SPEAr: clk: Add Fractional Synthesizer clock

All SPEAr SoC's contain Fractional Synthesizers. Their Fout is derived from
following equations:

Fout = Fin / (2 * div) (division factor)
div is 17 bits:-
     0-13 (fractional part)
     14-16 (integer part)
     div is (16-14 bits).(13-0 bits) (in binary)

     Fout = Fin/(2 * div)
     Fout = ((Fin / 10000)/(2 * div)) * 10000
     Fout = (2^14 * (Fin / 10000)/(2^14 * (2 * div))) * 10000
     Fout = (((Fin / 10000) << 14)/(2 * (div << 14))) * 10000

div << 14 is simply 17 bit value written at register.

This patch adds in support for this type of clock.

Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
Reviewed-by: Mike Turquette <mturquette@linaro.org>

3 files changed, 182 insertions, 1 deletions

diff --git a/drivers/clk/spear/Makefile b/drivers/clk/spear/Makefile
index e36d8c665724..182703622195 100644
--- a/drivers/clk/spear/Makefile
+++ b/drivers/clk/spear/Makefile
@@ -2,4 +2,4 @@
 # SPEAr Clock specific Makefile
 #
 
-obj-y   += clk.o clk-aux-synth.o clk-vco-pll.o
+obj-y   += clk.o clk-aux-synth.o clk-frac-synth.o clk-vco-pll.o
diff --git a/drivers/clk/spear/clk-frac-synth.c b/drivers/clk/spear/clk-frac-synth.c
new file mode 100644
index 000000000000..4dbdb3fe18e0
--- /dev/null
+++ b/drivers/clk/spear/clk-frac-synth.c
@@ -0,0 +1,165 @@
+/*
+ * Copyright (C) 2012 ST Microelectronics
+ * Viresh Kumar <viresh.kumar@st.com>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ *
+ * Fractional Synthesizer clock implementation
+ */
+
+#define pr_fmt(fmt) "clk-frac-synth: " fmt
+
+#include <linux/clk-provider.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/err.h>
+#include "clk.h"
+
+#define DIV_FACTOR_MASK         0x1FFFF
+
+/*
+ * DOC: Fractional Synthesizer clock
+ *
+ * Fout from synthesizer can be given from below equation:
+ *
+ * Fout= Fin/2*div (division factor)
+ * div is 17 bits:-
+ *      0-13 (fractional part)
+ *      14-16 (integer part)
+ *      div is (16-14 bits).(13-0 bits) (in binary)
+ *
+ *      Fout = Fin/(2 * div)
+ *      Fout = ((Fin / 10000)/(2 * div)) * 10000
+ *      Fout = (2^14 * (Fin / 10000)/(2^14 * (2 * div))) * 10000
+ *      Fout = (((Fin / 10000) << 14)/(2 * (div << 14))) * 10000
+ *
+ * div << 14 simply 17 bit value written at register.
+ * Max error due to scaling down by 10000 is 10 KHz
+ */
+
+#define to_clk_frac(_hw) container_of(_hw, struct clk_frac, hw)
+
+static unsigned long frac_calc_rate(struct clk_hw *hw, unsigned long prate,
+                int index)
+{
+        struct clk_frac *frac = to_clk_frac(hw);
+        struct frac_rate_tbl *rtbl = frac->rtbl;
+
+        prate /= 10000;
+        prate <<= 14;
+        prate /= (2 * rtbl[index].div);
+        prate *= 10000;
+
+        return prate;
+}
+
+static long clk_frac_round_rate(struct clk_hw *hw, unsigned long drate,
+                unsigned long *prate)
+{
+        struct clk_frac *frac = to_clk_frac(hw);
+        int unused;
+
+        return clk_round_rate_index(hw, drate, *prate, frac_calc_rate,
+                        frac->rtbl_cnt, &unused);
+}
+
+static unsigned long clk_frac_recalc_rate(struct clk_hw *hw,
+                unsigned long parent_rate)
+{
+        struct clk_frac *frac = to_clk_frac(hw);
+        unsigned long flags = 0;
+        unsigned int div = 1, val;
+
+        if (frac->lock)
+                spin_lock_irqsave(frac->lock, flags);
+
+        val = readl_relaxed(frac->reg);
+
+        if (frac->lock)
+                spin_unlock_irqrestore(frac->lock, flags);
+
+        div = val & DIV_FACTOR_MASK;
+
+        if (!div)
+                return 0;
+
+        parent_rate = parent_rate / 10000;
+
+        parent_rate = (parent_rate << 14) / (2 * div);
+        return parent_rate * 10000;
+}
+
+/* Configures new clock rate of frac */
+static int clk_frac_set_rate(struct clk_hw *hw, unsigned long drate,
+                                unsigned long prate)
+{
+        struct clk_frac *frac = to_clk_frac(hw);
+        struct frac_rate_tbl *rtbl = frac->rtbl;
+        unsigned long flags = 0, val;
+        int i;
+
+        clk_round_rate_index(hw, drate, prate, frac_calc_rate, frac->rtbl_cnt,
+                        &i);
+
+        if (frac->lock)
+                spin_lock_irqsave(frac->lock, flags);
+
+        val = readl_relaxed(frac->reg) & ~DIV_FACTOR_MASK;
+        val |= rtbl[i].div & DIV_FACTOR_MASK;
+        writel_relaxed(val, frac->reg);
+
+        if (frac->lock)
+                spin_unlock_irqrestore(frac->lock, flags);
+
+        return 0;
+}
+
+struct clk_ops clk_frac_ops = {
+        .recalc_rate = clk_frac_recalc_rate,
+        .round_rate = clk_frac_round_rate,
+        .set_rate = clk_frac_set_rate,
+};
+
+struct clk *clk_register_frac(const char *name, const char *parent_name,
+                unsigned long flags, void __iomem *reg,
+                struct frac_rate_tbl *rtbl, u8 rtbl_cnt, spinlock_t *lock)
+{
+        struct clk_init_data init;
+        struct clk_frac *frac;
+        struct clk *clk;
+
+        if (!name || !parent_name || !reg || !rtbl || !rtbl_cnt) {
+                pr_err("Invalid arguments passed");
+                return ERR_PTR(-EINVAL);
+        }
+
+        frac = kzalloc(sizeof(*frac), GFP_KERNEL);
+        if (!frac) {
+                pr_err("could not allocate frac clk\n");
+                return ERR_PTR(-ENOMEM);
+        }
+
+        /* struct clk_frac assignments */
+        frac->reg = reg;
+        frac->rtbl = rtbl;
+        frac->rtbl_cnt = rtbl_cnt;
+        frac->lock = lock;
+        frac->hw.init = &init;
+
+        init.name = name;
+        init.ops = &clk_frac_ops;
+        init.flags = flags;
+        init.parent_names = &parent_name;
+        init.num_parents = 1;
+
+        clk = clk_register(NULL, &frac->hw);
+        if (!IS_ERR_OR_NULL(clk))
+                return clk;
+
+        pr_err("clk register failed\n");
+        kfree(frac);
+
+        return NULL;
+}
diff --git a/drivers/clk/spear/clk.h b/drivers/clk/spear/clk.h
index c2290800503a..ac9030bbd6ce 100644
--- a/drivers/clk/spear/clk.h
+++ b/drivers/clk/spear/clk.h
@@ -55,6 +55,19 @@ struct clk_aux {
         spinlock_t              *lock;
 };
 
+/* Fractional Synth clk */
+struct frac_rate_tbl {
+        u32 div;
+};
+
+struct clk_frac {
+        struct                  clk_hw hw;
+        void __iomem            *reg;
+        struct frac_rate_tbl    *rtbl;
+        u8                      rtbl_cnt;
+        spinlock_t              *lock;
+};
+
 /* VCO-PLL clk */
 struct pll_rate_tbl {
         u8 mode;
@@ -87,6 +100,9 @@ struct clk *clk_register_aux(const char *aux_name, const char *gate_name,
                 const char *parent_name, unsigned long flags, void __iomem *reg,
                 struct aux_clk_masks *masks, struct aux_rate_tbl *rtbl,
                 u8 rtbl_cnt, spinlock_t *lock, struct clk **gate_clk);
+struct clk *clk_register_frac(const char *name, const char *parent_name,
+                unsigned long flags, void __iomem *reg,
+                struct frac_rate_tbl *rtbl, u8 rtbl_cnt, spinlock_t *lock);
 struct clk *clk_register_vco_pll(const char *vco_name, const char *pll_name,
                 const char *vco_gate_name, const char *parent_name,
                 unsigned long flags, void __iomem *mode_reg, void __iomem