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From:   Frank Oltmanns <frank@oltmanns.dev>
Date:   Sun, 02 Jul 2023 19:55:24 +0200
Subject: [PATCH v3 5/8] clk: sunxi-ng: nkm: Support finding closest rate
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Message-Id: <20230702-pll-mipi_set_rate_parent-v3-5-46dcb8aa9cbc@oltmanns.dev>
References: <20230702-pll-mipi_set_rate_parent-v3-0-46dcb8aa9cbc@oltmanns.dev>
In-Reply-To: <20230702-pll-mipi_set_rate_parent-v3-0-46dcb8aa9cbc@oltmanns.dev>
To:     Maxime Ripard <maxime@cerno.tech>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>, Chen-Yu Tsai <wens@csie.org>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Samuel Holland <samuel@sholland.org>,
        Andre Przywara <andre.przywara@arm.com>,
        Roman Beranek <me@crly.cz>
Cc:     linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org,
        Frank Oltmanns <frank@oltmanns.dev>
Precedence: bulk

When finding the best rate for a NKM clock, consider rates that are
higher than the requested rate, if the CCU_FEATURE_CLOSEST_RATE flag is
set.

Accommodate ccu_mux_helper_determine_rate to this change.

Signed-off-by: Frank Oltmanns <frank@oltmanns.dev>
---
 drivers/clk/sunxi-ng/ccu_mux.c | 23 +++++++++++++++-----
 drivers/clk/sunxi-ng/ccu_nkm.c | 48 +++++++++++++++++++++++++++++++-----------
 2 files changed, 54 insertions(+), 17 deletions(-)

diff --git a/drivers/clk/sunxi-ng/ccu_mux.c b/drivers/clk/sunxi-ng/ccu_mux.c
index 1d557e323169..8594d6a4addd 100644
--- a/drivers/clk/sunxi-ng/ccu_mux.c
+++ b/drivers/clk/sunxi-ng/ccu_mux.c
@@ -113,7 +113,7 @@ int ccu_mux_helper_determine_rate(struct ccu_common *common,
 	}
 
 	for (i = 0; i < clk_hw_get_num_parents(hw); i++) {
-		unsigned long tmp_rate, parent_rate;
+		unsigned long tmp_rate, parent_rate, best_diff = ULONG_MAX;
 		struct clk_hw *parent;
 
 		parent = clk_hw_get_parent_by_index(hw, i);
@@ -139,10 +139,23 @@ int ccu_mux_helper_determine_rate(struct ccu_common *common,
 			goto out;
 		}
 
-		if ((req->rate - tmp_rate) < (req->rate - best_rate)) {
-			best_rate = tmp_rate;
-			best_parent_rate = parent_rate;
-			best_parent = parent;
+		if (common->features & CCU_FEATURE_CLOSEST_RATE) {
+			unsigned long tmp_diff = req->rate > tmp_rate ?
+						 req->rate - tmp_rate :
+						 tmp_rate - req->rate;
+
+			if (tmp_diff < best_diff) {
+				best_rate = tmp_rate;
+				best_parent_rate = parent_rate;
+				best_parent = parent;
+				best_diff = tmp_diff;
+			}
+		} else {
+			if ((req->rate - tmp_rate) < (req->rate - best_rate)) {
+				best_rate = tmp_rate;
+				best_parent_rate = parent_rate;
+				best_parent = parent;
+			}
 		}
 	}
 
diff --git a/drivers/clk/sunxi-ng/ccu_nkm.c b/drivers/clk/sunxi-ng/ccu_nkm.c
index d83843e69c25..36d9e987e4d8 100644
--- a/drivers/clk/sunxi-ng/ccu_nkm.c
+++ b/drivers/clk/sunxi-ng/ccu_nkm.c
@@ -18,9 +18,11 @@ struct _ccu_nkm {
 };
 
 static unsigned long ccu_nkm_find_best_with_parent_adj(unsigned long *parent, unsigned long rate,
-						       struct _ccu_nkm *nkm, struct clk_hw *phw)
+						       struct _ccu_nkm *nkm, struct clk_hw *phw,
+						       unsigned long features)
 {
-	unsigned long best_rate = 0, best_parent_rate = *parent, tmp_parent = *parent;
+	unsigned long best_rate = 0, best_parent_rate = 0, tmp_parent = *parent;
+	unsigned long best_diff = ULONG_MAX;
 	unsigned long best_n = 0, best_k = 0, best_m = 0;
 	unsigned long _n, _k, _m;
 
@@ -28,16 +30,26 @@ static unsigned long ccu_nkm_find_best_with_parent_adj(unsigned long *parent, un
 		for (_n = nkm->min_n; _n <= nkm->max_n; _n++) {
 			for (_m = nkm->min_m; _m <= nkm->max_m; _m++) {
 				unsigned long tmp_rate;
+				unsigned long tmp_diff;
 
 				tmp_parent = clk_hw_round_rate(phw, rate * _m / (_n * _k));
 
 				tmp_rate = tmp_parent * _n * _k / _m;
-				if (tmp_rate > rate)
-					continue;
 
-				if ((rate - tmp_rate) < (rate - best_rate)) {
+				if (features & CCU_FEATURE_CLOSEST_RATE) {
+					tmp_diff = rate > tmp_rate ?
+						   rate - tmp_rate :
+						   tmp_rate - rate;
+				} else {
+					if (tmp_rate > rate)
+						continue;
+					tmp_diff = rate - tmp_diff;
+				}
+
+				if (tmp_diff < best_diff) {
 					best_rate = tmp_rate;
 					best_parent_rate = tmp_parent;
+					best_diff = tmp_diff;
 					best_n = _n;
 					best_k = _k;
 					best_m = _m;
@@ -56,9 +68,10 @@ static unsigned long ccu_nkm_find_best_with_parent_adj(unsigned long *parent, un
 }
 
 static unsigned long ccu_nkm_find_best(unsigned long parent, unsigned long rate,
-				       struct _ccu_nkm *nkm)
+				       struct _ccu_nkm *nkm, unsigned long features)
 {
 	unsigned long best_rate = 0;
+	unsigned long best_diff = ULONG_MAX;
 	unsigned long best_n = 0, best_k = 0, best_m = 0;
 	unsigned long _n, _k, _m;
 
@@ -66,13 +79,23 @@ static unsigned long ccu_nkm_find_best(unsigned long parent, unsigned long rate,
 		for (_n = nkm->min_n; _n <= nkm->max_n; _n++) {
 			for (_m = nkm->min_m; _m <= nkm->max_m; _m++) {
 				unsigned long tmp_rate;
+				unsigned long tmp_diff;
 
 				tmp_rate = parent * _n * _k / _m;
 
-				if (tmp_rate > rate)
-					continue;
-				if ((rate - tmp_rate) < (rate - best_rate)) {
+				if (features & CCU_FEATURE_CLOSEST_RATE) {
+					tmp_diff = rate > tmp_rate ?
+						   rate - tmp_rate :
+						   tmp_rate - rate;
+				} else {
+					if (tmp_rate > rate)
+						continue;
+					tmp_diff = rate - tmp_diff;
+				}
+
+				if (tmp_diff < best_diff) {
 					best_rate = tmp_rate;
+					best_diff = tmp_diff;
 					best_n = _n;
 					best_k = _k;
 					best_m = _m;
@@ -164,9 +187,10 @@ static unsigned long ccu_nkm_round_rate(struct ccu_mux_internal *mux,
 		rate *= nkm->fixed_post_div;
 
 	if (!clk_hw_can_set_rate_parent(&nkm->common.hw))
-		rate = ccu_nkm_find_best(*parent_rate, rate, &_nkm);
+		rate = ccu_nkm_find_best(*parent_rate, rate, &_nkm, nkm->common.features);
 	else
-		rate = ccu_nkm_find_best_with_parent_adj(parent_rate, rate, &_nkm, parent_hw);
+		rate = ccu_nkm_find_best_with_parent_adj(parent_rate, rate, &_nkm, parent_hw,
+							 nkm->common.features);
 
 	if (nkm->common.features & CCU_FEATURE_FIXED_POSTDIV)
 		rate /= nkm->fixed_post_div;
@@ -201,7 +225,7 @@ static int ccu_nkm_set_rate(struct clk_hw *hw, unsigned long rate,
 	_nkm.min_m = 1;
 	_nkm.max_m = nkm->m.max ?: 1 << nkm->m.width;
 
-	ccu_nkm_find_best(&parent_rate, rate, &_nkm);
+	ccu_nkm_find_best(parent_rate, rate, &_nkm, nkm->common.features);
 
 	spin_lock_irqsave(nkm->common.lock, flags);
 

-- 
2.41.0