clk: at91: Add sama5d4 sckc support

Starting with sama5d4, the crystal oscillator is always enabled at startup
and the SCKC doesn't have an OSC32EN bit anymore.

Add support for that new controller.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

Documentation/devicetree/bindings/clock/at91-clock.txt

@@ -6,7 +6,8 @@ This binding uses the common clock binding[1].
 
 Required properties:
 - compatible : shall be one of the following:
-	"atmel,at91sam9x5-sckc":
+	"atmel,at91sam9x5-sckc" or
+	"atmel,sama5d4-sckc":
 		at91 SCKC (Slow Clock Controller)
 		This node contains the slow clock definitions.
 

drivers/clk/at91/sckc.c

@@ -36,6 +36,15 @@ struct clk_slow_osc {
 
 #define to_clk_slow_osc(hw) container_of(hw, struct clk_slow_osc, hw)
 
+struct clk_sama5d4_slow_osc {
+	struct clk_hw hw;
+	void __iomem *sckcr;
+	unsigned long startup_usec;
+	bool prepared;
+};
+
+#define to_clk_sama5d4_slow_osc(hw) container_of(hw, struct clk_sama5d4_slow_osc, hw)
+
 struct clk_slow_rc_osc {
 	struct clk_hw hw;
 	void __iomem *sckcr;
@@ -417,3 +426,94 @@ static void __init of_at91sam9x5_sckc_setup(struct device_node *np)
 }
 CLK_OF_DECLARE(at91sam9x5_clk_sckc, "atmel,at91sam9x5-sckc",
 	       of_at91sam9x5_sckc_setup);
+
+static int clk_sama5d4_slow_osc_prepare(struct clk_hw *hw)
+{
+	struct clk_sama5d4_slow_osc *osc = to_clk_sama5d4_slow_osc(hw);
+
+	if (osc->prepared)
+		return 0;
+
+	/*
+	 * Assume that if it has already been selected (for example by the
+	 * bootloader), enough time has aready passed.
+	 */
+	if ((readl(osc->sckcr) & AT91_SCKC_OSCSEL)) {
+		osc->prepared = true;
+		return 0;
+	}
+
+	usleep_range(osc->startup_usec, osc->startup_usec + 1);
+	osc->prepared = true;
+
+	return 0;
+}
+
+static int clk_sama5d4_slow_osc_is_prepared(struct clk_hw *hw)
+{
+	struct clk_sama5d4_slow_osc *osc = to_clk_sama5d4_slow_osc(hw);
+
+	return osc->prepared;
+}
+
+static const struct clk_ops sama5d4_slow_osc_ops = {
+	.prepare = clk_sama5d4_slow_osc_prepare,
+	.is_prepared = clk_sama5d4_slow_osc_is_prepared,
+};
+
+static void __init of_sama5d4_sckc_setup(struct device_node *np)
+{
+	void __iomem *regbase = of_iomap(np, 0);
+	struct clk_hw *hw;
+	struct clk_sama5d4_slow_osc *osc;
+	struct clk_init_data init;
+	const char *xtal_name;
+	const char *parent_names[2] = { "slow_rc_osc", "slow_osc" };
+	bool bypass;
+	int ret;
+
+	if (!regbase)
+		return;
+
+	hw = clk_hw_register_fixed_rate_with_accuracy(NULL, parent_names[0],
+						      NULL, 0, 32768,
+						      250000000);
+	if (IS_ERR(hw))
+		return;
+
+	xtal_name = of_clk_get_parent_name(np, 0);
+
+	bypass = of_property_read_bool(np, "atmel,osc-bypass");
+
+	osc = kzalloc(sizeof(*osc), GFP_KERNEL);
+	if (!osc)
+		return;
+
+	init.name = parent_names[1];
+	init.ops = &sama5d4_slow_osc_ops;
+	init.parent_names = &xtal_name;
+	init.num_parents = 1;
+	init.flags = CLK_IGNORE_UNUSED;
+
+	osc->hw.init = &init;
+	osc->sckcr = regbase;
+	osc->startup_usec = 1200000;
+
+	if (bypass)
+		writel((readl(regbase) | AT91_SCKC_OSC32BYP), regbase);
+
+	hw = &osc->hw;
+	ret = clk_hw_register(NULL, &osc->hw);
+	if (ret) {
+		kfree(osc);
+		return;
+	}
+
+	hw = at91_clk_register_sam9x5_slow(regbase, "slowck", parent_names, 2);
+	if (IS_ERR(hw))
+		return;
+
+	of_clk_add_hw_provider(np, of_clk_hw_simple_get, hw);
+}
+CLK_OF_DECLARE(sama5d4_clk_sckc, "atmel,sama5d4-sckc",
+	       of_sama5d4_sckc_setup);