Message-ID: <c6e1d744-3a7a-fe1b-2c86-a3d49f022232@nvidia.com>
Date:   Fri, 2 Aug 2019 13:32:06 -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 8/2/19 1:17 PM, Dmitry Osipenko wrote:
> 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.

OK, So with separate function doing complete register save/restore for 
clk & rst, we can't do this thru clk_ops save/restore as clk_ops 
save_restore happens per peripheral wise. So if we decide to do this, 
then this should be invoked in clk-tegra210 driver suspend/resume.

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