MIPS: ralink: mt7620: Improve clock frequency detection

The current code assumes that the peripheral clock always
runs at 40MHz which is not true in all configuration. The
peripheral clock can also use the reference clock instead
of the fixed 40MHz rate. If the reference clock runs at a
different rate, various peripheries are behaving incorrectly.

Additionally, the currectly calculated system clock is also
wrong. The actual value what the code computes is the rate
of the DRAM which can be different from the system clock.

Add new helper functions to get the rate of the different
clocks and use the correct values for the registered clock
devices.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5755/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/ralink/mt7620.c

@@ -23,9 +23,6 @@
 /* does the board have sdram or ddram */
 static int dram_type;
 
-/* the pll dividers */
-static u32 mt7620_clk_divider[] = { 2, 3, 4, 8 };
-
 static struct ralink_pinmux_grp mode_mux[] = {
 	{
 		.name = "i2c",
@@ -140,34 +137,187 @@ struct ralink_pinmux rt_gpio_pinmux = {
 	.uart_mask = MT7620_GPIO_MODE_UART0_MASK,
 };
 
+static __init u32
+mt7620_calc_rate(u32 ref_rate, u32 mul, u32 div)
+{
+	u64 t;
+
+	t = ref_rate;
+	t *= mul;
+	do_div(t, div);
+
+	return t;
+}
+
+#define MHZ(x)		((x) * 1000 * 1000)
+
+static __init unsigned long
+mt7620_get_xtal_rate(void)
+{
+	u32 reg;
+
+	reg = rt_sysc_r32(SYSC_REG_SYSTEM_CONFIG0);
+	if (reg & SYSCFG0_XTAL_FREQ_SEL)
+		return MHZ(40);
+
+	return MHZ(20);
+}
+
+static __init unsigned long
+mt7620_get_periph_rate(unsigned long xtal_rate)
+{
+	u32 reg;
+
+	reg = rt_sysc_r32(SYSC_REG_CLKCFG0);
+	if (reg & CLKCFG0_PERI_CLK_SEL)
+		return xtal_rate;
+
+	return MHZ(40);
+}
+
+static const u32 mt7620_clk_divider[] __initconst = { 2, 3, 4, 8 };
+
+static __init unsigned long
+mt7620_get_cpu_pll_rate(unsigned long xtal_rate)
+{
+	u32 reg;
+	u32 mul;
+	u32 div;
+
+	reg = rt_sysc_r32(SYSC_REG_CPLL_CONFIG0);
+	if (reg & CPLL_CFG0_BYPASS_REF_CLK)
+		return xtal_rate;
+
+	if ((reg & CPLL_CFG0_SW_CFG) == 0)
+		return MHZ(600);
+
+	mul = (reg >> CPLL_CFG0_PLL_MULT_RATIO_SHIFT) &
+	      CPLL_CFG0_PLL_MULT_RATIO_MASK;
+	mul += 24;
+	if (reg & CPLL_CFG0_LC_CURFCK)
+		mul *= 2;
+
+	div = (reg >> CPLL_CFG0_PLL_DIV_RATIO_SHIFT) &
+	      CPLL_CFG0_PLL_DIV_RATIO_MASK;
+
+	WARN_ON(div >= ARRAY_SIZE(mt7620_clk_divider));
+
+	return mt7620_calc_rate(xtal_rate, mul, mt7620_clk_divider[div]);
+}
+
+static __init unsigned long
+mt7620_get_pll_rate(unsigned long xtal_rate, unsigned long cpu_pll_rate)
+{
+	u32 reg;
+
+	reg = rt_sysc_r32(SYSC_REG_CPLL_CONFIG1);
+	if (reg & CPLL_CFG1_CPU_AUX1)
+		return xtal_rate;
+
+	if (reg & CPLL_CFG1_CPU_AUX0)
+		return MHZ(480);
+
+	return cpu_pll_rate;
+}
+
+static __init unsigned long
+mt7620_get_cpu_rate(unsigned long pll_rate)
+{
+	u32 reg;
+	u32 mul;
+	u32 div;
+
+	reg = rt_sysc_r32(SYSC_REG_CPU_SYS_CLKCFG);
+
+	mul = reg & CPU_SYS_CLKCFG_CPU_FFRAC_MASK;
+	div = (reg >> CPU_SYS_CLKCFG_CPU_FDIV_SHIFT) &
+	      CPU_SYS_CLKCFG_CPU_FDIV_MASK;
+
+	return mt7620_calc_rate(pll_rate, mul, div);
+}
+
+static const u32 mt7620_ocp_dividers[16] __initconst = {
+	[CPU_SYS_CLKCFG_OCP_RATIO_2] = 2,
+	[CPU_SYS_CLKCFG_OCP_RATIO_3] = 3,
+	[CPU_SYS_CLKCFG_OCP_RATIO_4] = 4,
+	[CPU_SYS_CLKCFG_OCP_RATIO_5] = 5,
+	[CPU_SYS_CLKCFG_OCP_RATIO_10] = 10,
+};
+
+static __init unsigned long
+mt7620_get_dram_rate(unsigned long pll_rate)
+{
+	if (dram_type == SYSCFG0_DRAM_TYPE_SDRAM)
+		return pll_rate / 4;
+
+	return pll_rate / 3;
+}
+
+static __init unsigned long
+mt7620_get_sys_rate(unsigned long cpu_rate)
+{
+	u32 reg;
+	u32 ocp_ratio;
+	u32 div;
+
+	reg = rt_sysc_r32(SYSC_REG_CPU_SYS_CLKCFG);
+
+	ocp_ratio = (reg >> CPU_SYS_CLKCFG_OCP_RATIO_SHIFT) &
+		    CPU_SYS_CLKCFG_OCP_RATIO_MASK;
+
+	if (WARN_ON(ocp_ratio >= ARRAY_SIZE(mt7620_ocp_dividers)))
+		return cpu_rate;
+
+	div = mt7620_ocp_dividers[ocp_ratio];
+	if (WARN(!div, "invalid divider for OCP ratio %u", ocp_ratio))
+		return cpu_rate;
+
+	return cpu_rate / div;
+}
+
 void __init ralink_clk_init(void)
 {
-	unsigned long cpu_rate, sys_rate;
-	u32 c0 = rt_sysc_r32(SYSC_REG_CPLL_CONFIG0);
-	u32 c1 = rt_sysc_r32(SYSC_REG_CPLL_CONFIG1);
-	u32 swconfig = (c0 >> CPLL_SW_CONFIG_SHIFT) & CPLL_SW_CONFIG_MASK;
-	u32 cpu_clk = (c1 >> CPLL_CPU_CLK_SHIFT) & CPLL_CPU_CLK_MASK;
+	unsigned long xtal_rate;
+	unsigned long cpu_pll_rate;
+	unsigned long pll_rate;
+	unsigned long cpu_rate;
+	unsigned long sys_rate;
+	unsigned long dram_rate;
+	unsigned long periph_rate;
 
-	if (cpu_clk) {
-		cpu_rate = 480000000;
-	} else if (!swconfig) {
-		cpu_rate = 600000000;
-	} else {
-		u32 m = (c0 >> CPLL_MULT_RATIO_SHIFT) & CPLL_MULT_RATIO;
-		u32 d = (c0 >> CPLL_DIV_RATIO_SHIFT) & CPLL_DIV_RATIO;
+	xtal_rate = mt7620_get_xtal_rate();
 
-		cpu_rate = ((40 * (m + 24)) / mt7620_clk_divider[d]) * 1000000;
-	}
+	cpu_pll_rate = mt7620_get_cpu_pll_rate(xtal_rate);
+	pll_rate = mt7620_get_pll_rate(xtal_rate, cpu_pll_rate);
 
-	if (dram_type == SYSCFG0_DRAM_TYPE_SDRAM)
-		sys_rate = cpu_rate / 4;
-	else
-		sys_rate = cpu_rate / 3;
+	cpu_rate = mt7620_get_cpu_rate(pll_rate);
+	dram_rate = mt7620_get_dram_rate(pll_rate);
+	sys_rate = mt7620_get_sys_rate(cpu_rate);
+	periph_rate = mt7620_get_periph_rate(xtal_rate);
+
+#define RFMT(label)	label ":%lu.%03luMHz "
+#define RINT(x)		((x) / 1000000)
+#define RFRAC(x)	(((x) / 1000) % 1000)
+
+	pr_debug(RFMT("XTAL") RFMT("CPU_PLL") RFMT("PLL"),
+		 RINT(xtal_rate), RFRAC(xtal_rate),
+		 RINT(cpu_pll_rate), RFRAC(cpu_pll_rate),
+		 RINT(pll_rate), RFRAC(pll_rate));
+
+	pr_debug(RFMT("CPU") RFMT("DRAM") RFMT("SYS") RFMT("PERIPH"),
+		 RINT(cpu_rate), RFRAC(cpu_rate),
+		 RINT(dram_rate), RFRAC(dram_rate),
+		 RINT(sys_rate), RFRAC(sys_rate),
+		 RINT(periph_rate), RFRAC(periph_rate));
+
+#undef RFRAC
+#undef RINT
+#undef RFMT
 
 	ralink_clk_add("cpu", cpu_rate);
-	ralink_clk_add("10000100.timer", 40000000);
-	ralink_clk_add("10000500.uart", 40000000);
-	ralink_clk_add("10000c00.uartlite", 40000000);
+	ralink_clk_add("10000100.timer", periph_rate);
+	ralink_clk_add("10000500.uart", periph_rate);
+	ralink_clk_add("10000c00.uartlite", periph_rate);
 }
 
 void __init ralink_of_remap(void)