linux-kernel - Re: [PATCH] mfd: tc6393xb fail ohci suspend if full state restore is required

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Message-ID: <20141104092031.GL17577@x1>
Date:	Tue, 4 Nov 2014 09:20:31 +0000
From:	Lee Jones <lee.jones@...aro.org>
To:	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>
Cc:	kernel list <linux-kernel@...r.kernel.org>,
	Samuel Ortiz <sameo@...ux.intel.com>, stable@...r.kernel.org
Subject: Re: [PATCH] mfd: tc6393xb fail ohci suspend if full state restore is
 required

On Tue, 04 Nov 2014, Dmitry Eremin-Solenikov wrote:

> Hello.
> 
> 2014-11-03 17:56 GMT+03:00 Lee Jones <lee.jones@...aro.org>:
> > On Fri, 24 Oct 2014, Dmitry Eremin-Solenikov wrote:
> >
> >> Some boards with TC6393XB chip require full state restore during system
> >> resume thanks to chip's VCC being cut off during suspend (Sharp SL-6000
> >> tosa is one of them). Failing to do so would result in ohci Oops on
> >> resume due to internal memory contentes being changed. Fail ohci suspend
> >> on tc6393xb is full state restore is required.
> >>
> >> Recommended workaround is to unbind tmio-ohci driver before suspend and
> >> rebind it after resume.
> >>
> >> Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@...il.com>
> >> Cc: stable@...r.kernel.org
> >> ---
> >>  drivers/mfd/tc6393xb.c | 13 ++++++++++++-
> >>  1 file changed, 12 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/mfd/tc6393xb.c b/drivers/mfd/tc6393xb.c
> >> index 11c19e5..48579e5 100644
> >> --- a/drivers/mfd/tc6393xb.c
> >> +++ b/drivers/mfd/tc6393xb.c
> >> @@ -263,6 +263,17 @@ static int tc6393xb_ohci_disable(struct platform_device *dev)
> >>       return 0;
> >>  }
> >>
> >> +static int tc6393xb_ohci_suspend(struct platform_device *dev)
> >> +{
> >> +     struct tc6393xb_platform_data *tcpd = dev_get_platdata(dev->dev.parent);
> >> +
> >> +     /* We can't properly store/restore OHCI state, so fail here */
> >> +     if (tcpd->resume_restore)
> >> +             return -EBUSY;
> >
> > Wouldn't it be easier to just put these three lines into
> > tc6393xb_ohci_disable() instead off adding 7 superfluous lines and
> > making the Ops names inconsistent?
> 
> No. The problem only exists on suspend/resume path. tc6393xb_ohci_disable
> is also used on driver removal and can (should?) be used on device shutdown.
> Using the tc6393xb_ohci_disable() function in that paths is not a problem.
> 
> Also with this patch the Oops name will not be inconsistent - returning -EBUSY
> from this disable callback will cancel the device suspension with
> clearly stating
> that OHCI is busy in dmesg.

Understood.  Thanks for the explanation.

> >> +     return tc6393xb_ohci_disable(dev);
> >> +}
> >> +
> >>  static int tc6393xb_fb_enable(struct platform_device *dev)
> >>  {
> >>       struct tc6393xb *tc6393xb = dev_get_drvdata(dev->dev.parent);
> >> @@ -403,7 +414,7 @@ static struct mfd_cell tc6393xb_cells[] = {
> >>               .num_resources = ARRAY_SIZE(tc6393xb_ohci_resources),
> >>               .resources = tc6393xb_ohci_resources,
> >>               .enable = tc6393xb_ohci_enable,
> >> -             .suspend = tc6393xb_ohci_disable,
> >> +             .suspend = tc6393xb_ohci_suspend,
> >>               .resume = tc6393xb_ohci_enable,
> >>               .disable = tc6393xb_ohci_disable,
> >>       },
> 
> 

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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