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Subject[PATCH V3] clk: bcm: Add driver for Northstar ILP clock
Date
From: Rafał Miłecki <rafal@milecki.pl>

This clock is present on cheaper Northstar devices like BCM53573 or
BCM47189 using Corex-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
---
.../devicetree/bindings/clock/brcm,ns-ilp.txt | 40 ++++++
drivers/clk/bcm/Makefile | 1 +
drivers/clk/bcm/clk-ns-ilp.c | 146 +++++++++++++++++++++
3 files changed, 187 insertions(+)
create mode 100644 Documentation/devicetree/bindings/clock/brcm,ns-ilp.txt
create mode 100644 drivers/clk/bcm/clk-ns-ilp.c

diff --git a/Documentation/devicetree/bindings/clock/brcm,ns-ilp.txt b/Documentation/devicetree/bindings/clock/brcm,ns-ilp.txt
new file mode 100644
index 0000000..a18c73f
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/brcm,ns-ilp.txt
@@ -0,0 +1,40 @@
+Broadcom Northstar 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 Northstar devices using Corex-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,ns-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,ns-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..1389379 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_5301X) += clk-ns-ilp.o
diff --git a/drivers/clk/bcm/clk-ns-ilp.c b/drivers/clk/bcm/clk-ns-ilp.c
new file mode 100644
index 0000000..53b4a23
--- /dev/null
+++ b/drivers/clk/bcm/clk-ns-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 ns_ilp {
+ struct clk *clk;
+ struct clk_hw hw;
+ void __iomem *pmu;
+};
+
+static int ns_ilp_enable(struct clk_hw *hw)
+{
+ struct ns_ilp *ilp = container_of(hw, struct ns_ilp, hw);
+
+ writel(0x10199, ilp->pmu + PMU_SLOW_CLK_PERIOD);
+ writel(0x10000, ilp->pmu + 0x674);
+
+ return 0;
+}
+
+static unsigned long ns_ilp_recalc_rate(struct clk_hw *hw,
+ unsigned long parent_rate)
+{
+ struct ns_ilp *ilp = container_of(hw, struct ns_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 ns_ilp_clk_ops = {
+ .enable = ns_ilp_enable,
+ .recalc_rate = ns_ilp_recalc_rate,
+};
+
+static void ns_ilp_init(struct device_node *np)
+{
+ struct ns_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 = &ns_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(ns_ilp_clk, "brcm,ns-ilp", ns_ilp_init);
--
1.8.4.5
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