[ARM] MXC: Use a single function for decoding a PLL

We had 3 versions of this function in clock support for MX1/2/3
Use a single one instead. I picked the one from the MX3 as it seems
to calculate more accurate as the other ones. Also, on MX27 and MX31 mfn
can be negative, this hasn't been handled correctly on MX27 since now.

This patch has been tested on MX27 and MX31 and produces the same clock
frequencies for me.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

2 files changed, 46 insertions, 0 deletions

diff --git a/arch/arm/plat-mxc/clock.c b/arch/arm/plat-mxc/clock.c
index 0a38f0b396eb..888dd33abf76 100644
--- a/arch/arm/plat-mxc/clock.c
+++ b/arch/arm/plat-mxc/clock.c
@@ -328,3 +328,47 @@ static int __init mxc_setup_proc_entry(void)
 
 late_initcall(mxc_setup_proc_entry);
 #endif
+
+/*
+ * Get the resulting clock rate from a PLL register value and the input
+ * frequency. PLLs with this register layout can at least be found on
+ * MX1, MX21, MX27 and MX31
+ *
+ *                  mfi + mfn / (mfd + 1)
+ *  f = 2 * f_ref * --------------------
+ *                        pd + 1
+ */
+unsigned long mxc_decode_pll(unsigned int reg_val, u32 freq)
+{
+        long long ll;
+        int mfn_abs;
+        unsigned int mfi, mfn, mfd, pd;
+
+        mfi = (reg_val >> 10) & 0xf;
+        mfn = reg_val & 0x3ff;
+        mfd = (reg_val >> 16) & 0x3ff;
+        pd =  (reg_val >> 26) & 0xf;
+
+        mfi = mfi <= 5 ? 5 : mfi;
+
+        mfn_abs = mfn;
+
+#if !defined CONFIG_ARCH_MX1 && !defined CONFIG_ARCH_MX21
+        if (mfn >= 0x200) {
+                mfn |= 0xFFFFFE00;
+                mfn_abs = -mfn;
+        }
+#endif
+
+        freq *= 2;
+        freq /= pd + 1;
+
+        ll = (unsigned long long)freq * mfn_abs;
+
+        do_div(ll, mfd + 1);
+        if (mfn < 0)
+                ll = -ll;
+        ll = (freq * mfi) + ll;
+
+        return ll;
+}
diff --git a/arch/arm/plat-mxc/include/mach/clock.h b/arch/arm/plat-mxc/include/mach/clock.h
index d21f78e78819..b830655514eb 100644
--- a/arch/arm/plat-mxc/include/mach/clock.h
+++ b/arch/arm/plat-mxc/include/mach/clock.h
@@ -63,5 +63,7 @@ struct clk {
 int clk_register(struct clk *clk);
 void clk_unregister(struct clk *clk);
 
+unsigned long mxc_decode_pll(unsigned int pll, u32 f_ref);
+
 #endif /* __ASSEMBLY__ */
 #endif /* __ASM_ARCH_MXC_CLOCK_H__ */