linux-kernel - Re: [RFC PATCH v1 05/18] i2c: tegra: Fix runtime resume to re-init VI I2C

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Date:   Wed, 10 Jun 2020 09:58:28 -0700
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <frankc@...dia.com>, <hverkuil@...all.nl>,
        <sakari.ailus@....fi>, <robh+dt@...nel.org>,
        <helen.koike@...labora.com>
CC:     <sboyd@...nel.org>, <gregkh@...uxfoundation.org>,
        <linux-media@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-i2c@...r.kernel.org>
Subject: Re: [RFC PATCH v1 05/18] i2c: tegra: Fix runtime resume to re-init VI
 I2C


On 6/10/20 6:14 AM, Dmitry Osipenko wrote:
> 10.06.2020 09:02, Sowjanya Komatineni пишет:
>> VI I2C is on host1x bus and is part of VE power domain.
>>
>> During suspend/resume VE power domain goes through power off/on.
>>
>> So, controller reset followed by i2c re-initialization is required
>> after the domain power up.
>>
>> This patch fixes it.
>>
>> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
>> ---
>>   drivers/i2c/busses/i2c-tegra.c | 16 ++++++++++++++++
>>   1 file changed, 16 insertions(+)
>>
>> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
>> index dba38a5..650240d 100644
>> --- a/drivers/i2c/busses/i2c-tegra.c
>> +++ b/drivers/i2c/busses/i2c-tegra.c
>> @@ -293,6 +293,8 @@ struct tegra_i2c_dev {
>>   	bool is_curr_atomic_xfer;
>>   };
>>   
>> +static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev, bool clk_reinit);
>> +
>>   static void dvc_writel(struct tegra_i2c_dev *i2c_dev, u32 val,
>>   		       unsigned long reg)
>>   {
>> @@ -679,8 +681,22 @@ static int __maybe_unused tegra_i2c_runtime_resume(struct device *dev)
>>   		goto disable_slow_clk;
>>   	}
>>   
>> +	/*
>> +	 * VI I2C device is attached to VE power domain which goes through
>> +	 * power ON/OFF during PM runtime resume/suspend. So, controller
>> +	 * should go through reset and need to re-initialize after power
>> +	 * domain ON.
>> +	 */
>> +	if (i2c_dev->is_vi) {
>> +		ret = tegra_i2c_init(i2c_dev, true);
>> +		if (ret)
>> +			goto disable_div_clk;
>> +	}
>> +
>>   	return 0;
>>   
>> +disable_div_clk:
>> +	clk_disable(i2c_dev->div_clk);
>>   disable_slow_clk:
>>   	if (i2c_dev->slow_clk)
>>   		clk_disable(i2c_dev->slow_clk);
>>
> The clk_disable() can cope with a NULL argument. Won't it be cleaner to
> remove the conditions?
will remove in v2