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Subject: Re: [PATCH v2] i2c: designwear: Fix clk warning on suspend/resume
To: John Stultz <john.stultz@linaro.org>,
        lkml <linux-kernel@vger.kernel.org>
References: <1487045142-1434-1-git-send-email-john.stultz@linaro.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Wolfram Sang <wsa@the-dreams.de>, linux-i2c@vger.kernel.org
From: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Message-ID: <e0c3968e-cff1-5cc7-9c42-1c3858e76077@linux.intel.com>
Date: Tue, 14 Feb 2017 17:30:14 +0200
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On 14.02.2017 06:05, John Stultz wrote:
> On my HiKey board, I'm seeing clk warnings on suspend/resume,
> which seem to be caused by runtime pm suspending the device,
> then the same suspend hook being called again on suspend time.
>
> This patch fixes this by setting the SYSTEM_SLEEP_PM_OPS to
> using pm_runtime_force_suspend and  pm_runtime_force_resume.
>
> Cc: Jarkko Nikula <jarkko.nikula@linux.intel.com>
> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
> Cc: Wolfram Sang <wsa@the-dreams.de>
> Cc: linux-i2c@vger.kernel.org
> Suggested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
> v2: Switch to suggested fix by Jarkko.
>
>  drivers/i2c/busses/i2c-designware-platdrv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
> index 6ce4313..09f27ec 100644
> --- a/drivers/i2c/busses/i2c-designware-platdrv.c
> +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
> @@ -362,7 +362,7 @@ static int dw_i2c_plat_resume(struct device *dev)
>  static const struct dev_pm_ops dw_i2c_dev_pm_ops = {
>  	.prepare = dw_i2c_plat_prepare,
>  	.complete = dw_i2c_plat_complete,
> -	SET_SYSTEM_SLEEP_PM_OPS(dw_i2c_plat_suspend, dw_i2c_plat_resume)
> +	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)
>  	SET_RUNTIME_PM_OPS(dw_i2c_plat_suspend, dw_i2c_plat_resume, NULL)
>  };

We need to hold this a bit. I've been debugging this on our platforms 
but haven't figured out yet how to fix a regression it is causing with 
drivers/acpi/acpi_lpss.c :-(

With this change in i2c-designware-platdrv.c the suspend path in 
acpi_lpss.c changes. First it saves its the register context in 
acpi_lpss_runtime_suspend() and powers down. Then the device which is 
now off will save again the register context (now reads full of 0xff...) 
in acpi_lpss_suspend_late() and restores wrong context (0xff...) when 
resuming.

-- 
Jarkko