linux-kernel - Re: [RFC PATCH v4 04/14] i2c: tegra: Fix runtime resume to re-init VI I2C

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Message-ID: <d427f421-3c20-2aa3-b719-638be6aeca1d@gmail.com>
Date:   Mon, 27 Jul 2020 02:53:16 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.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 v4 04/14] i2c: tegra: Fix runtime resume to re-init VI
 I2C

24.07.2020 02:51, 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 7b93c45..1bf3666 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)
>  {
> @@ -675,8 +677,22 @@ 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:
>  	clk_disable(i2c_dev->slow_clk);
>  disable_fast_clk:
> 

This look okay, but isn't RPM usage a bit too expensive for VI? Maybe
RPM autodelay needs to be set for the I2C driver?

Reviewed-by: Dmitry Osipenko <digetx@...il.com>