linux-kernel - Re: [PATCH review for 4.4 19/26] i2c: at91: ensure state is restored after suspending

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Date:   Mon, 25 Sep 2017 09:22:34 +0200
From:   Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:     "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Wolfram Sang <wsa@...-dreams.de>
Subject: Re: [PATCH review for 4.4 19/26] i2c: at91: ensure state is restored
 after suspending

Hi,

I don't think it is worth backporting this patch to 4.4. Cutting VDD
core will only happen after mainline v4.12 or v4.9 for the vendor kernel.

On 25/09/2017 at 01:13:43 +0000, Levin, Alexander (Sasha Levin) wrote:
> From: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
> 
> [ Upstream commit e3ccc921b7d8fd1fcd10a00720e09823d8078666 ]
> 
> When going to suspend, the I2C registers may be lost because the power to
> VDDcore is cut. Restore them when resuming.
> 
> Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
> Acked-by: Ludovic Desroches <ludovic.desroches@...rochip.com>
> Signed-off-by: Wolfram Sang <wsa@...-dreams.de>
> Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
> ---
>  drivers/i2c/busses/i2c-at91.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
> index 10835d1f559b..dee0fc421054 100644
> --- a/drivers/i2c/busses/i2c-at91.c
> +++ b/drivers/i2c/busses/i2c-at91.c
> @@ -1131,6 +1131,7 @@ static int at91_twi_suspend_noirq(struct device *dev)
>  
>  static int at91_twi_resume_noirq(struct device *dev)
>  {
> +	struct at91_twi_dev *twi_dev = dev_get_drvdata(dev);
>  	int ret;
>  
>  	if (!pm_runtime_status_suspended(dev)) {
> @@ -1142,6 +1143,8 @@ static int at91_twi_resume_noirq(struct device *dev)
>  	pm_runtime_mark_last_busy(dev);
>  	pm_request_autosuspend(dev);
>  
> +	at91_init_twi_bus(twi_dev);
> +
>  	return 0;
>  }
>  
> -- 
> 2.11.0

-- 
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com