Date:   Thu, 1 Aug 2019 16:49:39 -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 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.
>

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