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

[Jacky Bai <ping.bai@nxp.com>]

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;

Signed-off-by: Jacky Bai <ping.bai@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(+)

diff --git a/drivers/clk/imx/clk-imx8mm.c b/drivers/clk/imx/clk-imx8mm.c
index 319af4deec01c188524807d39dff92bbd08f3601..6a031d7cd031c8b5f5b01e5531ce54360724ba44 100644
--- a/drivers/clk/imx/clk-imx8mm.c
+++ b/drivers/clk/imx/clk-imx8mm.c
@@ -298,6 +298,7 @@ static struct clk_hw **hws;
 
 static int imx8mm_clocks_probe(struct platform_device *pdev)
 {
+	struct clk_hw *audio_pll_hws[2];
 	struct device *dev = &pdev->dev;
 	struct device_node *np = dev->of_node;
 	void __iomem *base;
@@ -610,6 +611,11 @@ static int imx8mm_clocks_probe(struct platform_device *pdev)
 
 	imx_register_uart_clocks();
 
+	/* Add debug interface for audio PLLs */
+	audio_pll_hws[0] = hws[IMX8MM_AUDIO_PLL1];
+	audio_pll_hws[1] = hws[IMX8MM_AUDIO_PLL2];
+	audio_pll_debug_init(audio_pll_hws, ARRAY_SIZE(audio_pll_hws));
+
 	return 0;
 
 unregister_hws:
diff --git a/drivers/clk/imx/clk-pll14xx.c b/drivers/clk/imx/clk-pll14xx.c
index 39600ee22be3066683b562aa6f2a8b750d19c4cc..59f126f35474116bdad0aeda59777b9eb7f246cf 100644
--- a/drivers/clk/imx/clk-pll14xx.c
+++ b/drivers/clk/imx/clk-pll14xx.c
@@ -8,6 +8,7 @@
 #include <linux/bitfield.h>
 #include <linux/bits.h>
 #include <linux/clk-provider.h>
+#include <linux/debugfs.h>
 #include <linux/err.h>
 #include <linux/export.h>
 #include <linux/io.h>
@@ -551,3 +552,81 @@ struct clk_hw *imx_dev_clk_hw_pll14xx(struct device *dev, const char *name,
 	return hw;
 }
 EXPORT_SYMBOL_GPL(imx_dev_clk_hw_pll14xx);
+
+/*
+ * Debugfs interface for Audio PLL runtime monitoring and control
+ *
+ * This interface allows dynamic adjustment of the Audio PLL
+ * K-divider for precise frequency tuning, particularly useful
+ * for audio applications.
+ *
+ * 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;
+ */
+#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");
+
+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..9611ab127dad6f23770c18e22e1acbe2fc22bd4e 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@nxp.com>