build/patch/kernel/odroidc2-next/0070-clk-meson-add-audio-clock-divider-support.patch

From 293cec787c3f707d468e62a09d3d5a461717a3a8 Mon Sep 17 00:00:00 2001
From: Jerome Brunet <jbrunet@baylibre.com>
Date: Tue, 14 Feb 2017 00:13:55 +0100
Subject: [PATCH 70/93] clk: meson: add audio clock divider support

The audio divider needs a specific clock divider driver.
With am mpll parent clock, which is able to provide fairly precise rate,
the generic divider tends to select low value of the divider. In such case
the quality of the clock is very poor. For the same final rate, maximizing
the audio clock divider value and selecting the corresponding mpll rate
gives better results. This is what this driver aims to acheive. So far, so
good.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
---
 drivers/clk/meson/Makefile            |   2 +-
 drivers/clk/meson/clk-audio-divider.c | 188 ++++++++++++++++++++++++++++++++++
 drivers/clk/meson/clkc.h              |  10 ++
 3 files changed, 199 insertions(+), 1 deletion(-)
 create mode 100644 drivers/clk/meson/clk-audio-divider.c

diff --git a/drivers/clk/meson/Makefile b/drivers/clk/meson/Makefile
index 3495834..83b6d9d 100644
--- a/drivers/clk/meson/Makefile
+++ b/drivers/clk/meson/Makefile
@@ -2,6 +2,6 @@
 # Makefile for Meson specific clk
 #
 
-obj-$(CONFIG_COMMON_CLK_AMLOGIC) += clk-pll.o clk-cpu.o clk-mpll.o
+obj-$(CONFIG_COMMON_CLK_AMLOGIC) += clk-pll.o clk-cpu.o clk-mpll.o clk-audio-divider.o
 obj-$(CONFIG_COMMON_CLK_MESON8B) += meson8b.o
 obj-$(CONFIG_COMMON_CLK_GXBB)	 += gxbb.o gxbb-aoclk.o
diff --git a/drivers/clk/meson/clk-audio-divider.c b/drivers/clk/meson/clk-audio-divider.c
new file mode 100644
index 0000000..2263214
--- /dev/null
+++ b/drivers/clk/meson/clk-audio-divider.c
@@ -0,0 +1,188 @@
+/*
+ * This file is provided under a dual BSD/GPLv2 license.  When using or
+ * redistributing this file, you may do so under either license.
+ *
+ * GPL LICENSE SUMMARY
+ *
+ * Copyright (c) 2017 AmLogic, Inc.
+ * Author: Jerome Brunet <jbrunet@baylibre.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
+ * The full GNU General Public License is included in this distribution
+ * in the file called COPYING
+ *
+ * BSD LICENSE
+ *
+ * Copyright (c) 2017 AmLogic, Inc.
+ * Author: Jerome Brunet <jbrunet@baylibre.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *   * Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *   * Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in
+ *     the documentation and/or other materials provided with the
+ *     distribution.
+ *   * Neither the name of Baylibre nor the names of its
+ *     contributors may be used to endorse or promote products derived
+ *     from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/*
+ * Audio clock divider: The algorythm of clk-divider used with a very precise
+ * source clock such as the mpll tends to select low divider factor. This gives
+ * very poor results with this particular divider especially with high
+ * frequencies ( > 100 MHz)
+ *
+ * This driver try to select the maximum possible divider with the rate the mpll
+ * can provide.
+ */
+
+#include <linux/clk-provider.h>
+#include "clkc.h"
+
+#define to_meson_clk_audio_divider(_hw) container_of(_hw, \
+				struct meson_clk_audio_divider, hw)
+
+static int _div_round(unsigned long parent_rate, unsigned long rate,
+		      unsigned long flags)
+{
+	if (flags & CLK_DIVIDER_ROUND_CLOSEST)
+		return DIV_ROUND_CLOSEST_ULL((u64)parent_rate, rate);
+
+	return DIV_ROUND_UP_ULL((u64)parent_rate, rate);
+}
+
+static int _get_val(unsigned long parent_rate, unsigned long rate)
+{
+	return DIV_ROUND_UP_ULL((u64)parent_rate, rate) - 1;
+}
+
+static int _valid_divider(struct clk_hw *hw, int divider)
+{
+	struct meson_clk_audio_divider *adiv =
+		to_meson_clk_audio_divider(hw);
+	int max_divider;
+	u8 width;
+
+	width = adiv->div.width;
+	max_divider = 1 << width;
+
+	if (divider < 1)
+		return 1;
+	else if (divider > max_divider)
+		return max_divider;
+
+	return divider;
+}
+
+static unsigned long audio_divider_recalc_rate(struct clk_hw *hw,
+					       unsigned long parent_rate)
+{
+	struct meson_clk_audio_divider *adiv =
+		to_meson_clk_audio_divider(hw);
+	struct parm *p;
+	unsigned long reg, divider;
+
+	p = &adiv->div;
+	reg = readl(adiv->base + p->reg_off);
+	divider = PARM_GET(p->width, p->shift, reg) + 1;
+
+	return DIV_ROUND_UP_ULL((u64)parent_rate, divider);
+}
+
+static long audio_divider_round_rate(struct clk_hw *hw,
+				     unsigned long rate,
+				     unsigned long *parent_rate)
+{
+	struct meson_clk_audio_divider *adiv =
+		to_meson_clk_audio_divider(hw);
+	unsigned long max_prate;
+	int divider;
+
+	if (!(clk_hw_get_flags(hw) & CLK_SET_RATE_PARENT)) {
+		divider = _div_round(*parent_rate, rate, adiv->flags);
+		divider = _valid_divider(hw, divider);
+		return DIV_ROUND_UP_ULL((u64)*parent_rate, divider);
+	}
+
+	/* Get the maximum parent rate */
+	max_prate = clk_hw_round_rate(clk_hw_get_parent(hw), ULONG_MAX);
+
+	/* Get the corresponding rounded down divider */
+	divider = max_prate / rate;
+	divider = _valid_divider(hw, divider);
+
+	/* Get actual rate of the parent */
+	*parent_rate = clk_hw_round_rate(clk_hw_get_parent(hw),
+					 divider * rate);
+
+	return DIV_ROUND_UP_ULL((u64)*parent_rate, divider);
+}
+
+static int audio_divider_set_rate(struct clk_hw *hw,
+				  unsigned long rate,
+				  unsigned long parent_rate)
+{
+	struct meson_clk_audio_divider *adiv =
+		to_meson_clk_audio_divider(hw);
+	struct parm *p;
+	unsigned long reg, flags = 0;
+	int val;
+
+	val = _get_val(parent_rate, rate);
+
+	if (adiv->lock)
+		spin_lock_irqsave(adiv->lock, flags);
+	else
+		__acquire(adiv->lock);
+
+	p = &adiv->div;
+	reg = readl(adiv->base + p->reg_off);
+	reg = PARM_SET(p->width, p->shift, reg, val);
+	writel(reg, adiv->base + p->reg_off);
+
+	if (adiv->lock)
+		spin_unlock_irqrestore(adiv->lock, flags);
+	else
+		__release(adiv->lock);
+
+	return 0;
+}
+
+const struct clk_ops meson_clk_audio_divider_ro_ops = {
+	.recalc_rate	= audio_divider_recalc_rate,
+	.round_rate	= audio_divider_round_rate,
+};
+
+const struct clk_ops meson_clk_audio_divider_ops = {
+	.recalc_rate	= audio_divider_recalc_rate,
+	.round_rate	= audio_divider_round_rate,
+	.set_rate	= audio_divider_set_rate,
+};
diff --git a/drivers/clk/meson/clkc.h b/drivers/clk/meson/clkc.h
index ae38d69..3d4a5bc 100644
--- a/drivers/clk/meson/clkc.h
+++ b/drivers/clk/meson/clkc.h
@@ -101,6 +101,14 @@ struct meson_clk_mpll {
 	spinlock_t *lock;
 };
 
+struct meson_clk_audio_divider {
+	struct clk_hw hw;
+	void __iomem *base;
+	struct parm div;
+	u8 flags;
+	spinlock_t *lock;
+};
+
 #define MESON_GATE(_name, _reg, _bit)					\
 struct clk_gate _name = { 						\
 	.reg = (void __iomem *) _reg, 					\
@@ -121,5 +129,7 @@ struct clk_gate _name = { 						\
 extern const struct clk_ops meson_clk_cpu_ops;
 extern const struct clk_ops meson_clk_mpll_ro_ops;
 extern const struct clk_ops meson_clk_mpll_ops;
+extern const struct clk_ops meson_clk_audio_divider_ro_ops;
+extern const struct clk_ops meson_clk_audio_divider_ops;
 
 #endif /* __CLKC_H */
-- 
1.9.1