clk: axi-clkgen: Correctly handle nocount bit in recalc_rate()

If the nocount bit is set the divider is bypassed and the settings for the
divider count should be ignored and a divider value of 1 should be assumed.
Handle this correctly in the driver recalc_rate() callback.

While the driver sets up the part so that the read back dividers values
yield the correct result the power-on reset settings of the part might not
reflect this and hence calling e.g. clk_get_rate() without prior calls to
clk_set_rate() will yield the wrong result.

Signed-off-by: Lars-Peter Clausen <[email protected]>
Signed-off-by: Stephen Boyd <[email protected]>

drivers/clk/clk-axi-clkgen.c

@@ -40,6 +40,10 @@
 #define MMCM_REG_FILTER1	0x4e
 #define MMCM_REG_FILTER2	0x4f
 
+#define MMCM_CLKOUT_NOCOUNT	BIT(6)
+
+#define MMCM_CLK_DIV_NOCOUNT	BIT(12)
+
 struct axi_clkgen {
 	void __iomem *base;
 	struct clk_hw clk_hw;
@@ -315,12 +319,27 @@ static unsigned long axi_clkgen_recalc_rate(struct clk_hw *clk_hw,
 	unsigned int reg;
 	unsigned long long tmp;
 
-	axi_clkgen_mmcm_read(axi_clkgen, MMCM_REG_CLKOUT0_1, &reg);
-	dout = (reg & 0x3f) + ((reg >> 6) & 0x3f);
+	axi_clkgen_mmcm_read(axi_clkgen, MMCM_REG_CLKOUT0_2, &reg);
+	if (reg & MMCM_CLKOUT_NOCOUNT) {
+		dout = 1;
+	} else {
+		axi_clkgen_mmcm_read(axi_clkgen, MMCM_REG_CLKOUT0_1, &reg);
+		dout = (reg & 0x3f) + ((reg >> 6) & 0x3f);
+	}
+
 	axi_clkgen_mmcm_read(axi_clkgen, MMCM_REG_CLK_DIV, &reg);
-	d = (reg & 0x3f) + ((reg >> 6) & 0x3f);
-	axi_clkgen_mmcm_read(axi_clkgen, MMCM_REG_CLK_FB1, &reg);
-	m = (reg & 0x3f) + ((reg >> 6) & 0x3f);
+	if (reg & MMCM_CLK_DIV_NOCOUNT)
+		d = 1;
+	else
+		d = (reg & 0x3f) + ((reg >> 6) & 0x3f);
+
+	axi_clkgen_mmcm_read(axi_clkgen, MMCM_REG_CLK_FB2, &reg);
+	if (reg & MMCM_CLKOUT_NOCOUNT) {
+		m = 1;
+	} else {
+		axi_clkgen_mmcm_read(axi_clkgen, MMCM_REG_CLK_FB1, &reg);
+		m = (reg & 0x3f) + ((reg >> 6) & 0x3f);
+	}
 
 	if (d == 0 || dout == 0)
 		return 0;