[PATCH 09/13] clk: imx: pll14xx: consider active rate for re-config

[Benjamin Bara]

From: Benjamin Bara <benjamin.bara at skidata.com>

As the pll14xx might be the parent of multiple child clocks, the active
config is most likely still required by one of them. As the children
have divider, use the LCM of the old and the new rate to target for an
integer multiple of the active rate.

Signed-off-by: Benjamin Bara <benjamin.bara at skidata.com>
---
 drivers/clk/imx/clk-pll14xx.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/clk/imx/clk-pll14xx.c b/drivers/clk/imx/clk-pll14xx.c
index 0d58d85c375e..803e8b0a7a31 100644
--- a/drivers/clk/imx/clk-pll14xx.c
+++ b/drivers/clk/imx/clk-pll14xx.c
@@ -12,6 +12,7 @@
 #include <linux/export.h>
 #include <linux/io.h>
 #include <linux/iopoll.h>
+#include <linux/lcm.h>
 #include <linux/slab.h>
 #include <linux/jiffies.h>
 
@@ -36,6 +37,7 @@
 
 struct clk_pll14xx {
 	struct clk_hw			hw;
+	unsigned long			rate;
 	void __iomem			*base;
 	enum imx_pll14xx_type		type;
 	const struct imx_pll14xx_rate_table *rate_table;
@@ -235,6 +237,22 @@ static long clk_pll1443x_round_rate(struct clk_hw *hw, unsigned long rate,
 	struct clk_pll14xx *pll = to_clk_pll14xx(hw);
 	struct imx_pll14xx_rate_table t;
 
+	/*
+	 * If the PLL is configured more than once, we have to consider the
+	 * active config for the new rate. As the children have divider, also
+	 * allow multiples of the already configured rate. This is a simple
+	 * approach to enable dynamic re-config via SET_CLK_RATE_PARENT for more
+	 * than one consumer. E.g. on the imx8mp, when video_pll1 is parent of
+	 * media_ldb and media_disp2_pix (always 7:1).
+	 */
+	if (pll->rate) {
+		unsigned long want = rate;
+
+		rate = lcm(pll->rate, rate);
+		pr_debug("%s: old=%ld, want=%ld, new=%ld\n", clk_hw_get_name(hw),
+			 pll->rate, want, rate);
+	}
+
 	imx_pll14xx_calc_settings(pll, rate, *prate, &t);
 
 	return t.rate;
@@ -343,6 +361,8 @@ static int clk_pll1416x_set_rate(struct clk_hw *hw, unsigned long drate,
 	tmp &= ~BYPASS_MASK;
 	writel_relaxed(tmp, pll->base + GNRL_CTL);
 
+	pll->rate = rate->rate;
+
 	return 0;
 }
 

-- 
2.34.1