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    Subject[PATCH V4] clk: bcm: Add driver for BCM53573 ILP clock
    Date
    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.
    ---
    .../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..73f7d2b
    --- /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,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..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..53b4a23
    --- /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 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);
    --
    2.9.3
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