linux-kernel - Re: [PATCH v8 10/21] clk: tegra: clk-super: Add restore-context support

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Date:   Fri, 9 Aug 2019 10:08:50 -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>, <rjw@...ysocki.net>,
        <viresh.kumar@...aro.org>, <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v8 10/21] clk: tegra: clk-super: Add restore-context
 support


On 8/9/19 5:17 AM, Dmitry Osipenko wrote:
> 09.08.2019 2:46, Sowjanya Komatineni пишет:
>> This patch implements restore_context for clk_super_mux and clk_super.
>>
>> During system supend, core power goes off the and context of Tegra
>> CAR registers is lost.
>>
>> So on system resume, context of super clock registers are restored
>> to have them in same state as before suspend.
>>
>> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
>> ---
>>   drivers/clk/tegra/clk-super.c | 21 +++++++++++++++++++++
>>   1 file changed, 21 insertions(+)
>>
>> diff --git a/drivers/clk/tegra/clk-super.c b/drivers/clk/tegra/clk-super.c
>> index e2a1e95a8db7..74c9e913e41c 100644
>> --- a/drivers/clk/tegra/clk-super.c
>> +++ b/drivers/clk/tegra/clk-super.c
>> @@ -124,9 +124,18 @@ static int clk_super_set_parent(struct clk_hw *hw, u8 index)
>>   	return err;
>>   }
>>   
>> +static void clk_super_mux_restore_context(struct clk_hw *hw)
>> +{
>> +	struct clk_hw *parent = clk_hw_get_parent(hw);
>> +	int parent_id = clk_hw_get_parent_index(hw, parent);
>> +
>> +	clk_super_set_parent(hw, parent_id);
> All Super clocks have a divider, including the "MUX". Thus I'm wondering
> if there is a chance that divider's configuration may differ on resume
> from what it was on suspend.

tegra_clk_register_super_mux which uses tegra_clk_super_mux_ops doesn't 
do divider rate programming.

I believe you are referring to sclk_divider, cclklp_divider, 
cclkg_divider...

these are registered as clk_divider and are restored during clk_divider 
resume.

>> +}
>> +
>>   static const struct clk_ops tegra_clk_super_mux_ops = {
>>   	.get_parent = clk_super_get_parent,
>>   	.set_parent = clk_super_set_parent,
>> +	.restore_context = clk_super_mux_restore_context,
>>   };
>>   
>>   static long clk_super_round_rate(struct clk_hw *hw, unsigned long rate,
>> @@ -162,12 +171,24 @@ static int clk_super_set_rate(struct clk_hw *hw, unsigned long rate,
>>   	return super->div_ops->set_rate(div_hw, rate, parent_rate);
>>   }
>>   
>> +static void clk_super_restore_context(struct clk_hw *hw)
>> +{
>> +	struct tegra_clk_super_mux *super = to_clk_super_mux(hw);
>> +	struct clk_hw *div_hw = &super->frac_div.hw;
>> +	struct clk_hw *parent = clk_hw_get_parent(hw);
>> +	int parent_id = clk_hw_get_parent_index(hw, parent);
>> +
>> +	super->div_ops->restore_context(div_hw);
>> +	clk_super_set_parent(hw, parent_id);
>> +}
>> +
>>   const struct clk_ops tegra_clk_super_ops = {
>>   	.get_parent = clk_super_get_parent,
>>   	.set_parent = clk_super_set_parent,
>>   	.set_rate = clk_super_set_rate,
>>   	.round_rate = clk_super_round_rate,
>>   	.recalc_rate = clk_super_recalc_rate,
>> +	.restore_context = clk_super_restore_context,
>>   };
>>   
>>   struct clk *tegra_clk_register_super_mux(const char *name,
>>