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From: Sowjanya Komatineni <skomatineni@nvidia.com>
To: Dmitry Osipenko <digetx@gmail.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>,
	<rjw@rjwysocki.net>, <viresh.kumar@linaro.org>,
	<linux-pm@vger.kernel.org>
Subject: Re: [PATCH v8 14/21] clk: tegra210: Add suspend and resume support
Date: Sun, 11 Aug 2019 12:15:34 -0700
Message-ID: <805a825e-f19d-d056-83eb-8ed1cb1c089c@nvidia.com> (raw)
In-Reply-To: <4397de5d-772d-2b04-5f87-b2988f6c96c8@gmail.com>


On 8/11/19 10:39 AM, Dmitry Osipenko wrote:
> 09.08.2019 21:40, Sowjanya Komatineni пишет:
>> On 8/9/19 11:18 AM, Dmitry Osipenko wrote:
>>> 09.08.2019 19:19, Sowjanya Komatineni пишет:
>>>> On 8/9/19 6:56 AM, Dmitry Osipenko wrote:
>>>>> 09.08.2019 2:46, Sowjanya Komatineni пишет:
>>>>>> This patch adds support for clk: tegra210: suspend-resume.
>>>>>>
>>>>>> All the CAR controller settings are lost on suspend when core
>>>>>> power goes off.
>>>>>>
>>>>>> This patch has implementation for saving and restoring all PLLs
>>>>>> and clocks context during system suspend and resume to have the
>>>>>> clocks back to same state for normal operation.
>>>>>>
>>>>>> Clock driver suspend and resume are registered as syscore_ops as clocks
>>>>>> restore need to happen before the other drivers resume to have all their
>>>>>> clocks back to the same state as before suspend.
>>>>>>
>>>>>> Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
>>>>>> ---
>>>>>>    drivers/clk/tegra/clk-tegra210.c | 103 +++++++++++++++++++++++++++++++++++++--
>>>>>>    drivers/clk/tegra/clk.c          |  64 ++++++++++++++++++++++++
>>>>>>    drivers/clk/tegra/clk.h          |   3 ++
>>>>>>    3 files changed, 166 insertions(+), 4 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/clk/tegra/clk-tegra210.c b/drivers/clk/tegra/clk-tegra210.c
>>>>>> index 998bf60b219a..8dd6f4f4debb 100644
>>>>>> --- a/drivers/clk/tegra/clk-tegra210.c
>>>>>> +++ b/drivers/clk/tegra/clk-tegra210.c
>>>>>> @@ -9,13 +9,13 @@
>>>>>>    #include <linux/clkdev.h>
>>>>>>    #include <linux/of.h>
>>>>>>    #include <linux/of_address.h>
>>>>>> +#include <linux/syscore_ops.h>
>>>>>>    #include <linux/delay.h>
>>>>>>    #include <linux/export.h>
>>>>>>    #include <linux/mutex.h>
>>>>>>    #include <linux/clk/tegra.h>
>>>>>>    #include <dt-bindings/clock/tegra210-car.h>
>>>>>>    #include <dt-bindings/reset/tegra210-car.h>
>>>>>> -#include <linux/iopoll.h>
>>>>>>    #include <linux/sizes.h>
>>>>>>    #include <soc/tegra/pmc.h>
>>>>>>    @@ -220,11 +220,15 @@
>>>>>>    #define CLK_M_DIVISOR_SHIFT 2
>>>>>>    #define CLK_M_DIVISOR_MASK 0x3
>>>>>>    +#define CLK_MASK_ARM    0x44
>>>>>> +#define MISC_CLK_ENB    0x48
>>>>>> +
>>>>>>    #define RST_DFLL_DVCO 0x2f4
>>>>>>    #define DVFS_DFLL_RESET_SHIFT 0
>>>>>>      #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
>>>>>> @@ -2825,6 +2829,7 @@ 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)
>>>>>> @@ -2853,9 +2858,14 @@ static int tegra210_enable_pllu(void)
>>>>>>        reg |= PLL_ENABLE;
>>>>>>        writel(reg, clk_base + PLLU_BASE);
>>>>>>    -    readl_relaxed_poll_timeout_atomic(clk_base + PLLU_BASE, reg,
>>>>>> -                      reg & PLL_BASE_LOCK, 2, 1000);
>>>>>> -    if (!(reg & PLL_BASE_LOCK)) {
>>>>>> +    /*
>>>>>> +     * During clocks resume, same PLLU init and enable sequence get
>>>>>> +     * executed. So, readx_poll_timeout_atomic can't be used here as it
>>>>>> +     * uses ktime_get() and timekeeping resume doesn't happen by that
>>>>>> +     * time. So, using tegra210_wait_for_mask for PLL 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;
>>>>>>        }
>>>>>> @@ -3288,6 +3298,84 @@ static void tegra210_disable_cpu_clock(u32 cpu)
>>>>>>    }
>>>>>>      #ifdef CONFIG_PM_SLEEP
>>>>>> +/*
>>>>>> + * This array lists mask values for each peripheral clk bank
>>>>>> + * to mask out reserved bits during the clocks state restore
>>>>>> + * on SC7 resume to prevent accidental writes to these reserved
>>>>>> + * bits.
>>>>>> + */
>>>>>> +static u32 periph_clk_rsvd_mask[TEGRA210_CAR_BANK_COUNT] = {
>>>>> Should be more natural to have a "valid_mask" instead of "rsvd_mask".
>>>>>
>>>>> What's actually wrong with touching of the reserved bits? They must be NO-OP.. or the
>>>>> reserved bits are actually some kind of "secret" bits? If those bits have some use-case
>>>>> outside of Silicon HW (like FPGA simulation), then this doesn't matter for upstream and you
>>>>> have to keep the workaround locally in the downstream kernel or whatever.
>>>> Will rename as valid_mask.
>>>>
>>>> some bits in these registers are undefined and is not good to write to these bits as they
>>>> can cause pslverr.
>>> Okay, it should be explained in the comment.
>>>
>>> Is it possible to disable trapping of changing the undefined bits?
>> No its internal to design
> Okay.
>
> Also, what about to move the valid_mask into struct tegra_clk_periph_regs?

No, we cannot move to tegra_clk_periph_regs as its in tegra/clk.c and is 
common for all tegra.

Reserved bits are different on tegra chips so should come from Tegra 
chip specific clock driver like

clk-tegra210 for Tegra210.

>>>>>> +    0x23282006,
>>>>>> +    0x782e0c18,
>>>>>> +    0x0c012c05,
>>>>>> +    0x003e7304,
>>>>>> +    0x86c04800,
>>>>>> +    0xc0199000,
>>>>>> +    0x03e03800,
>>>>>> +};
>>>>>> +
>>>>>> +#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 u32 spare_reg_ctx, misc_clk_enb_ctx, clk_msk_arm_ctx;
>>>>>> +static u32 cpu_softrst_ctx[3];
>>>>>> +
>>>>>> +static int tegra210_clk_suspend(void)
>>>>>> +{
>>>>>> +    unsigned int i;
>>>>>> +
>>>>>> +    clk_save_context();
>>>>>> +
>>>>>> +    /*
>>>>>> +     * Save the bootloader configured clock registers SPARE_REG0,
>>>>>> +     * MISC_CLK_ENB, CLK_MASK_ARM, CPU_SOFTRST_CTRL.
>>>>>> +     */
>>>>>> +    spare_reg_ctx = readl_relaxed(clk_base + SPARE_REG0);
>>>>>> +    misc_clk_enb_ctx = readl_relaxed(clk_base + MISC_CLK_ENB);
>>>>>> +    clk_msk_arm_ctx = readl_relaxed(clk_base + CLK_MASK_ARM);
>>>>>> +
>>>>>> +    for (i = 0; i < ARRAY_SIZE(cpu_softrst_ctx); i++)
>>>>>> +        cpu_softrst_ctx[i] = car_readl(CPU_SOFTRST_CTRL, i);
>>>>>> +
>>>>>> +    tegra_clk_periph_suspend();
>>>>>> +    return 0;
>>>>>> +}
>>>>>> +
>>>>>> +static void tegra210_clk_resume(void)
>>>>>> +{
>>>>>> +    unsigned int i;
>>>>>> +
>>>>>> +    tegra_clk_osc_resume(clk_base);
>>>>>> +
>>>>>> +    /*
>>>>>> +     * Restore the bootloader configured clock registers SPARE_REG0,
>>>>>> +     * MISC_CLK_ENB, CLK_MASK_ARM, CPU_SOFTRST_CTRL from saved context.
>>>>>> +     */
>>>>>> +    writel_relaxed(spare_reg_ctx, clk_base + SPARE_REG0);
>>>>>> +    writel_relaxed(misc_clk_enb_ctx, clk_base + MISC_CLK_ENB);
>>>>>> +    writel_relaxed(clk_msk_arm_ctx, clk_base + CLK_MASK_ARM);
>>>>>> +
>>>>>> +    for (i = 0; i < ARRAY_SIZE(cpu_softrst_ctx); i++)
>>>>>> +        car_writel(cpu_softrst_ctx[i], CPU_SOFTRST_CTRL, i);
>>>>>> +
>>>>>> +    fence_udelay(5, clk_base);
>>>>>> +
>>>>>> +    /* enable all the clocks before changing the clock sources */
>>>>>> +    tegra_clk_periph_force_on(periph_clk_rsvd_mask);
>>>>> Why clocks need to be enabled before changing the sources?
>>>> To prevent glitchless frequency switch, Tegra clock programming recommended sequence is to
>>>> change MUX control or divisor or both with the clocks running.
>>> This should be explained in the comment.
>>>
>>>> Actual state of clocks before suspend are restored later after all PLL's and peripheral
>>>> clocks are restored.
>>>>
>>>>>> +    /* wait for all writes to happen to have all the clocks enabled */
>>>>>> +    wmb();
>>>>> fence_udelay() has exactly the same barrier at the very beginning of readl(), no need to
>>>>> duplicate it here.
>>> Actually, readl does the rmb() and it should be a more correct variant of fencing because it
>>> actually ensures that the write reached hardware. I suppose that something like fence_udelay
>>> should be used for the pinctrl as well.
>>>
>>>>>> +    fence_udelay(2, clk_base);
>>>>>> +
>>>>>> +    /* restore PLLs and all peripheral clock rates */
>>>>>> +    tegra210_init_pllu();
>>>>> Why USB PLL need to be restored at first?
>>>> USB PLL restore is independent to all other clocks restore. So this can be done either
>>>> before clk_restore_context or even after.
>>> Then why not to implement restore_context for PLLU?
>> pllu is registered as fixed_rate clock and we using clk core clk_register_fixed_rate which
>> uses clk_fixed_rate_ops from the same generic clk-fixed-rate driver.
>>
>> Also pllu init happens in the same clk-tegra210, so invoking it during resume which is the
>> same sequence needed during resume as well.
> Okay.
>

  reply index

Thread overview: 75+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-08 23:46 [PATCH v8 00/21] SC7 entry and exit support for Tegra210 Sowjanya Komatineni
2019-08-08 23:46 ` [PATCH v8 01/21] pinctrl: tegra: Fix write barrier placement in pmx_writel Sowjanya Komatineni
2019-08-09 11:38   ` Dmitry Osipenko
2019-08-12  9:20   ` Thierry Reding
2019-08-14  8:32   ` Linus Walleij
2019-08-08 23:46 ` [PATCH v8 02/21] pinctrl: tegra: Add write barrier after all pinctrl register writes Sowjanya Komatineni
2019-08-09 11:39   ` Dmitry Osipenko
2019-08-12  9:20   ` Thierry Reding
2019-08-14  8:33   ` Linus Walleij
2019-08-08 23:46 ` [PATCH v8 03/21] clk: tegra: divider: Save and restore divider rate Sowjanya Komatineni
2019-08-12  9:21   ` Thierry Reding
2019-08-08 23:46 ` [PATCH v8 04/21] clk: tegra: pllout: Save and restore pllout context Sowjanya Komatineni
2019-08-11 18:04   ` Dmitry Osipenko
2019-08-08 23:46 ` [PATCH v8 05/21] clk: tegra: pll: Save and restore pll context Sowjanya Komatineni
2019-08-09 11:33   ` Dmitry Osipenko
2019-08-09 17:39     ` Sowjanya Komatineni
2019-08-09 17:50       ` Dmitry Osipenko
2019-08-09 18:50         ` Sowjanya Komatineni
2019-08-11 17:24           ` Dmitry Osipenko
2019-08-09 12:46   ` Dmitry Osipenko
2019-08-08 23:46 ` [PATCH v8 06/21] clk: tegra: Support for OSC context save and restore Sowjanya Komatineni
2019-08-08 23:46 ` [PATCH v8 07/21] clk: Add API to get index of the clock parent Sowjanya Komatineni
2019-08-09 11:49   ` Dmitry Osipenko
2019-08-12  9:47   ` Thierry Reding
2019-08-08 23:46 ` [PATCH v8 08/21] clk: tegra: periph: Add restore_context support Sowjanya Komatineni
2019-08-09 11:55   ` Dmitry Osipenko
2019-08-09 12:20     ` Dmitry Osipenko
2019-08-09 16:55       ` Sowjanya Komatineni
2019-08-12  9:50   ` Thierry Reding
2019-08-08 23:46 ` [PATCH v8 09/21] clk: tegra: clk-super: Fix to enable PLLP branches to CPU Sowjanya Komatineni
2019-08-09 12:11   ` Dmitry Osipenko
2019-08-12  9:53   ` Thierry Reding
2019-08-08 23:46 ` [PATCH v8 10/21] clk: tegra: clk-super: Add restore-context support Sowjanya Komatineni
2019-08-09 12:17   ` Dmitry Osipenko
2019-08-09 17:08     ` Sowjanya Komatineni
2019-08-11 17:29       ` Dmitry Osipenko
2019-08-12  9:55   ` Thierry Reding
2019-08-08 23:46 ` [PATCH v8 11/21] clk: tegra: clk-dfll: Add suspend and resume support Sowjanya Komatineni
2019-08-09 12:23   ` Dmitry Osipenko
2019-08-09 16:39     ` Sowjanya Komatineni
2019-08-09 18:00       ` Dmitry Osipenko
2019-08-09 18:33         ` Sowjanya Komatineni
2019-08-09 18:52           ` Dmitry Osipenko
2019-08-12 10:01   ` Thierry Reding
2019-08-08 23:46 ` [PATCH v8 12/21] cpufreq: tegra124: " Sowjanya Komatineni
2019-08-12 10:07   ` Thierry Reding
2019-08-08 23:46 ` [PATCH v8 13/21] clk: tegra210: Use fence_udelay during PLLU init Sowjanya Komatineni
2019-08-11 18:02   ` Dmitry Osipenko
2019-08-11 19:16     ` Sowjanya Komatineni
2019-08-08 23:46 ` [PATCH v8 14/21] clk: tegra210: Add suspend and resume support Sowjanya Komatineni
2019-08-09 13:56   ` Dmitry Osipenko
2019-08-09 16:19     ` Sowjanya Komatineni
2019-08-09 18:18       ` Dmitry Osipenko
     [not found]         ` <cbe94f84-a17b-7e1a-811d-89db571784e1@nvidia.com>
2019-08-11 17:39           ` Dmitry Osipenko
2019-08-11 19:15             ` Sowjanya Komatineni [this message]
2019-08-12 16:25               ` Dmitry Osipenko
2019-08-12 17:28                 ` Sowjanya Komatineni
2019-08-12 18:19                   ` Dmitry Osipenko
2019-08-12 19:03                     ` Sowjanya Komatineni
2019-08-12 20:28                       ` Dmitry Osipenko
2019-08-12 10:17   ` Thierry Reding
2019-08-08 23:46 ` [PATCH v8 15/21] soc/tegra: pmc: Allow to support more tegras wake Sowjanya Komatineni
2019-08-11 17:52   ` Dmitry Osipenko
2019-08-08 23:46 ` [PATCH v8 16/21] soc/tegra: pmc: Add pmc wake support for tegra210 Sowjanya Komatineni
2019-08-09 13:28   ` Dmitry Osipenko
2019-08-08 23:46 ` [PATCH v8 17/21] arm64: tegra: Enable wake from deep sleep on RTC alarm Sowjanya Komatineni
2019-08-08 23:46 ` [PATCH v8 18/21] soc/tegra: pmc: Configure core power request polarity Sowjanya Komatineni
2019-08-09 13:13   ` Dmitry Osipenko
2019-08-08 23:46 ` [PATCH v8 19/21] soc/tegra: pmc: Configure deep sleep control settings Sowjanya Komatineni
2019-08-09 13:23   ` Dmitry Osipenko
2019-08-09 16:23     ` Sowjanya Komatineni
2019-08-09 17:24       ` Sowjanya Komatineni
2019-08-09 18:22         ` Dmitry Osipenko
2019-08-08 23:46 ` [PATCH v8 20/21] arm64: dts: tegra210-p2180: Jetson TX1 SC7 timings Sowjanya Komatineni
2019-08-08 23:47 ` [PATCH v8 21/21] arm64: dts: tegra210-p3450: Jetson Nano " Sowjanya Komatineni

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