Re: [PATCH v5 12/14] clk: tegra: Add EMC clock driver

[Mike Turquette]

Quoting Tomeu Vizoso (2014-11-18 04:13:14)
> From: Mikko Perttunen <mperttunen@xxxxxxxxxx>
> 
> The driver is currently only tested on Tegra124 Jetson TK1, but should
> work with other Tegra124 boards, provided that correct EMC tables are
> provided through the device tree. Older chip models have differing
> timing change sequences, so they are not currently supported.

Looks good to me.

Regards,
Mike

> 
> Signed-off-by: Mikko Perttunen <mperttunen@xxxxxxxxxx>
> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
> 
> ---
> 
> v5:     * Get a pointer to the EMC driver at runtime, to be used when
>           calling the EMC API.
>         * Misc. style fixes
>         * Fix logic for rounding down to a high rate
> 
> v4:     * Adapt to changes in the OF bindings
>         * Improve error handling
>         * Fix comment style
>         * Make static a few more functions
> 
> v3:     * Add some locking to protect the registers that are shared with the MC
>           clock
> 
> v2:     * Make sure that the clock is properly registered
>         * Bail out early from attempts to set the same rate
> ---
>  drivers/clk/tegra/Makefile       |   2 +-
>  drivers/clk/tegra/clk-emc.c      | 532 +++++++++++++++++++++++++++++++++++++++
>  drivers/clk/tegra/clk-tegra124.c |   4 +-
>  drivers/clk/tegra/clk.h          |   3 +
>  4 files changed, 539 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/clk/tegra/clk-emc.c
> 
> diff --git a/drivers/clk/tegra/Makefile b/drivers/clk/tegra/Makefile
> index f7dfb72..240e5b4 100644
> --- a/drivers/clk/tegra/Makefile
> +++ b/drivers/clk/tegra/Makefile
> @@ -14,4 +14,4 @@ obj-y                                 += clk-tegra-super-gen4.o
>  obj-$(CONFIG_ARCH_TEGRA_2x_SOC)         += clk-tegra20.o
>  obj-$(CONFIG_ARCH_TEGRA_3x_SOC)         += clk-tegra30.o
>  obj-$(CONFIG_ARCH_TEGRA_114_SOC)       += clk-tegra114.o
> -obj-$(CONFIG_ARCH_TEGRA_124_SOC)       += clk-tegra124.o
> +obj-$(CONFIG_ARCH_TEGRA_124_SOC)       += clk-tegra124.o clk-emc.o
> diff --git a/drivers/clk/tegra/clk-emc.c b/drivers/clk/tegra/clk-emc.c
> new file mode 100644
> index 0000000..399d945
> --- /dev/null
> +++ b/drivers/clk/tegra/clk-emc.c
> @@ -0,0 +1,532 @@
> +/*
> + * drivers/clk/tegra/clk-emc.c
> + *
> + * Copyright (c) 2014, NVIDIA CORPORATION.  All rights reserved.
> + *
> + * Author:
> + *     Mikko Perttunen <mperttunen@xxxxxxxxxx>
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#include <linux/clk-provider.h>
> +#include <linux/clk.h>
> +#include <linux/clkdev.h>
> +#include <linux/delay.h>
> +#include <linux/module.h>
> +#include <linux/of_address.h>
> +#include <linux/of_platform.h>
> +#include <linux/platform_device.h>
> +#include <linux/sort.h>
> +#include <linux/string.h>
> +
> +#include <soc/tegra/fuse.h>
> +#include <soc/tegra/emc.h>
> +
> +#include "clk.h"
> +
> +#define CLK_SOURCE_EMC 0x19c
> +
> +#define CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR_SHIFT 0
> +#define CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR_MASK 0xff
> +#define CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR(x) (((x) & CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR_MASK) << \
> +                                             CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR_SHIFT)
> +
> +#define CLK_SOURCE_EMC_EMC_2X_CLK_SRC_SHIFT 29
> +#define CLK_SOURCE_EMC_EMC_2X_CLK_SRC_MASK 0x7
> +#define CLK_SOURCE_EMC_EMC_2X_CLK_SRC(x) (((x) & CLK_SOURCE_EMC_EMC_2X_CLK_SRC_MASK) << \
> +                                         CLK_SOURCE_EMC_EMC_2X_CLK_SRC_SHIFT)
> +
> +static const char const *emc_parent_clk_names[] = {
> +       "pll_m", "pll_c", "pll_p", "clk_m", "pll_m_ud",
> +       "pll_c2", "pll_c3", "pll_c_ud"
> +};
> +
> +/*
> + * List of clock sources for various parents the EMC clock can have.
> + * When we change the timing to a timing with a parent that has the same
> + * clock source as the current parent, we must first change to a backup
> + * timing that has a different clock source.
> + */
> +
> +#define EMC_SRC_PLL_M 0
> +#define EMC_SRC_PLL_C 1
> +#define EMC_SRC_PLL_P 2
> +#define EMC_SRC_CLK_M 3
> +#define EMC_SRC_PLL_C2 4
> +#define EMC_SRC_PLL_C3 5
> +
> +static const char emc_parent_clk_sources[] = {
> +       EMC_SRC_PLL_M, EMC_SRC_PLL_C, EMC_SRC_PLL_P, EMC_SRC_CLK_M,
> +       EMC_SRC_PLL_M, EMC_SRC_PLL_C2, EMC_SRC_PLL_C3, EMC_SRC_PLL_C
> +};
> +
> +struct emc_timing {
> +       unsigned long rate, parent_rate;
> +       u8 parent_index;
> +       struct clk *parent;
> +       u32 ram_code;
> +};
> +
> +struct tegra_clk_emc {
> +       struct clk_hw hw;
> +       void __iomem *clk_regs;
> +       struct clk *prev_parent;
> +       bool changing_timing;
> +
> +       struct device_node *emc_node;
> +       struct tegra_emc *emc;
> +
> +       int num_timings;
> +       struct emc_timing *timings;
> +       spinlock_t *lock;
> +};
> +
> +/* Common clock framework callback implementations */
> +
> +static unsigned long emc_recalc_rate(struct clk_hw *hw,
> +                                    unsigned long parent_rate)
> +{
> +       struct tegra_clk_emc *tegra;
> +       u32 val, div;
> +
> +       tegra = container_of(hw, struct tegra_clk_emc, hw);
> +
> +       /*
> +        * CCF wrongly assumes that the parent won't change during set_rate,
> +        * so get the parent rate explicitly.
> +        */
> +       parent_rate = __clk_get_rate(__clk_get_parent(hw->clk));
> +
> +       val = readl(tegra->clk_regs + CLK_SOURCE_EMC);
> +       div = val & CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR_MASK;
> +
> +       return parent_rate / (div + 2) * 2;
> +}
> +
> +/*
> + * Rounds up unless no higher rate exists, in which case down. This way is
> + * safer since things have EMC rate floors. Also don't touch parent_rate
> + * since we don't want the CCF to play with our parent clocks.
> + */
> +static long emc_round_rate(struct clk_hw *hw, unsigned long rate,
> +                   unsigned long *parent_rate)
> +{
> +       struct tegra_clk_emc *tegra;
> +       u8 ram_code = tegra_read_ram_code();
> +       struct emc_timing *timing;
> +       int i;
> +
> +       tegra = container_of(hw, struct tegra_clk_emc, hw);
> +
> +       for (i = 0; i < tegra->num_timings; i++) {
> +               timing = tegra->timings + i;
> +               if (timing->ram_code != ram_code)
> +                       continue;
> +
> +               if (timing->rate >= rate)
> +                       return timing->rate;
> +       }
> +
> +       for (i = tegra->num_timings - 1; i >= 0; i--) {
> +               timing = tegra->timings + i;
> +               if (timing->ram_code != ram_code)
> +                       continue;
> +
> +               return timing->rate;
> +       }
> +
> +       return __clk_get_rate(hw->clk);
> +}
> +
> +static u8 emc_get_parent(struct clk_hw *hw)
> +{
> +       struct tegra_clk_emc *tegra;
> +       u32 val;
> +
> +       tegra = container_of(hw, struct tegra_clk_emc, hw);
> +
> +       val = readl(tegra->clk_regs + CLK_SOURCE_EMC);
> +
> +       return (val >> CLK_SOURCE_EMC_EMC_2X_CLK_SRC_SHIFT)
> +               & CLK_SOURCE_EMC_EMC_2X_CLK_SRC_MASK;
> +}
> +
> +static struct tegra_emc *emc_ensure_emc_driver(struct tegra_clk_emc *tegra)
> +{
> +       struct platform_device *pdev;
> +
> +       if (tegra->emc)
> +               return tegra->emc;
> +
> +       if (!tegra->emc_node)
> +               return NULL;
> +
> +       pdev = of_find_device_by_node(tegra->emc_node);
> +       if (!pdev) {
> +               pr_err("%s: could not get external memory controller\n",
> +                      __func__);
> +               return NULL;
> +       }
> +
> +       of_node_put(tegra->emc_node);
> +       tegra->emc_node = NULL;
> +
> +       tegra->emc = platform_get_drvdata(pdev);
> +       if (!tegra->emc) {
> +               pr_err("%s: cannot find EMC driver\n", __func__);
> +               return NULL;
> +       }
> +
> +       return tegra->emc;
> +}
> +
> +static int emc_set_timing(struct tegra_clk_emc *tegra,
> +                         struct emc_timing *timing)
> +{
> +       int err;
> +       u8 div;
> +       u32 car_value;
> +       unsigned long flags = 0;
> +       struct tegra_emc *emc = emc_ensure_emc_driver(tegra);
> +
> +       if (!emc)
> +               return -ENOENT;
> +
> +       pr_debug("going to rate %ld prate %ld p %s\n", timing->rate,
> +                timing->parent_rate, __clk_get_name(timing->parent));
> +
> +       if (emc_get_parent(&tegra->hw) == timing->parent_index &&
> +           clk_get_rate(timing->parent) != timing->parent_rate) {
> +               BUG();
> +               return -EINVAL;
> +       }
> +
> +       tegra->changing_timing = true;
> +
> +       err = clk_set_rate(timing->parent, timing->parent_rate);
> +       if (err) {
> +               pr_err("cannot change parent %s rate to %ld: %d\n",
> +                      __clk_get_name(timing->parent), timing->parent_rate,
> +                      err);
> +
> +               return err;
> +       }
> +
> +       err = clk_prepare_enable(timing->parent);
> +       if (err) {
> +               pr_err("cannot enable parent clock: %d\n", err);
> +               return err;
> +       }
> +
> +       div = timing->parent_rate / (timing->rate / 2) - 2;
> +
> +       err = tegra_emc_prepare_timing_change(emc, timing->rate);
> +       if (err)
> +               return err;
> +
> +       spin_lock_irqsave(tegra->lock, flags);
> +
> +       car_value = readl(tegra->clk_regs + CLK_SOURCE_EMC);
> +
> +       car_value &= ~CLK_SOURCE_EMC_EMC_2X_CLK_SRC(~0);
> +       car_value |= CLK_SOURCE_EMC_EMC_2X_CLK_SRC(timing->parent_index);
> +
> +       car_value &= ~CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR(~0);
> +       car_value |= CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR(div);
> +
> +       writel(car_value, tegra->clk_regs + CLK_SOURCE_EMC);
> +
> +       spin_unlock_irqrestore(tegra->lock, flags);
> +
> +       tegra_emc_complete_timing_change(emc, timing->rate);
> +
> +       __clk_reparent(tegra->hw.clk, timing->parent);
> +       clk_disable_unprepare(tegra->prev_parent);
> +
> +       tegra->prev_parent = timing->parent;
> +       tegra->changing_timing = false;
> +
> +       return 0;
> +}
> +
> +/*
> + * Get backup timing to use as an intermediate step when a change between
> + * two timings with the same clock source has been requested. First try to
> + * find a timing with a higher clock rate to avoid a rate below any set rate
> + * floors. If that is not possible, find a lower rate.
> + */
> +static struct emc_timing *get_backup_timing(struct tegra_clk_emc *tegra,
> +                                           int timing_index)
> +{
> +       int i;
> +       u32 ram_code = tegra_read_ram_code();
> +       struct emc_timing *timing;
> +
> +       for (i = timing_index+1; i < tegra->num_timings; i++) {
> +               timing = tegra->timings + i;
> +               if (timing->ram_code != ram_code)
> +                       continue;
> +
> +               if (emc_parent_clk_sources[timing->parent_index] !=
> +                   emc_parent_clk_sources[
> +                     tegra->timings[timing_index].parent_index])
> +                       return timing;
> +       }
> +
> +       for (i = timing_index-1; i >= 0; --i) {
> +               timing = tegra->timings + i;
> +               if (timing->ram_code != ram_code)
> +                       continue;
> +
> +               if (emc_parent_clk_sources[timing->parent_index] !=
> +                   emc_parent_clk_sources[
> +                     tegra->timings[timing_index].parent_index])
> +                       return timing;
> +       }
> +
> +       return NULL;
> +}
> +
> +static int emc_set_rate(struct clk_hw *hw, unsigned long rate,
> +                       unsigned long parent_rate)
> +{
> +       struct tegra_clk_emc *tegra;
> +       struct emc_timing *timing = NULL;
> +       int i, err;
> +       u32 ram_code = tegra_read_ram_code();
> +
> +       tegra = container_of(hw, struct tegra_clk_emc, hw);
> +
> +       if (__clk_get_rate(hw->clk) == rate)
> +               return 0;
> +
> +       /*
> +        * When emc_set_timing changes the parent rate, CCF will propagate
> +        * that downward to us, so ignore any set_rate calls while a rate
> +        * change is already going on.
> +        */
> +       if (tegra->changing_timing)
> +               return 0;
> +
> +       for (i = 0; i < tegra->num_timings; i++) {
> +               if (tegra->timings[i].rate == rate &&
> +                   tegra->timings[i].ram_code == ram_code) {
> +                       timing = tegra->timings + i;
> +                       break;
> +               }
> +       }
> +
> +       if (!timing) {
> +               pr_err("cannot switch to rate %ld without emc table\n", rate);
> +               return -EINVAL;
> +       }
> +
> +       if (emc_parent_clk_sources[emc_get_parent(hw)] ==
> +           emc_parent_clk_sources[timing->parent_index] &&
> +           clk_get_rate(timing->parent) != timing->parent_rate) {
> +               /*
> +                * Parent clock source not changed but parent rate has changed,
> +                * need to temporarily switch to another parent
> +                */
> +
> +               struct emc_timing *backup_timing;
> +
> +               backup_timing = get_backup_timing(tegra, i);
> +               if (!backup_timing) {
> +                       pr_err("cannot find backup timing\n");
> +                       return -EINVAL;
> +               }
> +
> +               pr_debug("using %ld as backup rate when going to %ld\n",
> +                        backup_timing->rate, rate);
> +
> +               err = emc_set_timing(tegra, backup_timing);
> +               if (err) {
> +                       pr_err("cannot set backup timing: %d\n", err);
> +                       return err;
> +               }
> +       }
> +
> +       return emc_set_timing(tegra, timing);
> +}
> +
> +/* Initialization and deinitialization */
> +
> +static int load_one_timing_from_dt(struct tegra_clk_emc *tegra,
> +                                  struct emc_timing *timing,
> +                                  struct device_node *node)
> +{
> +       int err, i;
> +       u32 tmp;
> +
> +       err = of_property_read_u32(node, "clock-frequency", &tmp);
> +       if (err) {
> +               pr_err("timing %s: failed to read rate\n", node->full_name);
> +               return err;
> +       }
> +
> +       timing->rate = tmp;
> +
> +       err = of_property_read_u32(node, "nvidia,parent-clock-frequency", &tmp);
> +       if (err) {
> +               pr_err("timing %s: failed to read parent rate\n",
> +                      node->full_name);
> +               return err;
> +       }
> +
> +       timing->parent_rate = tmp;
> +
> +       timing->parent = of_clk_get_by_name(node, "emc-parent");
> +       if (IS_ERR(timing->parent)) {
> +               pr_err("timing %s: failed to get parent clock\n",
> +                      node->full_name);
> +               return PTR_ERR(timing->parent);
> +       }
> +
> +       timing->parent_index = 0xff;
> +       for (i = 0; i < ARRAY_SIZE(emc_parent_clk_names); i++) {
> +               if (!strcmp(emc_parent_clk_names[i],
> +                           __clk_get_name(timing->parent))) {
> +                       timing->parent_index = i;
> +                       break;
> +               }
> +       }
> +       if (timing->parent_index == 0xff) {
> +               pr_err("timing %s: %s is not a valid parent\n",
> +                      node->full_name, __clk_get_name(timing->parent));
> +               clk_put(timing->parent);
> +               return -EINVAL;
> +       }
> +
> +       return 0;
> +}
> +
> +static int cmp_timings(const void *_a, const void *_b)
> +{
> +       const struct emc_timing *a = _a;
> +       const struct emc_timing *b = _b;
> +
> +       if (a->rate < b->rate)
> +               return -1;
> +       else if (a->rate == b->rate)
> +               return 0;
> +       else
> +               return 1;
> +}
> +
> +static int load_timings_from_dt(struct tegra_clk_emc *tegra,
> +                               struct device_node *node,
> +                               u32 ram_code)
> +{
> +       struct device_node *child;
> +       int child_count = of_get_child_count(node);
> +       int i = 0, err;
> +
> +       tegra->timings = kcalloc(child_count, sizeof(struct emc_timing),
> +                                GFP_KERNEL);
> +       if (!tegra->timings)
> +               return -ENOMEM;
> +
> +       tegra->num_timings = child_count;
> +
> +       for_each_child_of_node(node, child) {
> +               struct emc_timing *timing = tegra->timings + (i++);
> +
> +               err = load_one_timing_from_dt(tegra, timing, child);
> +               if (err)
> +                       return err;
> +
> +               timing->ram_code = ram_code;
> +       }
> +
> +       sort(tegra->timings, tegra->num_timings, sizeof(struct emc_timing),
> +            cmp_timings, NULL);
> +
> +       return 0;
> +}
> +
> +static const struct clk_ops tegra_clk_emc_ops = {
> +       .recalc_rate = emc_recalc_rate,
> +       .round_rate = emc_round_rate,
> +       .set_rate = emc_set_rate,
> +       .get_parent = emc_get_parent,
> +};
> +
> +struct clk *tegra_emc_init(struct device_node *np, void __iomem *clk_regs,
> +                          spinlock_t *lock)
> +{
> +       struct tegra_clk_emc *tegra;
> +       struct clk *clk;
> +       struct clk_init_data init;
> +       struct device_node *node;
> +       u32 node_ram_code;
> +       int err;
> +
> +       tegra = kcalloc(1, sizeof(*tegra), GFP_KERNEL);
> +       if (!tegra)
> +               return ERR_PTR(-ENOMEM);
> +
> +       tegra->clk_regs = clk_regs;
> +       tegra->lock = lock;
> +
> +       tegra->num_timings = 0;
> +
> +       for_each_child_of_node(np, node) {
> +               err = of_property_read_u32(node, "nvidia,ram-code",
> +                                          &node_ram_code);
> +               if (err) {
> +                       of_node_put(node);
> +                       continue;
> +               }
> +
> +               /*
> +                * Store timings for all ram codes as we cannot read the
> +                * fuses until the apbmisc driver is loaded.
> +                */
> +               err = load_timings_from_dt(tegra, node, node_ram_code);
> +               if (err)
> +                       return ERR_PTR(err);
> +               of_node_put(node);
> +               break;
> +       }
> +
> +       if (tegra->num_timings == 0)
> +               pr_warn("%s: no memory timings registered\n", __func__);
> +
> +       tegra->emc_node = of_parse_phandle(np,
> +                       "nvidia,external-memory-controller", 0);
> +       if (!tegra->emc_node)
> +               pr_warn("%s: couldn't find node for EMC driver\n", __func__);
> +
> +       init.name = "emc";
> +       init.ops = &tegra_clk_emc_ops;
> +       init.flags = 0;
> +       init.parent_names = emc_parent_clk_names;
> +       init.num_parents = ARRAY_SIZE(emc_parent_clk_names);
> +
> +       tegra->hw.init = &init;
> +
> +       clk = clk_register(NULL, &tegra->hw);
> +       if (IS_ERR(clk))
> +               return clk;
> +
> +       tegra->prev_parent = clk_get_parent_by_index(
> +               tegra->hw.clk, emc_get_parent(&tegra->hw));
> +       tegra->changing_timing = false;
> +
> +       /* Allow debugging tools to see the EMC clock */
> +       clk_register_clkdev(clk, "emc", "tegra-clk-debug");
> +
> +       clk_prepare_enable(clk);
> +
> +       return clk;
> +};
> diff --git a/drivers/clk/tegra/clk-tegra124.c b/drivers/clk/tegra/clk-tegra124.c
> index 07ec882..d56d1e2 100644
> --- a/drivers/clk/tegra/clk-tegra124.c
> +++ b/drivers/clk/tegra/clk-tegra124.c
> @@ -1383,7 +1383,6 @@ static struct tegra_clk_init_table init_table[] __initdata = {
>         {TEGRA124_CLK_XUSB_HOST_SRC, TEGRA124_CLK_PLL_RE_OUT, 112000000, 0},
>         {TEGRA124_CLK_SATA, TEGRA124_CLK_PLL_P, 104000000, 0},
>         {TEGRA124_CLK_SATA_OOB, TEGRA124_CLK_PLL_P, 204000000, 0},
> -       {TEGRA124_CLK_EMC, TEGRA124_CLK_CLK_MAX, 0, 1},
>         {TEGRA124_CLK_CCLK_G, TEGRA124_CLK_CLK_MAX, 0, 1},
>         {TEGRA124_CLK_MSELECT, TEGRA124_CLK_CLK_MAX, 0, 1},
>         {TEGRA124_CLK_CSITE, TEGRA124_CLK_CLK_MAX, 0, 1},
> @@ -1439,6 +1438,9 @@ static void __init tegra124_clock_init(struct device_node *np)
>         tegra_super_clk_gen4_init(clk_base, pmc_base, tegra124_clks,
>                                         &pll_x_params);
>         tegra_add_of_provider(np);
> +
> +       clks[TEGRA124_CLK_EMC] = tegra_emc_init(np, clk_base, &emc_lock);
> +
>         tegra_register_devclks(devclks, ARRAY_SIZE(devclks));
>  
>         tegra_clk_apply_init_table = tegra124_clock_apply_init_table;
> diff --git a/drivers/clk/tegra/clk.h b/drivers/clk/tegra/clk.h
> index 4e458aa..097f972 100644
> --- a/drivers/clk/tegra/clk.h
> +++ b/drivers/clk/tegra/clk.h
> @@ -623,6 +623,9 @@ void tegra_super_clk_gen4_init(void __iomem *clk_base,
>                         void __iomem *pmc_base, struct tegra_clk *tegra_clks,
>                         struct tegra_clk_pll_params *pll_params);
>  
> +struct clk *tegra_emc_init(struct device_node *np, void __iomem *clk_regs,
> +                          spinlock_t *lock);
> +
>  void tegra114_clock_tune_cpu_trimmers_high(void);
>  void tegra114_clock_tune_cpu_trimmers_low(void);
>  void tegra114_clock_tune_cpu_trimmers_init(void);
> -- 
> 1.9.3
> 
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