Re: [PATCH V5 11/18] clk: tegra210: Add support for Tegra210 clocks

[Sowjanya Komatineni <skomatineni@nvidia.com>]

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@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?
>>> 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?

currently no APIs are shared b/w clk/tegra driver and CPUFreq driver to 
invoke dfll suspend/resume in CPUFreq driver