[PATCH] clk: imx: Add audio PLL debugfs for K-divider control

[Jacky Bai]

> Subject: Re: [PATCH] clk: imx: Add audio PLL debugfs for K-divider control
> 
> On Tue, May 12, 2026 at 05:08:10PM +0800, Jacky Bai wrote:
> > Add debugfs support for runtime tuning of the audio PLL K divider,
> > which enables fine-grained frequency adjustments for audio PLL.
> > This is used for:
> >   - Audio clock calibration and testing
> >   - Debugging audio synchronization issues
> >
> > Two debug interfaces are exported to userspace:
> >   - delta_k: It is used to adjust the K divider in PLL based on small
> >     steps
> >   - pll_parameter: It is used for get PLL's current M-divider,
> >     P-divider, S-divider & K-divider setting in PLL register
> >
> > examples for the usage of the two interfaces:
> >    1): Get the current PLL setting of dividers
> >      cat /sys/kernel/debug/audio_pll_monitor/audio_pll1/pll_parameter
> >
> >    2): if want to adjust the K-divider by a delta_k '1', then
> >      echo 1 > /sys/kernel/debug/audio_pll_monitor/audio_pll1/delta_k;
> >
> >    3): if want to adjust the K-divider by a delta_k '-1', then
> >      echo -1 > /sys/kernel/debug/audio_pll_monitor/audio_pll1/delta_k;
> 
> Nit: needn't example, it is basic usage mode for debugfs.
> 

will drop it.

> >
> > Signed-off-by: Jacky Bai <ping.bai at nxp.com>
> > ---
> >  drivers/clk/imx/clk-imx8mm.c  |  6 ++++
> > drivers/clk/imx/clk-pll14xx.c | 79
> +++++++++++++++++++++++++++++++++++++++++++
> >  drivers/clk/imx/clk.h         |  1 +
> >  3 files changed, 86 insertions(+)

[...]

> > + *   3): if want to adjust the K-divider by a delta_k '-1', then
> > + *     echo -1 >
> /sys/kernel/debug/audio_pll_monitor/audio_pll1/delta_k;
> > + */
> 
> 2) and 3) keep one is enough, you better descript validate range for delta_k
> here, which is more valuable information.
> 

Ok, will refine the comment in next version.

> > +#ifdef CONFIG_DEBUG_FS
> > +static int pll_delta_k_set(void *data, u64 val) {
> > +	struct clk_pll14xx *pll = to_clk_pll14xx(data);
> > +	s16 delta_k = (s16)val;
> > +	u32 div_ctl1;
> > +	s16 kdiv;
> > +
> > +	div_ctl1 = readl_relaxed(pll->base + DIV_CTL1);
> > +	kdiv = FIELD_GET(KDIV_MASK, div_ctl1) + delta_k;
> > +	writel_relaxed(FIELD_PREP(KDIV_MASK, kdiv), pll->base + DIV_CTL1);
> > +
> > +	return 0;
> > +}
> > +DEFINE_DEBUGFS_ATTRIBUTE_SIGNED(delta_k_fops, NULL,
> pll_delta_k_set,
> > +"%lld\n");
> 
> generally, better also provide read for delta_k
> 
> cat /sys/kernel/debug/audio_pll_monitor/audio_pll1/delta_k because user
> want to check value by read it back naturally.
> 

Thx, will add it.

BR
> Frank
> > +
> > +static int pll_setting_show(struct seq_file *s, void *data) {
> > +	struct clk_pll14xx *pll = to_clk_pll14xx(s->private);
> > +	u32 div_ctl0, div_ctl1;
> > +	u32 mdiv, pdiv, sdiv, kdiv;
> > +
> > +	div_ctl0 = readl_relaxed(pll->base + DIV_CTL0);
> > +	div_ctl1 = readl_relaxed(pll->base + DIV_CTL1);
> > +
> > +	mdiv = FIELD_GET(MDIV_MASK, div_ctl0);
> > +	pdiv = FIELD_GET(PDIV_MASK, div_ctl0);
> > +	sdiv = FIELD_GET(SDIV_MASK, div_ctl0);
> > +	kdiv = FIELD_GET(KDIV_MASK, div_ctl1);
> > +
> > +	seq_printf(s, "Mdiv: 0x%x; Pdiv: 0x%x; Sdiv: 0x%x; Kdiv: 0x%x\n",
> > +	mdiv, pdiv, sdiv, kdiv);
> > +
> > +	return 0;
> > +}
> > +DEFINE_SHOW_ATTRIBUTE(pll_setting);
> > +
> > +void audio_pll_debug_init(struct clk_hw *hws[], unsigned int
> > +num_plls) {
> > +	struct dentry *rootdir, *audio_pll_dir;
> > +	const char *pll_name;
> > +	int i;
> > +
> > +	rootdir = debugfs_create_dir("audio_pll_monitor", NULL);
> > +
> > +	for (i = 0; i < num_plls; i++) {
> > +		pll_name = clk_hw_get_name(hws[i]);
> > +		audio_pll_dir = debugfs_create_dir(pll_name, rootdir);
> > +		debugfs_create_file_unsafe("delta_k", 0200, audio_pll_dir,
> > +				hws[i], &delta_k_fops);
> > +		debugfs_create_file("pll_parameter", 0444, audio_pll_dir,
> > +				hws[i], &pll_setting_fops);
> > +	}
> > +}
> > +#else /* !CONFIG_DEBUG_FS */
> > +void audio_pll_debug_init(struct clk_hw *hws[], unsigned int
> > +num_plls) { } #endif /* CONFIG_DEBUG_FS */
> > +EXPORT_SYMBOL_GPL(audio_pll_debug_init);
> > diff --git a/drivers/clk/imx/clk.h b/drivers/clk/imx/clk.h index
> >
> aa5202f284f3d1b7c1b4bf65e2329831832b43a5..9611ab127dad6f23770c18e
> 22e1a
> > cbe2fc22bd4e 100644
> > --- a/drivers/clk/imx/clk.h
> > +++ b/drivers/clk/imx/clk.h
> > @@ -487,4 +487,5 @@ struct clk_hw *imx_clk_gpr_mux(const char *name,
> const char *compatible,
> >  			       u32 reg, const char **parent_names,
> >  			       u8 num_parents, const u32 *mux_table, u32 mask);
> >
> > +void audio_pll_debug_init(struct clk_hw **hws, unsigned int
> > +num_plls);
> >  #endif
> >
> > ---
> > base-commit: e98d21c170b01ddef366f023bbfcf6b31509fa83
> > change-id: 20260421-imx8m_pll_debugfs-246d0fbbb617
> >
> > Best regards,
> > --
> > Jacky Bai <ping.bai at nxp.com>
> >