Date:   Thu, 1 Aug 2019 13:31:56 -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 1:17 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.


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

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