diff mbox series

[v2,5/6] clk: at91: clk-master: update for dvfs

Message ID 20210401122726.28528-6-claudiu.beznea@microchip.com (mailing list archive)
State Superseded, archived
Headers show
Series clk: at91: updates for power management and dvfs | expand

Commit Message

Claudiu Beznea April 1, 2021, 12:27 p.m. UTC 
SAMA7G5 supports CPU DVFS. The hardware block diagram for the clock
system generating CPU clock is as follows:

                               +--------+
                           +-->|divider1|--> CPU clock
                           |   +--------+
+--------+   +----------+  |   +--------+
|CPU PLL |-->|prescaller|--+-->|divider0|--> MCK0 clock
+--------+   +----------+      +--------+

The divider1 is not implemented in software since the supported CPU
frequencies could be directly retrieved from CPU PLL + prescaller.
Every time the CPU clock needs to be changed the MCK0 should also be
changed to avoid its over/under clocking and also to preserve its
initial value (200MHz). MCK0 feeds IPs that are glitch free aware.

The initial approach for implementing DVFS was to implement MCK0 and
CPU clocks as 2 different Linux clocks, to pass these two clocks to CPUFreq
driver and in CPUFreq driver to run clk_set_rate() on CPU and MCK clocks
accordingly. E.g. if 1GHz speed was requested by CPUFreq subsystem the
following were executed in CPUFreq driver:

/* ... */
clk_set_rate(mck0, intermediary_freq_to_avoid_over_under_clocking);
clk_set_rate(cpu, 1000000000);
clk_set_rate(mck0, initial_freq);
/ ... */

However, it has been proposed in [1] to use the generic cpufreq-dt driver
and to overload the necessary clocks operations in the proper clock
driver.

To address this proposal the master clock prescaller registers a clock
notifier that will update properly the master clock divider on
PRE_RATE_CHANGE and POST_RATE_CHANGE events to avoid master clock
divider over/under clocking and also to preserve its initial value
(200MHz).

[1] https://lore.kernel.org/lkml/1609842147-8161-1-git-send-email-claudiu.beznea@microchip.com/

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
---
 drivers/clk/at91/at91rm9200.c  |   2 +-
 drivers/clk/at91/at91sam9260.c |   2 +-
 drivers/clk/at91/at91sam9g45.c |   2 +-
 drivers/clk/at91/at91sam9n12.c |   2 +-
 drivers/clk/at91/at91sam9rl.c  |   2 +-
 drivers/clk/at91/at91sam9x5.c  |   2 +-
 drivers/clk/at91/clk-master.c  | 187 ++++++++++++++++++++-------------
 drivers/clk/at91/dt-compat.c   |   2 +-
 drivers/clk/at91/pmc.h         |   3 +-
 drivers/clk/at91/sam9x60.c     |   2 +-
 drivers/clk/at91/sama5d2.c     |   2 +-
 drivers/clk/at91/sama5d3.c     |   2 +-
 drivers/clk/at91/sama5d4.c     |   2 +-
 drivers/clk/at91/sama7g5.c     |   2 +-
 14 files changed, 130 insertions(+), 84 deletions(-)
diff mbox series

Patch

diff --git a/drivers/clk/at91/at91rm9200.c b/drivers/clk/at91/at91rm9200.c
index 428a6f4b9ebc..f8df6064d55d 100644
--- a/drivers/clk/at91/at91rm9200.c
+++ b/drivers/clk/at91/at91rm9200.c
@@ -144,7 +144,7 @@  static void __init at91rm9200_pmc_setup(struct device_node *np)
 					   &at91rm9200_master_layout,
 					   &rm9200_mck_characteristics,
 					   &rm9200_mck_lock, CLK_SET_RATE_GATE,
-					   INT_MIN);
+					   INT_MIN, 0);
 	if (IS_ERR(hw))
 		goto err_free;
 
diff --git a/drivers/clk/at91/at91sam9260.c b/drivers/clk/at91/at91sam9260.c
index b29843bea278..8db7bf141b45 100644
--- a/drivers/clk/at91/at91sam9260.c
+++ b/drivers/clk/at91/at91sam9260.c
@@ -420,7 +420,7 @@  static void __init at91sam926x_pmc_setup(struct device_node *np,
 					   &at91rm9200_master_layout,
 					   data->mck_characteristics,
 					   &at91sam9260_mck_lock,
-					   CLK_SET_RATE_GATE, INT_MIN);
+					   CLK_SET_RATE_GATE, INT_MIN, 0);
 	if (IS_ERR(hw))
 		goto err_free;
 
diff --git a/drivers/clk/at91/at91sam9g45.c b/drivers/clk/at91/at91sam9g45.c
index 15da0dfe3ef2..c139169b2d40 100644
--- a/drivers/clk/at91/at91sam9g45.c
+++ b/drivers/clk/at91/at91sam9g45.c
@@ -155,7 +155,7 @@  static void __init at91sam9g45_pmc_setup(struct device_node *np)
 					   &at91rm9200_master_layout,
 					   &mck_characteristics,
 					   &at91sam9g45_mck_lock,
-					   CLK_SET_RATE_GATE, INT_MIN);
+					   CLK_SET_RATE_GATE, INT_MIN, 0);
 	if (IS_ERR(hw))
 		goto err_free;
 
diff --git a/drivers/clk/at91/at91sam9n12.c b/drivers/clk/at91/at91sam9n12.c
index 7fe435f4b46b..a4e46c4026d0 100644
--- a/drivers/clk/at91/at91sam9n12.c
+++ b/drivers/clk/at91/at91sam9n12.c
@@ -182,7 +182,7 @@  static void __init at91sam9n12_pmc_setup(struct device_node *np)
 					   &at91sam9x5_master_layout,
 					   &mck_characteristics,
 					   &at91sam9n12_mck_lock,
-					   CLK_SET_RATE_GATE, INT_MIN);
+					   CLK_SET_RATE_GATE, INT_MIN, 0);
 	if (IS_ERR(hw))
 		goto err_free;
 
diff --git a/drivers/clk/at91/at91sam9rl.c b/drivers/clk/at91/at91sam9rl.c
index ecbabf5162bd..5f2b5dda24d0 100644
--- a/drivers/clk/at91/at91sam9rl.c
+++ b/drivers/clk/at91/at91sam9rl.c
@@ -124,7 +124,7 @@  static void __init at91sam9rl_pmc_setup(struct device_node *np)
 					   &at91rm9200_master_layout,
 					   &sam9rl_mck_characteristics,
 					   &sam9rl_mck_lock, CLK_SET_RATE_GATE,
-					   INT_MIN);
+					   INT_MIN, 0);
 	if (IS_ERR(hw))
 		goto err_free;
 
diff --git a/drivers/clk/at91/at91sam9x5.c b/drivers/clk/at91/at91sam9x5.c
index 5cce48c64ea2..53a524ff2818 100644
--- a/drivers/clk/at91/at91sam9x5.c
+++ b/drivers/clk/at91/at91sam9x5.c
@@ -202,7 +202,7 @@  static void __init at91sam9x5_pmc_setup(struct device_node *np,
 					   parent_names,
 					   &at91sam9x5_master_layout,
 					   &mck_characteristics, &mck_lock,
-					   CLK_SET_RATE_GATE, INT_MIN);
+					   CLK_SET_RATE_GATE, INT_MIN, 0);
 	if (IS_ERR(hw))
 		goto err_free;
 
diff --git a/drivers/clk/at91/clk-master.c b/drivers/clk/at91/clk-master.c
index 736406528824..1b2962289629 100644
--- a/drivers/clk/at91/clk-master.c
+++ b/drivers/clk/at91/clk-master.c
@@ -5,6 +5,7 @@ 
 
 #include <linux/clk-provider.h>
 #include <linux/clkdev.h>
+#include <linux/clk.h>
 #include <linux/clk/at91_pmc.h>
 #include <linux/of.h>
 #include <linux/mfd/syscon.h>
@@ -38,6 +39,9 @@  struct clk_master {
 	u8 div;
 };
 
+/* MCK div reference to be used by notifier. */
+static struct clk_master *master_div;
+
 static inline bool clk_master_ready(struct clk_master *master)
 {
 	unsigned int bit = master->id ? AT91_PMC_MCKXRDY : AT91_PMC_MCKRDY;
@@ -153,107 +157,127 @@  static const struct clk_ops master_div_ops = {
 	.restore_context = clk_master_div_restore_context,
 };
 
-static int clk_master_div_set_rate(struct clk_hw *hw, unsigned long rate,
-				   unsigned long parent_rate)
+static int clk_master_div_set(struct clk_master *master,
+			      unsigned long parent_rate, int div)
 {
-	struct clk_master *master = to_clk_master(hw);
 	const struct clk_master_characteristics *characteristics =
 						master->characteristics;
-	unsigned long flags;
-	unsigned int mckr, tmp;
-	int div, i;
+	unsigned long rate = parent_rate;
+	unsigned int max_div = 0, div_index = 0, max_div_index = 0;
+	unsigned int i, mckr, tmp;
 	int ret;
 
-	div = DIV_ROUND_CLOSEST(parent_rate, rate);
-	if (div > ARRAY_SIZE(characteristics->divisors))
-		return -EINVAL;
-
 	for (i = 0; i < ARRAY_SIZE(characteristics->divisors); i++) {
 		if (!characteristics->divisors[i])
 			break;
 
-		if (div == characteristics->divisors[i]) {
-			div = i;
-			break;
+		if (div == characteristics->divisors[i])
+			div_index = i;
+
+		if (max_div < characteristics->divisors[i]) {
+			max_div = characteristics->divisors[i];
+			max_div_index = i;
 		}
 	}
 
-	if (i == ARRAY_SIZE(characteristics->divisors))
-		return -EINVAL;
+	if (div > max_div)
+		div_index = max_div_index;
 
-	spin_lock_irqsave(master->lock, flags);
 	ret = regmap_read(master->regmap, master->layout->offset, &mckr);
 	if (ret)
-		goto unlock;
+		return ret;
 
 	tmp = mckr & master->layout->mask;
 	tmp = (tmp >> MASTER_DIV_SHIFT) & MASTER_DIV_MASK;
-	if (tmp == div)
-		goto unlock;
+	if (tmp == div_index)
+		return 0;
+
+	rate /= characteristics->divisors[div_index];
+	if (rate < characteristics->output.min)
+		pr_warn("master clk div is underclocked");
+	else if (rate > characteristics->output.max)
+		pr_warn("master clk div is overclocked");
 
 	mckr &= ~(MASTER_DIV_MASK << MASTER_DIV_SHIFT);
-	mckr |= (div << MASTER_DIV_SHIFT);
+	mckr |= (div_index << MASTER_DIV_SHIFT);
 	ret = regmap_write(master->regmap, master->layout->offset, mckr);
 	if (ret)
-		goto unlock;
+		return ret;
 
 	while (!clk_master_ready(master))
 		cpu_relax();
-unlock:
-	spin_unlock_irqrestore(master->lock, flags);
+
+	master->div = characteristics->divisors[div_index];
 
 	return 0;
 }
 
-static int clk_master_div_determine_rate(struct clk_hw *hw,
-					 struct clk_rate_request *req)
+static int at91_clk_master_div_notifier(struct notifier_block *notifier,
+					unsigned long code, void *data)
 {
-	struct clk_master *master = to_clk_master(hw);
 	const struct clk_master_characteristics *characteristics =
-						master->characteristics;
-	struct clk_hw *parent;
-	unsigned long parent_rate, tmp_rate, best_rate = 0;
-	int i, best_diff = INT_MIN, tmp_diff;
-
-	parent = clk_hw_get_parent(hw);
-	if (!parent)
-		return -EINVAL;
-
-	parent_rate = clk_hw_get_rate(parent);
-	if (!parent_rate)
-		return -EINVAL;
-
-	for (i = 0; i < ARRAY_SIZE(characteristics->divisors); i++) {
-		if (!characteristics->divisors[i])
-			break;
-
-		tmp_rate = DIV_ROUND_CLOSEST_ULL(parent_rate,
-						 characteristics->divisors[i]);
-		tmp_diff = abs(tmp_rate - req->rate);
+						master_div->characteristics;
+	struct clk_notifier_data *cnd = data;
+	unsigned long cur_rate, flags;
+	unsigned int mckr, cur_div, diff_div;
+	static unsigned int new_div;
+
+	/*
+	 * Need to increase/decrease div to avoid master div clock over/under
+	 * clocking
+	 */
+	spin_lock_irqsave(master_div->lock, flags);
+	switch (code) {
+	case PRE_RATE_CHANGE:
+		regmap_read(master_div->regmap, master_div->layout->offset,
+			    &mckr);
+		mckr &= master_div->layout->mask;
+		mckr = (mckr >> MASTER_DIV_SHIFT) & MASTER_DIV_MASK;
+
+		cur_div = characteristics->divisors[mckr];
+		cur_rate = DIV_ROUND_CLOSEST_ULL(cnd->old_rate, cur_div);
+		new_div = DIV_ROUND_CLOSEST(cnd->new_rate, cur_rate);
+		diff_div = abs(cur_div - new_div);
+
+		clk_master_div_set(master_div, cnd->old_rate,
+				   cur_div + diff_div);
+		break;
+
+	case POST_RATE_CHANGE:
+		clk_master_div_set(master_div, cnd->new_rate, new_div);
+		break;
+
+	default:
+		break;
+	}
+	spin_unlock_irqrestore(master_div->lock, flags);
 
-		if (!best_rate || best_diff > tmp_diff) {
-			best_diff = tmp_diff;
-			best_rate = tmp_rate;
-		}
+	return 0;
+}
 
-		if (!best_diff)
-			break;
-	}
+static struct notifier_block clk_master_notifier = {
+	.notifier_call = at91_clk_master_div_notifier,
+};
 
-	req->best_parent_rate = best_rate;
-	req->best_parent_hw = parent;
-	req->rate = best_rate;
+static unsigned long clk_master_div_recalc_rate_chg(struct clk_hw *hw,
+						    unsigned long parent_rate)
+{
+	struct clk_master *master = to_clk_master(hw);
 
-	return 0;
+	return DIV_ROUND_CLOSEST_ULL(parent_rate, master->div);
 }
 
 static void clk_master_div_restore_context_chg(struct clk_hw *hw)
 {
 	struct clk_master *master = to_clk_master(hw);
+	unsigned long flags;
 	int ret;
 
-	ret = clk_master_div_set_rate(hw, master->pms.rate,
-				      master->pms.parent_rate);
+	spin_lock_irqsave(master->lock, flags);
+	ret = clk_master_div_set(master, master->pms.parent_rate,
+				 DIV_ROUND_CLOSEST(master->pms.parent_rate,
+						   master->pms.rate));
+	spin_unlock_irqrestore(master->lock, flags);
 	if (ret)
 		pr_warn("Failed to restore MCK DIV clock\n");
 }
@@ -261,9 +285,7 @@  static void clk_master_div_restore_context_chg(struct clk_hw *hw)
 static const struct clk_ops master_div_ops_chg = {
 	.prepare = clk_master_prepare,
 	.is_prepared = clk_master_is_prepared,
-	.recalc_rate = clk_master_div_recalc_rate,
-	.determine_rate = clk_master_div_determine_rate,
-	.set_rate = clk_master_div_set_rate,
+	.recalc_rate = clk_master_div_recalc_rate_chg,
 	.save_context = clk_master_div_save_context,
 	.restore_context = clk_master_div_restore_context_chg,
 };
@@ -488,6 +510,8 @@  at91_clk_register_master_internal(struct regmap *regmap,
 	struct clk_master *master;
 	struct clk_init_data init;
 	struct clk_hw *hw;
+	unsigned int mckr;
+	unsigned long irqflags;
 	int ret;
 
 	if (!name || !num_parents || !parent_names || !lock)
@@ -510,6 +534,16 @@  at91_clk_register_master_internal(struct regmap *regmap,
 	master->chg_pid = chg_pid;
 	master->lock = lock;
 
+	if (ops == &master_div_ops_chg) {
+		spin_lock_irqsave(master->lock, irqflags);
+		regmap_read(master->regmap, master->layout->offset, &mckr);
+		spin_unlock_irqrestore(master->lock, irqflags);
+
+		mckr &= layout->mask;
+		mckr = (mckr >> MASTER_DIV_SHIFT) & MASTER_DIV_MASK;
+		master->div = characteristics->divisors[mckr];
+	}
+
 	hw = &master->hw;
 	ret = clk_hw_register(NULL, &master->hw);
 	if (ret) {
@@ -526,19 +560,24 @@  at91_clk_register_master_pres(struct regmap *regmap,
 		const char **parent_names,
 		const struct clk_master_layout *layout,
 		const struct clk_master_characteristics *characteristics,
-		spinlock_t *lock, u32 flags, int chg_pid)
+		spinlock_t *lock, u32 flags, int chg_pid, bool notifier)
 {
 	const struct clk_ops *ops;
+	struct clk_hw *hw;
 
 	if (flags & CLK_SET_RATE_GATE)
 		ops = &master_pres_ops;
 	else
 		ops = &master_pres_ops_chg;
 
-	return at91_clk_register_master_internal(regmap, name, num_parents,
-						 parent_names, layout,
-						 characteristics, ops,
-						 lock, flags, chg_pid);
+	hw = at91_clk_register_master_internal(regmap, name, num_parents,
+					       parent_names, layout,
+					       characteristics, ops,
+					       lock, flags, chg_pid);
+	if (!IS_ERR(hw) && notifier)
+		clk_notifier_register(hw->clk, &clk_master_notifier);
+
+	return hw;
 }
 
 struct clk_hw * __init
@@ -549,16 +588,22 @@  at91_clk_register_master_div(struct regmap *regmap,
 		spinlock_t *lock, u32 flags)
 {
 	const struct clk_ops *ops;
+	struct clk_hw *hw;
 
 	if (flags & CLK_SET_RATE_GATE)
 		ops = &master_div_ops;
 	else
 		ops = &master_div_ops_chg;
 
-	return at91_clk_register_master_internal(regmap, name, 1,
-						 &parent_name, layout,
-						 characteristics, ops,
-						 lock, flags, -EINVAL);
+	hw = at91_clk_register_master_internal(regmap, name, 1,
+					       &parent_name, layout,
+					       characteristics, ops,
+					       lock, flags, -EINVAL);
+
+	if (!IS_ERR(hw))
+		master_div = to_clk_master(hw);
+
+	return hw;
 }
 
 static unsigned long
diff --git a/drivers/clk/at91/dt-compat.c b/drivers/clk/at91/dt-compat.c
index a97b99c2dc12..99ad43ea6169 100644
--- a/drivers/clk/at91/dt-compat.c
+++ b/drivers/clk/at91/dt-compat.c
@@ -393,7 +393,7 @@  of_at91_clk_master_setup(struct device_node *np,
 	hw = at91_clk_register_master_pres(regmap, "masterck_pres", num_parents,
 					   parent_names, layout,
 					   characteristics, &mck_lock,
-					   CLK_SET_RATE_GATE, INT_MIN);
+					   CLK_SET_RATE_GATE, INT_MIN, 0);
 	if (IS_ERR(hw))
 		goto out_free_characteristics;
 
diff --git a/drivers/clk/at91/pmc.h b/drivers/clk/at91/pmc.h
index 86580ebd9ad9..2263f4df3a82 100644
--- a/drivers/clk/at91/pmc.h
+++ b/drivers/clk/at91/pmc.h
@@ -175,7 +175,8 @@  at91_clk_register_master_pres(struct regmap *regmap, const char *name,
 			      int num_parents, const char **parent_names,
 			      const struct clk_master_layout *layout,
 			      const struct clk_master_characteristics *characteristics,
-			      spinlock_t *lock, u32 flags, int chg_pid);
+			      spinlock_t *lock, u32 flags, int chg_pid,
+			      bool notifier);
 
 struct clk_hw * __init
 at91_clk_register_master_div(struct regmap *regmap, const char *name,
diff --git a/drivers/clk/at91/sam9x60.c b/drivers/clk/at91/sam9x60.c
index 5f6fa89571b7..8e1b89e05724 100644
--- a/drivers/clk/at91/sam9x60.c
+++ b/drivers/clk/at91/sam9x60.c
@@ -272,7 +272,7 @@  static void __init sam9x60_pmc_setup(struct device_node *np)
 	hw = at91_clk_register_master_pres(regmap, "masterck_pres", 3,
 					   parent_names, &sam9x60_master_layout,
 					   &mck_characteristics, &mck_lock,
-					   CLK_SET_RATE_GATE, INT_MIN);
+					   CLK_SET_RATE_GATE, INT_MIN, 0);
 	if (IS_ERR(hw))
 		goto err_free;
 
diff --git a/drivers/clk/at91/sama5d2.c b/drivers/clk/at91/sama5d2.c
index 3d1f78176c3e..40c64c605160 100644
--- a/drivers/clk/at91/sama5d2.c
+++ b/drivers/clk/at91/sama5d2.c
@@ -241,7 +241,7 @@  static void __init sama5d2_pmc_setup(struct device_node *np)
 					   parent_names,
 					   &at91sam9x5_master_layout,
 					   &mck_characteristics, &mck_lock,
-					   CLK_SET_RATE_GATE, INT_MIN);
+					   CLK_SET_RATE_GATE, INT_MIN, 0);
 	if (IS_ERR(hw))
 		goto err_free;
 
diff --git a/drivers/clk/at91/sama5d3.c b/drivers/clk/at91/sama5d3.c
index d376257807d2..7ec4a54982e1 100644
--- a/drivers/clk/at91/sama5d3.c
+++ b/drivers/clk/at91/sama5d3.c
@@ -176,7 +176,7 @@  static void __init sama5d3_pmc_setup(struct device_node *np)
 					   parent_names,
 					   &at91sam9x5_master_layout,
 					   &mck_characteristics, &mck_lock,
-					   CLK_SET_RATE_GATE, INT_MIN);
+					   CLK_SET_RATE_GATE, INT_MIN, 0);
 	if (IS_ERR(hw))
 		goto err_free;
 
diff --git a/drivers/clk/at91/sama5d4.c b/drivers/clk/at91/sama5d4.c
index 5cbaac68da44..94f0a574ace4 100644
--- a/drivers/clk/at91/sama5d4.c
+++ b/drivers/clk/at91/sama5d4.c
@@ -191,7 +191,7 @@  static void __init sama5d4_pmc_setup(struct device_node *np)
 					   parent_names,
 					   &at91sam9x5_master_layout,
 					   &mck_characteristics, &mck_lock,
-					   CLK_SET_RATE_GATE, INT_MIN);
+					   CLK_SET_RATE_GATE, INT_MIN, 0);
 	if (IS_ERR(hw))
 		goto err_free;
 
diff --git a/drivers/clk/at91/sama7g5.c b/drivers/clk/at91/sama7g5.c
index 9c87b50abbae..abc6563e6207 100644
--- a/drivers/clk/at91/sama7g5.c
+++ b/drivers/clk/at91/sama7g5.c
@@ -986,7 +986,7 @@  static void __init sama7g5_pmc_setup(struct device_node *np)
 	hw = at91_clk_register_master_pres(regmap, "cpuck", 1, parent_names,
 					   &mck0_layout, &mck0_characteristics,
 					   &pmc_mck0_lock,
-					   CLK_SET_RATE_PARENT, 0);
+					   CLK_SET_RATE_PARENT, 0, 1);
 	if (IS_ERR(hw))
 		goto err_free;