clk: renesas: rzv2h: Add support for DSI clocks

Add support for PLLDSI and its post-dividers in the RZ/V2H CPG driver and
export helper APIs for use by the DSI driver.

Introduce per-PLL-DSI state in the CPG private structure and provide a
set of helper functions that find valid PLL parameter combinations for
a requested frequency. The new helpers are rzv2h_get_pll_pars(),
rzv2h_get_pll_div_pars(), rzv2h_get_pll_divs_pars() and
rzv2h_get_pll_dtable_pars() and they are exported in the "RZV2H_CPG"
namespace for use by other consumers (notably the DSI driver). These
helpers perform iterative searches over PLL parameters (M, K, P, S)
and optional post-dividers and return the best match (or an exact
match when possible).

Move PLL/CLK related limits and parameter types into the shared
include (include/linux/clk/renesas.h) by adding struct rzv2h_pll_limits,
struct rzv2h_pll_pars and struct rzv2h_pll_div_pars plus the
RZV2H_CPG_PLL_DSI_LIMITS() helper macro to define DSI PLL limits.

This change centralises the PLLDSI algorithms so the CPG and DSI
drivers compute PLL parameters consistently and allows the DSI driver
to accurately request rates and program its PLL.

Co-developed-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Acked-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/20251015192611.241920-4-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

1 files changed, 145 insertions, 0 deletions

diff --git a/include/linux/clk/renesas.h b/include/linux/clk/renesas.h
index 0ebbe2f0b45e..69d8159deee3 100644
--- a/include/linux/clk/renesas.h
+++ b/include/linux/clk/renesas.h
@@ -10,7 +10,9 @@
 #ifndef __LINUX_CLK_RENESAS_H_
 #define __LINUX_CLK_RENESAS_H_
 
+#include <linux/clk-provider.h>
 #include <linux/types.h>
+#include <linux/units.h>
 
 struct device;
 struct device_node;
@@ -32,4 +34,147 @@ void cpg_mssr_detach_dev(struct generic_pm_domain *unused, struct device *dev);
 #define cpg_mssr_attach_dev	NULL
 #define cpg_mssr_detach_dev	NULL
 #endif
+
+/**
+ * struct rzv2h_pll_limits - PLL parameter constraints
+ *
+ * This structure defines the minimum and maximum allowed values for
+ * various parameters used to configure a PLL. These limits ensure
+ * the PLL operates within valid and stable ranges.
+ *
+ * @fout: Output frequency range (in MHz)
+ * @fout.min: Minimum allowed output frequency
+ * @fout.max: Maximum allowed output frequency
+ *
+ * @fvco: PLL oscillation frequency range (in MHz)
+ * @fvco.min: Minimum allowed VCO frequency
+ * @fvco.max: Maximum allowed VCO frequency
+ *
+ * @m: Main-divider range
+ * @m.min: Minimum main-divider value
+ * @m.max: Maximum main-divider value
+ *
+ * @p: Pre-divider range
+ * @p.min: Minimum pre-divider value
+ * @p.max: Maximum pre-divider value
+ *
+ * @s: Divider range
+ * @s.min: Minimum divider value
+ * @s.max: Maximum divider value
+ *
+ * @k: Delta-sigma modulator range (signed)
+ * @k.min: Minimum delta-sigma value
+ * @k.max: Maximum delta-sigma value
+ */
+struct rzv2h_pll_limits {
+	struct {
+		u32 min;
+		u32 max;
+	} fout;
+
+	struct {
+		u32 min;
+		u32 max;
+	} fvco;
+
+	struct {
+		u16 min;
+		u16 max;
+	} m;
+
+	struct {
+		u8 min;
+		u8 max;
+	} p;
+
+	struct {
+		u8 min;
+		u8 max;
+	} s;
+
+	struct {
+		s16 min;
+		s16 max;
+	} k;
+};
+
+/**
+ * struct rzv2h_pll_pars - PLL configuration parameters
+ *
+ * This structure contains the configuration parameters for the
+ * Phase-Locked Loop (PLL), used to achieve a specific output frequency.
+ *
+ * @m: Main divider value
+ * @p: Pre-divider value
+ * @s: Output divider value
+ * @k: Delta-sigma modulation value
+ * @freq_millihz: Calculated PLL output frequency in millihertz
+ * @error_millihz: Frequency error from target in millihertz (signed)
+ */
+struct rzv2h_pll_pars {
+	u16 m;
+	u8 p;
+	u8 s;
+	s16 k;
+	u64 freq_millihz;
+	s64 error_millihz;
+};
+
+/**
+ * struct rzv2h_pll_div_pars - PLL parameters with post-divider
+ *
+ * This structure is used for PLLs that include an additional post-divider
+ * stage after the main PLL block. It contains both the PLL configuration
+ * parameters and the resulting frequency/error values after the divider.
+ *
+ * @pll: Main PLL configuration parameters (see struct rzv2h_pll_pars)
+ *
+ * @div: Post-divider configuration and result
+ * @div.divider_value: Divider applied to the PLL output
+ * @div.freq_millihz: Output frequency after divider in millihertz
+ * @div.error_millihz: Frequency error from target in millihertz (signed)
+ */
+struct rzv2h_pll_div_pars {
+	struct rzv2h_pll_pars pll;
+	struct {
+		u8 divider_value;
+		u64 freq_millihz;
+		s64 error_millihz;
+	} div;
+};
+
+#define RZV2H_CPG_PLL_DSI_LIMITS(name)					\
+	static const struct rzv2h_pll_limits (name) = {			\
+		.fout = { .min = 25 * MEGA, .max = 375 * MEGA },	\
+		.fvco = { .min = 1600 * MEGA, .max = 3200 * MEGA },	\
+		.m = { .min = 64, .max = 533 },				\
+		.p = { .min = 1, .max = 4 },				\
+		.s = { .min = 0, .max = 6 },				\
+		.k = { .min = -32768, .max = 32767 },			\
+	}								\
+
+#ifdef CONFIG_CLK_RZV2H
+bool rzv2h_get_pll_pars(const struct rzv2h_pll_limits *limits,
+			struct rzv2h_pll_pars *pars, u64 freq_millihz);
+
+bool rzv2h_get_pll_divs_pars(const struct rzv2h_pll_limits *limits,
+			     struct rzv2h_pll_div_pars *pars,
+			     const u8 *table, u8 table_size, u64 freq_millihz);
+#else
+static inline bool rzv2h_get_pll_pars(const struct rzv2h_pll_limits *limits,
+				      struct rzv2h_pll_pars *pars,
+				      u64 freq_millihz)
+{
+	return false;
+}
+
+static inline bool rzv2h_get_pll_divs_pars(const struct rzv2h_pll_limits *limits,
+					   struct rzv2h_pll_div_pars *pars,
+					   const u8 *table, u8 table_size,
+					   u64 freq_millihz)
+{
+	return false;
+}
+#endif
+
 #endif