Messages in this thread | | | Subject | Re: [PATCH 1/4] i2c: designware-platdrv: Fix runtime PM initialization | From | Jarkko Nikula <> | Date | Thu, 21 Apr 2016 10:48:56 +0300 |
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Hi
On 04/21/2016 06:08 AM, Jisheng Zhang wrote: > Dear Jarkko, > > On Wed, 20 Apr 2016 16:53:08 +0300 Jarkko Nikula wrote: > >> 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@marvell.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 > > FWICT, on arm DT platform, the device usage counter is zero at the beginning, > once we enable rpm, the i2c have chance to runtime suspend. > Yes it is same also for ACPI platforms. What I like to understand what is actually causing the runtime suspend in your case.
If I add delay longer than 1 second between pm_runtime_enable() and i2c_dw_probe() suspends still happens only after probe finishes. It will be triggered by the drivers/base/dd.c: driver_probe_device() when code calls the pm_request_idle().
I'm wondering is it possible there is a race with deferred probe etc. that is causing the issue you are seeing.
-- Jarkko
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