clk: at91: clk-peripheral: add support for changeable parent rate

Some peripheral clocks on SAMA7G5 supports requesting parent to change
its rate (image related clocks: csi, csi2dc, isc). Add support
so that if registered with this option the clock rate to be
requested from parent.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/1595403506-8209-14-git-send-email-claudiu.beznea@microchip.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

1 files changed, 104 insertions, 5 deletions

diff --git a/drivers/clk/at91/clk-peripheral.c b/drivers/clk/at91/clk-peripheral.c
index 4c9a4147dfe5..7867eaf0447f 100644
--- a/drivers/clk/at91/clk-peripheral.c
+++ b/drivers/clk/at91/clk-peripheral.c
@@ -38,6 +38,7 @@ struct clk_sam9x5_peripheral {
 	u32 div;
 	const struct clk_pcr_layout *layout;
 	bool auto_div;
+	int chg_pid;
 };
 
 #define to_clk_sam9x5_peripheral(hw) \
@@ -238,6 +239,87 @@ clk_sam9x5_peripheral_recalc_rate(struct clk_hw *hw,
 	return parent_rate >> periph->div;
 }
 
+static void clk_sam9x5_peripheral_best_diff(struct clk_rate_request *req,
+					    struct clk_hw *parent,
+					    unsigned long parent_rate,
+					    u32 shift, long *best_diff,
+					    long *best_rate)
+{
+	unsigned long tmp_rate = parent_rate >> shift;
+	unsigned long tmp_diff = abs(req->rate - tmp_rate);
+
+	if (*best_diff < 0 || *best_diff >= tmp_diff) {
+		*best_rate = tmp_rate;
+		*best_diff = tmp_diff;
+		req->best_parent_rate = parent_rate;
+		req->best_parent_hw = parent;
+	}
+}
+
+static int clk_sam9x5_peripheral_determine_rate(struct clk_hw *hw,
+						struct clk_rate_request *req)
+{
+	struct clk_sam9x5_peripheral *periph = to_clk_sam9x5_peripheral(hw);
+	struct clk_hw *parent = clk_hw_get_parent(hw);
+	struct clk_rate_request req_parent = *req;
+	unsigned long parent_rate = clk_hw_get_rate(parent);
+	unsigned long tmp_rate;
+	long best_rate = LONG_MIN;
+	long best_diff = LONG_MIN;
+	u32 shift;
+
+	if (periph->id < PERIPHERAL_ID_MIN || !periph->range.max)
+		return parent_rate;
+
+	/* Fist step: check the available dividers. */
+	for (shift = 0; shift <= PERIPHERAL_MAX_SHIFT; shift++) {
+		tmp_rate = parent_rate >> shift;
+
+		if (periph->range.max && tmp_rate > periph->range.max)
+			continue;
+
+		clk_sam9x5_peripheral_best_diff(req, parent, parent_rate,
+						shift, &best_diff, &best_rate);
+
+		if (!best_diff || best_rate <= req->rate)
+			break;
+	}
+
+	if (periph->chg_pid < 0)
+		goto end;
+
+	/* Step two: try to request rate from parent. */
+	parent = clk_hw_get_parent_by_index(hw, periph->chg_pid);
+	if (!parent)
+		goto end;
+
+	for (shift = 0; shift <= PERIPHERAL_MAX_SHIFT; shift++) {
+		req_parent.rate = req->rate << shift;
+
+		if (__clk_determine_rate(parent, &req_parent))
+			continue;
+
+		clk_sam9x5_peripheral_best_diff(req, parent, req_parent.rate,
+						shift, &best_diff, &best_rate);
+
+		if (!best_diff)
+			break;
+	}
+end:
+	if (best_rate < 0 ||
+	    (periph->range.max && best_rate > periph->range.max))
+		return -EINVAL;
+
+	pr_debug("PCK: %s, best_rate = %ld, parent clk: %s @ %ld\n",
+		 __func__, best_rate,
+		 __clk_get_name((req->best_parent_hw)->clk),
+		 req->best_parent_rate);
+
+	req->rate = best_rate;
+
+	return 0;
+}
+
 static long clk_sam9x5_peripheral_round_rate(struct clk_hw *hw,
 					     unsigned long rate,
 					     unsigned long *parent_rate)
@@ -320,11 +402,21 @@ static const struct clk_ops sam9x5_peripheral_ops = {
 	.set_rate = clk_sam9x5_peripheral_set_rate,
 };
 
+static const struct clk_ops sam9x5_peripheral_chg_ops = {
+	.enable = clk_sam9x5_peripheral_enable,
+	.disable = clk_sam9x5_peripheral_disable,
+	.is_enabled = clk_sam9x5_peripheral_is_enabled,
+	.recalc_rate = clk_sam9x5_peripheral_recalc_rate,
+	.determine_rate = clk_sam9x5_peripheral_determine_rate,
+	.set_rate = clk_sam9x5_peripheral_set_rate,
+};
+
 struct clk_hw * __init
 at91_clk_register_sam9x5_peripheral(struct regmap *regmap, spinlock_t *lock,
 				    const struct clk_pcr_layout *layout,
 				    const char *name, const char *parent_name,
-				    u32 id, const struct clk_range *range)
+				    u32 id, const struct clk_range *range,
+				    int chg_pid)
 {
 	struct clk_sam9x5_peripheral *periph;
 	struct clk_init_data init;
@@ -339,10 +431,16 @@ at91_clk_register_sam9x5_peripheral(struct regmap *regmap, spinlock_t *lock,
 		return ERR_PTR(-ENOMEM);
 
 	init.name = name;
-	init.ops = &sam9x5_peripheral_ops;
-	init.parent_names = (parent_name ? &parent_name : NULL);
-	init.num_parents = (parent_name ? 1 : 0);
-	init.flags = 0;
+	init.parent_names = &parent_name;
+	init.num_parents = 1;
+	if (chg_pid < 0) {
+		init.flags = 0;
+		init.ops = &sam9x5_peripheral_ops;
+	} else {
+		init.flags = CLK_SET_RATE_GATE | CLK_SET_PARENT_GATE |
+			     CLK_SET_RATE_PARENT;
+		init.ops = &sam9x5_peripheral_chg_ops;
+	}
 
 	periph->id = id;
 	periph->hw.init = &init;
@@ -353,6 +451,7 @@ at91_clk_register_sam9x5_peripheral(struct regmap *regmap, spinlock_t *lock,
 		periph->auto_div = true;
 	periph->layout = layout;
 	periph->range = *range;
+	periph->chg_pid = chg_pid;
 
 	hw = &periph->hw;
 	ret = clk_hw_register(NULL, &periph->hw);