[PATCH V8] clk: bcm: Add driver for BCM53573 ILP clock

Rafał Miłecki
2016-09-13T07:07:54Z

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) multi-function
device so we use syscon (and regmap) for it.

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.
V6: Drop #include <linux/clk.h>
Use "int" as type where it matches usage
Add cpu_relax() in the loop
Add disable callback
Use _hw_ functions for registering struct clk_hw (new API)

Thanks a lot Stephen!
V7: Use syscon and regmap (thanks Rob!)
V8: Update Documentation (drop unused "reg", unit address)
---
.../bindings/clock/brcm,bcm53573-ilp.txt | 36 +++++
drivers/clk/bcm/Makefile | 1 +
drivers/clk/bcm/clk-bcm53573-ilp.c | 148 +++++++++++++++++++++
3 files changed, 185 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..2ebb107
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/brcm,bcm53573-ilp.txt
@@ -0,0 +1,36 @@
+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.
+
+ILP's rate has to be calculated on runtime and it depends on ALP clock
+which has to be referenced.
+
+This clock is part of PMU (Power Management Unit), a Broadcom's device
+handing power-related aspects. Its node must be sub-node of the PMU
+device.
+
+Required properties:
+- compatible: "brcm,bcm53573-ilp"
+- clocks: has to reference an ALP clock
+- #clock-cells: should be <0>
+- clock-output-names: from common clock bindings, should contain clock
+ name
+
+Example:
+
+pmu@18012000 {
+ compatible = "simple-mfd", "syscon";
+ reg = <0x18012000 0x00001000>;
+
+ ilp {
+ compatible = "brcm,bcm53573-ilp";
+ 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..1f4e30d
--- /dev/null
+++ b/drivers/clk/bcm/clk-bcm53573-ilp.c
@@ -0,0 +1,148 @@
+/*
+ * 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-provider.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/mfd/syscon.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/regmap.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_hw hw;
+ struct regmap *regmap;
+};
+
+static int bcm53573_ilp_enable(struct clk_hw *hw)
+{
+ struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);
+
+ regmap_write(ilp->regmap, PMU_SLOW_CLK_PERIOD, 0x10199);
+ regmap_write(ilp->regmap, 0x674, 0x10000);
+
+ return 0;
+}
+
+static void bcm53573_ilp_disable(struct clk_hw *hw)
+{
+ struct bcm53573_ilp *ilp = container_of(hw, struct bcm53573_ilp, hw);
+
+ regmap_write(ilp->regmap, PMU_SLOW_CLK_PERIOD, 0);
+ regmap_write(ilp->regmap, 0x674, 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);
+ struct regmap *regmap = ilp->regmap;
+ u32 last_val, cur_val;
+ int sum = 0, num = 0, loop_num = 0;
+ int avg;
+
+ /* Enable measurement */
+ regmap_write(regmap, PMU_XTAL_FREQ_RATIO, XTAL_CTL_EN);
+
+ /* Read initial value */
+ regmap_read(regmap, PMU_XTAL_FREQ_RATIO, &last_val);
+ last_val &= 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) {
+ regmap_read(regmap, PMU_XTAL_FREQ_RATIO, &cur_val);
+ cur_val &= 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;
+ }
+
+ cpu_relax();
+ }
+
+ /* Disable measurement to save power */
+ regmap_write(regmap, PMU_XTAL_FREQ_RATIO, 0x0);
+
+ avg = sum / num;
+
+ return parent_rate * 4 / avg;
+}
+
+static const struct clk_ops bcm53573_ilp_clk_ops = {
+ .enable = bcm53573_ilp_enable,
+ .disable = bcm53573_ilp_disable,
+ .recalc_rate = bcm53573_ilp_recalc_rate,
+};
+
+static void bcm53573_ilp_init(struct device_node *np)
+{
+ struct bcm53573_ilp *ilp;
+ struct clk_init_data init = { 0 };
+ const char *parent_name;
+ 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;
+ }
+
+ ilp->regmap = syscon_node_to_regmap(of_get_parent(np));
+ if (IS_ERR(ilp->regmap)) {
+ err = PTR_ERR(ilp->regmap);
+ 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;
+ err = clk_hw_register(NULL, &ilp->hw);
+ if (err)
+ goto err_free_ilp;
+
+ err = of_clk_add_hw_provider(np, of_clk_hw_simple_get, &ilp->hw);
+ if (err)
+ goto err_clk_hw_unregister;
+
+ return;
+
+err_clk_hw_unregister:
+ clk_hw_unregister(&ilp->hw);
+err_free_ilp:
+ kfree(ilp);
+ pr_err("Failed to init ILP clock: %d\n", err);
+}
+
+/* We need it very early for arch code, before device model gets ready */
+CLK_OF_DECLARE(bcm53573_ilp_clk, "brcm,bcm53573-ilp", bcm53573_ilp_init);
--
2.9.3