clk: at91: add PLLADIV driver

As said in the SAMA5D2 datasheet, the PLLA clock must be divided
by 2 by writing the PLLADIV2 bit in PMC_MCKR, if the ratio between
PCK and MCK is 3 (MDIV = 3). This is the purpose of the driver.

Signed-off-by: Wenyou Yang <wenyou.yang@microchip.com>

drivers/clk/at91/Makefile

@@ -3,7 +3,7 @@
 #
 
 obj-y += pmc.o sckc.o
-obj-y += clk-slow.o clk-main.o clk-plla.o clk-master.o
+obj-y += clk-slow.o clk-main.o clk-plla.o clk-plladiv.o clk-master.o
 obj-y += clk-system.o clk-peripheral.o
 
 obj-$(CONFIG_AT91_UTMI)		+= clk-utmi.o

drivers/clk/at91/clk-plladiv.c

@@ -0,0 +1,88 @@
+/*
+ * Copyright (C) 2018 Microhip / Atmel Corporation
+ *               Wenyou.Yang <wenyou.yang@microchip.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <clk-uclass.h>
+#include <dm/device.h>
+#include <linux/io.h>
+#include <mach/at91_pmc.h>
+#include "pmc.h"
+
+DECLARE_GLOBAL_DATA_PTR;
+
+static int at91_plladiv_clk_enable(struct clk *clk)
+{
+	return 0;
+}
+
+static ulong at91_plladiv_clk_get_rate(struct clk *clk)
+{
+	struct pmc_platdata *plat = dev_get_platdata(clk->dev);
+	struct at91_pmc *pmc = plat->reg_base;
+	struct clk source;
+	ulong clk_rate;
+	int ret;
+
+	ret = clk_get_by_index(clk->dev, 0, &source);
+	if (ret)
+		return -EINVAL;
+
+	clk_rate = clk_get_rate(&source);
+	if (readl(&pmc->mckr) & AT91_PMC_MCKR_PLLADIV_2)
+		clk_rate /= 2;
+
+	return clk_rate;
+}
+
+static ulong at91_plladiv_clk_set_rate(struct clk *clk, ulong rate)
+{
+	struct pmc_platdata *plat = dev_get_platdata(clk->dev);
+	struct at91_pmc *pmc = plat->reg_base;
+	struct clk source;
+	ulong parent_rate;
+	int ret;
+
+	ret = clk_get_by_index(clk->dev, 0, &source);
+	if (ret)
+		return -EINVAL;
+
+	parent_rate = clk_get_rate(&source);
+	if ((parent_rate != rate) && ((parent_rate) / 2 != rate))
+		return -EINVAL;
+
+	if (parent_rate != rate) {
+		writel((readl(&pmc->mckr) | AT91_PMC_MCKR_PLLADIV_2),
+		       &pmc->mckr);
+	}
+
+	return 0;
+}
+
+static struct clk_ops at91_plladiv_clk_ops = {
+	.enable = at91_plladiv_clk_enable,
+	.get_rate = at91_plladiv_clk_get_rate,
+	.set_rate = at91_plladiv_clk_set_rate,
+};
+
+static int at91_plladiv_clk_probe(struct udevice *dev)
+{
+	return at91_pmc_core_probe(dev);
+}
+
+static const struct udevice_id at91_plladiv_clk_match[] = {
+	{ .compatible = "atmel,at91sam9x5-clk-plldiv" },
+	{}
+};
+
+U_BOOT_DRIVER(at91_plladiv_clk) = {
+	.name = "at91-plladiv-clk",
+	.id = UCLASS_CLK,
+	.of_match = at91_plladiv_clk_match,
+	.probe = at91_plladiv_clk_probe,
+	.platdata_auto_alloc_size = sizeof(struct pmc_platdata),
+	.ops = &at91_plladiv_clk_ops,
+};