[PATCH v3 4/8] clk: sunxi-ng: nm: Support finding closest rate

[Frank Oltmanns]

Incorporate a new function, ccu_nm_find_best_closest, that selects the
closest possible rate instead of the closest rate that is less than the
requested rate. Utilizing rational_best_approximation has the additional
effect of boosting performance in clock rate selection.

In cases where the CCU_FEATURE_CLOSEST_RATE flag is set, use
ccu_nm_find_best_closest instead of the original ccu_nm_find_best
function.

Extend the macro SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK_MIN_MAX to allow
selecting additional features and update all usages of the macro with no
additional flags set.

Signed-off-by: Frank Oltmanns <frank@xxxxxxxxxxxx>
---
 drivers/clk/sunxi-ng/ccu-sun50i-a64.c |  6 ++++--
 drivers/clk/sunxi-ng/ccu-sun8i-h3.c   |  3 ++-
 drivers/clk/sunxi-ng/ccu-sun8i-r40.c  |  6 ++++--
 drivers/clk/sunxi-ng/ccu_nm.c         | 23 +++++++++++++++++++++--
 drivers/clk/sunxi-ng/ccu_nm.h         |  6 ++++--
 5 files changed, 35 insertions(+), 9 deletions(-)

diff --git a/drivers/clk/sunxi-ng/ccu-sun50i-a64.c b/drivers/clk/sunxi-ng/ccu-sun50i-a64.c
index a139a5c438d4..ebfab1fdbb96 100644
--- a/drivers/clk/sunxi-ng/ccu-sun50i-a64.c
+++ b/drivers/clk/sunxi-ng/ccu-sun50i-a64.c
@@ -80,7 +80,8 @@ static SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK_MIN_MAX(pll_video0_clk, "pll-video0",
 						297000000,	/* frac rate 1 */
 						BIT(31),	/* gate */
 						BIT(28),	/* lock */
-						CLK_SET_RATE_UNGATE);
+						CLK_SET_RATE_UNGATE,
+						0);		/* features */
 
 static SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK(pll_ve_clk, "pll-ve",
 					"osc24M", 0x018,
@@ -143,7 +144,8 @@ static SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK_MIN_MAX(pll_video1_clk, "pll-video1",
 						297000000,	/* frac rate 1 */
 						BIT(31),	/* gate */
 						BIT(28),	/* lock */
-						CLK_SET_RATE_UNGATE);
+						CLK_SET_RATE_UNGATE,
+						0);		/* features */
 
 static SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK(pll_gpu_clk, "pll-gpu",
 					"osc24M", 0x038,
diff --git a/drivers/clk/sunxi-ng/ccu-sun8i-h3.c b/drivers/clk/sunxi-ng/ccu-sun8i-h3.c
index bfebe8dbbe65..1e2669648a24 100644
--- a/drivers/clk/sunxi-ng/ccu-sun8i-h3.c
+++ b/drivers/clk/sunxi-ng/ccu-sun8i-h3.c
@@ -76,7 +76,8 @@ static SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK_MIN_MAX(pll_video_clk, "pll-video",
 						297000000, /* frac rate 1 */
 						BIT(31),   /* gate */
 						BIT(28),   /* lock */
-						CLK_SET_RATE_UNGATE);
+						CLK_SET_RATE_UNGATE,
+						0);        /* features */
 
 static SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK(pll_ve_clk, "pll-ve",
 					"osc24M", 0x0018,
diff --git a/drivers/clk/sunxi-ng/ccu-sun8i-r40.c b/drivers/clk/sunxi-ng/ccu-sun8i-r40.c
index 31eca0d3bc1e..63907b86ce06 100644
--- a/drivers/clk/sunxi-ng/ccu-sun8i-r40.c
+++ b/drivers/clk/sunxi-ng/ccu-sun8i-r40.c
@@ -82,7 +82,8 @@ static SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK_MIN_MAX(pll_video0_clk, "pll-video0",
 						297000000,  /* frac rate 1 */
 						BIT(31),    /* gate */
 						BIT(28),    /* lock */
-						CLK_SET_RATE_UNGATE);
+						CLK_SET_RATE_UNGATE,
+						0);         /* features */
 
 /* TODO: The result of N/M is required to be in [8, 25] range. */
 static SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK(pll_ve_clk, "pll-ve",
@@ -169,7 +170,8 @@ static SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK_MIN_MAX(pll_video1_clk, "pll-video1",
 						297000000,  /* frac rate 1 */
 						BIT(31),    /* gate */
 						BIT(28),    /* lock */
-						CLK_SET_RATE_UNGATE);
+						CLK_SET_RATE_UNGATE,
+						0);         /* features */
 
 static struct ccu_nkm pll_sata_clk = {
 	.enable		= BIT(31),
diff --git a/drivers/clk/sunxi-ng/ccu_nm.c b/drivers/clk/sunxi-ng/ccu_nm.c
index c1fd11542c45..97d8d9e3255c 100644
--- a/drivers/clk/sunxi-ng/ccu_nm.c
+++ b/drivers/clk/sunxi-ng/ccu_nm.c
@@ -6,6 +6,7 @@
 
 #include <linux/clk-provider.h>
 #include <linux/io.h>
+#include <linux/rational.h>
 
 #include "ccu_frac.h"
 #include "ccu_gate.h"
@@ -56,6 +57,18 @@ static unsigned long ccu_nm_find_best(unsigned long parent, unsigned long rate,
 	return best_rate;
 }
 
+static unsigned long ccu_nm_find_best_closest(unsigned long parent, unsigned long rate,
+				      struct _ccu_nm *nm)
+{
+	unsigned long best_rate = 0;
+
+	rational_best_approximation(rate, parent, nm->max_n, nm->max_m, &nm->n, &nm->m);
+
+	best_rate = ccu_nm_calc_rate(parent, nm->n, nm->m);
+
+	return best_rate;
+}
+
 static void ccu_nm_disable(struct clk_hw *hw)
 {
 	struct ccu_nm *nm = hw_to_ccu_nm(hw);
@@ -159,7 +172,10 @@ static long ccu_nm_round_rate(struct clk_hw *hw, unsigned long rate,
 	_nm.min_m = 1;
 	_nm.max_m = nm->m.max ?: 1 << nm->m.width;
 
-	rate = ccu_nm_find_best(*parent_rate, rate, &_nm);
+	if (nm->common.features & CCU_FEATURE_CLOSEST_RATE)
+		rate = ccu_nm_find_best_closest(*parent_rate, rate, &_nm);
+	else
+		rate = ccu_nm_find_best(*parent_rate, rate, &_nm);
 
 	if (nm->common.features & CCU_FEATURE_FIXED_POSTDIV)
 		rate /= nm->fixed_post_div;
@@ -210,7 +226,10 @@ static int ccu_nm_set_rate(struct clk_hw *hw, unsigned long rate,
 					   &_nm.m, &_nm.n);
 	} else {
 		ccu_sdm_helper_disable(&nm->common, &nm->sdm);
-		ccu_nm_find_best(parent_rate, rate, &_nm);
+		if (nm->common.features & CCU_FEATURE_CLOSEST_RATE)
+			ccu_nm_find_best_closest(parent_rate, rate, &_nm);
+		else
+			ccu_nm_find_best(parent_rate, rate, &_nm);
 	}
 
 	spin_lock_irqsave(nm->common.lock, flags);
diff --git a/drivers/clk/sunxi-ng/ccu_nm.h b/drivers/clk/sunxi-ng/ccu_nm.h
index 2904e67f05a8..a3825c4e8d42 100644
--- a/drivers/clk/sunxi-ng/ccu_nm.h
+++ b/drivers/clk/sunxi-ng/ccu_nm.h
@@ -116,7 +116,8 @@ struct ccu_nm {
 						 _frac_en, _frac_sel,	\
 						 _frac_rate_0,		\
 						 _frac_rate_1,		\
-						 _gate, _lock, _flags)	\
+						 _gate, _lock, _flags,	\
+						 _features)		\
 	struct ccu_nm _struct = {					\
 		.enable		= _gate,				\
 		.lock		= _lock,				\
@@ -129,7 +130,8 @@ struct ccu_nm {
 		.max_rate	= _max_rate,				\
 		.common		= {					\
 			.reg		= _reg,				\
-			.features	= CCU_FEATURE_FRACTIONAL,	\
+			.features	= CCU_FEATURE_FRACTIONAL |	\
+					  _features,	\
 			.hw.init	= CLK_HW_INIT(_name,		\
 						      _parent,		\
 						      &ccu_nm_ops,	\

-- 
2.41.0