SPEAr: clk: Add General Purpose Timer Synthesizer clock

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

Fout= Fin/((2 ^ (N+1)) * (M+1))

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, 172 insertions, 1 deletions

diff --git a/drivers/clk/spear/Makefile b/drivers/clk/spear/Makefile
index 182703622195..9e64824a8000 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-frac-synth.o clk-vco-pll.o
+obj-y   += clk.o clk-aux-synth.o clk-frac-synth.o clk-gpt-synth.o clk-vco-pll.o
diff --git a/drivers/clk/spear/clk-gpt-synth.c b/drivers/clk/spear/clk-gpt-synth.c
new file mode 100644
index 000000000000..b471c9762a97
--- /dev/null
+++ b/drivers/clk/spear/clk-gpt-synth.c
@@ -0,0 +1,154 @@
+/*
+ * 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.
+ *
+ * General Purpose Timer Synthesizer clock implementation
+ */
+
+#define pr_fmt(fmt) "clk-gpt-synth: " fmt
+
+#include <linux/clk-provider.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/err.h>
+#include "clk.h"
+
+#define GPT_MSCALE_MASK         0xFFF
+#define GPT_NSCALE_SHIFT        12
+#define GPT_NSCALE_MASK         0xF
+
+/*
+ * DOC: General Purpose Timer Synthesizer clock
+ *
+ * Calculates gpt synth clk rate for different values of mscale and nscale
+ *
+ * Fout= Fin/((2 ^ (N+1)) * (M+1))
+ */
+
+#define to_clk_gpt(_hw) container_of(_hw, struct clk_gpt, hw)
+
+static unsigned long gpt_calc_rate(struct clk_hw *hw, unsigned long prate,
+                int index)
+{
+        struct clk_gpt *gpt = to_clk_gpt(hw);
+        struct gpt_rate_tbl *rtbl = gpt->rtbl;
+
+        prate /= ((1 << (rtbl[index].nscale + 1)) * (rtbl[index].mscale + 1));
+
+        return prate;
+}
+
+static long clk_gpt_round_rate(struct clk_hw *hw, unsigned long drate,
+                unsigned long *prate)
+{
+        struct clk_gpt *gpt = to_clk_gpt(hw);
+        int unused;
+
+        return clk_round_rate_index(hw, drate, *prate, gpt_calc_rate,
+                        gpt->rtbl_cnt, &unused);
+}
+
+static unsigned long clk_gpt_recalc_rate(struct clk_hw *hw,
+                unsigned long parent_rate)
+{
+        struct clk_gpt *gpt = to_clk_gpt(hw);
+        unsigned long flags = 0;
+        unsigned int div = 1, val;
+
+        if (gpt->lock)
+                spin_lock_irqsave(gpt->lock, flags);
+
+        val = readl_relaxed(gpt->reg);
+
+        if (gpt->lock)
+                spin_unlock_irqrestore(gpt->lock, flags);
+
+        div += val & GPT_MSCALE_MASK;
+        div *= 1 << (((val >> GPT_NSCALE_SHIFT) & GPT_NSCALE_MASK) + 1);
+
+        if (!div)
+                return 0;
+
+        return parent_rate / div;
+}
+
+/* Configures new clock rate of gpt */
+static int clk_gpt_set_rate(struct clk_hw *hw, unsigned long drate,
+                                unsigned long prate)
+{
+        struct clk_gpt *gpt = to_clk_gpt(hw);
+        struct gpt_rate_tbl *rtbl = gpt->rtbl;
+        unsigned long flags = 0, val;
+        int i;
+
+        clk_round_rate_index(hw, drate, prate, gpt_calc_rate, gpt->rtbl_cnt,
+                        &i);
+
+        if (gpt->lock)
+                spin_lock_irqsave(gpt->lock, flags);
+
+        val = readl(gpt->reg) & ~GPT_MSCALE_MASK;
+        val &= ~(GPT_NSCALE_MASK << GPT_NSCALE_SHIFT);
+
+        val |= rtbl[i].mscale & GPT_MSCALE_MASK;
+        val |= (rtbl[i].nscale & GPT_NSCALE_MASK) << GPT_NSCALE_SHIFT;
+
+        writel_relaxed(val, gpt->reg);
+
+        if (gpt->lock)
+                spin_unlock_irqrestore(gpt->lock, flags);
+
+        return 0;
+}
+
+static struct clk_ops clk_gpt_ops = {
+        .recalc_rate = clk_gpt_recalc_rate,
+        .round_rate = clk_gpt_round_rate,
+        .set_rate = clk_gpt_set_rate,
+};
+
+struct clk *clk_register_gpt(const char *name, const char *parent_name, unsigned
+                long flags, void __iomem *reg, struct gpt_rate_tbl *rtbl, u8
+                rtbl_cnt, spinlock_t *lock)
+{
+        struct clk_init_data init;
+        struct clk_gpt *gpt;
+        struct clk *clk;
+
+        if (!name || !parent_name || !reg || !rtbl || !rtbl_cnt) {
+                pr_err("Invalid arguments passed");
+                return ERR_PTR(-EINVAL);
+        }
+
+        gpt = kzalloc(sizeof(*gpt), GFP_KERNEL);
+        if (!gpt) {
+                pr_err("could not allocate gpt clk\n");
+                return ERR_PTR(-ENOMEM);
+        }
+
+        /* struct clk_gpt assignments */
+        gpt->reg = reg;
+        gpt->rtbl = rtbl;
+        gpt->rtbl_cnt = rtbl_cnt;
+        gpt->lock = lock;
+        gpt->hw.init = &init;
+
+        init.name = name;
+        init.ops = &clk_gpt_ops;
+        init.flags = flags;
+        init.parent_names = &parent_name;
+        init.num_parents = 1;
+
+        clk = clk_register(NULL, &gpt->hw);
+        if (!IS_ERR_OR_NULL(clk))
+                return clk;
+
+        pr_err("clk register failed\n");
+        kfree(gpt);
+
+        return NULL;
+}
diff --git a/drivers/clk/spear/clk.h b/drivers/clk/spear/clk.h
index ac9030bbd6ce..3321c46a071c 100644
--- a/drivers/clk/spear/clk.h
+++ b/drivers/clk/spear/clk.h
@@ -68,6 +68,20 @@ struct clk_frac {
         spinlock_t              *lock;
 };
 
+/* GPT clk */
+struct gpt_rate_tbl {
+        u16 mscale;
+        u16 nscale;
+};
+
+struct clk_gpt {
+        struct                  clk_hw hw;
+        void __iomem            *reg;
+        struct gpt_rate_tbl     *rtbl;
+        u8                      rtbl_cnt;
+        spinlock_t              *lock;
+};
+
 /* VCO-PLL clk */
 struct pll_rate_tbl {
         u8 mode;
@@ -103,6 +117,9 @@ struct clk *clk_register_aux(const char *aux_name, const char *gate_name,
 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_gpt(const char *name, const char *parent_name, unsigned
+                long flags, void __iomem *reg, struct gpt_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