clk: imx: imx8ulp: Add divider closest support to get more accurate clock rate

If a divider's parent clock has fractional part, it will hard to round out a
more accurate clock rate for this divider, add the 'CLK_DIVIDER_ROUND_CLOSEST' flags
for such divider to get a more accurate clock rate.

Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Abel Vesa <abel.vesa@linaro.org>
Link: https://lore.kernel.org/r/20230331063814.2462059-3-peng.fan@oss.nxp.com
Signed-off-by: Abel Vesa <abel.vesa@linaro.org>

Author: JackyBai

drivers/clk/imx/clk-imx8ulp.c

@@ -275,14 +275,14 @@ static int imx8ulp_clk_cgc2_init(struct platform_device *pdev)
 	clks[IMX8ULP_CLK_PLL4_PFD2_DIV2_GATE] = imx_clk_hw_gate_dis("pll4_pfd2_div2_gate", "pll4_pfd2", base + 0x60c, 15);
 	clks[IMX8ULP_CLK_PLL4_PFD3_DIV1_GATE] = imx_clk_hw_gate_dis("pll4_pfd3_div1_gate", "pll4_pfd3", base + 0x60c, 23);
 	clks[IMX8ULP_CLK_PLL4_PFD3_DIV2_GATE] = imx_clk_hw_gate_dis("pll4_pfd3_div2_gate", "pll4_pfd3", base + 0x60c, 31);
-	clks[IMX8ULP_CLK_PLL4_PFD0_DIV1] = imx_clk_hw_divider("pll4_pfd0_div1", "pll4_pfd0_div1_gate", base + 0x608, 0, 6);
-	clks[IMX8ULP_CLK_PLL4_PFD0_DIV2] = imx_clk_hw_divider("pll4_pfd0_div2", "pll4_pfd0_div2_gate", base + 0x608, 8, 6);
-	clks[IMX8ULP_CLK_PLL4_PFD1_DIV1] = imx_clk_hw_divider("pll4_pfd1_div1", "pll4_pfd1_div1_gate", base + 0x608, 16, 6);
-	clks[IMX8ULP_CLK_PLL4_PFD1_DIV2] = imx_clk_hw_divider("pll4_pfd1_div2", "pll4_pfd1_div2_gate", base + 0x608, 24, 6);
-	clks[IMX8ULP_CLK_PLL4_PFD2_DIV1] = imx_clk_hw_divider("pll4_pfd2_div1", "pll4_pfd2_div1_gate", base + 0x60c, 0, 6);
-	clks[IMX8ULP_CLK_PLL4_PFD2_DIV2] = imx_clk_hw_divider("pll4_pfd2_div2", "pll4_pfd2_div2_gate", base + 0x60c, 8, 6);
-	clks[IMX8ULP_CLK_PLL4_PFD3_DIV1] = imx_clk_hw_divider("pll4_pfd3_div1", "pll4_pfd3_div1_gate", base + 0x60c, 16, 6);
-	clks[IMX8ULP_CLK_PLL4_PFD3_DIV2] = imx_clk_hw_divider("pll4_pfd3_div2", "pll4_pfd3_div2_gate", base + 0x60c, 24, 6);
+	clks[IMX8ULP_CLK_PLL4_PFD0_DIV1] = imx_clk_hw_divider_closest("pll4_pfd0_div1", "pll4_pfd0_div1_gate", base + 0x608, 0, 6);
+	clks[IMX8ULP_CLK_PLL4_PFD0_DIV2] = imx_clk_hw_divider_closest("pll4_pfd0_div2", "pll4_pfd0_div2_gate", base + 0x608, 8, 6);
+	clks[IMX8ULP_CLK_PLL4_PFD1_DIV1] = imx_clk_hw_divider_closest("pll4_pfd1_div1", "pll4_pfd1_div1_gate", base + 0x608, 16, 6);
+	clks[IMX8ULP_CLK_PLL4_PFD1_DIV2] = imx_clk_hw_divider_closest("pll4_pfd1_div2", "pll4_pfd1_div2_gate", base + 0x608, 24, 6);
+	clks[IMX8ULP_CLK_PLL4_PFD2_DIV1] = imx_clk_hw_divider_closest("pll4_pfd2_div1", "pll4_pfd2_div1_gate", base + 0x60c, 0, 6);
+	clks[IMX8ULP_CLK_PLL4_PFD2_DIV2] = imx_clk_hw_divider_closest("pll4_pfd2_div2", "pll4_pfd2_div2_gate", base + 0x60c, 8, 6);
+	clks[IMX8ULP_CLK_PLL4_PFD3_DIV1] = imx_clk_hw_divider_closest("pll4_pfd3_div1", "pll4_pfd3_div1_gate", base + 0x60c, 16, 6);
+	clks[IMX8ULP_CLK_PLL4_PFD3_DIV2] = imx_clk_hw_divider_closest("pll4_pfd3_div2", "pll4_pfd3_div2_gate", base + 0x60c, 24, 6);
 
 	clks[IMX8ULP_CLK_CGC2_SOSC_DIV1_GATE] = imx_clk_hw_gate_dis("cgc2_sosc_div1_gate", "sosc", base + 0x108, 7);
 	clks[IMX8ULP_CLK_CGC2_SOSC_DIV2_GATE] = imx_clk_hw_gate_dis("cgc2_sosc_div2_gate", "sosc", base + 0x108, 15);

drivers/clk/imx/clk.h

@@ -353,6 +353,15 @@ static inline struct clk_hw *imx_clk_hw_fixed_factor(const char *name,
 			CLK_SET_RATE_PARENT, mult, div);
 }
 
+static inline struct clk_hw *imx_clk_hw_divider_closest(const char *name,
+						const char *parent,
+						void __iomem *reg, u8 shift,
+						u8 width)
+{
+	return clk_hw_register_divider(NULL, name, parent, 0,
+				       reg, shift, width, CLK_DIVIDER_ROUND_CLOSEST, &imx_ccm_lock);
+}
+
 static inline struct clk_hw *__imx_clk_hw_divider(const char *name,
 						   const char *parent,
 						   void __iomem *reg, u8 shift,