linux-kernel - Re: [PATCH v3] i2c: designware: Fix unbalanced suspended flag

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Message-ID: <491f2a01-c2ae-8508-effb-dfd89bfe22a1@redhat.com>
Date:   Mon, 19 Dec 2022 12:35:16 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Richard Fitzgerald <rf@...nsource.cirrus.com>,
        jarkko.nikula@...ux.intel.com, andriy.shevchenko@...ux.intel.com,
        mika.westerberg@...ux.intel.com, jsd@...ihalf.com, wsa@...nel.org
Cc:     linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        patches@...nsource.cirrus.com
Subject: Re: [PATCH v3] i2c: designware: Fix unbalanced suspended flag

Hi,

On 12/19/22 12:20, Richard Fitzgerald wrote:
> Ensure that i2c_mark_adapter_suspended() is always balanced by a call to
> i2c_mark_adapter_resumed().
> 
> dw_i2c_plat_resume() must always be called, so that
> i2c_mark_adapter_resumed() is called. This is not compatible with
> DPM_FLAG_MAY_SKIP_RESUME, so remove the flag.
> 
> Since the controller is always resumed on system resume the
> dw_i2c_plat_complete() callback is redundant and has been removed.
> 
> The unbalanced suspended flag was introduced by
> commit c57813b8b288 ("i2c: designware: Lock the adapter while setting the
> suspended flag")
> 
> Before that commit, the system and runtime PM used the same functions. The
> DPM_FLAG_MAY_SKIP_RESUME was used to skip the system resume if the driver
> had been in runtime-suspend. If system resume was skipped, the suspended
> flag would be cleared by the next runtime resume. The check of the
> suspended flag was _after_ the call to pm_runtime_get_sync() in
> i2c_dw_xfer(). So either a system resume or a runtime resume would clear
> the flag before it was checked.
> 
> Having introduced the unbalanced suspended flag with that commit, a further
> commit 80704a84a9f8 ("i2c: designware: Use the
> i2c_mark_adapter_suspended/resumed() helpers")
> 
> changed from using a local suspended flag to using the
> i2c_mark_adapter_suspended/resumed() functions. These use a flag that is
> checked by I2C core code before issuing the transfer to the bus driver, so
> there was no opportunity for the bus driver to runtime resume itself before
> the flag check.
> 
> Signed-off-by: Richard Fitzgerald <rf@...nsource.cirrus.com>
> Fixes: c57813b8b288 ("i2c: designware: Lock the adapter while setting the suspended flag")

Thanks, patch looks good to me:

Reviewed-by: Hans de Goede <hdegoede@...hat.com>

Regards,

Hans



> ---
>  drivers/i2c/busses/i2c-designware-platdrv.c | 20 ++------------------
>  1 file changed, 2 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
> index ba043b547393..74182db03a88 100644
> --- a/drivers/i2c/busses/i2c-designware-platdrv.c
> +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
> @@ -351,13 +351,11 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
>  
>  	if (dev->flags & ACCESS_NO_IRQ_SUSPEND) {
>  		dev_pm_set_driver_flags(&pdev->dev,
> -					DPM_FLAG_SMART_PREPARE |
> -					DPM_FLAG_MAY_SKIP_RESUME);
> +					DPM_FLAG_SMART_PREPARE);
>  	} else {
>  		dev_pm_set_driver_flags(&pdev->dev,
>  					DPM_FLAG_SMART_PREPARE |
> -					DPM_FLAG_SMART_SUSPEND |
> -					DPM_FLAG_MAY_SKIP_RESUME);
> +					DPM_FLAG_SMART_SUSPEND);
>  	}
>  
>  	device_enable_async_suspend(&pdev->dev);
> @@ -419,21 +417,8 @@ static int dw_i2c_plat_prepare(struct device *dev)
>  	 */
>  	return !has_acpi_companion(dev);
>  }
> -
> -static void dw_i2c_plat_complete(struct device *dev)
> -{
> -	/*
> -	 * The device can only be in runtime suspend at this point if it has not
> -	 * been resumed throughout the ending system suspend/resume cycle, so if
> -	 * the platform firmware might mess up with it, request the runtime PM
> -	 * framework to resume it.
> -	 */
> -	if (pm_runtime_suspended(dev) && pm_resume_via_firmware())
> -		pm_request_resume(dev);
> -}
>  #else
>  #define dw_i2c_plat_prepare	NULL
> -#define dw_i2c_plat_complete	NULL
>  #endif
>  
>  #ifdef CONFIG_PM
> @@ -483,7 +468,6 @@ static int __maybe_unused 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_LATE_SYSTEM_SLEEP_PM_OPS(dw_i2c_plat_suspend, dw_i2c_plat_resume)
>  	SET_RUNTIME_PM_OPS(dw_i2c_plat_runtime_suspend, dw_i2c_plat_runtime_resume, NULL)
>  };