linux-kernel - Re: [PATCH 1/4] i2c: designware-platdrv: Fix runtime PM initialization

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Date:	Wed, 20 Apr 2016 16:53:08 +0300
From:	Jarkko Nikula <jarkko.nikula@...ux.intel.com>
To:	Jisheng Zhang <jszhang@...vell.com>,
	andriy.shevchenko@...ux.intel.com, mika.westerberg@...ux.intel.com,
	wsa@...-dreams.de
Cc:	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/4] i2c: designware-platdrv: Fix runtime PM
 initialization

On 04/14/2016 03:53 PM, Jisheng Zhang wrote:
> When pm_runtime_enable() was being called, the device's usage counter
> was 0, causing the PM layer to runtime-suspend the device.  We then
> went on to call i2c_dw_probe() on a suspended device, which could hung.
>
> Fix this by incrementing the usage counter before pm_runtime_enable().
>
> Signed-off-by: Jisheng Zhang <jszhang@...vell.com>
> ---
>   drivers/i2c/busses/i2c-designware-platdrv.c | 14 +++++++++++++-
>   1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
> index d656657..00f9e99 100644
> --- a/drivers/i2c/busses/i2c-designware-platdrv.c
> +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
> @@ -246,6 +246,7 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
>   	if (dev->pm_runtime_disabled) {
>   		pm_runtime_forbid(&pdev->dev);
>   	} else {
> +		pm_runtime_get_noresume(&pdev->dev);
>   		pm_runtime_set_autosuspend_delay(&pdev->dev, 1000);
>   		pm_runtime_use_autosuspend(&pdev->dev);
>   		pm_runtime_set_active(&pdev->dev);

pm_runtime_enable() here after pm_runtime_set_active() shouldn't suspend 
as far as I understand which made me thinking if there is some other 
issue that cause the symptoms what you are seeing? Like race with 
runtime PM or similar.

-- 
Jarkko