[PATCH] clk: socfpga: add divider registers to the main pll outputs

[Steffen Trumtrar <s.trumtrar@xxxxxxxxxxxxxx>]

From: Enrico Jorns <ejo@xxxxxxxxxxxxxx>

This patch is based on kernel patch 0691bb1b5a1865b3bbc9b7ce6e26eff546abb1cf
by Dinh Nguyen <dinguyen@xxxxxxxxxx>.

The C0(mpu_clk), C1(main_clk), and C2(dbg_base_clk) outputs from the main
PLL go through a pre-divider before coming into the system. These registers
were hidden for the CycloneV platform, but are now used for the ArriaV
platform.

This patch updates the clock driver to read the div-reg property for the
socfpga-periph-clk clocks.

Note: The registers used for the div-reg property are not documented but
set by the preloader.

Signed-off-by: Enrico Jorns <ejo@xxxxxxxxxxxxxx>
Signed-off-by: Steffen Trumtrar <s.trumtrar@xxxxxxxxxxxxxx>
---
 drivers/clk/socfpga.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/drivers/clk/socfpga.c b/drivers/clk/socfpga.c
index 37ed038be84c..6af0632cafc2 100644
--- a/drivers/clk/socfpga.c
+++ b/drivers/clk/socfpga.c
@@ -116,18 +116,27 @@ struct clk_periph {
 	const char *parent;
 	unsigned regofs;
 	unsigned int fixed_div;
+	void __iomem *div_reg;
+	unsigned int width;
+	unsigned int shift;
 };
 
 static unsigned long clk_periph_recalc_rate(struct clk *clk,
 		unsigned long parent_rate)
 {
 	struct clk_periph *periph = container_of(clk, struct clk_periph, clk);
-	u32 div;
+	u32 div, val;
 
-	if (periph->fixed_div)
+	if (periph->fixed_div) {
 		div = periph->fixed_div;
-	else
+	} else {
+		if (periph->div_reg) {
+			val = readl(periph->div_reg) >> periph->shift;
+			val &= div_mask(periph->width);
+			parent_rate /= (val + 1);
+		}
 		div = ((readl(clk_mgr_base_addr + periph->regofs) & 0x1ff) + 1);
+	}
 
 	return parent_rate / div;
 }
@@ -140,6 +149,7 @@ static struct clk *socfpga_periph_clk(struct device_node *node)
 {
 	struct clk_periph *periph;
 	int ret;
+	u32 div_reg[3];
 
 	periph = xzalloc(sizeof(*periph));
 
@@ -152,6 +162,15 @@ static struct clk *socfpga_periph_clk(struct device_node *node)
 	periph->clk.name = xstrdup(node->name);
 	periph->clk.ops = &clk_periph_ops;
 
+	ret = of_property_read_u32_array(node, "div-reg", div_reg, 3);
+	if (!ret) {
+		periph->div_reg = clk_mgr_base_addr + div_reg[0];
+		periph->shift = div_reg[1];
+		periph->width = div_reg[2];
+	} else {
+		periph->div_reg = 0;
+	}
+
 	of_property_read_u32(node, "reg", &periph->regofs);
 	of_property_read_u32(node, "fixed-divider", &periph->fixed_div);
 
-- 
2.8.1


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