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Subject: Re: [PATCH V5 11/18] clk: tegra210: Add support for Tegra210 clocks
To:     Sowjanya Komatineni <skomatineni@nvidia.com>,
        thierry.reding@gmail.com, jonathanh@nvidia.com, tglx@linutronix.de,
        jason@lakedaemon.net, marc.zyngier@arm.com,
        linus.walleij@linaro.org, stefan@agner.ch, mark.rutland@arm.com
Cc:     pdeschrijver@nvidia.com, pgaikwad@nvidia.com, sboyd@kernel.org,
        linux-clk@vger.kernel.org, linux-gpio@vger.kernel.org,
        jckuo@nvidia.com, josephl@nvidia.com, talho@nvidia.com,
        linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org,
        mperttunen@nvidia.com, spatra@nvidia.com, robh+dt@kernel.org,
        devicetree@vger.kernel.org
References: <1561687972-19319-1-git-send-email-skomatineni@nvidia.com>
 <1561687972-19319-12-git-send-email-skomatineni@nvidia.com>
 <a5e1a6df-dff7-9e0c-9551-f78103a5462f@gmail.com>
 <a9b5c364-52b4-bee1-5881-47197f043950@nvidia.com>
From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <e9d4bc0e-fd5d-ae02-2d67-86c7f7c9620f@gmail.com>
Date:   Mon, 15 Jul 2019 00:41:49 +0300
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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?