Message-ID: <85cd5100-467e-d08e-0ae5-ae57a6de5312@nvidia.com>
Date:   Thu, 1 Aug 2019 14:30:07 -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>
Subject: Re: [PATCH v7 07/20] clk: tegra: clk-periph: Add save and restore
 support


On 8/1/19 1:54 PM, Dmitry Osipenko wrote:
> 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@...dia.com>
>>>>>>>>>> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.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?
Thats what I was doing in first version of patch. But later as we moved 
to use clk_save_context and clk_restore_context, peripheral clk_hw RST & 
CLK enables happen thru its corresponding save/restore after source restore

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