Re: [PATCH V3] clk: bcm: Add driver for Northstar ILP clock

[Jon Mason <jon.mason@broadcom.com>]

On Wed, Aug 10, 2016 at 8:05 AM, Rafał Miłecki <zajec5@gmail.com> wrote:
> 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>;

I don't see a corresponding DT entry in this patch, but 18012000 is
the PCI block.  So, I am concerned this will collide if used there.

I looked at the NS register reference guide, and I cannot find the
registers you are trying to reference.  Is this supposed to be
referencing the LCPLL clock registers in DMU?  If so, there is already
a driver in there for this (see drivers/clk/bcm/clk-nsp.c).

> +       #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
>