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

From: Sam Protsenko
Date: Thu Oct 07 2021 - 09:56:03 EST


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
>