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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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From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <a64472fd-46b7-5ff9-3140-11f71d5f88ff@gmail.com>
Date:   Fri, 2 Aug 2019 23:13:18 +0300
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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@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.
>>>>>>>
>>> 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.