On Monday, January 06, 2014 09:20:51 AM Yanmin Zhang wrote:
> On 二, 2013-12-24 at 09:35 +0800, shuox....@intel.com wrote:
> > From: Zhang Yanmin <yanmin.zh...@intel.com>
> >
> > pnp pnp_bus_suspend/_resume have an issue.
> > pnp_bus_suspend calls pnp_stop_dev to disable the device. With ACPI,
> > pnp_stop_dev turns off the dev usually. Then,
> > pnp_bus_suspend=>pnp_dev->protocol->suspend accesses the device and
> > suspend it again.
> >
> > pnp_bus_resume has the similar issue.
> >
> > Another issue is firmware might just provide _DIS, but no_STS method.
> >
> > The patch fixes it by adding a checking. If there is
> > pnp_dev->protocol->suspend, pnp_bus_suspend doesn't call pnp_stop_dev.
> > Do the similar thing for _resume.
> Rafael,
>
> What's your idea about this patch?
I haven't had the time to look deeper into that, sorry. I'll let you know
when I do that.
Thanks!
> We hit the issue when enabling Android on a latest tablet. After
> suspend-to-ram wakeup, serial console doesn't work.
> This serial port is bound by pnpcore driver.
> At suspending,
> static int __pnp_bus_suspend(struct device *dev, pm_message_t state)
> {
> ...
>
> if (pnp_can_disable(pnp_dev)) {
> error = pnp_stop_dev(pnp_dev);
> if (error)
> return error;
> }
>
> if (pnp_dev->protocol->suspend)
> pnp_dev->protocol->suspend(pnp_dev, state);
> return 0;
> }
>
> pnp_stop_dev calls dev->protocol->disable.
> As for ACPI device, that disable callback calls _DIS. Based
> on ACPI spec, driver need turn off the device before disabling it
> by _DIS. That means, after pnp_stop_dev returns, the device is at OFF
> state.
>
> Then, __pnp_bus_suspend calls pnp_dev->protocol->suspend, which
> continues to access the device while the device is at OFF.
>
> Our firmware just provides _DIS for the device. There is no _STS
> method. Then, after wakeup, the device doesn't work.
>
> But just like what the patch points out, pnp_dev->protocol->suspend
> continues to access the device while the device is at OFF. It's not safe.
>
> The patch looks like a workaround. Another possible fix is to just
> delete the calling of pnp_stop_dev in function __pnp_bus_suspend, as
> suspend is not equal to _disable_.
> The deletion might be a little intrusive. That's why we sent a workaround
> patch to LKML.
>
> Which one is better?
>
> Thanks,
> Yanmin
>
> >
> > Signed-off-by: Zhang Yanmin <yanmin.zh...@intel.com>
> > Signed-off-by: Liu ShuoX <shuox....@intel.com>
> > ---
> > drivers/pnp/driver.c | 6 ++----
> > 1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/pnp/driver.c b/drivers/pnp/driver.c
> > index f748cc8..2512e47 100644
> > --- a/drivers/pnp/driver.c
> > +++ b/drivers/pnp/driver.c
> > @@ -176,7 +176,7 @@ static int __pnp_bus_suspend(struct device *dev,
> > pm_message_t state)
> > return error;
> > }
> >
> > - if (pnp_can_disable(pnp_dev)) {
> > + if (pnp_can_disable(pnp_dev) && !pnp_dev->protocol->suspend) {
> > error = pnp_stop_dev(pnp_dev);
> > if (error)
> > return error;
> > @@ -215,9 +215,7 @@ static int pnp_bus_resume(struct device *dev)
> > error = pnp_dev->protocol->resume(pnp_dev);
> > if (error)
> > return error;
> > - }
> > -
> > - if (pnp_can_write(pnp_dev)) {
> > + } else if (pnp_can_write(pnp_dev)) {
> > error = pnp_start_dev(pnp_dev);
> > if (error)
> > return error;
>
>
> --
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--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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