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Message-ID: <aa823801-00c7-df88-0f63-45338bffa854@gmail.com>
Date: Fri, 9 Aug 2019 21:18:15 +0300
From: Dmitry Osipenko <digetx@...il.com>
To: Sowjanya Komatineni <skomatineni@...dia.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
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?
>>
>>> + 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?
>>> + clk_restore_context();
>>> +
>>> + /* restore all peripheral clocks enable and reset state */
>>> + tegra_clk_periph_resume();
>>> +}
>> [snip]
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