On 11.11.2019 05:18, Chanwoo Choi wrote:
> Hi Leonard,
>
> On 11/9/19 7:39 AM, Leonard Crestez wrote:
>> Add driver for dynamic scaling the DDR Controller on imx8m chips. Actual
>> frequency switching is implemented inside TF-A, this driver wraps the
>> SMC calls and synchronizes the clk tree.
>>
>> The DRAM clocks on imx8m have the following structure (abridged):
>>
>> +----------+ |\ +------+
>> | dram_pll |-------|M| dram_core | |
>> +----------+ |U|---------->| D |
>> /--|X| | D |
>> dram_alt_root | |/ | R |
>> | | C |
>> +---------+ | |
>> |FIX DIV/4| | |
>> +---------+ | |
>> composite: | | |
>> +----------+ | | |
>> | dram_alt |----/ | |
>> +----------+ | |
>> | dram_apb |-------------------->| |
>> +----------+ +------+
>>
>> The dram_pll is used for higher rates and dram_alt is used for lower
>> rates. The dram_alt and dram_apb clocks are "imx composite" and their
>> parent can also be modified.
>>
>> This driver will prepare/enable the new parents ahead of switching (so
>> that the expected roots are enabled) and afterwards it will call
>> clk_set_parent to ensure the parents in clock framework are up-to-date.
>>
>> The driver relies on dram_pll dram_alt and dram_apb being marked with
>> CLK_GET_RATE_NOCACHE for rate updates.
>>
>> Signed-off-by: Leonard Crestez <leonard.crestez@xxxxxxx>
>> ---
>> drivers/devfreq/Kconfig | 10 +
>> drivers/devfreq/Makefile | 1 +
>> drivers/devfreq/imx8m-ddrc.c | 416 +++++++++++++++++++++++++++++++++++
>> 3 files changed, 427 insertions(+)
>> create mode 100644 drivers/devfreq/imx8m-ddrc.c
>>
>> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
>> index defe1d438710..c519fd27808f 100644
>> --- a/drivers/devfreq/Kconfig
>> +++ b/drivers/devfreq/Kconfig
>> @@ -90,10 +90,20 @@ config ARM_EXYNOS_BUS_DEVFREQ
>> Each memory bus group could contain many memoby bus block. It reads
>> PPMU counters of memory controllers by using DEVFREQ-event device
>> and adjusts the operating frequencies and voltages with OPP support.
>> This does not yet operate with optimal voltages.
>>
>> +config ARM_IMX8M_DDRC_DEVFREQ
>> + tristate "i.MX8M DDRC DEVFREQ Driver"
>> + depends on ARCH_MXC || COMPILE_TEST
>> + select DEVFREQ_GOV_SIMPLE_ONDEMAND
>> + select DEVFREQ_GOV_USERSPACE
>> + select PM_OPP
>
> It doesn't need to add. CONFIG_DEVFREQ add 'select PM_OPP'
> because 'PM_OPP' is mandatory for devfreq.
OK.
All other drivers select PM_OPP, this was just copied
>> + help
>> + This adds the DEVFREQ driver for the i.MX8M DDR Controller. It allows
>> + adjusting DRAM frequency.
>> +
>> config ARM_TEGRA_DEVFREQ
>> tristate "NVIDIA Tegra30/114/124/210 DEVFREQ Driver"
>> depends on ARCH_TEGRA_3x_SOC || ARCH_TEGRA_114_SOC || \
>> ARCH_TEGRA_132_SOC || ARCH_TEGRA_124_SOC || \
>> ARCH_TEGRA_210_SOC || \
>> diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
>> index 338ae8440db6..3eb4d5e6635c 100644
>> --- a/drivers/devfreq/Makefile
>> +++ b/drivers/devfreq/Makefile
>> @@ -7,10 +7,11 @@ obj-$(CONFIG_DEVFREQ_GOV_POWERSAVE) += governor_powersave.o
>> obj-$(CONFIG_DEVFREQ_GOV_USERSPACE) += governor_userspace.o
>> obj-$(CONFIG_DEVFREQ_GOV_PASSIVE) += governor_passive.o
>>
>> # DEVFREQ Drivers
>> obj-$(CONFIG_ARM_EXYNOS_BUS_DEVFREQ) += exynos-bus.o
>> +obj-$(CONFIG_ARM_IMX8M_DDRC_DEVFREQ) += imx8m-ddrc.o
>> obj-$(CONFIG_ARM_RK3399_DMC_DEVFREQ) += rk3399_dmc.o
>> obj-$(CONFIG_ARM_TEGRA_DEVFREQ) += tegra30-devfreq.o
>> obj-$(CONFIG_ARM_TEGRA20_DEVFREQ) += tegra20-devfreq.o
>>
>> # DEVFREQ Event Drivers
>> diff --git a/drivers/devfreq/imx8m-ddrc.c b/drivers/devfreq/imx8m-ddrc.c
>> new file mode 100644
>> index 000000000000..51903fee21a7
>> --- /dev/null
>> +++ b/drivers/devfreq/imx8m-ddrc.c
>> @@ -0,0 +1,416 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright 2019 NXP
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/device.h>
>> +#include <linux/of_device.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/devfreq.h>
>> +#include <linux/pm_opp.h>
>> +#include <linux/clk.h>
>> +#include <linux/clk-provider.h>
>> +#include <linux/arm-smccc.h>
>> +
>> +#define IMX_SIP_DDR_DVFS 0xc2000004
>> +
>> +/* Values starting from 0 switch to specific frequency */
>> +#define IMX_SIP_DDR_FREQ_SET_HIGH 0x00
>> +
>> +/* Deprecated after moving IRQ handling to ATF */
>> +#define IMX_SIP_DDR_DVFS_WAIT_CHANGE 0x0F
>> +
>> +/* Query available frequencies. */
>> +#define IMX_SIP_DDR_DVFS_GET_FREQ_COUNT 0x10
>> +#define IMX_SIP_DDR_DVFS_GET_FREQ_INFO 0x11
>> +
>> +/*
>> + * This should be in a 1:1 mapping with devicetree OPPs but
>> + * firmware provides additional info.
>> + */
>> +struct imx8m_ddrc_freq {
>> + unsigned long rate;
>> + unsigned long smcarg;
>> + int dram_core_parent_index;
>> + int dram_alt_parent_index;
>> + int dram_apb_parent_index;
>> +};
>> +
>> +/* Hardware limitation */
>> +#define IMX8M_DDRC_MAX_FREQ_COUNT 4
>> +
>> +/*
>> + * i.MX8M DRAM Controller clocks have the following structure (abridged):
>> + *
>> + * +----------+ |\ +------+
>> + * | dram_pll |-------|M| dram_core | |
>> + * +----------+ |U|---------->| D |
>> + * /--|X| | D |
>> + * dram_alt_root | |/ | R |
>> + * | | C |
>> + * +---------+ | |
>> + * |FIX DIV/4| | |
>> + * +---------+ | |
>> + * composite: | | |
>> + * +----------+ | | |
>> + * | dram_alt |----/ | |
>> + * +----------+ | |
>> + * | dram_apb |-------------------->| |
>> + * +----------+ +------+
>> + *
>> + * The dram_pll is used for higher rates and dram_alt is used for lower rates.
>> + *
>> + * Frequency switching is implemented in TF-A (via SMC call) and can change the
>> + * configuration of the clocks, including mux parents. The dram_alt and
>> + * dram_apb clocks are "imx composite" and their parent can change too.
>> + *
>> + * We need to prepare/enable the new mux parents head of switching and update
>> + * their information afterwards.
>> + */
>> +struct imx8m_ddrc {
>> + struct devfreq_dev_profile profile;
>> + struct devfreq *devfreq;
>> +
>> + /* For frequency switching: */
>> + struct clk *dram_core;
>> + struct clk *dram_pll;
>> + struct clk *dram_alt;
>> + struct clk *dram_apb;
>> +
>> + int freq_count;
>> + struct imx8m_ddrc_freq freq_table[IMX8M_DDRC_MAX_FREQ_COUNT];
>> +};
>> +
>> +static struct imx8m_ddrc_freq *imx8m_ddrc_find_freq(struct imx8m_ddrc *priv,
>> + unsigned long rate)
>> +{
>> + struct imx8m_ddrc_freq *freq;
>> + int i;
>> +
>> + /*
>> + * Firmware reports values in MT/s, so we round-down from Hz
>> + * Rounding is extra generous to ensure a match.
>> + */
>> + rate = DIV_ROUND_CLOSEST(rate, 250000);
>> + for (i = 0; i < priv->freq_count; ++i) {
>> + freq = &priv->freq_table[i];
>> + if (freq->rate == rate ||
>> + freq->rate + 1 == rate ||
>> + freq->rate - 1 == rate)
>> + return freq;
>> + }
>> +
>> + return NULL;
>> +}
>> +
>> +static void imx8m_ddrc_smc_set_freq(int target_freq)
>> +{
>> + struct arm_smccc_res res;
>> + u32 online_cpus = 0;
>> + int cpu;
>> +
>> + local_irq_disable();
>
> local_irq_disable is more proper than local_irq_save()?
There's no need to use save/restore because we know that irqs are
enabled when entering the function. This is only called from devfreq
set_target which runs in process context.
>
>> +
>> + for_each_online_cpu(cpu)
>> + online_cpus |= (1 << (cpu * 8));
>> +
>> + /* change the ddr freqency */
>> + arm_smccc_smc(IMX_SIP_DDR_DVFS, target_freq, online_cpus,
>> + 0, 0, 0, 0, 0, &res);
>> +
>> + local_irq_enable();
>
> ditto. local_irq_restore() instead of local_irq_enable()
>
>> +}
>> +
>> +struct clk *clk_get_parent_by_index(struct clk *clk, int index)
>> +{
>> + struct clk_hw *hw;
>> +
>> + hw = clk_hw_get_parent_by_index(__clk_get_hw(clk), index);
>> +
>> + return hw ? hw->clk : NULL;
>> +}
>> +
>> +static int imx8m_ddrc_set_freq(struct device *dev, struct imx8m_ddrc_freq *freq)
>> +{
>> + struct imx8m_ddrc *priv = dev_get_drvdata(dev);
>> + struct clk *new_dram_core_parent;
>> + struct clk *new_dram_alt_parent;
>> + struct clk *new_dram_apb_parent;
>> + int ret;
>> +
>> + new_dram_core_parent = clk_get_parent_by_index(
> > You can use 'clk_hw_get_parent_by_index' directly.
The helper above avoids duplicating ?:
> And, you need to check whether the return value is NULL or not.
Yes for dram_core_parent but others are deliberately allowed to be NULL.
For some setpoints some parents might be indifferent or require no
changes. For example when dram_core has pll as parent the expectation is
that dram_all will be OFF so parent is irrelevant.
Driver relies on the fact that clock API ignores prepare/enable for NULL
clocks. I can add a comment explaining that.
>> + priv->dram_core, freq->dram_core_parent_index - 1);
>> + new_dram_alt_parent = clk_get_parent_by_index(
>
> ditto.
>
>> + priv->dram_alt, freq->dram_alt_parent_index - 1);
>> + new_dram_apb_parent = clk_get_parent_by_index(
>
> ditto.
>> + priv->dram_apb, freq->dram_apb_parent_index - 1);
>> +
>> + /* increase reference counts and ensure clks are ON before switch */
>> + ret = clk_prepare_enable(new_dram_core_parent);
>> + if (ret) {
>> + dev_err(dev, "failed enable new dram_core parent: %d\n", ret);
>> + goto out;
>> + }
>> + ret = clk_prepare_enable(new_dram_alt_parent);
>> + if (ret) {
>> + dev_err(dev, "failed enable new dram_alt parent: %d\n", ret);
>> + goto out_dis_core;
>
> I think that 'dis' is not general expression for 'disable'.
> Just, I think that 'out_disable_core' is better than 'out_dis_core'.
OK
>> + }
>> + ret = clk_prepare_enable(new_dram_apb_parent);
>> + if (ret) {
>> + dev_err(dev, "failed enable new dram_apb parent: %d\n", ret);
>> + goto out_dis_alt;
>
> ditto.
>
>> + }
>> +
>> + imx8m_ddrc_smc_set_freq(freq->smcarg);
>> +
>> + /* update parents in clk tree after switch. */
>> + ret = clk_set_parent(priv->dram_core, new_dram_core_parent);
>> + if (ret)
>> + dev_err(dev, "failed set dram_core parent: %d\n", ret);
>
> if you don't return directly, you better to use 'dev_warn' instead of 'dev_err'.
OK.
>> + if (new_dram_alt_parent) {
>> + ret = clk_set_parent(priv->dram_alt, new_dram_alt_parent);
>> + if (ret)
>> + dev_err(dev, "failed set dram_alt parent: %d\n", ret);
>
> ditto. Use dev_warn.
>
>> + }
>> + if (new_dram_apb_parent) {
>> + ret = clk_set_parent(priv->dram_apb, new_dram_apb_parent);
>> + if (ret)
>> + dev_err(dev, "failed set dram_apb parent: %d\n", ret);
>
> ditto. Use dev_warn.
>
>> + }
>> +
>> + /*
>> + * Explicitly refresh dram PLL rate.
>> + *
>> + * Even if it's marked with CLK_GET_RATE_NOCACHE the rate will not be
>
> nitpick:
> What is more proper description either or 'Even if' or 'if' ?
Rate updates work for dram_alt/apb but not for dram_pll because
additional clocks might be present between the PLL and dram_core mux.
This happens *even if* pll is marked with CLK_GET_RATE_NOCACHE.
>> + * automatically refreshed when clk_get_rate is called on children.
>> + */
>> + clk_get_rate(priv->dram_pll);
>> +
>> + /*
>> + * clk_set_parent transfer the reference count from old parent.
>> + * now we drop extra reference counts used during the switch
>> + */
>> + clk_disable_unprepare(new_dram_apb_parent);
>> +out_dis_alt:
>> + clk_disable_unprepare(new_dram_alt_parent);
>> +out_dis_core:
>> + clk_disable_unprepare(new_dram_core_parent);
>> +out:
>> + return ret;
>> +}
>> +
>> +static int imx8m_ddrc_target(struct device *dev, unsigned long *freq, u32 flags)
>> +{
>> + struct imx8m_ddrc *priv = dev_get_drvdata(dev);
>> + struct imx8m_ddrc_freq *freq_info;
>> + struct dev_pm_opp *new_opp;
>> + unsigned long old_freq, new_freq;
>> + int ret;
>> +
>> + new_opp = devfreq_recommended_opp(dev, freq, flags);
>> + if (IS_ERR(new_opp)) {
>> + ret = PTR_ERR(new_opp);
>> + dev_err(dev, "failed to get recommended opp: %d\n", ret);
>> + return ret;
>> + }
>> + dev_pm_opp_put(new_opp);
>> +
>> + old_freq = clk_get_rate(priv->dram_core);
>> + if (*freq == old_freq)
>> + return 0;
>> +
>> + freq_info = imx8m_ddrc_find_freq(priv, *freq);
>> + if (!freq_info)
>> + return -EINVAL;
>> + ret = imx8m_ddrc_set_freq(dev, freq_info);
>
> Need to check whether 'ret' is valid or not.
>
>> +
>> + /* Also read back the clk rate to verify switch was correct */
>> + new_freq = clk_get_rate(priv->dram_core);
>> + if (ret || *freq != new_freq)
>
> You should check 'ret' right after imx8m_ddrc_set_freq()
> instead of this position.
OK, I can add two error paths.
>> + dev_err(dev, "ddrc failed freq set to %lu from %lu, now at %lu\n",
>> + old_freq, *freq, new_freq);
>> + else
>> + dev_dbg(dev, "ddrc freq set to %lu (was %lu)\n",
>> + *freq, old_freq);
>> +
>> + return ret;
>> +}
>> +
>> +static int imx8m_ddrc_get_cur_freq(struct device *dev, unsigned long *freq)
>> +{
>> + struct imx8m_ddrc *priv = dev_get_drvdata(dev);
>> +
>> + *freq = clk_get_rate(priv->dram_core);
>> +
>> + return 0;
>> +}
>> +
>> +static int imx8m_ddrc_init_freq_info(struct device *dev)
>> +{
>> + struct imx8m_ddrc *priv = dev_get_drvdata(dev);
>> + struct arm_smccc_res res;
>> + int index;
>> +
>> + /*
>> + * An error here means DDR DVFS API not supported by firmware
>> + */
>
> Don't need to add multiple line comments. It is possible to be change as following:
>
> /* An error here means DDR DVFS API not supported by firmware */
OK.
>> + arm_smccc_smc(IMX_SIP_DDR_DVFS, IMX_SIP_DDR_DVFS_GET_FREQ_COUNT,
>> + 0, 0, 0, 0, 0, 0, &res);
>> + priv->freq_count = res.a0;
>> + if (priv->freq_count <= 0 ||
>> + priv->freq_count > IMX8M_DDRC_MAX_FREQ_COUNT)
>> + return -ENODEV;
>> +
>> + for (index = 0; index < priv->freq_count; ++index) {
>> + struct imx8m_ddrc_freq *freq = &priv->freq_table[index];
>> +
>> + arm_smccc_smc(IMX_SIP_DDR_DVFS, IMX_SIP_DDR_DVFS_GET_FREQ_INFO,
>> + index, 0, 0, 0, 0, 0, &res);
>> + /* Result should be strictly positive */
>> + if ((long)res.a0 <= 0)
>> + return -ENODEV;
>> +
>> + freq->rate = res.a0;
>> + freq->smcarg = index;
>> + freq->dram_core_parent_index = res.a1;
>> + freq->dram_alt_parent_index = res.a2;
>> + freq->dram_apb_parent_index = res.a3;
>> +
>> + /* dram_core has 2 options: dram_pll or dram_alt_root */
>> + if (freq->dram_core_parent_index != 1 &&
>> + freq->dram_core_parent_index != 2)
>> + return -ENODEV;
>> + /* dram_apb and dram_alt have exactly 8 possible parents */
>> + if (freq->dram_alt_parent_index > 8 ||
>> + freq->dram_apb_parent_index > 8)
>> + return -ENODEV;
>> + /* dram_core from alt requires explicit dram_alt parent */
>> + if (freq->dram_core_parent_index == 2 &&
>> + freq->dram_alt_parent_index == 0)
>> + return -ENODEV;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +/* imx8m_ddrc_check_opps() - disable OPPs not supported by firmware */
>
> nitpick:
> On this driver, there are no some description for internal function.
> In order to keep the coding style, you better to move this comment
> into function before 'freq = ULONG_MAX'.
Is it a problem if only some internal functions have documentation? I
can add docs to more functions.
BTW: how can I generate devfreq documentation from these comments?
>> +static int imx8m_ddrc_check_opps(struct device *dev)
>> +{
>> + struct imx8m_ddrc *priv = dev_get_drvdata(dev);
>> + struct imx8m_ddrc_freq *freq_info;
>> + struct dev_pm_opp *opp;
>> + unsigned long freq;
>> +
>> + freq = ULONG_MAX;
>> + while (true) {
>> + opp = dev_pm_opp_find_freq_floor(dev, &freq);
>> + if (opp == ERR_PTR(-ERANGE))
>> + break;
>> + if (IS_ERR(opp)) {
>> + dev_err(dev, "Failed enumerating OPPs: %ld\n",
>> + PTR_ERR(opp));
>> + return PTR_ERR(opp);
>> + }
>> + dev_pm_opp_put(opp);
>> +
>> + freq_info = imx8m_ddrc_find_freq(priv, freq);
>> + if (!freq_info) {
>> + dev_info(dev, "Disable unsupported OPP %luHz %luMT/s\n",
>> + freq, DIV_ROUND_CLOSEST(freq, 250000));
>> + dev_pm_opp_disable(dev, freq);
>> + }
>> +
>> + freq--;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static void imx8m_ddrc_exit(struct device *dev)
>> +{
>> + dev_pm_opp_of_remove_table(dev);
>> +}
>> +
>> +static int imx8m_ddrc_probe(struct platform_device *pdev)
>> +{
>> + struct device *dev = &pdev->dev;
>> + struct imx8m_ddrc *priv;
>> + const char *gov = DEVFREQ_GOV_USERSPACE;
>> + int ret;
>> +
>> + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
>> + if (!priv)
>> + return -ENOMEM;
>> +
>> + platform_set_drvdata(pdev, priv);
>> +
>> + ret = imx8m_ddrc_init_freq_info(dev);
>> + if (ret) {
>> + dev_err(dev, "failed to init firmware freq info: %d\n", ret);
>> + return ret;
>> + }
>> +
>> + priv->dram_core = devm_clk_get(dev, "core");
>> + priv->dram_pll = devm_clk_get(dev, "pll");
>> + priv->dram_alt = devm_clk_get(dev, "alt");
>> + priv->dram_apb = devm_clk_get(dev, "apb");
>> + if (IS_ERR(priv->dram_core) ||
>> + IS_ERR(priv->dram_pll) ||
>> + IS_ERR(priv->dram_alt) ||
>> + IS_ERR(priv->dram_apb)) {
>> + ret = PTR_ERR(priv->devfreq);
>> + dev_err(dev, "failed to fetch clocks: %d\n", ret);
>> + return ret;
>> + }
>> +
>> + ret = dev_pm_opp_of_add_table(dev);
>> + if (ret < 0) {
>> + dev_err(dev, "failed to get OPP table\n");
>> + return ret;
>> + }
>> +
>> + ret = imx8m_ddrc_check_opps(dev);
>> + if (ret < 0)
>> + goto err;
>> +
>> + priv->profile.polling_ms = 1000;
>> + priv->profile.target = imx8m_ddrc_target;
>> + priv->profile.exit = imx8m_ddrc_exit;
>> + priv->profile.get_cur_freq = imx8m_ddrc_get_cur_freq;
>> + priv->profile.initial_freq = clk_get_rate(priv->dram_core);
>> +
>> + priv->devfreq = devm_devfreq_add_device(dev, &priv->profile,
>> + gov, NULL);
>> + if (IS_ERR(priv->devfreq)) {
>> + ret = PTR_ERR(priv->devfreq);
>> + dev_err(dev, "failed to add devfreq device: %d\n", ret);
>> + goto err;
>> + }
>> +
>> + return 0;
>> +
>> +err:
>> + dev_pm_opp_of_remove_table(dev);
>> + return ret;
>> +}
>> +
>> +static const struct of_device_id imx8m_ddrc_of_match[] = {
>> + { .compatible = "fsl,imx8m-ddrc", },
>> + { /* sentinel */ },
>> +};
>> +MODULE_DEVICE_TABLE(of, imx8m_ddrc_of_match);
>> +
>> +static struct platform_driver imx8m_ddrc_platdrv = {
>> + .probe = imx8m_ddrc_probe,
>> + .driver = {
>> + .name = "imx8m-ddrc-devfreq",
>> + .of_match_table = of_match_ptr(imx8m_ddrc_of_match),
>> + },
>> +};
>> +module_platform_driver(imx8m_ddrc_platdrv);
>> +
>> +MODULE_DESCRIPTION("i.MX8M DDR Controller frequency driver");
>> +MODULE_AUTHOR("Leonard Crestez <leonard.crestez@xxxxxxx>");
>> +MODULE_LICENSE("GPL v2");
