -       if (core->num_parents > 0)
> +       if (core->num_parents > 0) {
> +#ifdef CLOCK_ALLOW_WRITE_DEBUGFS
> +               if (core->num_parents > 1) {
> +                       debugfs_create_file("clk_parent", 0644, root, core,
> +                                           &current_parent_rw_fops);
> +               } else {
> +                       debugfs_create_file("clk_parent", 0444, root, core,
> +                                           &current_parent_fops);
> +               }
> +#else
>                 debugfs_create_file("clk_parent", 0444, root, core,
>                                     &current_parent_fops);
> +#endif
> +       }
>
> -       if (core->num_parents > 1)
> +       if (core->num_parents > 1) {
>                 debugfs_create_file("clk_possible_parents", 0444, root, core,
>                                     &possible_parents_fops);
> +       }
>
>         if (core->ops->debug_init)
>                 core->ops->debug_init(core->hw, core->dentry);
> --
> 2.30.2
>