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Subject: Re: [PATCH v7 07/20] clk: tegra: clk-periph: Add save and restore
 support
To:     Sowjanya Komatineni <skomatineni@nvidia.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
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 <50bad1d3-df41-d1e5-a7c7-4be9c661ed14@nvidia.com>
From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <62a5c6ed-21b1-8403-6fac-9c5d99b5a255@gmail.com>
Date:   Thu, 1 Aug 2019 23:54:34 +0300
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01.08.2019 23:31, Sowjanya Komatineni пишет:
> 
> On 8/1/19 1:17 PM, Dmitry Osipenko wrote:
>> 01.08.2019 22:42, Sowjanya Komatineni пишет:
>>> On 8/1/19 12:00 PM, Dmitry Osipenko wrote:
>>>> 01.08.2019 20:58, Sowjanya Komatineni пишет:
>>>>> On 7/31/19 4:09 PM, Sowjanya Komatineni wrote:
>>>>>> On 7/31/19 3:44 AM, Dmitry Osipenko wrote:
>>>>>>> 31.07.2019 12:50, Dmitry Osipenko пишет:
>>>>>>>> 31.07.2019 3:20, Sowjanya Komatineni пишет:
>>>>>>>>> This patch implements save and restore context for peripheral
>>>>>>>>> fixed
>>>>>>>>> clock ops, peripheral gate clock ops, sdmmc mux clock ops, and
>>>>>>>>> peripheral clock ops.
>>>>>>>>>
>>>>>>>>> During system suspend, core power goes off and looses the settings
>>>>>>>>> of the Tegra CAR controller registers.
>>>>>>>>>
>>>>>>>>> So during suspend entry clock and reset state of peripherals is
>>>>>>>>> saved
>>>>>>>>> and on resume they are restored to have clocks back to same
>>>>>>>>> rate and
>>>>>>>>> state as before suspend.
>>>>>>>>>
>>>>>>>>> Acked-by: Thierry Reding <treding@nvidia.com>
>>>>>>>>> Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
>>>>>>>>> ---
>>>>>>>>>     drivers/clk/tegra/clk-periph-fixed.c | 33
>>>>>>>>> ++++++++++++++++++++++++++++++++
>>>>>>>>>     drivers/clk/tegra/clk-periph-gate.c  | 34
>>>>>>>>> +++++++++++++++++++++++++++++++++
>>>>>>>>>     drivers/clk/tegra/clk-periph.c       | 37
>>>>>>>>> ++++++++++++++++++++++++++++++++++++
>>>>>>>>>     drivers/clk/tegra/clk-sdmmc-mux.c    | 28
>>>>>>>>> +++++++++++++++++++++++++++
>>>>>>>>>     drivers/clk/tegra/clk.h              |  6 ++++++
>>>>>>>>>     5 files changed, 138 insertions(+)
>>>>>>>>>
>>>>>>>>> diff --git a/drivers/clk/tegra/clk-periph-fixed.c
>>>>>>>>> b/drivers/clk/tegra/clk-periph-fixed.c
>>>>>>>>> index c088e7a280df..21b24530fa00 100644
>>>>>>>>> --- a/drivers/clk/tegra/clk-periph-fixed.c
>>>>>>>>> +++ b/drivers/clk/tegra/clk-periph-fixed.c
>>>>>>>>> @@ -60,11 +60,44 @@ tegra_clk_periph_fixed_recalc_rate(struct
>>>>>>>>> clk_hw *hw,
>>>>>>>>>         return (unsigned long)rate;
>>>>>>>>>     }
>>>>>>>>>     +static int tegra_clk_periph_fixed_save_context(struct clk_hw
>>>>>>>>> *hw)
>>>>>>>>> +{
>>>>>>>>> +    struct tegra_clk_periph_fixed *fixed =
>>>>>>>>> to_tegra_clk_periph_fixed(hw);
>>>>>>>>> +    u32 mask = 1 << (fixed->num % 32);
>>>>>>>>> +
>>>>>>>>> +    fixed->enb_ctx = readl_relaxed(fixed->base +
>>>>>>>>> fixed->regs->enb_reg) &
>>>>>>>>> +             mask;
>>>>>>>>> +    fixed->rst_ctx = readl_relaxed(fixed->base +
>>>>>>>>> fixed->regs->rst_reg) &
>>>>>>>>> +             mask;
>>>>>>>>> +
>>>>>>>>> +    return 0;
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static void tegra_clk_periph_fixed_restore_context(struct clk_hw
>>>>>>>>> *hw)
>>>>>>>>> +{
>>>>>>>>> +    struct tegra_clk_periph_fixed *fixed =
>>>>>>>>> to_tegra_clk_periph_fixed(hw);
>>>>>>>>> +    u32 mask = 1 << (fixed->num % 32);
>>>>>>>>> +
>>>>>>>>> +    if (fixed->enb_ctx)
>>>>>>>>> +        writel_relaxed(mask, fixed->base +
>>>>>>>>> fixed->regs->enb_set_reg);
>>>>>>>>> +    else
>>>>>>>>> +        writel_relaxed(mask, fixed->base +
>>>>>>>>> fixed->regs->enb_clr_reg);
>>>>>>>>> +
>>>>>>>>> +    udelay(2);
>>>>>>>>> +
>>>>>>>>> +    if (!fixed->rst_ctx) {
>>>>>>>>> +        udelay(5); /* reset propogation delay */
>>>>>>>>> +        writel_relaxed(mask, fixed->base + fixed->regs->rst_reg);
>>>>>>>>> +    }
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>>     static const struct clk_ops tegra_clk_periph_fixed_ops = {
>>>>>>>>>         .is_enabled = tegra_clk_periph_fixed_is_enabled,
>>>>>>>>>         .enable = tegra_clk_periph_fixed_enable,
>>>>>>>>>         .disable = tegra_clk_periph_fixed_disable,
>>>>>>>>>         .recalc_rate = tegra_clk_periph_fixed_recalc_rate,
>>>>>>>>> +    .save_context = tegra_clk_periph_fixed_save_context,
>>>>>>>>> +    .restore_context = tegra_clk_periph_fixed_restore_context,
>>>>>>>>>     };
>>>>>>>>>       struct clk *tegra_clk_register_periph_fixed(const char
>>>>>>>>> *name,
>>>>>>>>> diff --git a/drivers/clk/tegra/clk-periph-gate.c
>>>>>>>>> b/drivers/clk/tegra/clk-periph-gate.c
>>>>>>>>> index 4b31beefc9fc..6ba5b08e0787 100644
>>>>>>>>> --- a/drivers/clk/tegra/clk-periph-gate.c
>>>>>>>>> +++ b/drivers/clk/tegra/clk-periph-gate.c
>>>>>>>>> @@ -25,6 +25,8 @@ static DEFINE_SPINLOCK(periph_ref_lock);
>>>>>>>>>       #define read_rst(gate) \
>>>>>>>>>         readl_relaxed(gate->clk_base + (gate->regs->rst_reg))
>>>>>>>>> +#define write_rst_set(val, gate) \
>>>>>>>>> +    writel_relaxed(val, gate->clk_base +
>>>>>>>>> (gate->regs->rst_set_reg))
>>>>>>>>>     #define write_rst_clr(val, gate) \
>>>>>>>>>         writel_relaxed(val, gate->clk_base +
>>>>>>>>> (gate->regs->rst_clr_reg))
>>>>>>>>>     @@ -110,10 +112,42 @@ static void clk_periph_disable(struct
>>>>>>>>> clk_hw *hw)
>>>>>>>>>         spin_unlock_irqrestore(&periph_ref_lock, flags);
>>>>>>>>>     }
>>>>>>>>>     +static int clk_periph_gate_save_context(struct clk_hw *hw)
>>>>>>>>> +{
>>>>>>>>> +    struct tegra_clk_periph_gate *gate = to_clk_periph_gate(hw);
>>>>>>>>> +
>>>>>>>>> +    gate->clk_state_ctx = read_enb(gate) &
>>>>>>>>> periph_clk_to_bit(gate);
>>>>>>>>> +    gate->rst_state_ctx = read_rst(gate) &
>>>>>>>>> periph_clk_to_bit(gate);
>>>>>>>>> +
>>>>>>>>> +    return 0;
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static void clk_periph_gate_restore_context(struct clk_hw *hw)
>>>>>>>>> +{
>>>>>>>>> +    struct tegra_clk_periph_gate *gate = to_clk_periph_gate(hw);
>>>>>>>>> +
>>>>>>>>> +    if (gate->clk_state_ctx)
>>>>>>>>> +        write_enb_set(periph_clk_to_bit(gate), gate);
>>>>>>>>> +    else
>>>>>>>>> +        write_enb_clr(periph_clk_to_bit(gate), gate);
>>>>>>>>> +
>>>>>>>>> +    udelay(5);
>>>>>>>>> +
>>>>>>>>> +    if (!(gate->flags & TEGRA_PERIPH_NO_RESET) &&
>>>>>>>>> +        !(gate->flags & TEGRA_PERIPH_MANUAL_RESET)) {
>>>>>>>>> +        if (gate->rst_state_ctx)
>>>>>>>>> +            write_rst_set(periph_clk_to_bit(gate), gate);
>>>>>>>>> +        else
>>>>>>>>> +            write_rst_clr(periph_clk_to_bit(gate), gate);
>>>>>>>>> +    }
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>>     const struct clk_ops tegra_clk_periph_gate_ops = {
>>>>>>>>>         .is_enabled = clk_periph_is_enabled,
>>>>>>>>>         .enable = clk_periph_enable,
>>>>>>>>>         .disable = clk_periph_disable,
>>>>>>>>> +    .save_context = clk_periph_gate_save_context,
>>>>>>>>> +    .restore_context = clk_periph_gate_restore_context,
>>>>>>>>>     };
>>>>>>>>>       struct clk *tegra_clk_register_periph_gate(const char *name,
>>>>>>>>> diff --git a/drivers/clk/tegra/clk-periph.c
>>>>>>>>> b/drivers/clk/tegra/clk-periph.c
>>>>>>>>> index 58437da25156..06fb62955768 100644
>>>>>>>>> --- a/drivers/clk/tegra/clk-periph.c
>>>>>>>>> +++ b/drivers/clk/tegra/clk-periph.c
>>>>>>>>> @@ -99,6 +99,37 @@ static void clk_periph_disable(struct clk_hw
>>>>>>>>> *hw)
>>>>>>>>>         gate_ops->disable(gate_hw);
>>>>>>>>>     }
>>>>>>>>>     +static int clk_periph_save_context(struct clk_hw *hw)
>>>>>>>>> +{
>>>>>>>>> +    struct tegra_clk_periph *periph = to_clk_periph(hw);
>>>>>>>>> +    const struct clk_ops *gate_ops = periph->gate_ops;
>>>>>>>>> +    struct clk_hw *gate_hw = &periph->gate.hw;
>>>>>>>>> +
>>>>>>>>> +    if (!(periph->gate.flags & TEGRA_PERIPH_NO_GATE))
>>>>>>>>> +        gate_ops->save_context(gate_hw);
>>>>>>>>> +
>>>>>>>>> +    periph->parent_ctx = clk_periph_get_parent(hw);
>>>>>>>>> +
>>>>>>>>> +    return 0;
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static void clk_periph_restore_context(struct clk_hw *hw)
>>>>>>>>> +{
>>>>>>>>> +    struct tegra_clk_periph *periph = to_clk_periph(hw);
>>>>>>>>> +    const struct clk_ops *gate_ops = periph->gate_ops;
>>>>>>>>> +    struct clk_hw *gate_hw = &periph->gate.hw;
>>>>>>>>> +    const struct clk_ops *div_ops = periph->div_ops;
>>>>>>>>> +    struct clk_hw *div_hw = &periph->divider.hw;
>>>>>>>>> +
>>>>>>>>> +    clk_periph_set_parent(hw, periph->parent_ctx);
>>>>>>>>> +
>>>>>>>>> +    if (!(periph->gate.flags & TEGRA_PERIPH_NO_DIV))
>>>>>>>>> +        div_ops->restore_context(div_hw);
>>>>>>>> Could you please point to where the divider's save_context()
>>>>>>>> happens?
>>>>>>>> Because I can't see it.
>>>>>>> Ah, I now see that there is no need to save the dividers context
>>>>>>> because
>>>>>>> clk itself has enough info that is needed for the context's
>>>>>>> restoring
>>>>>>> (like I pointed in the review to v6).
>>>>>>>
>>>>>>> Looks like you could also implement a new clk_hw_get_parent_index()
>>>>>>> generic helper to get the index instead of storing it manually.
>>>>>> clk_periph_get_parent basically invokes existing clk_mux_ops
>>>>>> get_parent() which is then saved in tegra_clk_periph.
>>>>>>
>>>>>> All existing drivers are using directly get_parent() from clk_mux
>>>>>> which actually gets index from the register read.
>>>>>>
>>>>>> To have this more generic w.r.t save/restore context point of view,
>>>>>> probably instead of implementing new get_parent_index helper, I think
>>>>>> its better to implement save_context and restore_context to
>>>>>> clk_mux_ops along with creating parent_index field into clk_mux to
>>>>>> cache index during set_parent.
>>>>>>
>>>>>> So we just need to invoke mux_ops save_context and restore_context.
>>>>>>
>>>>> I hope its ok to add save/restore context to clk_mux_ops to be more
>>>>> generic w.r.t save/restore context rather than get_parent_index API.
>>>>> Please confirm if you agree.
>>>> Sounds like a good idea. I see that there is a 'restoring' helper for
>>>> the generic clk_gate, seems something similar could be done for the
>>>> clk_mux. And looks like anyway you'll need to associate the parent
>>>> clock
>>>> with the hw index in order to restore the muxing.
>>> by 'restoring' helper for generic clk_gate, are you referring to
>>> clk_gate_restore_context API?
>> Yes.
>>
>>> clk_gate_restore_context is API that's any clk drivers can use for
>>> clk_gate operation restore for custom gate clk_ops.
>>>
>>> But clk-periph is directly using generic clk_mux ops from clk_mux so I
>>> think we should add .restore_context to clk_mux_ops and then during
>>> clk-periph restore need to invoke mux_ops->restore_context.
>> I'm not sure whether it will be good for every driver that uses generic
>> clk_mux ops. Should be more flexible to have a generic helper function
>> that any driver could use in order to restore the clock's parent.
>>
>> The clk-periph restoring also includes case of combining divider and
>> parent restoring, so generic helper could be useful in that case as well.
>>
>> It also looks like you could actually use the clk_gate_restore_context()
>> instead of manually saving the clock's enable-state, couldn't you?
> 
> ok for clk_mux, can add generic clk_mux_restore_context API rather than
> using restore_context in clk_ops and will invoke that during clk_periph
> restore.
> 
> 
> Reg clk_gate, looks like we cant use generic clk_gate_restore_context
> for clk-periph as it calls enable/disable callbacks and
> clk_periph_enable/disable in clk-periph-gate also updated refcnt and
> depending on that actual enable/disable is set.
> 
> During suspend, peripherals that are already enabled have their refcnt >
> 1, so they dont go thru enable/disable on restore if we use same
> enable/disable callback.

Looks like you could just decrement the gate's enable_refcnt on
save_context, wouldn't that work?

> 
> Also to align exact reset state along with CLK (like for case where CLK
> is enabled but peripheral might be in reset state), implemented
> save/restore in tegra specific tegra_clk_periph_gate_ops

I'm wondering whether instead of saving/restoring reset-state of every
clock, you could simply save/restore the whole RST_DEV_x_SET register.
Couldn't you?