Message-ID: <20190716092046.7e23b6b2@dimatab>
Date:   Tue, 16 Jul 2019 09:20:46 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>
Cc:     <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>,
        <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>
Subject: Re: [PATCH V5 11/18] clk: tegra210: Add support for Tegra210 clocks

В Tue, 16 Jul 2019 08:37:01 +0300
Dmitry Osipenko <digetx@...il.com> пишет:

> В Mon, 15 Jul 2019 21:37:09 -0700
> Sowjanya Komatineni <skomatineni@...dia.com> пишет:
> 
> > On 7/15/19 8:50 PM, Dmitry Osipenko wrote:  
> > > 16.07.2019 6:00, Sowjanya Komatineni пишет:    
> > >> On 7/15/19 5:35 PM, Sowjanya Komatineni wrote:    
> > >>> 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@...dia.com>
> > >>>>>>> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.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.
> > >>>    
> > >> One more thing, CLDVFS peripheral clock enable is also needed to
> > >> be enabled to program DFLL Controller and all peripheral clock
> > >> context is restored only after their PLL sources are restored.
> > >>
> > >> DFLL restore involves dfll source clock resume along with CLDVFS
> > >> periheral clock enable and reset
> > >>    
> > > I don't quite see why you can't simply add suspend/resume
> > > callbacks to the CPUFreq driver to:
> > >
> > > On suspend:
> > > 1. Switch CPU to PLLP (or whatever "safe" parent)
> > > 2. Disable/teardown DFLL
> > >
> > > On resume:
> > > 1. Enable/restore DFLL
> > > 2. Switch CPU back to DFLL    
> > 
> > dfll runtime suspend/resume are already part of dfll_pm_ops. Don't
> > we want to use it for suspend/resume as well?  
> 
> Looks like no. Seems runtime PM of that driver is intended solely for
> the DFLL's clk management.
> 
> > currently no APIs are shared b/w clk/tegra driver and CPUFreq driver
> > to invoke dfll suspend/resume in CPUFreq driver
> >   
> 
> Just add it. Also, please note that CPUFreq driver is optional and
> thus you may need to switch CPU to a safe parent on clk-core suspend
> as well in order to resume properly if CPU was running off unsafe
> parent during boot and CPUFreq driver is disabled in kernel build (or
> failed to load).

Although, if PLLs are restored before CCLK, then it should be fine
as-is.

> The other thing that also need attention is that T124 CPUFreq driver
> implicitly relies on DFLL driver to be probed first, which is icky.
> 

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