Message-ID: <d82de63a-02a3-8fb0-57e7-7fe00d6b86ab@nvidia.com>
Date:   Fri, 2 Aug 2019 16:51:58 -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 2:15 PM, Dmitry Osipenko wrote:
> 02.08.2019 23:32, Sowjanya Komatineni пишет:
>> 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

Just to be clear, clk_mux don't have cached parent. get_parent is by 
register read. So, cant directly use get_parent and then set during restore.

So will create both clk_mux_save/restore_context in generic clk driver 
and will invoke them during tegra peripheral clock suspend/resume.



>>>>>>>>>>> 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.
> Yes, per-clock save/restore should be used for setting rate and parent.
> The ungating and resetting could be done separately to keep things cleaner.
>

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