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Message-ID: <805a825e-f19d-d056-83eb-8ed1cb1c089c@nvidia.com>
Date: Sun, 11 Aug 2019 12:15:34 -0700
From: Sowjanya Komatineni <skomatineni@...dia.com>
To: Dmitry Osipenko <digetx@...il.com>, <thierry.reding@...il.com>,
<jonathanh@...dia.com>, <tglx@...utronix.de>,
<jason@...edaemon.net>, <marc.zyngier@....com>,
<linus.walleij@...aro.org>, <stefan@...er.ch>,
<mark.rutland@....com>
CC: <pdeschrijver@...dia.com>, <pgaikwad@...dia.com>,
<sboyd@...nel.org>, <linux-clk@...r.kernel.org>,
<linux-gpio@...r.kernel.org>, <jckuo@...dia.com>,
<josephl@...dia.com>, <talho@...dia.com>,
<linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<mperttunen@...dia.com>, <spatra@...dia.com>, <robh+dt@...nel.org>,
<devicetree@...r.kernel.org>, <rjw@...ysocki.net>,
<viresh.kumar@...aro.org>, <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v8 14/21] clk: tegra210: Add suspend and resume support
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@...dia.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.
>
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