Re: [PATCH V5 11/18] clk: tegra210: Add support for Tegra210 clocks

[Sowjanya Komatineni <skomatineni@nvidia.com>]

On 7/14/19 2:41 PM, Dmitry Osipenko wrote:
> 13.07.2019 8:54, Sowjanya Komatineni пишет:
>> On 6/29/19 8:10 AM, Dmitry Osipenko wrote:
>>> 28.06.2019 5:12, Sowjanya Komatineni пишет:
>>>> This patch adds system suspend and resume support for Tegra210
>>>> clocks.
>>>>
>>>> All the CAR controller settings are lost on suspend when core power
>>>> goes off.
>>>>
>>>> This patch has implementation for saving and restoring all the PLLs
>>>> and clocks context during system suspend and resume to have the
>>>> clocks back to same state for normal operation.
>>>>
>>>> Acked-by: Thierry Reding <treding@nvidia.com>
>>>> Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
>>>> ---
>>>>    drivers/clk/tegra/clk-tegra210.c | 115
>>>> ++++++++++++++++++++++++++++++++++++++-
>>>>    drivers/clk/tegra/clk.c          |  14 +++++
>>>>    drivers/clk/tegra/clk.h          |   1 +
>>>>    3 files changed, 127 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/clk/tegra/clk-tegra210.c
>>>> b/drivers/clk/tegra/clk-tegra210.c
>>>> index 1c08c53482a5..1b839544e086 100644
>>>> --- a/drivers/clk/tegra/clk-tegra210.c
>>>> +++ b/drivers/clk/tegra/clk-tegra210.c
>>>> @@ -9,10 +9,12 @@
>>>>    #include <linux/clkdev.h>
>>>>    #include <linux/of.h>
>>>>    #include <linux/of_address.h>
>>>> +#include <linux/of_platform.h>
>>>>    #include <linux/delay.h>
>>>>    #include <linux/export.h>
>>>>    #include <linux/mutex.h>
>>>>    #include <linux/clk/tegra.h>
>>>> +#include <linux/syscore_ops.h>
>>>>    #include <dt-bindings/clock/tegra210-car.h>
>>>>    #include <dt-bindings/reset/tegra210-car.h>
>>>>    #include <linux/iopoll.h>
>>>> @@ -20,6 +22,7 @@
>>>>    #include <soc/tegra/pmc.h>
>>>>      #include "clk.h"
>>>> +#include "clk-dfll.h"
>>>>    #include "clk-id.h"
>>>>      /*
>>>> @@ -225,6 +228,7 @@
>>>>      #define CLK_RST_CONTROLLER_RST_DEV_Y_SET 0x2a8
>>>>    #define CLK_RST_CONTROLLER_RST_DEV_Y_CLR 0x2ac
>>>> +#define CPU_SOFTRST_CTRL 0x380
>>>>      #define LVL2_CLK_GATE_OVRA 0xf8
>>>>    #define LVL2_CLK_GATE_OVRC 0x3a0
>>>> @@ -2820,6 +2824,7 @@ static int tegra210_enable_pllu(void)
>>>>        struct tegra_clk_pll_freq_table *fentry;
>>>>        struct tegra_clk_pll pllu;
>>>>        u32 reg;
>>>> +    int ret;
>>>>          for (fentry = pll_u_freq_table; fentry->input_rate; fentry++) {
>>>>            if (fentry->input_rate == pll_ref_freq)
>>>> @@ -2847,10 +2852,10 @@ static int tegra210_enable_pllu(void)
>>>>        fence_udelay(1, clk_base);
>>>>        reg |= PLL_ENABLE;
>>>>        writel(reg, clk_base + PLLU_BASE);
>>>> +    fence_udelay(1, clk_base);
>>>>    -    readl_relaxed_poll_timeout_atomic(clk_base + PLLU_BASE, reg,
>>>> -                      reg & PLL_BASE_LOCK, 2, 1000);
>>>> -    if (!(reg & PLL_BASE_LOCK)) {
>>>> +    ret = tegra210_wait_for_mask(&pllu, PLLU_BASE, PLL_BASE_LOCK);
>>>> +    if (ret) {
>>>>            pr_err("Timed out waiting for PLL_U to lock\n");
>>>>            return -ETIMEDOUT;
>>>>        }
>>>> @@ -3283,6 +3288,103 @@ static void tegra210_disable_cpu_clock(u32 cpu)
>>>>    }
>>>>      #ifdef CONFIG_PM_SLEEP
>>>> +static u32 cpu_softrst_ctx[3];
>>>> +static struct platform_device *dfll_pdev;
>>>> +#define car_readl(_base, _off) readl_relaxed(clk_base + (_base) +
>>>> ((_off) * 4))
>>>> +#define car_writel(_val, _base, _off) \
>>>> +        writel_relaxed(_val, clk_base + (_base) + ((_off) * 4))
>>>> +
>>>> +static int tegra210_clk_suspend(void)
>>>> +{
>>>> +    unsigned int i;
>>>> +    struct device_node *node;
>>>> +
>>>> +    tegra_cclkg_burst_policy_save_context();
>>>> +
>>>> +    if (!dfll_pdev) {
>>>> +        node = of_find_compatible_node(NULL, NULL,
>>>> +                           "nvidia,tegra210-dfll");
>>>> +        if (node)
>>>> +            dfll_pdev = of_find_device_by_node(node);
>>>> +
>>>> +        of_node_put(node);
>>>> +        if (!dfll_pdev)
>>>> +            pr_err("dfll node not found. no suspend for dfll\n");
>>>> +    }
>>>> +
>>>> +    if (dfll_pdev)
>>>> +        tegra_dfll_suspend(dfll_pdev);
>>>> +
>>>> +    /* Enable PLLP_OUT_CPU after dfll suspend */
>>>> +    tegra_clk_set_pllp_out_cpu(true);
>>>> +
>>>> +    tegra_sclk_cclklp_burst_policy_save_context();
>>>> +
>>>> +    clk_save_context();
>>>> +
>>>> +    for (i = 0; i < ARRAY_SIZE(cpu_softrst_ctx); i++)
>>>> +        cpu_softrst_ctx[i] = car_readl(CPU_SOFTRST_CTRL, i);
>>>> +
>>>> +    return 0;
>>>> +}
>>>> +
>>>> +static void tegra210_clk_resume(void)
>>>> +{
>>>> +    unsigned int i;
>>>> +    struct clk_hw *parent;
>>>> +    struct clk *clk;
>>>> +
>>>> +    /*
>>>> +     * clk_restore_context restores clocks as per the clock tree.
>>>> +     *
>>>> +     * dfllCPU_out is first in the clock tree to get restored and it
>>>> +     * involves programming DFLL controller along with restoring CPUG
>>>> +     * clock burst policy.
>>>> +     *
>>>> +     * DFLL programming needs dfll_ref and dfll_soc peripheral clocks
>>>> +     * to be restores which are part ofthe peripheral clocks.
>                                              ^ white-space
>
> Please use spellchecker to avoid typos.
>
>>>> +     * So, peripheral clocks restore should happen prior to dfll clock
>>>> +     * restore.
>>>> +     */
>>>> +
>>>> +    tegra_clk_osc_resume(clk_base);
>>>> +    for (i = 0; i < ARRAY_SIZE(cpu_softrst_ctx); i++)
>>>> +        car_writel(cpu_softrst_ctx[i], CPU_SOFTRST_CTRL, i);
>>>> +
>>>> +    /* restore all plls and peripheral clocks */
>>>> +    tegra210_init_pllu();
>>>> +    clk_restore_context();
>>>> +
>>>> +    fence_udelay(5, clk_base);
>>>> +
>>>> +    /* resume SCLK and CPULP clocks */
>>>> +    tegra_sclk_cpulp_burst_policy_restore_context();
>>>> +
>>>> +    /*
>>>> +     * restore CPUG clocks:
>>>> +     * - enable DFLL in open loop mode
>>>> +     * - switch CPUG to DFLL clock source
>>>> +     * - close DFLL loop
>>>> +     * - sync PLLX state
>>>> +     */
>>>> +    if (dfll_pdev)
>>>> +        tegra_dfll_resume(dfll_pdev, false);
>>>> +
>>>> +    tegra_cclkg_burst_policy_restore_context();
>>>> +    fence_udelay(2, clk_base);
>>>> +
>>>> +    if (dfll_pdev)
>>>> +        tegra_dfll_resume(dfll_pdev, true);
>>>> +
>>>> +    parent =
>>>> clk_hw_get_parent(__clk_get_hw(clks[TEGRA210_CLK_CCLK_G]));
>>>> +    clk = clks[TEGRA210_CLK_PLL_X];
>>>> +    if (parent != __clk_get_hw(clk))
>>>> +        tegra_clk_sync_state_pll(__clk_get_hw(clk));
>>>> +
>>>> +    /* Disable PLL_OUT_CPU after DFLL resume */
>>>> +    tegra_clk_set_pllp_out_cpu(false);
>>>> +}
>>>> +
>>>>    static void tegra210_cpu_clock_suspend(void)
>>>>    {
>>>>        /* switch coresite to clk_m, save off original source */
>>>> @@ -3298,6 +3400,11 @@ static void tegra210_cpu_clock_resume(void)
>>>>    }
>>>>    #endif
>>>>    +static struct syscore_ops tegra_clk_syscore_ops = {
>>>> +    .suspend = tegra210_clk_suspend,
>>>> +    .resume = tegra210_clk_resume,
>>>> +};
>>>> +
>>>>    static struct tegra_cpu_car_ops tegra210_cpu_car_ops = {
>>>>        .wait_for_reset    = tegra210_wait_cpu_in_reset,
>>>>        .disable_clock    = tegra210_disable_cpu_clock,
>>>> @@ -3583,5 +3690,7 @@ static void __init tegra210_clock_init(struct
>>>> device_node *np)
>>>>        tegra210_mbist_clk_init();
>>>>          tegra_cpu_car_ops = &tegra210_cpu_car_ops;
>>>> +
>>>> +    register_syscore_ops(&tegra_clk_syscore_ops);
>>>>    }
>>> Is it really worthwhile to use syscore_ops for suspend/resume given
>>> that drivers for
>>> won't resume before the CLK driver anyway? Are there any other options
>>> for CLK
>>> suspend/resume?
>>>
>>> I'm also not sure whether PM runtime API could be used at all in the
>>> context of
>>> syscore_ops ..
>>>
>>> Secondly, what about to use generic clk_save_context() /
>>> clk_restore_context()
>>> helpers for the suspend-resume? It looks to me that some other
>>> essential (and proper)
>>> platform driver (soc/tegra/? PMC?) should suspend-resume the clocks
>>> using the generic
>>> CLK Framework API.
>> Clock resume should happen very early to restore peripheral and cpu
>> clocks very early than peripheral drivers resume happens.
> If all peripheral drivers properly requested all of the necessary clocks
> and CLK driver was a platform driver, then I guess the probe should have
> been naturally ordered. But that's not very achievable with the
> currently available infrastructure in the kernel, so I'm not arguing
> that the clocks should be explicitly resumed before the users.
>
>> this patch series uses clk_save_context and clk_restore_context for
>> corresponding divider, pll, pllout.. save and restore context.
> Now I see that indeed this API is utilized in this patch, thank you for
> the clarification.
>
>> But as there is dependency on dfll resume and cpu and pllx clocks
>> restore, couldnt use clk_save_context and clk_restore_context for dfll.
>>
>> So implemented recommended dfll resume sequence in main Tegra210 clock
>> driver along with invoking clk_save_context/clk_restore_context where
>> all other clocks save/restore happens as per clock tree traversal.
> Could you please clarify what part of peripherals clocks is required for
> DFLL's restore? Couldn't DFLL driver be changed to avoid that quirkness
> and thus to make DFLL driver suspend/resume the clock?

DFLL source ref_clk and soc_clk need to be restored prior to dfll.

I see dfllCPU_out parent to CCLK_G first in the clock tree and dfll_ref 
and dfll_soc peripheral clocks are not resumed by the time dfll resume 
happens first.

ref_clk and soc_clk source is from pll_p and clock tree has these 
registered under pll_p which happens later.

tegra210_clock_init registers in order plls, peripheral clocks, 
super_clk init for cclk_g during clock driver probe and dfll probe and 
register happens later.