Date:   Fri, 2 Aug 2019 23:17:24 +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
Subject: Re: [PATCH v7 07/20] clk: tegra: clk-periph: Add save and restore
 support

02.08.2019 23:13, Dmitry Osipenko пишет:
> 02.08.2019 21:33, Sowjanya Komatineni пишет:
>>
>> On 8/2/19 5:38 AM, Dmitry Osipenko wrote:
>>> 02.08.2019 2:49, Sowjanya Komatineni пишет:
>>>> On 8/1/19 4:19 PM, Sowjanya Komatineni wrote:
>>>>> On 8/1/19 2:30 PM, Sowjanya Komatineni wrote:
>>>>>> 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.
>>>>>>>>
>>>> digging thru looks like for clk_periph source restore instead of
>>>> clk_mux_restore_context, i can directly do clk_hw_get_parent and
>>>> clk_set_parent with mux_hw as they invoke mux_ops get/set parent anyway.
>>>> Will do this for periph clk mux
>>>>>>>> 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?
>>>>>>>
>>>>> gate->enable_refcnt is within clk-periph-gate which gets updated when
>>>>> enable/disable callbacks get execute thru clk_core_enable/disable.
>>>>> But actual enable_count used in clk_gate_restore_context is the one
>>>>> which gets updated with in the clk core enable/disable functions which
>>>>> invokes these callbacks. Depending on this enable_count in clk core it
>>>>> invokes enable/disable.
>>>>>
>>>>> So, this will cause mismatch if we handle refcnt during save/restore
>>>>> of tegra_clk_periph_gate_ops and also enable/disable thru this
>>>>> clk_gate_restore_context is based on enable_count from clk core.
>>>>>
>>>>>>>> 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
>>>>>
>>>>> Also, to align both CLK & RST to the exact state of register, doing
>>>>> save/restore in tegra_clk_periph_gate_ops and invoking this after
>>>>> source restore for peripheral clock, seems cleaner to avoid any
>>>>> misconfiguration b/w rst & clk settings.
>>>>>
>>> It looks to me that it is very wasteful to store/restore each individual
>>> gate and reset state, also given that some of them are shared. I think
>>> that the gates and resets should be restored separately for the
>>> peripherals by a custom tegra_clk_save/restore_periph_gates/resets().
>> clk_periph_fixed_disable just disables clock only without deasserting
>> the corresponding peripheral.
>>
>> corresponding peripheral drivers can also issue reset assert/deassert
>> thru reset_control_assert/deassert.
>>
>> So, we will not get the actual state of clk and rst unless we read and
>> save state of reset and clock separately during save_context.
>>
>> Currently patch is already using custom
>> tegra_clk_periph_fixed_save/restore_context for corresponding clk_ops.
>> Are you suggesting to do save and restore of complete CLK_ENB/RST_DEV
>> register settings instead of individual peripheral bits? 
> 
> Yes, I'm suggesting to do a complete ungate/reset handling of the
> devices in a separate function. All enabling/deassertion will be done in
> a single hop, hence using 7us delay and four u32 words, which is much
> nicer IMHO.

Actually six words, three for CLKs and three for RSTs.

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