[PATCH V5] clk: bcm: Add driver for BCM53573 ILP clock

["Rafał Miłecki" <zajec5@gmail.com>]

From: Rafał Miłecki <rafal@milecki.pl>

This clock is present on BCM53573 devices (including BCM47189) that use
Cortex-A7. ILP is a part of PMU (Power Management Unit) and so it should
be defined as one of its subnodes (subdevices). For more details see
Documentation entry.

Unfortunately there isn't a set of registers related to ILP clock only.
We use registers 0x66c, 0x674 and 0x6dc and between them there are e.g.
"retention*" and "control_ext" regs. This is why this driver maps all
0x1000 B of space.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
---
V2: Rebase on top of clk-next
    Use ALP as parent clock
    Improve comments
    Switch from ioremap_nocache to ioremap
    Check of_clk_add_provide result for error
V3: Drop #include <linux/moduleh>
    Make ILP DT entry part of PMU
    Describe ILP as subdevice of PMU in Documentation
V4: Use BCM53573 name as suggested by Jon and Ray. It seems "Northstar"
    (even if used in some resources) should be used in relation to
    Cortex-A9 devices only.
V5: Rename remaining "ns" references to "bcm53573", sorry, I sent V4 too
    early.
---
 .../bindings/clock/brcm,bcm53573-ilp.txt           |  40 ++++++
 drivers/clk/bcm/Makefile                           |   1 +
 drivers/clk/bcm/clk-bcm53573-ilp.c                 | 146 +++++++++++++++++++++
 3 files changed, 187 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/clock/brcm,bcm53573-ilp.txt
 create mode 100644 drivers/clk/bcm/clk-bcm53573-ilp.c

diff --git a/Documentation/devicetree/bindings/clock/brcm,bcm53573-ilp.txt b/Documentation/devicetree/bindings/clock/brcm,bcm53573-ilp.txt
new file mode 100644
index 0000000..5ab3107
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/brcm,bcm53573-ilp.txt
@@ -0,0 +1,40 @@
+Broadcom BCM53573 ILP clock
+===========================
+
+This binding uses the common clock binding:
+    Documentation/devicetree/bindings/clock/clock-bindings.txt
+
+This binding is used for ILP clock (sometimes referred as "slow clock")
+on Broadcom BCM53573 devices using Cortex-A7 CPU.
+
+This clock is part of PMU (Power Management Unit), a Broadcom's device
+handing power-related aspects. Please note PMU contains more subdevices,
+ILP is only one of them.
+
+ILP's rate has to be calculated on runtime and it depends on ALP clock
+which has to be referenced.
+
+Required properties:
+- compatible: "brcm,bcm53573-ilp"
+- reg: iomem address range of PMU (Power Management Unit)
+- reg-names: "pmu", the only needed & supported reg right now
+- clocks: has to reference an ALP clock
+- #clock-cells: should be <0>
+
+Example:
+
+pmu@18012000 {
+	compatible = "simple-bus";
+	ranges = <0x00000000 0x18012000 0x00001000>;
+	#address-cells = <1>;
+	#size-cells = <1>;
+
+	ilp: ilp@0 {
+		compatible = "brcm,bcm53573-ilp";
+		reg = <0 0x1000>;
+		reg-names = "pmu";
+		clocks = <&alp>;
+		#clock-cells = <0>;
+		clock-output-names = "ilp";
+	};
+};
diff --git a/drivers/clk/bcm/Makefile b/drivers/clk/bcm/Makefile
index 1d79bd2..4b8c56d 100644
--- a/drivers/clk/bcm/Makefile
+++ b/drivers/clk/bcm/Makefile
@@ -10,3 +10,4 @@ obj-$(CONFIG_COMMON_CLK_IPROC)	+= clk-ns2.o
 obj-$(CONFIG_ARCH_BCM_CYGNUS)	+= clk-cygnus.o
 obj-$(CONFIG_ARCH_BCM_NSP)	+= clk-nsp.o
 obj-$(CONFIG_ARCH_BCM_5301X)	+= clk-nsp.o
+obj-$(CONFIG_ARCH_BCM_53573)	+= clk-bcm53573-ilp.o
diff --git a/drivers/clk/bcm/clk-bcm53573-ilp.c b/drivers/clk/bcm/clk-bcm53573-ilp.c
new file mode 100644
index 0000000..b7ac0eb
--- /dev/null
+++ b/drivers/clk/bcm/clk-bcm53573-ilp.c
@@ -0,0 +1,146 @@
+/*
+ * Copyright (C) 2016 Rafał Miłecki <rafal@milecki.pl>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/slab.h>
+
+#define PMU_XTAL_FREQ_RATIO			0x66c
+#define  XTAL_ALP_PER_4ILP			0x00001fff
+#define  XTAL_CTL_EN				0x80000000
+#define PMU_SLOW_CLK_PERIOD			0x6dc
+
+struct bcm53573_ilp {
+	struct clk *clk;
+	struct clk_hw hw;
+	void __iomem *pmu;
+};
+
+static int bcm53573_ilp_enable(struct clk_hw *hw)
+{
+	struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);
+
+	writel(0x10199, ilp->pmu + PMU_SLOW_CLK_PERIOD);
+	writel(0x10000, ilp->pmu + 0x674);
+
+	return 0;
+}
+
+static unsigned long bcm53573_ilp_recalc_rate(struct clk_hw *hw,
+					      unsigned long parent_rate)
+{
+	struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);
+	void __iomem *pmu = ilp->pmu;
+	u32 last_val, cur_val;
+	u32 sum = 0, num = 0, loop_num = 0;
+	u32 avg;
+
+	/* Enable measurement */
+	writel(XTAL_CTL_EN, pmu + PMU_XTAL_FREQ_RATIO);
+
+	/* Read initial value */
+	last_val = readl(pmu + PMU_XTAL_FREQ_RATIO) & XTAL_ALP_PER_4ILP;
+
+	/*
+	 * At minimum we should loop for a bit to let hardware do the
+	 * measurement. This isn't very accurate however, so for a better
+	 * precision lets try getting 20 different values for and use average.
+	 */
+	while (num < 20) {
+		cur_val = readl(pmu + PMU_XTAL_FREQ_RATIO) & XTAL_ALP_PER_4ILP;
+
+		if (cur_val != last_val) {
+			/* Got different value, use it */
+			sum += cur_val;
+			num++;
+			loop_num = 0;
+			last_val = cur_val;
+		} else if (++loop_num > 5000) {
+			/* Same value over and over, give up */
+			sum += cur_val;
+			num++;
+			break;
+		}
+	}
+
+	/* Disable measurement to save power */
+	writel(0x0, pmu + PMU_XTAL_FREQ_RATIO);
+
+	avg = sum / num;
+
+	return parent_rate * 4 / avg;
+}
+
+static const struct clk_ops bcm53573_ilp_clk_ops = {
+	.enable = bcm53573_ilp_enable,
+	.recalc_rate = bcm53573_ilp_recalc_rate,
+};
+
+static void bcm53573_ilp_init(struct device_node *np)
+{
+	struct bcm53573_ilp *ilp;
+	struct resource res;
+	struct clk_init_data init = { 0 };
+	const char *parent_name;
+	int index;
+	int err;
+
+	ilp = kzalloc(sizeof(*ilp), GFP_KERNEL);
+	if (!ilp)
+		return;
+
+	parent_name = of_clk_get_parent_name(np, 0);
+	if (!parent_name) {
+		err = -ENOENT;
+		goto err_free_ilp;
+	}
+
+	/* TODO: This looks generic, try making it OF helper. */
+	index = of_property_match_string(np, "reg-names", "pmu");
+	if (index < 0) {
+		err = index;
+		goto err_free_ilp;
+	}
+	err = of_address_to_resource(np, index, &res);
+	if (err)
+		goto err_free_ilp;
+	ilp->pmu = ioremap(res.start, resource_size(&res));
+	if (IS_ERR(ilp->pmu)) {
+		err = PTR_ERR(ilp->pmu);
+		goto err_free_ilp;
+	}
+
+	init.name = np->name;
+	init.ops = &bcm53573_ilp_clk_ops;
+	init.parent_names = &parent_name;
+	init.num_parents = 1;
+
+	ilp->hw.init = &init;
+	ilp->clk = clk_register(NULL, &ilp->hw);
+	if (WARN_ON(IS_ERR(ilp->clk)))
+		goto err_unmap_pmu;
+
+	err = of_clk_add_provider(np, of_clk_src_simple_get, ilp->clk);
+	if (err)
+		goto err_clk_unregister;
+
+	return;
+
+err_clk_unregister:
+	clk_unregister(ilp->clk);
+err_unmap_pmu:
+	iounmap(ilp->pmu);
+err_free_ilp:
+	kfree(ilp);
+	pr_err("Failed to init ILP clock: %d\n", err);
+}
+CLK_OF_DECLARE(bcm53573_ilp_clk, "brcm,bcm53573-ilp", bcm53573_ilp_init);
-- 
2.9.3